Basics
Before Modifications O2 sensor voltages for tuning wot performance Mass Air Flow Sensor (MAF) Throttle Position Sensor Adjustment IAC Adjustment Cam Sensor Crank Sensor EGR Wastegate Solenoid Fuel Injector Sizing Fuel Pump Sizing Fuel Pump Hot Wiring Factory Fuel Pump Relay Detonation Detonation Sensor False Detonation Turbo Articles Boost Control Dynamic Compression Compression Ratio Calculation/Dimensions Oil Pump Torque Converter Lock Up Cruise Control
Long ago when Lawrence Conley used to regularly write articles on turbo Buick performance, he was fond of saying, "There are no magic parts". Best that I can tell, that is still true.
Now lots of vendors have shelves full of magic parts. It's their job to sell stuff. Some try harder than others. If you ask a vendor if a 70 mm throttle body will make your car run faster, some will say, "For sure!". And, it might, if you are trying to run nines.
I always find it interesting to read signatures and see all these parts listed, and then, look at the posted times and see 12-14s for time slips. My first thought is, "A vendor's dream!". I have bought lots of stuff that did nothing over the years so I am not necessarily smarter, just experienced.
For a car to run well, it has to be mechanically and electrically sound, and, the added pieces have to work well with one another. All too often, we see people in a spending frenzy after they buy a car, and then, they are disappointed when they don't run tens when they go to the track.
What does it take to be mechanically sound? The engine has to have reasonable compression and not be pumping oil. The timing chain cannot be worn and teeth falling off the cam gear. The camshaft cannot have worn lobes, bad lifters, and worn rockers. The valves should be good and not gunked up with carbon deposits on the back of the face and the valve springs have to be good. The injectors have to be spraying correctly and putting out equivalent amounts across the board. The turbo has to be sound with no in and out play on the compressor shaft, and it should not be pumping oil thru the intercooler and into the throttle body. The intercooler must be clean inside and out and not have any major leaks in the core or through the hoses. The fuel pump must be in good condition and capable of delivering sufficient volume to support the horsepower being generated while being able to increase fuel pressure one pound for each pound of boost increase. To do this, it takes a good pump, sufficient voltage at the pump, a good regulator, a clean fuel filter, and no kinks or internal faults in the rubber lines in the rear of the car, or the ones at the front of the car. The radiator may not be doing its job and the engine may be running hotter than desired. The engine mounts must be in good condition and not cracked or broken.
Then we get to the next link in the line of power which is the transmission. It has to be in good condition with no slippage, shift properly, and have the right torque converter in front of it. The factory converter should work well into the elevens if functioning correctly. This means it should brake stall around 2300-2400 rpm when you stand on the brake and give it the gas in Drive and the turbo should make at least 5# of boost before the rear wheels begin to turn (this assumes that the turbo is stock to maybe a TE44). An external transmission oil cooler is virtually mandatory to prolong transmission life.
Moving on to the rear of the car, good U-joints may not make you go faster, but, they will keep you going fast, safely. I strongly suggest a driveshaft loop for any car that is going to run sticky tires. It's cheap insurance. Quick cars have to have good short times. While the G-Bodies don't have very good rear suspension geometries stock, they will still hook up well if the bushings are in good condition, the posi is not slipping, and the lower control arms are boxed. Good, sticky tires are a necessity, obviously. Good shocks and springs are also required. With a stiffer rear anti-roll bar, the front sway bar may be disconnected at the track for better weight transfer.
Electrically, the systems in these cars are 16-17 years old and the harnesses are deteriorating, connectors may have corrosion in them, or not always make good contact when plugged in, be frayed, etc. Grounds may be poor, insufficient voltage getting to the ignition, the fuel pump, etc. The injector harness may be intermittent. The plug wires must be in good condition and not change resistance when flexed. Low resistance is not important as long as the resistance is proportional to wire length. Plugs should be gapped from .032 to .035 and platinum plugs should not be used. The coil and module must function properly as do all other sensors. Being that the engine fuel and spark systems are controlled by input from sensors to the the ECM, if there is a break down in a sensor, or the electrical circuits that carry information, it will not run right no matter how many of those magic parts you buy. In fact, it may run worse.
Now, there may not be a lot of glamour in taking care of the basics, but, all the performance parts in the world will have a difficult time in improving the performance of a drive train that is inherently flawed to begin with. Consider this. A bone stock Regal in good condition should run in the 14s on stock tires, in the 13s with some more boost, cold air intake, free flowing exhaust, and a modern chip. Put some sticky tires on it, an alcohol injection system or race gas in tank, a modern programmable chip, and it should be in the 12s.
When it comes to tuning, the most important thing to accomplish is to not blow it up! Detonation is the enemy of any forced aspiration engine. A bit too much, and you lose a headgasket. A bit more, and you become a member of the Drive Over the Crankshaft Club. This means you must have some means of monitoring detonation. I suggest a Scanmaster and a knock alarm with an audible warning. The Scanmaster will show the amount of timing retard commanded and the audible alarm will allow you to watch where you are going when at WOT. Once you have become familar with the Scanmaster and decide you wish to do some serious tuning, the PowerLogger is an ideal logging tool that works in conjunction with the Scanmaster. You will wonder how you ever did without it.
An accurate boost gauge is another necessity.
Now, Let's clear up some myths and look at the basics. Remember, there is no set of Cliff's Notes that will make you a tuning expert over night. I am not, and, I have been playing with these cars since 1986. If you take the time to learn the basics, however, it will make things a lot easier as you go along. There is nothing new on these cars with regard to theory. What is new is the integration and control of fuel and spark thru electronic controls. Newer cars are far more sophisticated then these. You have two choices, learn how things work, or find a good mechanic that will do things for you.
O2 sensor voltages for tuning wot performance
The oem Oxygen sensor is a narrow band, or switching, sensor. Here is a graph that depicts how it works.
The sole function that the oem sensor performs is to signal the ecm if the exhaust gas passing over the sensor is either rich or lean with the stochiometric A/F point of 14.7 being the dividing line. It simply acts as a switch that is used to correct fueling at part throttle to optimize mileage and emissions. It is NOT used to determine fueling at wide open throttle.
Not only is the sensor extremely insensitive on either side of stochiometric, it is also affected by exhaust gas temperature. As the sensor heats or cools, its output voltage changes even if the A/F ratio does not.
Trying to use the output voltage of the stock sensor to determine an optimum A/F ratio for a given car is essentially a futile exercise due to the very nature of the sensor and the changes that may be incurred with temperature swings.
When someone says that the fueling should be adjusted to some magic number such as 765 mv, the above curve will show the futility of that effort. 765 mv might be anything from an air fuel ration of 14 to 1 to 12 to 1, or even broader depending upon the individual combination, the exhaust gas temperature, and the condition of the sensor, etc.
Below is a log comparing the output from a wideband O2 to the output from the factory narrow band. During the period under boost there is more than a 20% variation in actual air to fuel ratio when the factory O2 voltage is basically flat. Something to think about.
Note that when someone says the O2s should be 800 or whatever other magic number they like, they are referring to wide open throttle O2s at the top of 3rd gear. My experience has shown that Alky Injection has allowed me to safely run lower O2's on the oem sensor. I used the wide band for tuning though.
My best advice is to buy a wideband O2 in order to obtain meaningful air/fuel ratios for consistent tuning as using the factory O2s for tuning is simply a meaningless exercise except in the very broadest sense. Let me say, however, that thousands of people have gotten by for 20 years with the oem narrow band sensor. If one is careful to stay out of timing retard, then one is okay. On the other hand, if one has a modern programmable chip with options to tweak the A/F at various parts of the rpm range, and/or in different gears, then the WB is a big help in optimizing performance.
In normal driving the O2s should be bouncing back and forth across stochiometric which may be either 0.45 v or 0.500 v depending upon which scan tool one is using.
Note that a properly functioning O2 sensor is required for proper performance and mileage from any chip that is closed loop like the factory chips. This means virtually all chips other than the MaxEfforts, and some of the Turbotweaks. History has shown that the AC Delco sensors are more reliable than the Bosch replacements. Recently, some have had good luck with the Denso sensors which may be more lead resistant that the originals. Some prefer to use a Delco heated sensor in the belief that they work longer in the presence of leaded race gas if turned on and allowed to warm up for a few seconds before starting the engine. Personally, I don't like them as they tend to fail by losing range rather than simply dying.
There are two common systems in use on most fuel injected engines for deriving air flow into the engine for fueling purposes. Our cars came from the factory with a mass air flow sensor while some of us use the speed density system.
Mass air cars use the mass air flow sensor in the intake to measure the mass of the air flowing thru the system while speed density cars use the MAP (manifold absolute pressure) sensor and compute air flow based upon the output from the sensor. Both types use other sensors and variables in the calculations--rpm, tps, temp, etc.
Note that the MAP is not input to the ecm on our cars. However, speed density conversions require the MAP input into the computer. The easiest means to do so is by using Bob Bailey's PowerLogger. If the MAP is connected to the PowerLogger, its data will be transmitted to the ECM and that eliminates having to have the ECM modified to add the necessary inputs.
The oem MAF on our cars measures airflow from 3-150 grams per second. Normally, when the key is ON, and, the engine is OFF, the maf will still display a number on the scantool....as above 3 is the minimum. Our scantools display 0-255 when using the factory maf and conventional chip (Extender chips will read higher).
At normal idle, the maf will read 4-7 on the scantool (again, this is with conventional chips-Extenders may read less).
At wide open throttle, the reading will depend upon air flow. Typically stock engines around 15# of boost would show something like 240-245 on the scantool maf parameter. As I recall, very few hit 255 until the boost was around 17#, or a bit higher.
Now, the output from the maf is one of the prime drivers of fueling by the ecm. The ecm delivers a fueling rate based upon the maf numbers and trims the amount with feedback from the O2 sensor.
At wide open throttle, the airflow may exceed the capability of the factory maf to measure, and, the ecm goes to a preset fueling curve as called for by the chip programmer. This is normally not a big thing when using chips from well experienced programmers who have dialed in their chips.
MAF Screen Removal...the factory maf has two screens on the inlet side of the unit. There are no screens on the outlet end. The purpose of the screens is to smooth air flow across the sensor. Without the screens, the sensor does not measure the air flow correctly. It is very common to see the removal of one, or both screens suggested in the belief that the extra air flow would be beneficial. In practice, this is seldom the case. Removing one screen is often acceptable although the occasional car will not idle well. Removing both screens is an almost surefire means of screwing idle up. What happens is that the airflow is distorted and the sensor does not output the quantity passing by correctly to the ECM. I believe the number reported is lower than the actual airflow. This causes the ecm to provide less than optimal fuel which in turn screws up the idle quality. A few chip makers have mastered the correct technique to compensate, but, my experience shows that unless the car is making near nine second power, removing both screens is futile when it comes to performance increase.
The calibration of the maf sensor is extremely important. If it does not report the correct airflow, it throws the fueling off and causes drivability problems. Most modern programmers probably force the ecm to see full airflow at wide open throttle in order to assure there is adequate fuel delivery even if the maf is not functioning 100% correctly. This takes some of the variability out of performance, but, it does not make a flaky maf operate correctly at idle and part throttle-thus drivability is still affected.
Unfortunately, the oem mafs were quite fragile and often incurred what would be premature failure. Even more unfortunate is the difficulty in finding an aftermarket rebuilt maf sensor that is actually calibrated for our engines rather than some generic calibration. On top of that, many of the mafs sold don't even match our original units physically. Some are necked down inside which restricts air flow while others have a different configuration of connector.
Based upon reported experiences, it is very seldom that one can find a rebuilt unit that works 100%.
That brings us to today. I suspect that almost every original oem maf still in use is flaky to some degree. So, what do we do?
Modern mafs output voltage while our originals output frequency as a measurement of airflow.
A few years ago, Bob Bailey developed the Translator which takes the output from a modern GM MAF and converts it from volts to frequency, and, calibrates it to match our original units. These modern MAFs are very durable and appear to last much longer than the originals without acting up. See the Full Throttle Board for information on these systems. These MAFs range from 3" to 4" in diameter. Perfectly adequate to support the power required to run well into the Nines.
Bob has continued the evolution of these systems with many bells and whistles available today that enable one to tweak tuning to suit ones needs.
The Translators may be used with conventional chips, or with Bob's Extender series which allows the MAF to measure two and three times the original airflow limits of the factory mafs.
Also note that maf calculations are dependent upon mounting location, orientation, etc. An open element air filter that is exposed to the air blast from the radiator fan may cause the maf numbers to jump around when the fan starts, or, stops. This can often result in a screwy idle.
I believe it is worth the cost to convert any car still using an oem MAF to a Translator set up in order to improve all aspects of performance. OR,
The other option, as mentioned above, is to eliminate the the MAF altogether and go to a speed density system using either a set up like the TranslatorPro from Bob, or the TurboTweak SD chip from Eric Marshall of TurboTweak.
This may not be an option in an area that has strict emissions' testing, however.
Expensive aftermarket systems such as BigStuff, etc. really bring more problems than solutions until one is well into the Nines, in my opinion. Of course, your vendor may not concur. :)
Throttle Position Sensor Adjustment
The TPS sensor is used to tell the ECM how far open the throttle blade is open in order to assist in determining how much fuel should be injected at any given moment. This is not the only tool used. Air flow, engine load (LV8), etc. are also calculated and input for fuel control.
TPS adjustment is another area where folk lore has long persisted with no basis in fact. The sensor may be adjusted for idle voltage and wide open throttle voltage.
Let's start with wide open throttle settings.
Folk lore has long taught that some magic number such as 4.65 volts, or 4.80 volts is required from the TPS in order for the ECM to command Power Enrichment which provides the additional fuel required which the engine is under boost.
If you go Here and look at the chip dumps provided by Dave Huinker, and go down to line 1410 of the dump, you will see the factory commands power enrichment at 75% of TPS which is 3.75 volts.
Now, if you have Power Logger, or, Direct Scan, it shows when PE is invoked. You will notice that PE may come in at a much lower voltage such as 2.5v. This is because the TPS point is overridden by engine load (LV8) at part throttle in many cases.
So, is there any reason to have a wide open throttle tps setting greater than 3.75 v? There are a couple of reason. First, the factory programming shuts down the AC compressor at 4.0 volts so the compressor is not working when you go wide open throttle.
Secondly some chip makers specify a certain window for both the idle range and the wide open throttle range when using their programmable chips. These guidelines must be followed in order to correctly program their chips. Read the instructions that come with the chip and follow them in order to ensure proper function with these chips.
I normally set mine somewhere in the range of 4.2-4.8 v.
The main thing to understand is that performance does not change however you adjust the tps in the upper end.
If you have too high a wot tps voltage, then you will throw a code 21 (see trouble codes under troubleshooting section so it is best not to set the wot tps over 4.8 even if it will go higher.
Far more important, than worrying about why you only have 4.48 volts at wide open throttle, is to be sure that the throttle blade has moved as far as it can when you put the pedal to the floor. Look at the throttle blade lever when the pedal is pressed to the floor and see if it has gone all the way to the stop signifying that the blade is wide open.
If it is not all the way open, there are generally three possible reasons as to why it has not.
a) The floor mat is restricting the pedal from traveling as far as it should
b) The throttle valve cable from the transmission has been adjusted too tightly and is not letting the the lever move as far as it should
c) The throttle cable has stretched and is not moving until the pedal has moved a short distance. If you get down in the floor board and look at the pedal bell crank where it connects to the cable, you can see the slack, if it exists, between the ball on the end of the cable and the bell crank. An easy fix for this problem is to put a small tie wrap around the cable between the ball and the bell crank to take up the slack. This will make the throttle blade begin to move as soon as the pedal moves and should restore full blade opening.
To determine the source of the problem,
grab the throttle lever and move it by hand...
If it goes all the way and the blade is open, or nearly so...then it would
appear to be a cable stretch problem.
If it goes all the way, but, the blade is substantially a distance from being
wide open...removing some off the lever for more throw should help. I have never
seen this problem but, I guess that anything is possible.
If it does not go all the way and make contact with the throttle body housing,
then be sure there is nothing obstructing the pedal such as the mat. If there is
not, then disconnect the tv cable and see if the lever will now move the rest of
the way. If it does, then you know the problem is with the tv cable.
Now, let's look at the idle TPS setting.
It does not matter with regard to idle quality whether the idle TPS voltage is 0.38 volts or 0.46 volts. The ECM looks at the initial voltage when the engine is started and creates a reference mark for fueling so there is no difference in fueling whether the voltage is 0.38 or 0.46. Now, if the voltage is above 0.46, the ECM will think the engine is not in the idle mode and will change the fueling, thereby messing up the idle. Normally, when you turn the key to "Run" (engine not running) and check the TPS voltage, you will note the setting such as 0.42 volts. Now if you start the engine, you will see the voltage now reads 0.44 volts. For this reason, we usually try to set the voltage no greater than 0.44 in order to be sure it does not slip out of the idle range and confuse the ECM when the engine is started. (The factory spec appears to be 0.40 +/- .05v.....in other words, 0.35-0.45 v)
So how do we adjust TPS voltage?
Turn the key to "Run" but, do NOT start the engine. Loosen the two bolts that hold the TPS in place enough that the TPS can be moved. Note that the TPS is slotted so that the sensor may be rotated as well as moved fore and aft. Push the entire sensor as far forward as possible so that the two bolts are up against the back ends of the slots. Then, rotate the top of the sensor CCW a bit until your scan tool indicates an idle TPS voltage of say 0.38-0.44 volts and tighten the retaining bolts so that the sensor cannot move. Note that the idle may change as you move the sensor. Don't be deceived that you have changed or improved the idle. When you shut the engine off and restart, the idle will go back to where it was before you moved the sensor unless the sensor was out of range to begin with. As stated prior, the ecm rezeros the idle at each start.
The ecm does not look at tps voltage when adjusting fueling. Rather, it looks at the tps percentage of full scale. Whatever the idle voltage, it is auto-zero'd to 0 percent when the car is started. Therefore fueling is not changed whether the idle voltage is 0.38 or 0.46 as the computer is feeding zero percent and commanding the fueling specified for idle fueling. Once the engine is started, and the tps set to zero percent, any movement of the tps is reflected as percent change even if the change is within the idle window checked when the engine was first started.
Having set the idle voltage, now recheck the wide open throttle voltage. It will probably be around 4.5 v. If someone tells you that you should file the slots so you can get more voltage out of it, ignore them.
After finishing, slowly open the throttle while watching the TPS voltage on the scantool. It should increment smoothly and steadily with no dead spots or jumps which would indicate a problem within the sensor.
If you do not have a scantool yet, you can use a digital voltmeter. Put the positive probe on the dark blue wire coming out of the TPS sensor and the negative probe on a good ground point such as the intake. With the key on, you will read the TPS voltage.
One further note on the TPS voltages. If you adjust the IAC, turning the screw CW will increase your TPS voltages and the opposite will reduce them. Be sure that you don't let the TPS get out of the idle range.
IAC (Idle Air Control) Adjustment
The IAC function maintains idle quality through commands from the ECM, but, has NO impact beyond the idle range. Idle speed is set by the chip, not by the IAC adjustment screw. Looking at the inside of the throttle body, there are two holes in the lower portion fore and aft of the throttle blade. At idle, the blade is essentially closed and air enters the front hole, goes past the IAC plunger, and exits behind the throttle blade into the plenum. The IAC plunger is pulsed by the ECM to maintain a steady idle with varying engine load.
When the IAC is adjusted, we seem to typically look for IAC counts on our scantool somewhere between 15-25 when the car is in Park, the engine fully warmed up, and the A/C is off. The lower the IAC number, the less control the ECM has over the idle as the throttle blade begins to be opened. This setting may not be as critical as we often make it. You may find your car idles just as well at 40 counts as it does at 15.
With car in Park, engine fully warm, A/C off, look at the IAC counts on the scantool. If you wish to lower the count number, turn the adjustment screw clockwise. To increase the counts, turn it counterclockwise. Turn the screw a small increment, turn the engine off, and restart. This insures that the IAC resets and confirms the adjusted number. Continue until the desired number is achieved. Often, on stock set ups, about 1-1 1/2 threads of the adjustment screw will emerge thru on the lever side of the throttle body. Restarting also rezeros the tps as stated in the prior section and removes any effect on idle speed that may have occurred due to tps movement. The IAC counts will probably be 30 counts, or more, higher on a cold engine than on a warmed up engine. The counts will also be much higher in gear as compared to Park, and, higher with the AC turned on.
Remember that the IAC adjustment will change the TPS and that if the TPS moves past 0.46 volts, the idle may increase in speed as the ecm no longer thinks the car is in idle range. Therefore, if you are going to decrease IAC counts very much, it is a good idea to first lower the TPS down to 0.38 volts or so in order to prevent it from rising out of the idle range as you adjust the IAC.
It is not a bad idea to clean the throttle body out periodically with carb cleaner to keep the passages clean and to insure that the IAC function works correctly. Remove the IAC from the housing and clean any carbon or gum off the tip of the plunger and clean the seat as well. Don't power up the IAC when the unit is not installed. Otherwise, you may find the plunger is pushed out of the sensor. When reinstalling, very little torque is required. Just tighten enough to compress the gasket to prevent an air leak. Over tightening may crack the plastic interior of the IAC.
The cam sensor has nothing to do with ignition timing. Its primary purpose is to locate cylinder #6 in order to synch injector pulse to the the correct cylinder on the intake stroke so that the injector sprays at the proper point in the intake cycle and to the correct cylinder.
If the cam sensor is not working, the engine will not start.
If it is bad, you will have no start due to no injector pulse. See the troubleshooting pages.
Once the engine has been started, the cam sensor may be disconnected and the engine will continue to run. The ecm has been told where number 6 is and the spark will continue to be correct. What does change is the technique of applying injector pulses. The injectors will normally fire in a sequential mode. If the cam sensor is disconnected after starting the engine, the injectors start firing in batch mode. In the early days, we often put a switch on the cam sensor and turned it off before making a run thinking that the engine might get more fuel that way. Later we decided that that might not be true, and, we had a lot better selection of injectors, fuel pumps, chips, etc. to cover the fuel problem. At wide open throttle, the injectors are probably on as long as they can be with regard to duty cycle so this should not be beneficial with today's larger injectors.
Note that the cam sensor must be reconnected again or the engine will not start after being shut off.
So, remember that the cam sensor controls the point that the injector sprays, but not ignition timing.
In order for the engine to start, and to run properly, the cam sensor must be installed correctly. Go here for install directions. Note that the new Casper's replacement cap is installed with the timing mark set at zero rather than 25 degs ATDC. It has an led in the top that comes on when the cam sensor is installed correctly, and, this greatly simplifies installation if the sensor has been removed, or, the original cap has failed. Read the instructions that come with it and ignore the install directions I have provided.
I highly suggest reading the cam sensor article on GNTTYPE by Tom Chou who worked at Delco. It explains in detail the workings of the sensor and what it does.
For years, a number of experienced Buick guys have suggested moving the cam sensor about 1/8" counterclockwise from the theoretical setting point especially if you have a modified engine with a larger cam. I always do, myself. This has absolutely nothing to do with ignition timing, but, it does alter the point where the injectors begin to spray. It might help engines with larger cams as prior stated. If moved so much that the sensor is on the wrong (next) window, it will probably backfire very badly and that ain't good.
If the sensor is installed 180 degrees out (as if you were not on top dead center, but were one crank revolution out), then the fuel will be sprayed on the exhaust stroke rather than the intake stroke and the engine will idle badly, and generally not run well at all. Make sure the crank is properly referenced to TDC before you install the sensor.
Remembering that our cars have a waste spark system where three coils each serve two cylinders so that one coil is firing one cylinder on the ignition cycle while firing another cylinder on the exhaust stroke.....the crank sensor is triggered by the three blades on the back of the damper that pass thru the air gap on the sensor. As stated above, without the the Cam Sensor, the ecm would not know how to locate the proper cylinder to fire as the crank sensor alone cannot determine which is cylinder #6 to synch ignition and fuel.
Therefore, a broken crank sensor will eliminate the spark, but, not the injector pulse.
One of the most common failures that causes the engine to die and refuse to restart is a broken crank sensor bracket, and more rarely, a bad sensor.
It is extremely important that the air gap is correct on all three blades of the damper. Otherwise erratic engine performance may result.
See crank sensor install instructions here.
The EGR valve should only function while cruising. It has no effect on idle or wide open throttle operation. It is controlled by the EVRV (electronic vacuum regulator valve) mounted on the intake manifold just above the rear of the driver's side valve cover. The EVRV valve controls the vacuum applied to the EGR valve during cruise mode.
The EGR (exhaust gas recirculation) recirculates a small amount of spent exhaust gas back thru the intake which tends to cool the exhaust gas down a bit which reduces the creation of Nox for emission's purposes. As the addition of spent exhaust tends to replace some of the oxygen in the charge, the mixture becomes richer and the ECM compensates by reducing the amount of fuel injected during cruise. If the EGR system is defeated, one may incur some light detonation at cruise because the ECM has leaned the mixture down anticipating less fresh air in the charge. This can be overcome with a chip mod if it occurs.
There is no reason in a street car to do away with an EGR, however. It simply does not affect performance. It can be removed when using those chips that deactivate it. Be very careful to seal the hole that is left to prevent any potential leaks.
The EVRV has a round cap on it about the size of a bottle cap. Under this cap is a filter. If it gets too dirty, it can cause a malfunction of the valve operation and throw a code. It needs to be replaced periodically.
If the EGR has a small leak around its base, it can really screw up the idle. If the leak is a bit bigger, it won't idle at all.
The wastegate solenoid is an electronic bleeder that is pulsed by the ECM in order to control boost. It functions by bypassing boost through the solenoid into the atmosphere. As this happens, the amount of boost reaching the wastegate actuator is reduced and it takes more total boost to overcome the wastegate actuator spring. Minimum boost is obtained when the solenoid is closed and not pulsed. As the pulsewidth transmitted from the the ECM increases, the solenoid is effectively held open longer, more boost is diverted thru it, and the actuator is delayed in opening so that more boost is produced before the puck opens.
Note that the wastegate solenoid has two ports...one is connected to the "Y" hose arrangement from the actuator and compressor housing. The other is open to the atmosphere. From the factory, there was a small piece of foam attached to the open port as a filter. It does not matter which port the "Y" hose is connected to. This pertains to the intercooled cars only.
In the plastic "y", one end has a small restrictor in it. This restrictor is connected to the compressor housing port. The hole in the restrictor is normally .045-.050". Boost control will not be right if the hole diameter does not fit into this range. Some dealer replacements do not. The function of this restrictor is to prevent the wastegate solenoid from being overwhelmed by the volume of the boost coming from the compressor port and thereby being rendered ineffective.
Connect the "y" in reverse with the restrictor leg going to the actuator and you will have 12# of boost with a stock actuator and about 17# with an HD model. Shortening the wastegate rod will not do much in this case.
Get a crack or leak in the hoses and you may find your boost is way over the desired limit and it's a good way to get some practice changing headgaskets.
The factory solenoid has been discontinued. This number, ACD214-1073 which was used on the turbo diesels, will work in its place and is a lot cheaper than the $100-$200 that some greedy vendors have been asking. I understand the connector does not lock as original but the connector does plug into the solenoid. This solenoid has two ports just like the original.
Before getting to the wherewithal's of injector size selection, let me say one thing. Contrary to all the internet comments, injector color rings are virtually totally meaningless these days! Green stripes, blue tops, red stripes, etc. don't mean a damn thing. Manufacturers have changed both the color coding and the numbers of injectors over the years. Look at the number on the injector in question and do a search online to see what it is. Note that injector manufacturers have also changed numbers over the years and you may find more than one number on various injectors and they may still be the same injector-just another vintage. Although I have provided a link on this site to some injector listings, it may be easiest to go to a bulletin board and do a search. Someone asks "What injector is this?" constantly.
One more comment. Larger injectors will not add performance to an engine unless the current injectors are too small for the engine combination. In other words, adding 50# injectors to a completely stock engine will do nothing to increase the hp of the engine as the stock injectors are adequately sized for the stock engine combination.
For proper performance and maximum head gasket life, the fuel injectors must be adequately sized to the horsepower potential of the engine. This is a bit of a catch-22 situation as an engine cannot achieve it's horsepower potential without sufficient fuel, but, merely supplying fuel will not make more horsepower as it is but one of the components required.
Brake specific fuel consumption (B.S.F.C.) is one of the primary components in projecting fuel requirements. Simply, it is the number of pounds of fuel required to make one horsepower for an hour.
This number depends upon total engine configuration and may vary a bit from engine to engine depending upon configuration, test, and ambient conditions. Typically, a naturally aspirated engine will use 0.45-0.50 lbs of gasoline per hour per horsepower. A forced aspirated engine will consume 0.55-0.65 lbs of gasoline per hour per horsepower.
My personal preference is 0.60 lbs per hour per horsepower.
The other variable involved is the injector duty cycle (D.C.). It has been commonly accepted that when an injector is pulsed to reach 80% duty cycle, it is effectively at its maximum output. However, some evidence has been presented lately that would appear to contradict this belief. This evidence would suggest that at least some injectors may continue to increase in output all the way to almost 100%. Effective Duty Cycle is related to engine rpm. The faster the engine turns, the less time the injector has to be open on the intake stroke.
I would suggest not using more than 85% DC in order to leave a little room for error just in case you end up needing more fuel than you calculated. It is always safer to have more fuel delivery capability than you need than to have too little. Injectors price differential is not that great and good chips are available for most.
The formula used to calculate projected injector size is-
(B.S.F.C. times horsepower) divided by (number of injectors times DC) = Injector Size.
As an example: (0.6 x 500 hp) divided by (6 injectors x 0.85 DC) =62 lb/hour injectors.
A couple of more comments. Injector output is affected by fuel pressure and most injectors are commonly rated at 3 bars by the sellers. One bar of atmospheric pressure equals approximately 14.5 lbs/sq. inch of pressure. Therefore, 3 bars is close to 43.5 lbs of fuel pressure.
Injector output then varies with changes of fuel pressure from the rated pressure. It does not vary linearly, however. It varies with the square root of the (new pressure divided by the original pressure) multiplied by the flow rating.
For instance, take an injector that is rated at 50 lbs per hour at 43.5 lbs/square inch pressure. Raise the pressure to 48 lbs/inch. 48/43.5= 1.10. The square root of 1.10 is 1.033. Multiplying 1.033 x 50=51.65 lbs per hour.
The moral of this story is that increasing fuel pressure to make up for undersized injectors is a waste of time in most cases. If fuel pressure variation is too great in an attempt to make up for a fuel delivery problem at wide open throttle, then the idle and cruise mixtures may be overly rich as well.
It is always safer to oversize injectors as opposed to undersizing as a good chip maker can dial them into to your needs.
For a more exhaustive discussion, go Here. Java formulas are provided at the bottom so you don't have to get out your calculators.
In the section on injector sizing, formulas were provided to determine the size injector required to support a given amount of horsepower. it was stated that a Brake Specific Fuel Consumption (B.S.F.C.) of 0.6 lbs per hour per horsepower was typically a safe number to use in calculations. That means to adequately support a 500 h.p. engine, we need to have a fuel pump that will deliver 300 lbs of fuel per hour to the proper sized injectors.
Now, we typically refer to injector ratings in this part of the world as lbs per hour while we often rate fuel pumps in gallons per hour. What's up with that? I have no idea, but, a gallon of gasoline normally weighs very close to 6 lbs so the above 300 lbs of fuel per hour translates to 50 gallons per hour. The clinger is that this 50 gallons must be at the fuel pump pressure that is required for a given boost.
Now, in order to maintain a desired Air/Fuel ratio as boost increases, fuel pressure must increase one pound for each pound of boost increase.
The second clinger is that fuel pump delivery volume drops as pressure requirement increases. This means we have to be careful when selecting a pump in order to maintain sufficient volume at full boost.
Now, let's look at some pictures and see if we can put it all together. I borrowed this from www.gnttype.org from the fuel section. There is a lot of excellent material there and I consider it to be a must read.
This graph was supplied to www.gnttype.org by Dan Goldstein. It represents the flow of a Walbro 307 pump at both 12.0 volts and at 13.5 volts. Note that the flow increase at 13.5 volts is almost constant, but, that when computed as a percentage of the 12.0 volt curve, it begins to exceed 20% at higher delivery rates.
This is a good time to emphasize the need for a good "hot wire" kit and an electrical system that is being charged correctly. Factory wiring was small and made from aluminum with high resistance and the ground path was poor as well. On my own cars, I have noted voltage drops from the alternator to the fuel pump in excess of 1.0 volt.
Note that the fuel volume delivery rate begins to fall off more rapidly at 60 psi representing the performance of the stock bypass spring.
Also, in the initial comments, it was stated that we needed 300 lbs of fuel per hour or 50 gallons per hour of fuel delivery to safely support 500 hp.
On the graph above, we see that we must stay at 70 psi or less to at 13.5 volts to the pump to maintain that rate. That infers a combination of initial fuel pressure plus boost that does not exceed 70 psi. For example, 45 psi with the hose off at idle plus 25 psi of boost which then equals a total of 70 psi.
Some run voltage boosters to provide more voltage to the pump in order to increase pump output to maintain a greater margin for error. This also emphasizes the need to run adequately sized injectors so that fuel pressure at idle may be kept low rather than pushing 50+ lbs trying to make up for small injectors.
Whether, or not, one runs a volt booster, it is important to insure that full voltage reaches the pump in order to maintain desired flow. Factory wiring was marginal in 1986 and is much worse today. It is not uncommon to find the voltage at the rear of the car is as much as a volt less than is measured at the alternator. This is why fuel pump hot wires and tank grounds are a necessity.
Now, let's look at another graph.
This graph was also supplied to www.gnttype.org by Dan Goldstein. It is a comparison of the flow rates and current draws of a Walbro 307 versus a Walbro 340. It is run at the standard fuel pump test voltage of 12.0 so outputs will be considerably more at higher voltages as noted in the discussion of the first graph.
There are two important things to consider when comparing the two pumps.
First, the 340 has a different bypass springs and does not begin to fall off in delivery with regard to bypass for another ten pounds. This means it flows more at higher pressures when compared to a 307. This means it can be run at higher initial pressures and continue to deliver more volume at higher pressures than the 307.
The second important difference is that the 340 has a different motor than the 307 and pulls less current across the board than the 307. This means it does not generate as much heat and maintains efficiency better as noted by John in the prior section.
Today, with a minimum price difference, I consider the 307 obsolete although it works well if you already have one as long as it can provide the required delivery volume for your combination.
Now, one last graph.
This was provided to www.gnttype.org by Red Armstrong. It represents the performance of his XP Double Pumper at 13.0 volts, 14.0 volts, and 15.0 volts. I believe the XP was a 307 Walbro. Looking at the delivery rates we see at least two things.
First, the volume is much higher as would be expected when comparing dual pumps compared to a single pump.
Secondly, the delivery rates do not fall off sharply at 60 psi as do the ones shown on the first graph at the beginning of this section. I had an XP long ago and it had a piece of what appeared to be 12 gauge wire jammed into the bypass spring which basically rendered it inoperative. As stated by John, this makes the pump work a lot harder and may not be good for the long term life expectancy of the pump(s). That is conjecture on my part.
Again, we can see the importance of supplying adequate voltage to the pumps.
One last comment on sizing. It is the pressure at the fuel regulator that counts, not, the pressure at the pump. Our stock fuel line is 3/8" and the return is 5/16". As fuel delivery requirements increase, the stock lines become a bottleneck both on delivery and return. This means that pressure at the pump may actually be 3-4 psi higher than what we measure at the fuel rail which puts further demands on the pump and which should be considered in sizing. We get by the return side of the problem with double pumpers, as John noted, by turning the second pump on at higher boosts, and rpms, when the engine can consume the fuel and the stock return line can deal with the amount of fuel being recirculated.
When we go to larger external pumps, we must typically run larger lines. Some have run a new line for delivery and used the 3/8" line for the return.
Without doing any calculations, I think a single 340 is very capable down to a 10.9. Then for safety's sake, a double pumper arrangement should be considered.
Going to a good, external, high volume pump can add quite a bit more expensive in the next step.
Now, I don't like double pumpers in spite of what is said above. I consider them an outdated kluge that is not needed at the present given the state of modern fuel pump technology. When the second pump kicks on, it can cause a momentary surge in pressure and volume until the regulator kicks in and catches up. This can make tuning difficult, particularly on street driven cars that may not always run high boost and which can get flaky when the second pump kicks in... Do yourself a favor and if you are building a car that will run into the tens, go ahead and put a sump on the bottom of the tank, add a modern external fuel pump, and replumb the car with larger supply and return lines. I think this can be done for around $400 these days. Not bad considering the price of double pumpers and the irritations they can bring.
As stated above, the factory pump wiring is small and made from aluminum. It was marginal from the factory, and, with age, does not do the job when combined with larger pumps and increased demand.
Commercially made hot wire kits are available from a number of vendors.
Alternatively, you can make your own kit if you have access to a crimp on connector tool, or, a soldering iron.
All you need is some 10 gauge wire, a HD inline fuse holder and a 30 amp fuse plus a 30 amp name brand relay and some crimp on connectors.
Mount the relay on the driver's side inner fender next to the fan relays. Run a wire from the the back of the alternator, through the 30 amp fuse and on to the input power terminal on the relay. Run another wire from the output power terminal on the relay along the inner fender, down the firewall, and into the frame rail. Pull this wire through the frame and out the rear end. Run it up and over the top of the fuel tank using tie wraps to keep it from rubbing any moving suspension pieces. Cut the fuel tank power feed wire on the tank side of the factory WeatherPak connector and connect the new wire to the wire going to the pump. I always put a connector at this point so I can disconnect the hot wire and reconnect the factory wire as a back up. I have never had a failure but, the back up might come in handy one day.
Now, go back to the new relay you mounted and make a ground wire that goes from the ground terminal on the relay and then to the inner fender sheet metal. This can be a short wire that loops back to the screw that mounts the relay to the inner fender.
That leaves one wire to be connected. Run a wire from the fuel pump test connector just behind and below the alternator to the trigger terminal of the new relay. This allows the normal two second activation of the the relay when starting the engine. That's all it takes.
After installing the hot wire, take your meter and measure the voltage drop from the tank to the factory sheet metal (not the frame). the engine needs to be running. Clean off a spot by the tank strap pivot on the underside of the trunk floor. Set the meter to volts and put one probe on the tank and one on the spot you just cleaned off....don't be surprised to find several tenths of a volt on the meter readout. This indicates the voltage being lost due to the poor factory ground.
Go to the folded up corner of the tank, and, drill a hole as close to the edge of the flap as possible. The trick here is to be outside the pinchweld that joins the two tank halves together. Otherwise you will be sealing a slow drip if the hole is inboard to the seam! Drill another hold in the tank strap bracket and install a ground strap, or a piece of 12-12 gauge wire between the two holes...metal screws will hold the two end connectors. With the engine running, recheck the voltage drop...it should be far less than one tenth of a volt now.
Contrary to popular belief, the factory relay does not shut down the engine if the oil pressure drops, or is lost. The factory relay is backed up by the factory oil pressure switch which has two functions. First, the switch turns on the oil pressure idiot light if the oil pressure falls below 4 psi.
Secondly, the factory oil pressure switch completes the circuit to the fuel pump when the oil pressure rises above 4# as a back up in case the factory fuel pressure relay fails. Normally, the ecm signals the relay to start the pump and run it for about two seconds when the key is switched to "Run", then it cuts off if the engine is not started. If the relay fails, there would be no fuel delivery from the pump unless there was a back up circuit. This is the second function of the oil pressure switch. Even if the relay fails and one cranks the engine, the fuel pump will be turned on when the oil pressure reaches 4 psi during cranking. One of the signs of a factory relay failure is delayed engine start when the engine is cranked as it gets no fuel until oil pressure is above 4 psi.
Now, if the factory relay has failed and the engine suddenly loses oil pressure to below 4 psi, then the voltage to the pump would be cut at this point and the engine would stop...that is the only time.
There seems to be fairly universal agreement that detonation is classified as abnormal combustion. Some seem to consider preignition which is a form of abnormal combustion that occurs before the spark plug is fired as detonation, and, others only refer to that abnormal combustion that occurs after the plug has fired as detonation which is the more correct definition. No matter, both are detrimental to engine life although preignition is the most deadly.
Normal combustion occurs when the spark plug ignites the air/fuel mixture in the cylinder and the flame front spreads smoothly across the top of the piston. The spark is initiated before the piston has reached top dead center and maximum combustion pressure is reached several degrees after top dead center which causes the crankshaft to continue rotating in the normal direction.
Abnormal combustion occurs when additional flame fronts appear that are not associated with the normal spark plug initiated burn. These additional fronts may occur due to excessive cylinder pressure, hot spots in the chamber/piston face, or insufficient fuel octane. These abnormal events cause sudden spikes in the cylinder pressure rather than the smooth build up associated with the plug burn.
Preignition, which occurs before the plug has been fired, occurs before the piston has reached top dead center. It is often caused by a hot spot that is glowing in the combustion chamber such as carbon build up, or something such as a sharp edge on a valve relief on the piston which creates excessive heat. Because it occurs before top dead center, the sharp build up of cylinder pressure tries to reverse the direction of the crankshaft rotation which may soon cause cracked pistons, broken rods or crank, and hammered bearings.
Abnormal combustion which occurs after the initiation of spark often occurs near, or after, top dead center. It tends to push the crankshaft in the proper rotational direction, but, the sudden build up of cylinder pressure is hard on the piston ring lands as well as the piston face, piston pin area, and the bearings. It may not destroy the engine as quickly as preignition, but, it is continually eating away at the engine internals.
Here are two links that offer a more in depth explanation of detonation or abnormal combustion events.
http://www.zhome.com/ZCMnL/PICS/detonation/detonation.html
http://www.streetrodstuff.com/Articles/September_2000/Engine_Basics_I.php
The detonation (knock) sensor is screwed into the rear of the block just behind the intake manifold and to the driver's side of the coil mounting bracket. It's a bit hard to see with the coil mounted. Essentially, it is a microphone that picks up the engine/drivetrain noises and transmits them to the ESC (Electronic Spark Control) module mounted on the passenger side inner fender.
The job of the ESC is to filter out the noises that are not related to detonation. As I recall, the noise generated by abnormal combustion is somewhere around 6000 Hz in our engines. I think bore diameter is the primary determinant regarding detonation frequency. The ESC is a form of bandpass filter that only allows frequencies in the detonation range to pass. If nothing in the detonation range is detected, then the ESC sends a voltage of approximately 9 volts to the ECM and no timing is removed. If frequencies in the detonation band are detected, the signal sent to the ECM goes to zero and the ECM begins to remove timing, up to a maximum of 20 degrees, until the signal is restored.
The signal wire is on B7 at the ECM and is a yellow/black wire from the ESC module coming from terminal C.
The theory is fairly simple, but, there is one catch in the equation. The ECM considers any noise passed thru by the ESC to be detonation whether or not it actually is.
We call noise that is not created by an abnormal combustion event, False Detonation. It really has no relation to detonation, but, the ECM thinks it is and pulls timing out thereby harming performance. Obviously this is not good.
When apparent detonation is monitored, the ECM begins to reduce timing in an effort to remove the cause of the apparent detonation under an assumption that it is timing related. The amount of timing that may be run depends upon the engine combination, quality of fuel, compression ratio, charge temperature/density, ambient weather conditions, and the boost curve.
Two things to consider here-First, the ECM is reacting to an abnormal event and damage is already being done as the ECM begins to pull the timing. How fast it pulls and then restores timing is dependent upon the chip programmer.
Secondly, the ECM can only help control those abnormal combustion events that are tied to spark timing. Preignition events are not normally caused by the timing of the plug firing and removing timing does not address the root cause of the problem. Preignition events can be much more damaging than common detonation.
Many profess to believe that a little timing retard is okay. I would contend that consistent timing retard, even in small amounts, is a sign that damage is being done to your engine in a continual mode. There is no doubt that small amounts of timing retard at 14# of boost is far less damaging than that incurred at 28# of boost when considering the same amount of timing retard.
Actual detonation tends to increase with engine load. Therefore, it may be minimal, or non-existent, in low gear, but may appear in a higher gear such as third as engine load increases and exhaust temperatures increase. The magnitude of timing retard tends to increase with time and the detonation symptoms don't go away until one lifts off the gas.
I consider a knock alarm with audible warning a required addition to any serious car.
As stated above, False Detonation is a noise that falls within the band pass frequency of actual detonation or abnormal combustion and causes the ECM to remove timing just as it would in the normal course of events.
This is very bad as it severely limits power as timing is removed. Sometimes, false detonation is fairly obvious as it occurs at launch, or on the one-two shift and quickly subsides. Other times it is not so obvious as it may occur more continuously and it can be difficult to identify.
I think the most common causes of false detonation occur from wheel hop, or, the downpipe contacting the passenger side rear of the upper control arm when a bad engine mount on the driver's side allows the engine to rotate too much.
Rear wheel hop is more a problem at launch in low gear while the downpipe hitting the control arm often occurs on the shift point.
Other known causes are such things as the exhaust hitting the bottom of the firewall, crossover pipe banging the manifold on the passenger side, a loose exhaust pipe at the rear hanger off the tranny mount, a noisy valve train, loose torque converter, loose converter inspection cover, rattling lines from the tranny to the radiator, a missing bolt in the AC compressor, bad idler pulley bearing, loose intercooler bracket, and/or a too tight engine hold down strap. Piston slap on a cold engine with excessive clearance has been reported and such things as a bent push rod will also trigger the detonation sensor.
If the detonation sensor is over tightened, it may become too sensitive. Factory torque setting is 14 lbs-ft....just barely more than finger tight. Make sure someone has not cranked it in excessively.
There are two basic means of controlling boost on our cars.
The factory uses an internal wastegate puck mounted within the turbo exhaust housing which is opened and closed by a wastegate actuator mounted on the turbo.
An alternate, and theoretically better, means is with an external wastegate that may be mounted on the cross over pipe or by the turbo depending upon the system used. Sometimes two external wastegates are used if the engine is pumping more air than a single may control. This method avoids some turbulence in the exhaust housing which may interfere with exhaust flow into the downpipe.
Both techniques divert exhaust flow as required in order to modulate the turbine (exhaust wheel) to the speed required for a given boost. I believe that most don't run fast enough to reap significant benefits from an external gate when the economics are considered.
The stock wastegate consists of a puck covering a hole that bypasses exhaust flow when the puck is opened. This decreases the amount of exhaust flow going across the turbine so that the speed slows down and boost is maintained at the desired level. How well the boost control function works boils down to the size of the bypass hole with relation to the amount of exhaust flow that must be diverted to maintain the desired boost, and the ability of the wastegate actuator to control the puck as it opens and closes.
The factory style wastegate actuator consists of a spring loaded arm that pulls against the wastegate puck along with a diaphram that forces the actuator rod outward when boost against the diaphram is sufficient to override the spring tension.
Combined with the factory wastegate solenoid and factory wastegate hose arrangement with the factory "y", boost is bled off before it reaches the wastegate actuator until the desired boost is obtained and the wastegate actuator spring is overidden at the desired boost level. Normally, stock actuators have an approximately 12# spring inside. This tension can be increased by shortening the length of the actuator rod to less than the normal length.
Cutting to the chase, the factory controlled boost by controlling the duty cycle of the wastegate solenoid. The longer it is held open, the more boost is bled off thru it and the higher the boost required to open the puck. To a certain degree, boost may be increased by the chip programmer by increasing duty cycle. At some point, however, the spring tension becomes the determining point for max boost as the solenoid nears 100% duty cycle and cannot continue to increase the bleed off rate and boost kicks open the puck.
We can get around this to some extent by shortening the rod and increasing the pressure required to open the puck.
Two problems may arise from this, however. First, if the spring gets too tight, it may delay the puck opening beyond the desired level for a moment which can lead to boost spiking. The second problem that arises is that the actuator rod can only be extended a finite difference by the actuator diaphram. This means that the distance the puck can be swung open becomes limited by the length of the rod when extended by the diaphram and it may not open enuf to sufficiently bleed off excess boost. This can cause significant boost creep, particularly in third gear. This problem is much greater with larger turbos that flow much higher volumes. Bigger wastegate holes and puck sizes to match help to some degree.
The combination of the above puts a practical limit on the level of boost that may be effectively controlled by a stock actuator. Moving to a HD actuator with a spring that requires 17#, or so, of pressure to over come and open the puck is a better solution if one is trying to run much over 20# of boost in my opinion.
Now, let's double back and consider how we can control boost with the normal factor style of wastegate.
First, we can increase the duty cycle of the solenoid in the chip.
If this is not sufficient, we could gimmick it by using two solenoids to increase the potential bleed rate. As this is done in parallel, it would decrease the sensitivity of the precision of control but would increase the total boost that may be obtained.
Or, we could add a "bleeder valve" inline with the factory solenoid and crack it slightly to raise the amount of air being bypassed. Opening this bleeder will increase the base amount of boost being controlled by the solenoid so that the minimum boost level is now higher. Kenne-Bell used to sell a small aluminum block that went inline with the hose. It came with a series of screw in buttons with various size holes drilled in them which would vary the amount of fixed bleed added by the block.
Another variation would be to remove the factory solenoid and replace it with an air compressor style regulator with a light spring in it so that bleed rate does not vary much with a turn of the knob. Vendors normally carry a Norgren valve equipped with the right spring for our application.
One can also eliminate the factory solenoid and hosing arrangement by simply running a hose straight from the compressor port to the actuator port and simply control the boost by the length of the actuator rod. This works okay with smaller turbos although a HD actuator may be required to obtain boosts much past 20#. If larger turbos are used, one may find problems with the afore mentioned spiking and creep, however.
Electronic boost controllers that provide more sophisticated control of the wastegate solenoid than the ecm provides are available as well. This can be the trick on really fast cars, but, I tend to consider them unnecessary on cars that are not quicker than mid-tens. Some people love bells and whistles and some of us prefer to keep it simple.
I believe that the most precise control occurs when the tension applied to the wastegate puck arm is about 1/8". This provides sufficient tension to eliminate leakage during spool up and enough length to allow the puck to open sufficiently to avoid creep in third gear. Boost is then controlled by the amount of bleed created.
I am going to gloss over external wastegates, but, they tend to produce more precise control for really quick cars when installed correctly and they should make more power as they control the amount of flow reaching the turbo rather than the flow coming thru the turbo. Therefore, there is less turbulence created in the exhaust housing and downpipe entry which interferes with flow. They can be a hassle to maintain and not all are created equal. Consult your trusted vendor to determine which are better for the street/strip.
Dynamic Compression David Vizard article on relationship of compression, cam timing, water temperature, etc.
I find this very interesting as I believe in adding compression to street engines as Lawrence Conley and Kenny Duttweiller often do. This article shows how the various factors in the engine combination affect each other and how detonation risk may be minimized. David wrote this article for Popular Hot Rodding and I think the principles stated apply to our engines. Go Here for the article. Here is another one on the subject, also by David.
Compression Ratio Calculations/Dimensions
This information was taken from the mailing list. It was posted by Jim Beeler. Note the effects upon compression ratio by using different head gaskets, milling decks, heads, etc.
Been awhile so guess I'll post this again for the newer members. Been
running one steel shim @ 9.31 cr with Caterpillar bolts since '91.
"Lifted" the head once, these steels don't "blow" out, just loose
sealing ability and make a neat whistling sound.
V6 Cylinder Head and Gasket Combinations
Stock cylinder head cc=48cc
" " " milled.025"-.030" cc=43cc
Stock head gasket (.060" compressed) cc=11.15cc
P/N 1000 Fel Pro (.0375" compressed) cc= 7.8cc
P/N 1007 Fel Pro (for "o ringed" heads)
(.039" compressed) cc= 8.6cc
Two steel shim .018" (.036") cc= 6.9cc
One steel shim .018" cc= 3.45cc
Piston deck height (.030") cc= 5.57cc
Piston dome(+cc)/dish(-cc) cc=-24cc
Formula:
c-p+g+d+v
cr (compression ratio) = _________
c-p+g+d
c= head volume (stock 48cc)
p= piston dome/volume (-24cc)
g= gasket volume (11.15cc)
v= cyl volume (b/2)2 X s X 51.48 = (bore/2)2 = 3.8"/2= (1.9)2
=3.61 X s (stroke 3.4") = 12.274 X 51.48 = 631.87 swept volume
d= deck height (5.57cc)
Sample 48-(-24)+11.15+5.57+631.87 =720.59
cr= ________________________ ______ = 8.122 cr
48-(-24)+11.15+5.57 = 88.72
Substituting values we get:
Head milled .025-.030" (43cc) w/stock .060" = 8.55 cr
" " " " " 1000 Fel Pro .0375" = 8.86 cr
" " " " " 2 steel shim .036" = 8.95 cr
" " " " " 1 steel shim .018" = 9.31 cr
Stock (48cc) with stock gasket .060" = 8.122cr
Stock " with P/N 1000 Fel Pro .0375" = 8.40 cr
Stock " with 2 steel shim .036" = 8.48 cr
Stock " with 1 steel shim .018" = 8.79 cr
As stated by Lawrence Conley at the Turbo Tech sessions in 93 and
94, "there are no downsides to increased compression." Some of
the engines being built by them are running 10.1 ratios. They
will require "good" gas as boost levels increase above 15 lbs.
Jim Beeler, jbeeler@ telepath.com
GSCA 3526, 11.51 @ 119.63mph
Oil Pump (Click to go to appropriate page)