It's supposed to keep the exhaust gasses at a higher temperature, and therefore keep the pressure in the exhaust down and the gas flow speed up. Thus giving a little more power.

You car has heat shields (well, unless they're broken like mine ) that do a similar job.

I read somewhere that it's a bad idea to wrap cast headers - anyone care to comment as to why? Is it something to do with them cracking due to heat spots?

[Edited by dnb - 8/1/2003 11:31:45 AM]

 

Serious question, is it just a heat retention thing to stop under bonnet temps getting too hot or is there a performance angle regarding the exhaust temps?
I'm thinking on the one hand, that if the exhaust is wrapped and the heat has nowhere to go but out the back then this would make popping/banging flames etc more likely. Then on the other hand i'm thinking that my car does all that anyway without so I doubt adding some wrap is gonna make such a hugh difference.
Is exhaust wrap just another one of "those" products that makes people feel good but doesn't actually do owt?

Dunno

Mikey

 

Can't believe i spelt huge as hugh

Mikey

 

Higher temperatures mean the exhaust gas volume will be bigger (boyles law or Charles law or whatever) so I would have thought pressures would be higher not lower. But yes velocities will therefore be higher so the scavenging will be better. Whether this is a bigger or smaller effect than the higher pressure is anybody's guess. Whether either of these effects are worth more than a fraction of a BHP is also doubtful to me.

On a turbo car I would think pressures more important than on a NA car and scavenging is less important.

But don't discount the underbody temperature, this has a significant effect on engine power so if exhaust wrap keeps underbody temps down then it's worthwhile for this reason alone.

 

Erm. Sort of. Hotter gases take up more space so must flow faster, which is where it's handy with the turbo.
Wrapping keeps heat in, so it doesn't get to bits of the car that should be cool (eg wrap the exhaust/hot side of the turbo to stop heat getting to the inlet/cold side will technically improve spool up & reduce charge temps). Keeping heat in also means that things are hotter. Cast things don't like heat that much - they cope, but are very brittle, whereas steel is far more ductile so the heat cycling doesn't get to it (far less likely to crack). This is the difference between 'heat shield' (standard headers) and 'wrapping' (tubular/stainless headers).

 

Main reason I wrapped my downpipe was to reduce the noise in the cabin.. car does upto 1200miles some weeks and I like the noise but the family don't..

Anything else was just a bonus for me.. not expensive.. it does pop lots..

JGM

 

Keeps heat in and noise down IMO, run long enough with and without to know.

Steven

 

and P20 SPD advised me to wrap it.. oh and you and David fitted it in the end too lol..



Simon

 

Guys, what wrap did you use?
I'm getting a downpipe to go on the P1 (and Tek3 so it doesn't blow up!) but can't face going back to the droning noise that the downpipe on my old MY00 used to make. I understand that wrapping will smother a lot of the noise.

 

It is worth wrapping certainly before the turbo because the heat is part of the total energy contained in the exhaust gases and if you allow it to dissipate then some of the energy to drive the turbo is lost. I have wrapped my headers(standard and ported) and up pipe( Hayward & Scott) for that reason. The headers are fine up to now and the heat under the bonnet is reduced.

I also wrapped the downpipe (SS non catted) once again to reduce the heat radiation and also found that the noise is significantly reduced in the car. I used the 2" fibreglass stuff and sprayed it with Halford's VHT paint to protect the material from oil etc. So far it is holding together very well. Got rid of the noise from a cracked heatshield too

Les

 

If you have non stainless steel pipes they burn out faster with exhaust wrap.

 

cooltech from demon tweeks is what i used.

 

Chelspeed,

It can't be Boyles Law, I learnt that as a nipper,

"Watts pots never Boyle!" nothing about exhausts.....?

Must be Charles!