"Reading" an engine tune by color
 

Can someone explain what the different colors of the piston and head mean as far as the tune of the engine is concerned.
If it's light brown, what does that mean?
If it's dark brown, what does that mean?
What is the optimal color?

There is no direct telling about light or darker colored pistons, it depends the fuel. The higher the volume of the castor oil the darker the piston will get.

But if you have a brown color it seems to be OK, when it has a rough gray surface it is to lean or the compression is to high.
And what you can reed is the length of the exhaust, on the piston you can see a ( shaped mark, that has to be somewhere between the exhaust port and the middle of the piston.

Roelof if understand you very well,the height of this mark in the piston depends of the exhaust length,right?
can you post some pics?
thanks!

That makes total sense. I was seeing a light brown piston top, then I was advised to add some castor oil to my fuel, after the first day of running with the extra castor the piston was noticeably darker. Thanks for the info!

I have no pics but indeed, the placing of this mark is depending on the length of the exhaust, it is created by the shockwave coming back from the exhaust.

so is there a base exhaust length for all engines??? i kno i have a matched pipe to my .12JLR(Skyline VR12)(atleast i was told it was matched darn good with that engine), but i have a .18 hpi T3.0 engine with an stock Duratrax Stpro muffler on it .. im worried its too short ...

No most engines are specific to the tune they want. I have seen people have a base line to start at from the center of the piston to the center of the taper of the pipe. But this is what changes the pipes performance on engines in general. The shape of the pipe as well as the length of the header and the length of the pipe. And the standard lengths that I have seen have been on marine engines and they to also very from manufacture to manufacture. When the pipe is longer meaning the chamber not the header length general rule of thumb will be more lower end torque and power when the shorter the chamber the more top you will gain. But like I said before this is a rule of thumb the engines do react different at times to all the variables.

No, the lenght is based on the specs of the engine like boring, exhaust port height etc. Also the cooling and shape of the exhaust can make differences in the ideal length. Thats why you can play with several manifolds.

Beside that, with playing with the exhaust length you can determ in which rpm range the maximum powerband is.

i've been waiting for his part of the explanation a long time :blush: i need a pipe set that can boost my engine potential on low-mid rpm since its a small track. can u suggest what dimension should i look at? im using OS speed spec2(magnesium heatsink) with old HEC turbo pipe for the time being.