[Mk2] [Turbo] wrapped or not ????

[robsgts]

Hi all goin to fit my downpipe soon and was wondering is it a good idea to wrap it with the white heat wrap or leave it as is ?

Rob

[king_stephen_paterson]

If its a stainless downpipe I don't think its considered a good idea to heat wrap it as this can increase the chances of the DP cracking. Then you've got the hassle of taking it off, getting it welded and putting it back on.

[Martin F]

it might be an idea as the wrap is meant to keep some off the heat in and release it further down the exhaust thus reducing a little bit of heat under your engine bay, saying that i doubt if you would actually notice any difference as there are so many other things under there that create a lot of heat...

if it was my car then i would though

[mark239]

I wrapped mine, and I think it actually is slightly cooler in the bay after i stop- more than likely my imagination.

[tarmac terrorist]

it is a good idea to wrap the exhaust down pipe ,the reason for wrapping the pipe is to keep the heat in the exhaust,& reduce the chance of hot spots in the exhaust system.. by doing this it makes the exhaust gasses flow faster through the exhaust system. it is also worth wrapping the front pipe to reduce the heat transmitting to the engine sump & again will increase the speed of exhaust gases flowing through the exhaust system...hope this helps.

[mark239]

i got my wrap at merlinmotorsport.co.uk btw

[alan_d]

I wrapped both of my stainless manis on my EP82 starlet turbos when I had them, and both cracked, both at every welded joint on each runner, both used the stock cat which was braced to the block to support the turbo and thus reduce weight hanging on the mani.

I may have pics somewhere!

is the probability of the same happening on an NA 3sge MR2 likely given that no turbo is hanging from them?

ceramic coating seems to be the way forward.

[king_stephen_paterson]

[quote="alan_d"]is the probability of the same happening on an NA 3sge MR2 likely given that no turbo is hanging from them?quote]

its a 3SGTE so there is a turbo hanging from it!

what kind of DP is it? does it have a support bracket?

[Tim-B]

Wrapping the downpipe isn't a good idea. I did this on my first build and caused nothing but problems. The wrap doesn't allow the stainless to breathe properly causing hot spots in the metal. This adds to metal fatigue and makes it more likely for it to crack.

Personally i wouldn't worry about it.

Tim

[tarmac terrorist]

metal fatigue!!!!i would say that is more like the pipe u have is made out of a low grade stainless steel

[enigma]

Alan, on your Starlet motors if you had tubular manifolds and the cat pipe hard bolted to the block that's the most likely cause of the cracking.
I'll explain if i can. Tubular manifolds will by nature of what they are, grow in a couple of directions when heating and contract when cooling, so this is obviously movement that "needs" to happen to remain in one piece.
When you brace a part of it (cat pipe in your example) it stresses the stainless and it cracks.

Lagging pipes and manifolds IS a good idea and anyone who says it causes cracks is defending crap ideas or materials.
As already mentioned the heat retension in the pipes is beneficial to gas flow and can actually improve spool up and power (slightly), and has the benefit of keeping heat away from your intake.
Hope that makes sense.

Mark

[2Crooky]

JimGTS wrapped his extreme boost and it has just snapped clean in half!!!!!

[Rev2_mike]

Lagging pipes and manifolds IS a good idea and anyone who says it causes cracks is defending crap ideas or materials.
As already mentioned the heat retension in the pipes is beneficial to gas flow and can actually improve spool up and power (slightly), and has the benefit of keeping heat away from your intake.
Hope that makes sense.

Mark

Thats quite an interesting idea - is it worth the gains given by wrapping the DP against the risk of cracks in the metal? What sort of gains are you realistically expecting on a fairly standardish roadcar running around 270-300bhp? I wouldnt have thought wrapping the DP would make much difference?

[king_stephen_paterson]

Lagging pipes and manifolds IS a good idea and anyone who says it causes cracks is defending crap ideas or materials.

Mark

thats funny, why does wrapping an Aussie downpipe invalidate the warranty then? I've had a wrapped s/s DP on my mr2 and it cracked. I removed it, removed the heat wrap, had it welded and put it back on without heat wrap and it was fine after that, no more cracks. I've just fitted a HSR downpipe to my GT4 today and there's no way I'll be wrapping it. If you're that bothered about keeping the heat in get one of the Aussie HPC DP's with a heat treatment coating on them which is intended to do the same job as exhaust wrap.

the following link may also be of interest:

http://www.imoc.co.uk/forums/viewtopic.php?t=74218

oh, more people who think that wrapping your DP is a bad idea!

[enigma]

"oh, more people who think that wrapping your DP is a bad idea! [thumleft]"

Not really conclusive though is it lol.

Jim himself says the bracket may have snapped before the pipe went. This is classic cheap stainless cracking when put under extra stress- nothing to do with the heat.
As mentioned in the other thread nur specs if not fitting great will cause enough stress further up the system to find the weak link which (because of the natural angle) the down pipe.

Think of the heat in extremes (no pun intended) If you had a piece of pipe on the bench and you heated it up til cherry red then dunked it into a vat of water, then re-heated it and kept doing it, would you expect it to last very long or become brittle?
Now heat the same type of pipe til cherry then let it cool a controlled enviroment (like an oven or heat wrap) so it cools slower. Does this make you think it would cause things to crack?

This problem only appears to be on cars with transversely mounted engines (although i'm sure there would be probs with some longitudinally mounted too) and i believe this is due to poor mounting of the exhausts or no stress relief in the correct areas for the engine to move without pulling on the pipe so when cheap steel is used its inevitable it will break eventually.

[enigma]

I've just had a look at the Aussie site and they use MILD steel so its no wonder they dont want you to lag them, as the wrap will hold moisture when the pipe is cold and they would rot. The coated ones look ok though.

[TheRoadWarrior]

This is classic cheap stainless cracking when put under extra stress- nothing to do with the heat.

Jim's extreme boost DP is 321 grade stainless steel.. far from low quality 'cheap stainless'.

If you had a piece of pipe on the bench and you heated it up til cherry red then dunked it into a vat of water, then re-heated it and kept doing it, would you expect it to last very long or become brittle?
Now heat the same type of pipe til cherry then let it cool a controlled enviroment (like an oven or heat wrap) so it cools slower.

Sorry but that analogy is just irrelevant! Besides a wrapped pipe will run far hotter than an unwrapped one because its INSULATED like your house roof- so the heat will be held in causing greater thermal stress on the part. Why else would the engine bay be cooler with heatwrap on?

[jimGTS]

This is classic cheap stainless cracking when put under extra stress- nothing to do with the heat.

Jim's extreme boost DP is 321 grade stainless steel.. far from low quality 'cheap stainless'.

true, id like to know somewhere that does the downpipe with more expensive and better materials???
enigma, perhaps you can show/tell me where to get such a pipe?

[oBladeo]

This is a really handy thread as i was going todo this myself sometime.

Has anyone seen the same problems with wrapping a 4 branch manifold?

[Driftlimits Performance]

it is a good idea to wrap the exhaust down pipe ,the reason for wrapping the pipe is to keep the heat in the exhaust,& reduce the chance of hot spots in the exhaust system.. by doing this it makes the exhaust gasses flow faster through the exhaust system. it is also worth wrapping the front pipe to reduce the heat transmitting to the engine sump & again will increase the speed of exhaust gases flowing through the exhaust system...hope this helps.

Everyone, listen to this man. He knows his shizzle from his nizzle