BustedRX

Ive seen quite a few people talk about using heat wraps on downpipes, or even going so far as having them jet coated or other varients of heat coatings. I understand that the goal is ultimately to reduce underhood temps and such, but where does all the heat that is retained within the pipe go? Ideally it would all exit through the exhaust system. But without dissipating heat to the surrounding airflow, couldnt this cause some sort of heat soak back into to motor/turbo system??

DCrosby

Absolutely that and the Cat / Mipipe will get the brunt of that heat... so I persoanlly can undertsnad it if you're buying a steel DP, and want to prevent it from rusing... but if you squelsh someting in one spot, it's likely to cause you troubble in others...

dgeesaman

iTrader: (7)

Well, like you said the heat must go either up or down the pipe. Mine is unwrapped, simply because the japanese versions aren't insulated and I figure that's closer to the engineered temps for the exhaust manifold. I also think it's a waste of time/money/effort.

However, I am concerned with the heat applied to the main cat and insulating the downpipe would probably make a small contribution.

Dave

BustedRX

Thanks for clarifying guys.

911GT2

The wraps on the downpipe help keep the heat in the pipe and not outside of it in your engine bay. The cat will likely see the same temperature air coming into it with or without the wrap, so it wouldn't kill the cat any faster. The point is just to reduce underhood temps. Hotter air flows faster anyways, so it actually helps it exit the car quicker too, thus expelling the heat faster while keeping it in the pipes.

zullo

I would think that wrapping/coating the DP could make a significant difference in interior noise, i.e. provide some noise dampening where it counts on the exhaust.
Can anyone comment on that? Installing M2 DP this weekend, and am debating this.... thanks!

WVRx7

There are no ignorant downpipes, just ignorant people.

911GT2 is right. The hope with the wrap and coatings is that more of the heat will be trapped within the pipe. Sure, it doesn't work as well as they would like, but overall a wrap or coating is probably an ok idea.

One thing to consider is that while moving (driving) underhood temperatures aren't much of a problem.

The underhood heat problem comes from when the car is parked. The heat simply bakes and cooks everything in the engine compartment. Things are worse if the car has been parked for a short time and then you start it again. The heat soaked coolant is instantly subjected to new heat and the cycle starts all over again.

To combat these effects I nearly always pop the hood when I park the car. If I am in a public place, I sometimes just pop it and leave it resting on the safety latch. If I am at home or in a less public area I will open it all the way up.

You would be amazed how much heat is evacuated in just 5 minutes with the hood open. Even just cracking the hood lets lots of heat escape. (here is where vented hoods are great)

Sure, its a pain in the *** to continually pop the hood but since my car isn't a primary driver I am usually out having fun with it anyway. Obviously, I wouldn't want to be doing this if I was going to work, etc.

RonKMiller

100% correctamundo. It's known as "scavenging".
Not only does it keep things cooler it also helps performance.

An engine is nothing more than an air pump. Anything you can do to make it more efficient will result in better performance.

Both methods (wrapping and jet coat) work great - it's just a matter of cost and climate. I would NOT wrap a mild steel pipe East of the Mississippi, or anywhere you'll be driving in a humid or wet climate in the winter. Make sure you never wrap the head of the dp or cat. Everything else is fair game and well worth the effort.

One big negative for wrapping: It may incur the wrath of an overzealous emissions ****. (while waving on that exempted "eco-friendly" 2001 Expedition past you since its a light truck) If you go the jet coat route keep it "dull".

Stealth is ALWAYS good.