Dyno Tuning Checklist 101

by COBB_Tuning5/21/2012 Filed Under: COBB Tuning Dyno Checklist Engine 
We have created this dyno tuning checklist as a guide for you to follow to ensure your engine and vehicle are in proper condition prior to your tuning session. The most common cause of unsatisfactory tuning results stem from mechanical issues that could have easily been found and corrected prior to the tune.

Go through each of the steps in this Dyno Tuning Checklist to identify and resolve common problem areas that can effect the tuning of your car.

Section 1: Mechanical Engine Health

You need to make sure you are tuning a healthy engine. We suggest you complete a compression test prior to your tuning appointment (and a Cylinder Leakdown Test [CLT] if possible). Typical compression test results should be as follows (at sea level):

· 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)

Compression Tests should be performed on a warm engine, with the fuel injectors unplugged, and the throttle should be held fully open while testing. These pressure values will be less at higher elevations, and can be lower on engines with more mileage. 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 mechanical 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 Compression Leakdown Test (CLT) 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 either of 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 any negative symptoms and consult with you about the consequences of further tuning your engine.

Check for any engine oil, other lubrication, or fluid leaks. Be sure to use the proper turbo oil feed and return lines and that they are installed properly. Any oil/fluid leak will likely only get worse once the engine/drivetrain is warmed up while on the dyno. An engine's oil lubrication system must be properly sealed in order for dyno tuning to safely continue.

NEXT: Section 2 - MAF, Intake, Charge Pipe/Intercooler System, Turbo and Vacuum Line Integrity


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