Boost Controllers and System Boost Levels
Most of you that seriously contemplate a dyno-session will likely have a boost controller already installed and for those that only have boost jets, you can skip this portion of the testing, but you might want to read just to bring yourself up to speed.
It is important that a few key items are tested to ensure your boost control is working properly. You likely already have the controller installed and it is working as advertised without flaw, or at least, to the best of your knowledge it is working without flaw. Granted, some of you know all the settings of the BC inside and out and also have a good mental model of how they are doing their job. Unfortunately, most people do not understand the relatively complex nature of the boost control system even in stock form, much less with the introduction of an electronic controller. For those of you who are unfamiliar with all of the parameters of your boost controller, my suggestion would be to get the users manual and spend a day on some less-traveled back-road and learn every element of how your controller works and what all of the settings are for. Some controllers have control functions that others do not, such as threshold boost level before start, set gain, and some incorporate multiple parameters into one single parameter. Bottom line, the more boost control functions you have, the better the ability you have to produce the best possible boost response from your turbochargers. This will directly affect your vehicle’s performance and it will show its ugly face on the dyno. Unfortunately there are far too many boost controllers out there and giving my full advice on them would easily constitute yet another lengthy document (ooooh). My best advice to you is to give yourself the time and patience to try and learn it – if all else fails, you have resources on the internet or you may want to ask a friend who is knowledgeable on the subject to give you a hand in showing you how it works or even have them set it up for you. Just keep in mind that this is a very important element of tuning and you do not want to simply dismiss this element – even if you think your BC is properly setup, chances are, there is still some optimization that could be performed to enhance spoolup and boost stability.
If you find that your car is not achieving the peak boost level that the turbochargers you have are supposed to generate, you may have a boost leak or your wastegate actuators aren’t tight enough. If during your pre-dyno checks you find that you do not have a boost leak and the boost controller is properly connected, tightening the wastegate actuators is your only solution. The following section will cover this topic as well as covering the importance of balancing the turbochargers.
Wastegate Actuator Balance
For those of you that have replaced your turbochargers with any aftermarket turbo setup, there is high probability that your wastegate actuators are not balanced to each other. I have seen this problem many times and it is one of the most common problems I encounter that needs addressing.
| The wastegate actuator is simply a spring-loaded diaphragm unit that controls the position of the wastegate valve for use in controlling turbocharger boost pressure. The internal spring of the actuator is used to hold the wastegate shut against the pressure of the exhaust gases in the exhaust manifold and turbine housing. Without the spring, the wastegate would simply ‘flap’ around, allowing the pressure in the exhaust manifold to be dissipated into the downpipe/exhaust rather than through the turbine wheel and this would result in the in-ability of the turbochargers to actually produce any boost pressure. While the spring is an integral part of the actuator and it would be hard to believe someone would install a set of turbos without the actuators in place, it is not as hard to believe that the pre-load of the springs between two turbochargers is not the same. Considering the turbochargers are different only mostly by the location of the actuators themselves and the orientations of the housings with respect to each other, it is very easy to understand that this can be a really big problem. Unfortunately, if you do not have a wideband O2 sensor that you can switch between sides, you will not be able to determine if this is a problem until you get to the dyno. Purchasing wideband sensor is a choice that you will need to make as a Z owner - it is about a $300 proposition to purchase two units. Most people will elect to take it to the dyno and perform this test early into the session and hope it isn’t a problem. The issue of balancing the turbochargers and increasing peak boost will be covered again later in the document, but keep this in mind. |
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This post would not be complete without the 6 P's. This is a slightly revised version, changes made only to clarify points a little better. Every one of these steps should be followed closely and none of them should be skipped - it could mean a wasted day at the dyno.
The 6 P’s: Proper Preparation Prevents Piss Poor Performance
***** REVISED!!! ******
This is a compilation I have produced in which ANYONE contemplating or performing any upgrades on their car should perform. It is also a comprehensive diagnostic procedure for anyone considering the purchase of a new Z. These preliminary tests will ensure that your car (or the one you are looking at buying) is in good working order and prepared to safely meet the demands your upgrades are going to place on it.
These tests are not only beneficial for those who plan to upgrade, but should be a battery of tests that one continually abides to perform. 3000 mile oil changes are a MUST with these vehicles and I would suggest the same mileage interval to test most of these specifics I am about to detail.
The primary concerns one should have when they begin modifying the original design parameters of their vehicle is simple.
1) Is it getting enough fuel?
2) Is it getting proper ignition?
3) Is it getting proper air?
These three components are what enable your engine to effectively and safely produce power. With only one of these components missing, the engine will not run at all. With any one of these improperly 'configured', it could mean poor gas mileage, poor drivability, or much worse - catastrophic engine failure.
The tests you are about to perform will ensure that these three components are properly working and configured for producing reliable output.
Introducing: The Weapons of War :
These are the required components to effectively perform the tests outlined in this document.
Starting at upper left is a timing light (the thing that looks like a gun).
Immediately to the right of the timing light is a pressure gauge. I acquired this from AutoZone for about $20. It is used for oil pressure testing, but that's inconsequential - it tests up to 100psi with 5psi increments. Perfectly suited for testing fuel pressure, but not designed to be an internally (in cabin) installed gauge. I acquired a "T" connector for 8mm (5/16") to allow easy "T-ing" into the fuel line. I simply soldered the "T" connector to the end of the pressure testers fitting and used a 4" piece of hose and a hose clamp to secure everything together.
Immediately to the right of the pressure gauge is a 10mm socket on a 3/8" ratchet wrench. This will be used to loosen the bolts on the CAS to allow for you to adjust the base timing. We'll get to that in a few.
Immediately to the right of that is a compression tester. This is used to determine the condition of the combustion chamber components and their ability to compress and seal the air and fuel that enters into it. A brand new engine will produce 170psi whereas a worn, tired engine will produce 120psi or less.
Just below the wrench is my pressure tester. It is actually a speaker magnet that I drilled a hole through the center of and simply inserted a wheel valve stem to allow me to pump air into the intake system. You can get creative here as well and build your own, but I believe there is also a member here that produces a pressure testing kit that you can purchase inexpensively. This will allow you to easily isolate any intake tract leaks and fix them.
At the very bottom is a 'feeler gauge'. This tool is simply an assortment of metal strips of various thicknesses. Each one is labeled as to its thickness and we will be using it to gauge the gap of the spark plug.
Test #1: IGNITION TIMING
Ignition timing is essentially telling you when the spark plug is being fired in relation to the position of the piston and crankshaft. The value you are used to seeing is a value in degrees. This is angular degrees, not thermal degrees. In the VG30, the base timing (or the timing advance at idle) is 15 degrees. This means the ECU is making the engine fire at 15 degrees BTDC, or Before Top Dead Center (now you may see why I stated "...relation to the position of the piston and crankshaft.") BTDC means that as the piston is in its upward motion on the compression stroke, the plug is being fired when the crankshaft is 15 degrees before the piston reaches top dead center of the cylinder. The object here in setting base timing is to make the ECU and the timing mark on the pulley agrees with each other. This is simply a calibration of the ignition timing components.
Typical timing lights use an inductive pickup to detect when the plug is being fired and when detected it causes a strobe light to fire off. This basic principle allows us to see exactly when the plug is being fired off in relation to the crankshaft position. On the front of the engine is a timing indicator which shows a range of degrees on what looks like a ruler. The values go from 0 to 30, from left to right. On the pulley is a mark that indicates the position of cylinder #1. When the mark is lined up to "0" on the indicator, this means the piston is all the way at the top of the cylinder.
Timing lights also require power in order to fire that strobe light off so be sure to connect the power leads as such.
The inductive pickup:
NOTE :! Using this point as the pickup I have found to be the quickest, most accurate method of hooking up the timing light. There is also a black loop on the PTU harness that is supposed to be used for this, however, I have on a number of occasions seen vary peculiar results - sometimes getting two points of indication on the pulley and sometimes it being so far off you can't even see it. I DO NOT RECOMMEND using the inductive pickup loop on the PTU harness. Try this method first and if it doesn't work at first, wiggle the pickup around a little on the wire. You should get a pulse. If it still doesn't want to behave, you should pull the coil pack out and use a plug wire extension and put the inductive pickup on the high voltage line going to the plug. I simply have seen the inductive loop do way too many weird things to really trust it with something like ignition timing.
Once you have everything properly hooked up, point the light at the pulley and observe. This is what you should see.
NISSAN FACTORY BASE TIMING IS 15 DEGREES BTDC. They also say +/- 2 degrees, but it’s not hard to get it dead on.
To adjust the timing, the CAM ANGLE SENSOR, or CAS for short, it used to adjust the base timing.
There are three 10mm bolts that hold the CAS in place. Loosen these with the engine off.
Since the engine rotates clockwise (looking at it from this perspective), turning the CAS clockwise will retard the timing whereas turning it counterclockwise advances the timing. Move the CAS in the appropriate direction to adjust the base timing. Of course, the engine must be running to test it and once you have the CAS loose a little, you can start the engine and then begin moving the CAS a little to get the timing mark aligned to 15 degrees.
This process ensures that the timing values in the ignition timing map of the ECU are in fact, correctly calibrated to what the engine is actually doing. All the CAS is for is simply to make the value in the ECU agree with the actual timing being run. The timing light allows you to verify what the ACTUAL timing is because it flashes the light off when the plug REALLY fires and the markings on the pulley allow you to see what the position of the crankshaft REALLY is.
FUEL PRESSURE
In order to check the fuel rail pressure, you need a pressure sensor put inline with the fuel line to the fuel rail. The pressure sensor defined above will allow us to do this, but we have to connect it in. Since the fuel system always holds some degree of pressure, even when the car is not running, we must ensure that we don’t unhook a line a pour raw fuel into the atmosphere, or into a hot engine bay. We start first by cutting off the fuel to the filter as such.
Since the rest of the system is also under pressure, we must clamp off the other side where we are going to disconnect the fuel line from and tie in the pressure gauge. We also use a rag here because even in this short piece of hose, there remains enough pressure to spew a catastrophic amount of fuel out and start a fire. Ideally, one would do this while the engine is cold. Relieving as much pressure as possible by removing the gas cap also helps.
Once done, place your rag as follows and loosen the hose clamp and remove the hose from the filter.
In the VG30, as well as most other fuel injected vehicles, have an operating fuel pressure of ~3bar. 1bar = 14.5psi so 3bar is effectively ~43.5psi. The aspect that complicates this simplicity is the fact that the manifold is not always at 0psi. In fact, it is rarely at 0psi. Since the tip of the injectors is inside of the manifold, this means that the vacuum or pressure that the injector tip 'feels' also affects the fuel delivery. Since the ECU controls the duration of time that the injector is held open, it assumes that the fuel pressure is always the same, there must always be a 43.5psi differential between the fuel rail pressure and the manifold pressure. This is to ensure that no matter what vacuum/pressure the manifold is under, an 'x' millisecond pulse of the injector will always deliver the same amount of fuel. You can see what I mean here:
Ok, now that you have everything connected, you are ready to test your fuel pressure. You can see in this picture that there is about 10psi of pressure on the gauge. The engine is not running here and hasn't been started since the install of the gauge, but you can now see why I pinched off the hoses. 10psi of fuel pressure will puke enough fuel to start a Sonny's BBQ in your driveway so BE SAFE!
Now, in this picture you can see that the fuel pressure is appx. 33.5psi. Remember the pressure differential I was talking about? Well, at idle, the manifold is at about -10psi of pressure. In order to maintain linear fuel delivery, there must always be approximately a 43.5psi pressure differential; so 35 + 10 = 45psi. We are good here.
This next picture is a demonstration of how the fuel pressure regulator works. The hose I am holding in my hand is what connects the fuel pressure regulator to the manifold. The fuel pressure regulator is the device that maintains this 'pressure differential' such that the fuel delivery is linear per pulse-width of the injector. Since I have unplugged the FPR(fuel pressure regulator), the FPR 'thinks' the manifold is at 0psi. You can see here that the fuel pressure has now risen to ~44psi, as it should.
I want to point out that since the fuel pressure control systems are a 'passive' system and not 'active', there will always be slight variations in fuel pressure from what you see here. However, there should not be anything greater than about a 5psi difference in these tests. This is primarily what makes the difference between one Z and the next - some fuel systems simply work a little better/worse than the next Z, but the actual effect on the system as a whole is marginal as long as there aren't large variances.
I have setup the fuel pressure gauge as well as a manifold pressure gauge to demonstrate how the fuel pressure regulation system works in finer detail.
You can see here that the fuel pressure is slightly higher at 0psi of manifold pressure than it was in the original test. This is due to the fact that the ECU ALSO varies the fuel pump voltage (which affects its output). You can see here that at 45MPH with the manifold at 0psi, the fuel pressure is at 55psi. This is actually a little on the high side as we should be seeing a fuel rail pressure of ~44psi at 0psi of manifold pressure, but this is due to the fact that I am still using a non-turbo fuel pump controller in my car (my car was converted from non-turbo). However, this is not bad, if anything, it is simply safer. In this condition you should see at least 44psi at the fuel rail. If you see less than 44-45psi, you have a problem and it must be fixed.
In the following picture you can see that the manifold is at 5psi of pressure and we ALSO see that the fuel pressure has risen up from 55psi to 60psi. This is the fuel pressure regulator at work. Since the manifold is at 5psi more pressure, it also raises the fuel rail pressure so that the fuel delivery per injector pulse-width is consistent. This is important as the ECU is assuming that no matter what pressure the manifold is at, 'x' millisecond of injector pulse-width will ALWAYS deliver the same amount of fuel. This is very important when tuning a car too.
The next test is running the engine at 7000RPM, which is at 95% of its operating range. You can see that the manifold pressure is at ~15psi and the fuel rail pressure is at ~65psi. This is 10psi more at the fuel rail than when the manifold was at 5psi of pressure. 55+10 = 65psi of fuel rail pressure. This is consistent with what we should see.
IMPORTANT!! : The engine is running at 7000RPM here in the above photo. This is when the fuel system is at 95% of its expected delivery rate. You have to consider that as the engine RPM increases, so does the fuel rate. When I converted my non-turbo to turbo, I used the non-turbo fuel pump. It worked great at ~14psi. However, when I raised the boost to 16psi on the non-turbo pump, as the RPM increased to around 5500RPM, I began noticing the fuel pressure falling off all the way down to 45psi! This is VERY BAD! The reason this occurred is because the non-turbo fuel pump was unable to keep up with the demand of fuel at higher RPM. It maintained ~65psi until around 5000RPM and then sharply fell off at 5500RPM down to 45psi at the fuel rail. This is a catastrophic failure waiting to happen because when the fuel pressure falls, so does the fuel delivery. This is not a problem with the fuel pressure regulator; this was simply the non-turbo pump falling short of what was needed. I corrected this problem by putting a twin-turbo fuel pump into my car.
THIS IS THE PHENOMENON THAT YOU DO NOT WANT TO SEE!
You want to ensure that the fuel pressure is maintained ALL THE WAY THROUGH THE RPM RANGE that your engine operates within. If it does not maintain this pressure, the fuel delivery will fall and this will cause a lean condition. Lean conditions lead to detonation, broken pistons, burned valves, and catastrophic engine failure.
This test concludes the 'fuel delivery' aspect. If your fuel system does not maintain proper pressure, you simply need a bigger pump.
AIRFLOW:
This is one of the three vital components to proper engine performance. Just as much as a dirty air filter will affect performance, a leak in the intake system will also promote piss poor performance.
The intake system of the Z, in both the non-turbo as well as the twin-turbo version, consists of a multitude of intake plumbing components. In the non-turbo Z there is a total of ~10 feet of piping between the air filter and the throttle bodies. The twin-turbo variation has over 20 feet of plumbing. Unfortunately this system is not composed of a single pipe. In fact, there are a dizzying number of clamps, hoses, and pipes that comprise the intake system.
In the power-plant design of the Z32, the engineers employed a Mass Airflow Sensor for use by the ECU (Engine Control Unit). This sensor measures the intake air's mass which the ECU uses to determine proper fuel delivery, as well as enable the ECU to handle a multitude of other control parameters that are dependent on airflow. Since this system relies so heavily on the accuracy of the measured intake air, it is critical to have an 'air tight system' in order for it to properly perform. In order to ensure that the intake system has no leaks, we can refer to Bernoulli's principle: PRESSURE
The test is simple and requires simple equipment. For those who have a single intake, removal of the MAS and filter and installation of the 'plug' is easy. Those with dual intake systems need to dig up their original intake "T" and use it for this test. The hardware is installed as such:
In the picture above you can see that the manifold is at 5psi of pressure. DO NOT EXCEED THIS PRESSURE
The reason the intake system is at 5psi and no more is because of the fact that 1/4" of the intake system is not subjected to positive pressure. None of the non-turbo intake system is under pressure. In addition, since the intake system is also part of the PCV system (positive crankcase ventilation), you do not want to over-pressurize the crankcase for fear of blowing out the oil seals along the camshafts and crankshaft. 5psi is enough to hear any leaks and not too much to blowout seals. Once you have the system pressurized, you will be able to easily locate any boost leaks. Typically it only involves tightening the loose hose clamps that hold the system together. Locate all leaks and fix them.
SPARK PLUGS
In the stock configured Z32, the NGK (Japanese manufactured) platinum tipped plugs are used.
NA stock = PFR6B-11 gapped to 0.044" (1.1mm)
TT stock = PFR5B-11B gapped to 0.044" (1.1mm)
While these plugs perform well under stock configuration, they do not perform well under a modified, high output configuration. The nomenclature used in the plug numbering denotes several aspects of the plug's design and performance. What interests us the most is the 4th character in the naming scheme. The NA is a "6" and the TT is a "5" in the above examples. This number denotes the ability of the plug to diffuse heat away from the tip and into the plug body, where the cooling system absorbs the heat. This means the higher the number, the better the plug's ability to keep the tip 'cooler'. As you increase the output of the engine, the cylinder temperatures also increase. What this means is that you need a spark plug that also increases in its ability to dissipate the heat. By not changing the plug's thermal dissipation when you increase the output of the engine, you raise the likelihood of 'spark knock'. This phenomenon is analogous to detonation and it should be avoided at all costs.
To mitigate the possibility of 'spark knock', you should use a spark plug that has a higher ability to dissipate heat. This simply means you need a plug with a higher 'thermal dissipation' number. Here's the breakdown:
NA stock: PFR6B-11 ; upgrade to the PFR7B-11
TT stock: PFR5B-11B ; upgrade to the PFR6B-11B
For the NA guys, this is all you need to do. However, for the TT guys, there is an additional parameter that you must concern yourself with. Since a stage3+ upgrade to a twin-turbo ALSO includes running higher boost pressures, we have to account for the higher air/fuel densities in the combustion chamber. In the stock configuration, the plug gap is set to 0.044" (1.1mm). While this performs well in both low and stock high load conditions, it will not perform well in high load conditions above ~14psi. The higher density of air and fuel in the combustion chamber (a result of running higher boost) requires a higher voltage for the spark to 'jump' the gap. Since you do not have the ability to easily increase the spark intensity, you must resort to alternative and less expensive methods of promoting proper ignition. Instead of increasing the spark intensity, one can simply reduce the gap of which the spark has to jump. The typical plug gap is 0.044", but by reducing the gap to 0.035", one can increase the chances that the spark will actually 'jump' the gap. -0.035" has proven to be an 'ideal' gap to set the plugs to. Conversely, if you make the gap too small, you will notice misfiring at low load/cruising conditions as the spark is simply too small to ignite the low density of air and fuel in the combustion chamber. This is why you don’t set the plug gap to 0.010" and expect it to perform well - just about everything is a tradeoff and this one falls at mid-road of the equation.
Using the feeler gauge pictured in the "Weapons Of War", you can properly gap your plugs.
COMPRESSION TEST:
Since you already have your plugs out because you are changing them to the proper plug and gapping them to the right spec, you are already set to perform a compression test. A compression test simply shows you the engine's ability to perform one of its most vital functions: compressing the air and fuel mixture sufficiently. The reason the engine compresses the mixture of air and fuel is because it optimizes the oxidation of fuel to create pressure and heat energy to push the piston, which is connected to the crankshaft and eventually to the wheels. A worn out engine will yield lower compression numbers simply because the cylinder or rings are no longer producing an 'airtight' seal, or the valves and/or valve-seats are burned/broken. Since the non-turbo engine has a different 'compression ratio' than the twin-turbo, you will be expecting different compression values between the two. Here are the factory specs:
Non-turbo: 186psi is 'perfect', minimum of 136psi.
Twin-turbo: 174psi is 'perfect', minimum of 121psi.
If you perform a compression test and you see numbers lower than the minimum specified, your engine is worn the "F" out and you need to rebuild it BEFORE you plan on upgrading it. If your test yields higher numbers than 'perfect', there is likely a problem with your compression tester and you should acquire a new unit and perform the test again.
Typically you will see ~150psi for a twin-turbo in good shape and ~165psi for a non-turbo in good shape, but anything less than the OEM Minimum values is indicative of a problem and it should be addressed.
ECU Self-Diagnostic, ConZult, or NProbe
The process as well as the self-diagnostic codes are defined in the link below. For ConZult or NProbe users, please refer to your user’s manual for info on checking and clearing ECU codes.
[ ECU Diagnostics ]
Ensuring that your ECU has not detected any faults with any sensors is critical. In the AshSPEC ECU programming, when the ECU detects that there is an issue with a sensor, the ECU enters a ‘fault’ mode in which it will operate the engine according to a different set of parameters, which are catered towards a lower power output in an attempt to preserve the engine. A/F ratios will drop significantly and ignition timing values will also be retarded several degrees Although the JWT programming does not have this function, it is still very important that you check for ECU codes. Even if you just checked them last week, do not rest totally assured that a problem hasn’t come up since then. This test should be performed BOTH before you go to the dyno so that you can address any issues ahead of time, but you should also perform a diagnostic just before making your dyno pulls to eliminate any possibilities.
DYNO-Day! Ok, now that you have gone through every element of your Zs powertrain system and ensured that there are no problems and you have your appointment already made, it would be a good idea to take a notepad and pen so as to note your dyno pulls. Might also want to grab a digi camera and/or video camera too if you plan to share or document it for yourself. Most dyno shops also have tools of their own, but it would be a good idea to bring some of your own basic hand-tools in the event you have to fix a hose or some other small incident – you also don’t want to wait for a tech to find you a tool – remember, TIME IS MONEY. It probably goes without mention, but clean your car – both inside and outside – before going to the dyno. A trashy interior laden with empty soda cans, papers, clothes, whatever, all are going to add to any frustration you may have when on the dyno – the last thing you want to be looking at is an old pair of underwear with skid-marks bigger than a top-fuel burnout. A clean car always seems to run better too. ?
Setting up at the Dyno
You should ensure that your Z is loaded onto the machine by someone who knows what they are doing and familiar with the process. I recall seeing pictures from some car show where an Integra came loose from the dyno and rolled onto its side off the edge of the dynamometer. You DON’T want to be that guy! Check all of the tie-downs – there should be 4 tie-downs used; two attached to the rear lower control arms at the sub-frame (I do not recommend strapping the car down using the rear tow-hooks) and the other two should be locked into the front tow hooks. Wheel-chocks should also be used both in front as well as behind the front wheels. The dyno-shop will need to setup three fans: one for each sidemount intercooler, and one for the center/radiator inlet. High-output industrial grade fans are typically used as they provide ample airflow for the engine systems.
Request that the dyno-operator either clean or replace the filter for the wideband O2 sensor pump (for tail-pipe ‘sniffer’ units). A dirty/clogged filter will cause the reading to appear leaner than it really is, which will result in your tuned A/F being much richer than you think.
As the dyno-operator is setting up the computer with your information, request for them to set the following parameters in the dyno-jet software:
- Specify your rev-limiter
- You want to use SAE correction factor.
- Ask them to add notes to the dyno-jet run files for each run and specify the unique parameters of the particular run.
- If you are performing any tuning, you will need to display horsepower, torque, and A/F. If only two parameters can be displayed at once (dependent on the dyno-jet software used), you will need torque and A/F. You do not tune a car based on horsepower!
You should make your pulls in 4th gear for 5speed vehicles, and for automatic vehicles, you will need to build your own lockup-circuit switch. Entertaining a dyno-session with an automatic transmission and no ‘lockup circuit’ will be a frustrating challenge to keep the car in 3rd gear and not downshift. 5speed transmissions in 4th gear are engaged in a 1:1 ratio where the engine RPM and driveshaft RPM are the same. This provides the least wear on your transmission, the least resistance through the transmission, and provides sufficient load on the engine to achieve peak boost and accurate dyno results.
An automatic ‘lockup circuit’ can be easily built from some wire, a couple alligator clips, and a switch. You can search for this wiring setup in the forum – it has been covered before.
Racefuel & Pumpfuel:
If you are intending to make any pulls using racefuel, you will want to ‘time’ your fuel refill prior to dyno-day such that you are arriving at the dyno with no more than 1/8th of a tank of pumpfuel. You don’t want to dilute expensive high-octane fuel with trashtane pumpgas, but you want to make sure you aren’t going to run out of pumpfuel before you are finished making your pumpfuel runs. 1/8th of a tank is plenty enough to carry you through a pumpfuel tuning session, with extra left over to get you easily to the next gas station afterwards. I recommend the use of VP fuels as I have personally found it to be some of the best fuel available. VP110 should be used for Zs falling into the <500RWHP level as higher octane fuel is not necessary until you are producing more power. C16 is an excellent high-performance fuel that will cost you a little more, but it definitely gives the added insurance one needs when “turning everything up to 11”. If you have less then 1/8th of a tank of pumpfuel left, be sure to add in at least 4-5 gallons of racefuel before making your next sequence of pulls.
When using pumpfuel, your maximum boost on 93 octane fuel regardless of turbocharger is going to be around 20-22psi, but you will very likely find that 18-19psi is going to be your ‘happy medium’ between performance and safety for any aftermarket turbocharger. For stock turbochargers this is going to be less.
Your target A/F ratio should be around 11.5:1 for pump fuel, 12:1 maximum, and on race fuel you should be looking for around 12:1 to 12.2:1, no leaner.
Baseline Dyno-Pull
The very first pull you make on the dyno is called your ‘baseline pull.’ This pull should be performed with your boost controller off (if you have one) and this will usually put you at around 7psi, but this value it dependent on the car and its modifications. The idea here is to make a pull at the lowest possible power output. It will ensure that the car is strapped down properly (you should not experience bucking or surging of the car) and provide a ‘starting point’ for your day.
Give Ample Time Between Pulls
If you have a ConZult, NProbe, Techtom, or any similar kind of device for displaying engine operating conditions, pay special attention to your coolant temperature. Your target temperature should be 180F, but dependent on environmental conditions, you may only be able to get the car down to 190F. You should not perform a pull if the temperature is above 200F, you have coolant problems if you are exceeding 210F, and the ECU is going to dump a lot of fuel if you breach 217F. If you do not have a means to monitor your temperature and you note the auxiliary fan turn on or see a significant drop in your A/F readings, you are overheating and you need to address the issue ASAP.
Bringing the engine back down to a specific temperature before making another pull has benefits:
- Differences in power and torque will only be as a result of differences in tuning.
- You run less chance of ‘heat-soaking’ the power-plant and its supporting systems.
- Producing consistent figures from pull to pull (for no-change ‘back to back’ pulls)
If you do not have the above mentioned equipment to monitor the coolant temperature, you still have a temperature gauge on the dashboard - keep your eye on it!
A/F Ratio Balance
In all the time I have been in the Z scene, I have yet to see or hear of anyone testing the A/F difference between the two sides of the engine. THIS IS A CRITICAL TEST! While just about every mildly-modded Z (Since the MAS is only connected to the driver’s side turbocharger, it is the ‘reference’ side for the air metering system – the ECU only ‘sees’ what is going on with this side. However, the driver’s side turbocharger actually feeds air into the passenger bank of cylinders (the intake manifold ‘crosses-over’). This means that the passenger side exhaust is the reference side for determining your base A/F ratio – what you see as the A/F on the passenger side of a dual-pop configuration is the ‘actual’ A/F that the ECU is generating. Here are the logistics:
Example 1: If the driver’s side exhaust is running leaner than the passenger side, it means that your passenger turbo actuator is tighter than the driver’s side, thereby making the passenger turbo spool more and flow more air into the driver’s side of the engine.
Solution1: Since the passenger side actuator is the most difficult to get to, and in this case, it is the stiffer of the two and you should adjust the driver’s turbo actuator to increase the preload on the actuator rod. This will cause the driver’s turbo to spool more like the passenger turbo as well as rise to a shaft speed closer to the passenger side as well. Adjustments should be made ~1/8” at a time and tested with two consecutive pulls to test the A/F results between the sides. If it is still leaner than the passenger side, you need to shorten the actuator rod a little more. Continue doing this until you achieve an A/F balance between the sides of no greater than 0.2 A/F.
Example 2: If the driver’s side exhaust is running richer than the passenger side, it means that your passenger turbo actuator is looser than the driver’s side, thereby making the passenger turbo slower to spool and moving less air than the driver’s side turbo.
Solution 2: In this case, you are going to have to tackle the passenger side actuator and tighten it up a little. You might want to just go ahead and shorten the rod a full ¼” to 3/8” just so you won’t have to do it a second time if it wasn’t enough. You can always tighten (shorten) the driver’s side actuator afterwards if you went a little too far on the passenger side.
By no means do you want to loosen an actuator rod to correct either one of the problems shown above. The problem you may face if you loosen them is decreased peak boost – the turbos simply wont make the peak boost they are supposed to. However, in the case that your lowest boost is <18psi and you cant go any lower, you may need to loosen your actuator rods on both sides to get your base-boost level back down to a manageable level. Only do this after verifying that all of the boost control hoses are properly connected and that they have no holes in them. You will also need to verify that there are no leaks in the actuator diaphragms as well. Loosening the actuator rods is a ‘last ditch effort’ to curing an over-boost issue as there are a plethora of other causes for this that are much easier to correct.
An unfortunate reality of this test and repair is that it pretty much requires the use of a dynamometer to correct as the dyno provides A/F feedback that is vital to this process. Some may believe that simply setting the actuators to open at the same time by applying air pressure to both actuators and adjusting as necessary will correct this, but unfortunately this is not the case. The actuators will be the same between both sides, however, the angle of which the actuator rod connects to the wastegate control arm is slightly different from each side. You can get things ‘pretty close’ by using this method, but when you really start turning up the boost to higher levels, you will run the risk of one side leaning out and possibly damaging the engine.
Increasing Maximum Boost
If you are finding that with the boost controller turned all the way up your turbos simply are not achieving the boost levels that they are supposed to produce, you are going to need to increase the preload on the actuators by shortening the length of both actuator rods and performing the balance test as outlined above. This particular test can be performed prior to going to the dyno by simply road-testing the vehicle, but it will require that you have high-octane fuel in order to test the boost ceiling.
If All Is Well, Make Your Pulls!
- It is important to make sure the engine is up to normal temperature before you make your first pull.
- During the tuning process, you are going to be increasing the boost pressure – for every ~5psi of boost you increase and at your maximum boost level, you will need to perform an A/F balance check between the sides. Make adjustments as necessary.
- Keep an eye out for any liquids on the ground beneath the vehicle – you don’t want to leave a mess at the dyno and you don’t want to damage your engine either.
- If you have a buddy with you, use them! You cannot watch every gauge at the same time and your A/F is one of the most important. If you are performing a pull to verify some other sensor such as EGTs or your boost controller, let your buddy know that you don’t want it to go any leaner than ‘x:1’. This can be applied to any gauge information, but it helps to have helpers.
- Be sure to include notes on your dyno-pulls. This is not hard to do and the dyno-operator should have no problems doing this for you. These notes will be valuable to you once you’ve fully tuned your car and made some 20+ pulls. You will not remember what you did on each pull once you are done otherwise.
- Be careful handling race fuel – they usually contain tri-ethyl lead which is not good for you and of course, it is flammable. Be sure to load an ample amount of race fuel based on the remaining pumpfuel in your tank. Do not let the car run out of fuel! Once you have made your final tune, it is strongly recommended to perform a high-load, multi-gear (starting in 3rd gear at 1500RPM), WOT, run to about 150MPH (in 5th gear), apply dyno brake to slow to ~40MPH, and repeat process one to two more times without stopping. The idea here is to simulate an extreme condition to observe for any detonation. Be-it from bad fuel, high environmental temperatures, or a girlfriend driving the car and putting lawnmower gas in it, the tune you have put together in this instance is only catered to the conditions of the day, with the fuel you have, and on a dyno rather than the actual road. Running the vehicle in a condition that introduces a ‘controlled’ amount of heat-soak will ensure that you won’t have any problems down the road. The last thing you want to do is squeeze every last ounce out of the car and leave yourself no buffering for safety. If detonation is detected in this procedure, make changes as necessary.
After the Session
Be sure to observe a proper cool-down period for your turbos after your last pull.
Let the dyno-operator unload your vehicle; don’t try to do it yourself. (Just make sure the e-brake is on!)
Once the vehicle is off the dyno, inspect the floor for any fluids.
You obviously will want to generate the documentation of HP, TQ, and A/F. Request the dyno-operator to print the result in landscape format rather than portrait – the graph comes out with better scale this way. Be sure to tell them to include the notes on the printout too.
At this point you are ready to scoot! If you have race fuel in your car, enjoy it while you can. Don’t worry about the race fuel contaminating your O2 sensors – this is a farce. Just fill your tank all the way up with pump fuel once you’ve expended the race fuel supply. Be sure to turn down your boost and load appropriate mappings if you have such hardware when you fill up with pumpfuel. Be sure to keep a close ear and eye out on the car for the next few days. Do not turn your radio wide open and exercise that long pedal on the right – you should ensure that your car performs without detonation as environmental conditions change from day to day. If your tuning was successful, you are well on your way to many reliable miles and I can only hope to have eased the process for you.
In Closing…
The dyno, when used as a tuning tool, offers enormous benefits over any other method of tuning a vehicle. It is a controlled environment and tests and tuning performed are governed by a scientific-like method. The guidelines and suggestions I have presented here are only that: suggestions. The more dynamic your tests are, the more refined your tune will be. Use your imagination, it will carry you much further than any knowledge I can provide!
Well, that sure was a long read and I assure you, it has been a long write, but as always, enjoyable. Thanks!
[ ashleypowers.com ]
[ agpowers@bellsouth.net ] Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast?
If you are out to describe the truth, leave elegance to the tailor.
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The "Dyno-Dissertation": Things you might want to know... - 
