Heat soak theory

I was told the steel for charge pipes will create hotter intake temperatures and cause knock. I simply don't believe this but I wanted your opinion.

In my own opinion I have aluminum intercooler and intercooler piping outside the engine bay and steel inside the engine bay. I ceramic-coated the steel and I will also thermal wrap the steel. My theory was the steel will take so long to heat up that it will actually reduce the intake temperatures over having bear aluminum everywhere. Obviously if you just sit there idling however thermal soak will set in no matter what you have in there. Opinions?

It's going to depend on the relative temperatures of the air mass inside the tubing and the temperature of the outside of the tubing - the latter will be dependent on the air temperature around it and the amount of radiated heat it receives from the engine.

When the vehicle is in motion, and under boost, I would expect the temperature to be higher inside, so the greater heat transfer of aluminium would probably cool the compressed air by transferring heat energy to the surrounding air. Ceramic coating the steel would further reduce the heat transfer.

That said, I really don't think it's going to be of any significant, either way, when you consider the air mass passing though the tube and the relative difference in potential heat transfer.

I don't know your specific setup, but I wouldn't worry about it unless I did a back-to-back test - anyone?

Oh, normal practice is to use just aluminium tubing, any reason for using steel as the small cost savings will probably be cancelled by the coating and wrap costs?

As an aside, I have seen idiots driving around with their exposed charge cooler pipework wrapped in thermal insulation - FFS, people, the tubing is in cold air and could be getting ride of more heat...

I have had Stainless, Silicon and Aluminum pipework on my race car over the years, I also run a lot of sensors (Pre-turbo Pressure & Temp, Post-turbo P & T, Intercooler Inlet Tank P & T, Intercooler Exhaust Tank P & T, Boost P, Pre-throttle T and Inlet Manifold P & T) in the car so I have quite a bit of quantifiable data available.

From this experience the aluminum pipework has the best heat rejection, with the temperature being shed through the whole system, and silicon the worst for retaining heat (it is also the best for preventing heat soak, but once it is heat soaked it takes longer to remove the heat from the pipework). The stainless was in between but was also the heaviest per meter of pipework.

Thanks for the information. I only have a mig welder so that's why I went that route. I won't worry about it any longer and I'll just watch the data.