Heat wrapping downpipe,yes or no

[220bhp]

Is there any advantage in heat rapping the 3inch down pipe on my rs2 spec 3b before I fit it.Any BTDT.

[Rusty]

I'd say yes as it'll keep the engine bay a little cooler but I've not done it personally.

[Acidburn]

pros - it keeps temps down

cons - its rusts the downpipe without you noticing as it absorbs moisture.

I've not seen anyone on here thats needed to wrap the d/p but could be worth a shot.

[Keeper of The Kitten]

I'd always been given to believe that hotter gases would flow with increased velocity - which would make lagging the whole of the hot side (including the turbo) seem like a good idea? (And this is something I've seen on the LM cars) ...but then there is the question of longevity, as increased heat within those areas will surely cause premature failure of the hottest parts. I am sure others have mentioned manifold cracking due to excessive heat. But for just the DP this might not be such an issue.

Also, once the heat has soaked through the lagging and into the engine bay, the effect is diminished ...but I would have to say that anything which takes heat from the engine bay would be beneficial in pure performance terms, and maybe just the DP would be a good compromise? Especially if the stock intake pipe location has been retained and still travels over that hot area towards the rear right hand side of the engine.

[Acidburn]

http://www.s2forum.com/forum/showthread.php?t=4746

[Keeper of The Kitten]

Spot on Pete, just what I seemed to remember

[Rusty]

Hot gas is denser so to maintain gas flow it needs to flow faster...

[Jamo]

Make sure you coat the wrapping so it wont catch fire

[JP]

Mixed feelings on wrapping downpipes. But as a reference point increased heat = increased pressure = increased velocity assuming the gas has an exit point. So by ceramic coating exhaust manifolds you keep the gas speed up to the turbo.

However on the downpipe side you want as much as a drop in pressure as possible in order to offer less resistance to the exhaust gasses exiting the spinning blades of the turbo. So the physics now dictates that the colder the downpipe is the more freely the turbo spools.

This however has it's cons as depending how much downpipe is exposed in the bay and how tight it is in there you can get performance losses from hot intake temperatures. So as a rule of thumb look at the setup and then decide what is best for you by weighing out the pro's and con's.

[Thuppu]

I had wrappings on the ex manifold and DP. It really cools down the engine bay prety much.

http://koti.mbnet.fi/pro-ht/Audi_URS4/turbo-heatshield_01.jpg

http://koti.mbnet.fi/pro-ht/Audi_URS4/turbo-heatshield_02.jpg

[QuattroFever]

think of it as a liquid and not a gas. oil will flow much faster when hot because of the viscosity. The same applies to air just at a different level.

EDIT: I would say heat wrapping your cat could be more beneficial to performance, if you have one.

[driftin jo]

think of it as a liquid and not a gas. oil will flow much faster when hot because of the viscosity. The same applies to air just at a different level.

EDIT: I would say heat wrapping your cat could be more beneficial to performance, if you have one.

You could not be more wrong !
Liquid viscosity behaves the opposite way to gaseous viscosity .

While liquids get runnier as they get hotter, gases get thicker. (If one can imagine a "thick" gas.) The viscosity of gases increases as temperature increases and is approximately proportional to the square root of temperature. This is due to the increase in the frequency of intermolecular collisions at higher temperatures. Since most of the time the molecules in a gas are flying freely through the void, anything that increases the number of times one molecule is in contact with another will decrease the ability of the molecules as a whole to engage in the coordinated movement.
So as exhaust gas cools it's pressure lowers and thus flows better. If you could run a huge freezer system on an exhaust pipe to remove heat from it you could use a much smaller diameter pipe and flow the same .

[loxxrider]

Yeah...I was going through and reading this thinking wow, this contradicts everything I ever learned in Thermodynamics lol

[QuattroFever]

i think you'll find im not wrong, im putting it in a way thats easy to relate to.

Your talking about mass flowrate not volumetric.

Have you considered laminar resistance relevant to the subject?

[driftin jo]

i think you'll find im not wrong, im putting it in a way thats easy to relate to.

Your talking about mass flowrate not volumetric.

Have you considered laminar resistance relevant to the subject?

so physics is wrong and you are right ??

The engine needs to exhaust x amount in mass of gas not volume that's where you are going wrong. The volume of x amount of mass of gas is only temperature related .

If you put a 1 inch exhaust on an s2 the gas out of the tail pipe will be flowing a lot faster but this would not be better would it !

A lot of people make this mistake as they assume that a hotter gas flows better. well it does flow faster in terms of volume but not in terms of mass . Heating gas makes it flow faster in terms of volume as temperature increases the pressure , but does not increase the mass of gas flowed.
Since the engine needs to remove x amount of gas in terms of mass not volume there is a negative effect from high temperature in an exhaust system .
The amount of gas expressed as a volume that the engine needs to flow is totally dependent on temperature thus as I said above if you could cool down the gas enough 'theoretically' you could super cool the exhaust and turn the gas into a liquid that could flow 500hp from a ½ inch pipe .