View Full Version : Manifolds: To wrap or not to wrap

9th July 2003, 10:21
This question from StevieTurbo (from exhaust gasket thread) is, I beleive, worth a thread of its own:

"While on the subject of manifolds. I know everyone wraps their manifolds, and that heat retention is good.
Ive also read threads were the heat from the manifolds have in some cases, melted various bits of car.
So, is it totally necessary to wrap them, and is it to insulate to keep heat in, or to protect the car??? or both.
Has anyone tried them unwrapped?? does it make any difference performance wise?? is the car melting bit, limited to a few select cases??
And finally...would leaving tehm unwrapped possibly reduce the chances of flange warpage due to excessive heat build up ??"

9th July 2003, 10:36
Judging by the location on the subaru, the manifolds will always get a lot of cool airflow around them... so I suspect that wrapping them will be less likely to bring temperatures up to levels that can lead to serious metal fatigue problems.

When I was running MRT headers, they were wrapped, but the current headers are not. I shall endeavour to wrap them when an appropriate opportunity presents itself (e.g. the engine lets go or I rob a bank and and buy a 4 poster ramp http://bbs.22b.com/ubb/wink.gif ).

I suspect that wrapping the headers and uppipe should help drop my boost threshold at least by a hundred or so rpm. However, the EGT's would climb a bit and I would have to be more careful with the use of antilag. http://bbs.22b.com/ubb/smile.gif

9th July 2003, 11:42
Your (ex)headers, wrapped on the whole with a bit of a gap, surrounded by a molten fan connector http://bbs.22b.com/ubb/smile.gif

Hmm, just noticed it's not very clear - the slip joint isn't exactly quite at the right angle http://bbs.22b.com/ubb/rolleyes.gif if you use your imagination a tad...
So I think Pat's magnificent wrapping http://bbs.22b.com/ubb/biggrin.gif did the job nicely until something happened (presumably a breif bit of overenthusiastic EGTs) so the slip joint err, 'overslipped', rubbed against something, removed the wrapping and melted the connector.

So there's a nice topical story.
With a pretty piccy.

[This message has been edited by nom (edited 09 July 2003).]

[This message has been edited by nom (edited 09 July 2003).]

9th July 2003, 12:24
exhaust rule number 3.

when using sprung slip joints, always fit an emergency bowden cable to prevent catastrophic separation.

Any kart racing bod will tell you that, as the exhaust is only held on with springs.


9th July 2003, 12:51
Fortunately there's no catastophe http://bbs.22b.com/ubb/smile.gif They were very well behaved...

I'm interested in hearing exhaust rules 1 & 2 too, to see if I'm ignoring them as well http://bbs.22b.com/ubb/biggrin.gif

9th July 2003, 18:23

I suspect rules number 1 and 2 might suggest ensuring that any joints actually join. That slip joint isn't actually joined. Bet that was noisy. http://bbs.22b.com/ubb/smile.gif


10th July 2003, 06:41
I always wrap - but I did once run very lean on track (split inlet pipe), requiring an up shift around 6k before det started.

The engine survived this, but not the wrapped headers - I assume the lean mixture was raising egt's and a slip joint retaining bracket's weld failed. Oh well, fixed the det problem...much lees boost http://bbs.22b.com/ubb/smile.gif

Another set of headers I tried were HPC coated - it was, quite frankly, rubbish. It raidiated huge amounts of heat at standstill - but on the move I guess airflow kept things reasonable?

On two cars now I've also seen loom damage up under the side where the up-pipe goes (even with wrapping). Not sure if RHD/LHD ABS position is the same, but one of them lost ABS on track due to touching wires.....and I'd lent the b*stard a set of P-Zero's which were flat spotted within 5 laps because of it http://bbs.22b.com/ubb/wink.gif

Reminds me though - as a result I wrapped wiring looms with exhaust wrap as I didn't have any heat reflective stuff available. Is this OK?


29th August 2003, 21:20
Is there any problem with refitting the undertray with unwrapped headers? I'm fitting a set of Gruppe-S but I want to keep my engine pristine!

30th August 2003, 20:42
<BLOCKQUOTE>quote:</font><HR>Originally posted by Pblamire:
exhaust rule number 3.

when using sprung slip joints, always fit an emergency bowden cable to prevent catastrophic separation.

Any kart racing bod will tell you that, as the exhaust is only held on with springs.


Paul, is this also the case for a uppipe that has a slip joint ?????

Carlos H.

Adam M
30th August 2003, 23:15

I wouldn't bother with an undertray at all, ask bob rawle how much difference it made to his oil temps!

If you have to, then consider a minimal metal undertray that might actually provide some sacrificial protection.

Am certain tubular headers unwrapped and possibly wrapped too, would melt it.

31st August 2003, 09:21
Thanks, Adam. I've already noticed that my oil temps are up slightly since fitting the FMIC (although, strangely, water temp seems to be down slightly!) I might chop up the tray and just refit the rearmost part to try and keep the worst of the road muck off the engine.

1st September 2003, 13:06

If you leave the undertray off altogether you should find the up and downpipes will have more cooling air available.

My STI came without any undertray. It's never been a problem.

1st September 2003, 19:59
I'm persuaded http://bbs.22b.com/ubb/smile.gif Better not park in long grass now though... http://bbs.22b.com/ubb/rolleyes.gif

22nd September 2003, 20:35
Does the undertray actually provide much protection from road dirt? Any suggestions on where to source metal undertrays?

I'm also fitting the Gruppe-S headers and hadn't considered the possibility of (wrapped) headers melting the OE tray!

23rd September 2003, 11:27
If you do remove the main under tray then also remove the gearbox under tray as this will remove itself at 140mph!


Jolly Green Monster 2
23rd September 2003, 11:38
Gearbox undertray??

They must be on the newer that 96 cars?!

Not one on mine when I got it.


23rd September 2003, 12:45
Mine has a gearbox undertray. I can confirm it stays intact at 158MPH with the engine undertray removed, although it wouldnt have liked it. It's now removed. http://bbs.22b.com/ubb/biggrin.gif

Taking the undertray off has dropped oil temps on cruise by 5 degrees C.

26th September 2003, 23:37
Has anyone actually measured gearbox oil temps? http://bbs.22b.com/ubb/smile.gif


27th September 2003, 09:19
I know mark has bosses in his for an oil cooler.. so suppose he may soon me doing this..