Exhaust Manifold Wrap: Good or Bad?

[JohnD]

Wow, Jonny, I agree with every word!
Would that you had tried a heat shield between your exhaust before the free/expensive ceramic coating.
I'm willing to bet that the cost per degree drop in the seat back would be a lot less!

I understand (and you will know) that Jaguar use a heat shield around their exhaust primaries, not to keep anything outside cool but to speed the heating of the catalyst.
And it's just thin ?1.5mm mild steel with a 3mm air gap!
In other words, it works just like a ceramic coating for a fraction of the cost!

John
PS How did you do in Formula Student?

[Jonny-Jimbo]

Yes John, that is undeniable - the Zircotec coating is expensive, which is what I said previously, it's only worth going for if you're into the realms of finding fractions of a second at hundreds of pounds. Would you use it on a Ferrari 250 GTO worth millions? Yes. Would you use it on stock engined Vauxhall Corsa? No. As you said as well, the cost per degree loss is much better with a heat shield.

However, the point in the Zircotec, to an extent, is to keep the heat in the exhaust gas as much as keep the heat out of the engine bay.

I believe that our heat shields are aluminium, but they have a ceramic composite core in them too.

We did okay at FS, but we were never going to win against the likes of Charmers (Chalmers?), and Graz etc. They had sponsorship from Volvo and Red Bull etc. We did what we wanted to though, we knew we couldn't win so we set ourselves our own targets. We came 3rd overall in the presentations, including the business one, so that made our vehicle a more 'credible' item if it were to be manufactured and sold as a single seater track day type car. We had the wrong engine, chosen for the right reasons. We used a GPZ500 twin, it was a good chunk lighter than the standard R6 engine, and cheap - we bought 5 of them for £100, including all ancillaries etc. But it didn't make as much power as the R6 and there is a lot less tuning knowledge out there for the GPZ.

Oh, and Warwick Uni got blue flagged to get out our way on the endurance race which was a goal. It was a good strong car, and reasonably light though, during testing our driver got the car up onto two wheels at about 30 degrees or so whilst cornering without a loss of stability or braking - as James Hunt once said 'Big Balls'.

[dazzer]

Wow interesting thread. Thought I'd give my practical/factual experience of the exhaust wrap question.

Exhaust wrap. Firstly I may have missed something but never wrap a cast manifold it will disintegrate.

Stainless manifold absolutely fine and yes it does glow red of an evening if you take a look and the manifold looks sh***@ when you remove the wrap but practicable it offers two advantages over not wrapping. One it definitely reduces the heat which causes the fuelling problems (may factual experience over 50k and many rallies) and two, it produces the most wonderful exhaust note... and a blue flame out of the tail pipe! Its worth it just for that.

Lots of technical blurb about stainless manifolds disintegrating over time with wrap. I'm 50k and five years in and the manifold is still in one piece, its just discoloured. I've run the car without wrap and its a different beast, sounds light weight and the fuel vaporisation problems re appear where they never did before.

I also use heat shields (wrapped with plumbers pads) and have a large fan blowing on the carbs. So its a belt and braces job, but the full package works and the fan is particularly useful in competition. You can feel hesitation as the heat builds up but flick on the fan and it disappears almost instantaneously.

I initially had the manifold wrapped completely down to where it attaches to the front pipe, with locking wire holding everything on. I then reduced it to all the individual six pipes.

I'm rebuilding my rally car and its all going back on. It really does alter the exhaust note.

My manifold is one of CWs extractors on the old narrow head.

Cheers
Dazzer

[JohnD]

GOSH!   Manifold glowing red  AND a blue flame from the exhaust.
And "the most wonderful exhaust note".

You must have a very retarded ignition, so that combustion is continuing as the exhaust valves open.

I don't doubt that you have diligently timed the ignition, but this has to be a symptom of a shifted crankshaft damper pulley.
John

[dazzer]

Hi John

I forgot to elaborate that the blue flame is most prominent at switch off and lights the drive way up after dark. Also accompanied by a lovely WHOOPH!  

Its a combination of a dizzy with a retarded curve, (idle at 14 deg btdc) an early PI cam and a 10.75.1 comp.

The result, technically speaking of course, is that it goes like stink.

Dazzer

[Jonny-Jimbo]

That sounds rather fun Dazzer - fancy bringing it to the treasure hunt in July 😉

[dazzer]

Would love to if I get a minute away from the job. Sounds great

Cheers

Darren

[Jonny-Jimbo]

Interesting video about exhaust manifold abuse - https://www.youtube.com/watch?v=azPKIjxmmdU