exhaust flame

[dazzer]

Just an observation.

After changing my head gasket i didnt re wrap the extractor manifold as id planned to take the engine out in the near future anyway.
Result: The impressive flame flash and pop has gone on switching off and it doesnt sound quite as good as it did. Its lost some of its deep growl.

Im guessing the manifold no longer glowing cherry red is failing to ignite unspent fuel as the ignition is switched off.

Its had the wrap on for 40k and manifold still in one piece. Doesnt look pretty though.

[JohnD]

A red hot exhaust indicates severely retarded ignition, dazzer, not a lack of wrapping.
But you knew that.
John

[Davemate]

570 wrote:

The impressive flame flash and pop has gone on switching off and it doesnt sound quite as good as it did. Its lost some of its deep growl.
.

Don't you just hate it when that happens  :-/

[James]

The wrap insulates, right?

So it's now cooler — thus the exhaust gases are cooler — thus the unburnt fuel doesn't explode when it comes out the tail pipe and hits oxygen?

That's my logic anyway.

[dazzer]

Always impressive when pulling up outside the chippy.

Where the wrap had started to disintegrate, if you opened the bonnet on an evening you could see the glow of the exhaust pipe between the bands of exhaust wrap. Amazing that it can be heated up to a cherry red then cooled again and still be in one piece after 40k. I did read that it shortens the life of a manifold.

It was a CW variety although being the MK1 version didnt line up very well with the head ports. I've had to heat up and 'adjust' previously.

Cheers

Dazzer

[josh18]

I would have thought that heat wrap would help make the exhaust glow, as it keeps the heat in. Im with Dazzer on that one. If there is no heat wrap the pipe gets more air cooling and might not glow as much I guess.
Actually on the subject of heat proofing, has anyone tried ceramic coating? I particularly ask because since I made up my headers they have got a fair of surface rust formed. I wondered if whatever treatment they do before ceramic coating removes the rust.
Cheers

[James]

I got my M-T-P mild steel 6-3-1 manifold aluminium coated — that has stopped it from rusting and adds some insulating thermal qualities (I believe).

At least last time I looked it hadn't rusted.

Cost about £100.

[josh18]

Thanks James. Do MS exhausts tend to rust on the inside any way I wonder. I know the coaters could sand blast anything off the outside but wondered if they could do anything about the inside. I should just ask a coater hey.....

[James]

No idea — I wouldn't worry too much about the inside — where would the moisture come from? (condensation?)

[Clive]

Manifold the bit least likely to suffer condensation. It gets the hottest, plus no where for it to hide, unlike a box.....

And yes, huge amount of water is produced during combustion (ie exhausts on a cold day!) In fact, back of fagbox calc gives approx a gallon of water produced for every gallon of petrol.

[Paul64]

Indeed, 1 gallon for a gallon burned is what I heard too...
I suppose exhaust corrosion might be getting less now with the lower and lower sulphur levels in the fuel - I think it's sulphurous acid that's formed towards the end of the exhaust as the gas cools enough to allow the moisture to condense - not ideal!

Paul

[Jonny-Jimbo]

Agreed with most of the above, if the wrap isn't on then exhaust will be cooler and engine bay hotter. This will mean the gas flow is less too. On one exhaust I made a while ago I welded a stainless steel spike into the collector that would glow very hot, then heat the exhaust gas meaning if travelled even faster. But that was more for fun than anything.

In terms of the ceramic coating, I had a stainless steel exhaust I made coated white (bad choice, looks good until you touch it!!) I made the exhaust from port to tip including silencer box.

It was in a formula type car, and we ran the engine on the dyno and in the chassis a few times before having it coated, and it did definitely mean the car was cooler as a result. We did it from a packaging point of view, so hard to say what the actual gains were performance wise. But in the space of about 1ft cube we had the exhaust system, fuel filler, fuel tank and some of the other vehicle electrics.

We didn't blast the exhaust, we just took it to Zircotec and they did it all for us.

[josh18]

Thanks for that Jonny, very informative! If I get it coated I reckon I will get the "Jet hot" chrome llok ceramic coating done- just for bling.
From a performance standpoint I think wrapping or ceramic coating could have benefits on the non cross flow style engine in triumphs, as the incoming fuel is less likely to be too hot.
Cheers

[Jonny-Jimbo]

Agreed Josh, for a non-XFlow engine it should pay off well. As a general rule I say the following works best;

Stainless exhaust - heat wrap / ceramic coat
Mild steel - shielding / ceramic coat.

I wouldn't wrap a mild steel exhaust as it can soak up water and cause premature rusting.

We had a big issue with heat in our car - there was less than an inch between the exhaust and the fuel tank. I'd made the exhaust out of 0.9mm wall thickness 316 Stainless. It was all Tig welded, with no separable joins other than the tail piece on the silencer to repack it. When we went to noise testing we passed at 110dB(A)... the limit was 110dB(A). Spot on! But due to the wall thickness heat was an issue, and the pipes glowed red. It was fantastic.... glad I wasn't driving the thing though!!

[piman]

Hello Jonny,

Stainless steel is a poorer heat conductor than mild steel so retains more exhaust heat.

Alec

[Jonny-Jimbo]

That is true Alec, but we wanted to retain heat in the exhaust in our case. Well, in all cases you ideally want the heat to stay in the gas and not transfer to the pipe, but as that is physically impossible, we did out best to ensure we didn't cook the fuel tank etc.