Just making sure we're on the same track, reducing engine bay heat is not the main purpose of wrapping but may be a desirable side effect. The purpose is to keep the heat in the extractors to raise the temperature overall, hotter air travels faster.

I honestly doubt that there will be much difference in bonnet temperature after a long hard run, or in racing conditions?

I've deduced that for a road car and longevity the best thing to do is ceramic coat the extractors. Racers may wrap but then again they also rebuild their engines every season or more often so can afford to give up longevity for abit of oomph.

Tid bit: If exhaust wrapping were a cheap, free hp gain with no concequences you'd think that car manufacturers would catch on and apply this to their cars, but they don't. Why? Whereas Alpha for one, ceramic coat their extractors...

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Lillee - 1969 Morris Mini K

Many do fit heat sheilds for this reason and to try to reduce under bonnet temps.....

From a mass manufactoring piont of view, wrapping would be a pain in the
@ss. It would be cheaper to coat exhausts.
But very few cars come with high performance exhaust systems, so there is
absolutely no performance advantage whatsoever to coat or wrap the
manifold. So they put on a heat shield for cabin comfort and ect.
But for the individual engine builder wrapping does have its advantages,
although heat coating would have to be superior.
With both systems (wrapping or coating) you kill two birds with one stone.

If you coat it, it still gets awful bloody hot...
Coating is mainly to protect the metal- Jags used to coat their cast iron headers with vitreous enamel.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

How well did it last?

10 or 15 years...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

i always wondered about this.. the honda crew always seem so eager to rip off their heat shields to show off their exhaust bling
example;

the exhaust manifold on a mini is directly below the carbs and periods of idle have more effect than most cars modern cars where the carbs and exhaust manifold are on opposite sides of the engine. on that honda, having a heat shield installed would be to minimal advantage. it may reduce ambient underbonnet temps but not by much. a heat shield on a mini however would be beneficial

The Honda heat shield is to protect the owner's hands when reaching for the dipstick (which sits between No2 and No3 exhaust primaries).
So it's to stop lawsuits, rather than for car performance.

The standard heatshield wouldn't fit on that aftermarket exhaust, but if it was my car I'd be more worried about the lack of air filters (sorry, off topic).

You have to ask, are we talking about exhaust wrap for performance modifications or comfort/aesthetics? I am coming from the performance point of view, anything else is just unnecessary bling and/or extra weight which reduces performance...

PS. When i suggested by manufacturers don't wrap their exhausts, i meant on higher end cars, not Corollas and Mazdas. Ones that don't mind PITA tasks to increase performance. It's just not a std practice outside of competitive racing is my point.

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Lillee - 1969 Morris Mini K

It makes a very big difference to the temp under the bonnet. I never did any temp readings on the HQ but it was a huge noticeable drop in temp.
You could hold on to the extractors after a race.
With the HQ the starter and alternator are buried under the extractors and I was forever changing starters, alternators and wiring due to excessive heat. After wrapping I didn't have any problems.
There was an improvement in lap times after fitting the wrap. It was only small but it was an improvement. I doubt that the gain was from gasflow, it was more likely from being able to run more advance without pinging.

Well Morris, I totally understand that you are talking about benefits on the HQ's...

But if the wraping worked that well that you could grab the extractors after a race, then it will do the job that I (for one) want it to,, and thats stop the fuel in the float bowls coming to a boil when your in one of those situations where the car ends up idling to long at a stand still.

Thanks

Isn't that what a heat shield is for? I hope you are using one, with SUs...
I've never had this problem on the wife's car (twin HS4s and S/S heat shields).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Me neither

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Simon

The adventures of an owner builder in the Tallarook Ranges

I've had the fuel vapourise in the bowls with the standard heat sheilds pleanty of times....

Is there something else your doing here doc?