What about coating the chamber on an aluminum head?

I was thinking that maybe without coating some more of the heat created by the compression stroke can be absorbed by the aluminum which is a very good conductor of heat. Since our engines have oil squirters the pistons can be cooled down very quickly, and the head has water/coolant to help it.

Or do you think that the squirters and water wont would quick enough and that coating would help the squirters and water keep up with the heat produced?

Thanx.

 

I know there are some big NA tuners out there...please guys just need some info to munch on.

 

Ive never heard of the combustion chambrt themselves being coated. However, Some people have the the skirts of the pistons moly coated and the tops cermaic coated for better heat transfer. I know JDM CTR and ITR pistons have their skirts moly coated and I believe ceramic coating as well.

 

Confusing. You mean the coating that the JDM ITR's have HELPS heat transfer...or do you mean prevents it?

 

Every thermal piston crown coating I have seen is to insulate the piston from heat and to keep it from being scorched. ITR/CTR pistons have the moly skirt coat, but I am pretty sure they don't have a ceramic crown coat.

Thermal coating the pistons CAN be BAD, WHEN the piston doesn't absorb enough heat from the compressing gasses to keep the air/fuel from detonating before spark time, shocking the bottom end. Less heat in the piston, combustion chamber, or valves means more heat in the air/fuel charge, and makes it more likely to detonate.

Ususally, when pistons burn, they start burning from the outside (ring lands and outer circumference) then further in, but that depends on your combustion chamber, piston, and use (boost/nitrous/real lean NA). So, it can be useful to coat at the outer edges of the piston and leave the majority of the center of it bare.

When professional builders build racing engines from the ground up, they can design the engine to compromise with the coatings.

 

Pistons dont absorb heat from the a/f charge. The pistons GIVE heat which
causes detonation. Thermally coating the pistons keeps the heat transfer
down which helps pervent detonation.

ANd no, factory pistons dont have a thermal coating.

 

are there ever any issues with these types of coatings "wearing" out or anything, which could lead to something bad by any chance?

 

i have seem moly skirt coatings wear out over time, nothing bad will happen, they'll just lose their effectiveness

 

Sure, residual heat in the piston heats a fresh a/f charge, having just pushed out the exhaust; and a coated piston, having absorbed less heat doesn't give as much heat to a fresh air fuel charge.

I mean that when (if) the chamber, piston, and valves are coated, the a/f charge wants to "diesel," rather than explode before it should because of a hot spot, just because of the compressing of the mixture alone.

I was just going on what I have heard and what made sense to me before. What makes more sense to me now is that the heat in the piston from the exhaust stroke is more significant to making detonation than just compressing the charge, raising the initial temperature of the air before it is even comrpessed.

Thanks sgT, I hadn't though of it that way.

 

Thanx sgT. Your right the pistons are comp. much to fast for any heat to be transferred. The charge remains adiabatic mostly at high engine speeds. At low engine speeds with big cams it doesn't matter cause the static comp. will be low cause of the late valve closing time.

Cool, thanx for giving me some diff. perspectives to view the question from from.


[Modified by vwandhondaboy, 2:17 AM 9/4/2002]