I just got this in a newsletter from COBB. It covers some basics about the FAQ's of pre-dyno tuning & things of that nature.
Thanks to Christian for the write-up.
Dyno Tuning Checklist v1.00
s t = Mechanical Issues
You need to make sure you are tuning a healthy engine.
We suggest you complete a compression test prior to your tuning appointment. Typical compression test results should be as
8:1-8.5:1 compression: 150-170 psi per cylinder
8.5:1~9.5:1 compression: 170-210 psi per cylinder
9.5:1~11:1 compression: 210-275 psi per cylinder
11:1+ compression: 250+ per cylinder (highly depends on cams being used)
These pressure values will be less at higher elevations. Compression Tests should be performed on a warm engine and the
throttle should be held fully open while testing. YOU SHOULD NOT have more than 20psi variance between cylinders. If you
have one cylinder that is showing a greater variance than 20psi then you will need to repair that problem prior to your dyno
tuning appointment. The additional cylinder pressure realized after a custom tune will only exploit the existing mechanical
problem causing further and usually more severe engine failure.
A Cylinder Leakdown Tests can also be performed on a warm engine. YOU SHOULD NOT have a cylinder leakage of more
than 7% in any cylinder. If you do, then you will need to further test to see where the air is leaking from and to; intake valve
seat, exhaust valve seat, head gasket, piston rings, etc. Please know that even if these test results look good, you can still
have an engine that has some mechanical damage and the tuner/calibrator should be able to recognize the systems and
consult with you about the consequences of further tuning your engine.
n d = MAF, Turbo, Vacuum Lines, & Intercooler Systems
Make sure that your intake, vacuum lines, and intercooler piping are sealed when under vacuum and sealed when pressurized like when running full boost. This is super critical especially if the vehicle is using a MASS AIR FLOWsensor to meter air. A vacuum leak after the MAF sensor, but prior to the turbo will make the engine run leaner. A
boost leak after the turbo, but before the engine will make the engine run richer. Major leaks can usually be found
while dyno tuning because the data will look incorrect, but minor leaks are very difficult to find so please pressure test
these parts of your intercooler system.
Make sure you have secured all of your vacuum lines and your intercooler piping so they do not blow off at the tuning
Make sure all of the bolts are tightened, in particular, the exhaust system bolts. An exhaust leak prior to the turbo will
lose power and make part throttle tuning almost impossible.
Make sure the blow off valve properly lubricated, seals tight, and is functioning properly.
Copyright © 2007 Cobb Tuning, Inc. All Rights Reserved.
Be sure to use the proper oil feed and return lines and that they are installed properly.
Turbo shaft play. You cannot expect a turbo to operate properly if has worn excessively, have the turbo rebuilt or buy
a new one.
rd = General Pre-Tuning Maintenance
Make sure all fluid levels are up to par; this includes engine oil, anti-freeze, transmission fluid, differential/transfer
case fluid, brake fluid, clutch hydraulic fluid, etc.
Alignment and wheel balancing, the vehicle must be able to drive straight if it is to be tuned on a chassis dyno.
Bleed the coolant system before you come for the appointment. If your engine has an overheating problem, DO NOT
come for the appointment. Because we cannot tune a car that is overheating.
The vehicle must be streetable and the driveline and drivetrain systems must be in tact and safe, if you have any
clicking CV joints then repair them prior to the tuning appointment. Be sure to inspect your wheel bearings as well.
The same stresses that your vehicles sees on the street are seen on the chassis dyno, although a failure on the
chassis dyno puts your vehicle and the tuner/calibrator in a very unsafe environment until the vehicle and chassis
dyno come to a complete stop.
Inspect and replace your fuel filter (if need be), any blockage in fuel flow to the engine will cause pre-mature fuel
pump wear and can lead to engine damage if the fuel filter clog causes a lean burn condition. Make sure that you
have the proper fuel octane and enough fuel to complete the tune. If you want a tune for race gas, we suggest you
schedule two different tunes because your engine will most likely be heat soaked after the pump gas tune and will
need significant time to cool off. Fuel Pumps, you should not have installed the fuel pump if you see dirt, debris, or
rust in the tank. If there is rust in the tank, replace the fuel tank. You will starve the engine of fuel if you leave junk in
the fuel tank.
If you engine oil and filter have been run for more than 3,000 miles, please replace the filter and your engine oil.
If you spark plugs (& wires) have more than 5,000 miles on them (if they are copper plugs) or 15,000 miles on them (if
they are iridium/platinum), please replace them with new ones. Be sure to gap them appropriately and to use a small
amount of anti-seize when installing the new spark plugs. Bring extra spark plugs, during tuning it is possible to foul
the plugs to a point where they will need to be replaced. New spark plugs are NOT included in the tuning rate.
Make sure you have appropriately functioning brakes on the vehicle that are suited for your power level. We drive
each vehicle we tune on the street after the dyno tune to verify proper operation. We should feel safe riding in your
car after the tune.
IF YOUR VEHICLE IS OVER 5 YEARS OLD, we highly suggest you remove your fuel injectors and have them
cleaned and calibrated by an injector cleaning facility like DeatschWerks, RC Engineering, or WitchHunter, Since the
tuner/calibrator is only metering the Lambda (Air/Fuel Ratio) from one location the assumption is that all fuel injectors
are flowing the same rate. If you have one poorly flowing fuel injector, then it is possible to further damage your
engine by completing a dyno tune.
If your vehicle is over 5 years old or is driven in a humid oceanic environment, we suggest you clean your engine
grounds and grounding attachment points. A vehicles electrical signals need to be as clean as possible so the ECM
has good signals coming in and going out. The engine harness should have no exposed wires. Also, do no twist and
tape wires together. Take the time to properly crimp or solder them together!
Battery/Alternator - Make sure these items are strong and operating properly.
Check Engine Lights or Codes - Do not come for a tuning appointment if you a check engine light is on. Please have
this problem diagnosed and fixed prior to your appointment.
If you have a new engine please read through our document about How to Break-in Your Newly Built Engine.
REMEMBER, dyno tuning time starts when the vehicle is driven into the chassis dyno cell so our goal is to make this time as
effective as possible in order to make the cost to the client as little as possible. A tuner/calibrator's job is to develop a tuned
calibration specific to your vehicle, not fix everything that is wrong with it. If you come to an appointment with a car that is not
in proper working order you may be asked to leave depending upon the severity of the issue. If the problem is a minor and can
be easily fixed at the shop during normal operating hours, then we can fix it, but NOT FOR FREE.
Copyright © 2007 Cobb Tuning, Inc. All Rights Reserved.