Advantages of heat proof wrapping

[Tassie_Devil]

What are the advantages of using heat proof wrapping?

[graham bahr]

things not catching fire or melting are number one i guess!

there are lots of claims of increased power by keeping the heat inside the exhaust, but personnally i doubt it unless the intakes are being warmed up with radiant heat.

one thing i have learnt this year is that wrapping turbo downpipes with heat wrap is a waste of time, after only a few meetings the wrap falls apart and needs replacing

[Chris Y]

Theoretically, gas will flow faster when it is hotter. How this relates to practice is a little 'fuzzier'

[graham bahr]

agreed.

in all probability its only a few aplications when you would see power gains for such reasons.

i've never seen anysort of motorcycle, or F1 car for that matter with exhaust wrap.

i guess in some circumstances i.e a sytem thats a bit restrictive ,things may work better if the gasses are cooler and therefore taking up less space???

[greenamex2]

Yes gas will flow faster when it is hotter, but it is also occupying more volume so it has too!

It's good for stopping the coils in my starter motor melting so quickly though.

[phoenix]

On turbo engines keeping maintaining high exhaust gas velocity is very important as it is the energy in the gas that drives the turbo. High velocity in n/a engines adds to the kinetic energy in the gas and can improve cylinder filling during overlap, if cam timing permits.

Although F1 engines can't be seen to have 'lagged' pipes like us poor people use, there are other ways of keeping the heat in the exhaust - basicly the choice of material(s) used to fabricate the exhaust and the ceramics used to coat them.

And don't let me hear anyone say that ceramics don't insulate. Spot the difference between a space shuttle with all it's ceramic tiles, and one without all it's tiles.

[zefarelly]

I use it as my engines precrossflow, to try and keep the heat away from the carburettors, and if fuel where to spill maybe to avoid fire, but whether in reality it helps or not I don't know

1 thing I do know for sure is it makes your arms itch !

[graham bahr]

Originally Posted by zefarelly

I use it as my engines precrossflow, to try and keep the heat away from the carburettors, !

yes as i said earlier, i doubt it does anything unless it can keep the intake temps down, which it surely would with your pre x

[graham bahr]

[QUOTE=phoenix]On turbo engines keeping maintaining high exhaust gas velocity is very important as it is the energy in the gas that drives the turbo. QUOTE]

sorry but i dont buy it,

yes high exhaust gas velocity is important to a turbo, but wrapping the downpipe will do naf all, it might be a different case if you could wrap the manifold, but seeing as on my own turbo which has a wrapped downpipe and the wrap falls apart every few races i cant see a wrapped manifold on a turbo lasting a race distance.

in any case with a turbo its far more important to size the turbo correctly and get the whole lot well set up than to go chasing a few degrees of exhaust temp, i dare say the turbo itself will have a longer lifespan if allowed to run a little cooler by NOT lagging it

[graham bahr]

Originally Posted by phoenix

And don't let me hear anyone say that ceramics don't insulate. Spot the difference between a space shuttle with all it's ceramic tiles, and one without all it's tiles.

agreed, but they are also a couple of inches thick!

[BertMk2]

Exhaust wrap can also soak up oil that's spraying around your engine bay when the oil filler has come off - of course it then catches fire quite nicely. Not that that's ever happened to us of course

We haven't put the heat wrap back on and so far it doesn't appear to have made any difference, nothings melted so I guess temperatures under the bonnet are ok (except when it's on fire).

[phoenix]

[QUOTE=graham bahr]

Originally Posted by phoenix

On turbo engines keeping maintaining high exhaust gas velocity is very important as it is the energy in the gas that drives the turbo. QUOTE]

sorry but i dont buy it,

yes high exhaust gas velocity is important to a turbo, but wrapping the downpipe will do naf all, it might be a different case if you could wrap the manifold, but seeing as on my own turbo which has a wrapped downpipe and the wrap falls apart every few races i cant see a wrapped manifold on a turbo lasting a race distance.

in any case with a turbo its far more important to size the turbo correctly and get the whole lot well set up than to go chasing a few degrees of exhaust temp, i dare say the turbo itself will have a longer lifespan if allowed to run a little cooler by NOT lagging it

I wasn't talking about wrapping the tailpipe, of course, just the manifold.

The truth of whether it works or not is easily found on the dyno. And in our case it gives a measurable improvement. The difference to turbo life could be an issue, but if the turbo oil temperature is under control then it shouldn't be.

[graham bahr]

Originally Posted by phoenix

I wasn't talking about wrapping the tailpipe, of course, just the manifold.

be.

yes but what i'm saying if you wrap the down pipe immediatly after the turbo the heat destroies it in no time, so wrap on the manifold which might do so good wont last anytime at all.

in anycase i just cant see it making any real difference unless you have radiant heat problems either melting stuff or heating up the intakes.

over the last two years i have had many indepth conversations with turbo technics who have built my turbos, and emerald who make and set up the management ecu's that i use, i have learnt much and lots of effort has been put into development, the one thing neither company have suggested or spoken about as a way to improve things is heat wrap.

[R59]

Originally Posted by Tassie_Devil

What are the advantages of using heat proof wrapping?

Stops (a) my starter motor from cooking
(b) my left leg from burning (and the paint on the gearbox tunnel)

Regardless of the wonderful effects of hot gases through cooler pipes.

And there is that clever coating process that's supposed to work well too (a ceramic coating).

Rob.

[graham bahr]

Originally Posted by phoenix

but if the turbo oil temperature is under control then it shouldn't be.

agreed until you either turn the thing off, or end up stranded in a gravel trap with a stinking hot engine and turbo and no oil circulation.

fortunatly i dont do that too often, well not here in the uk anyway,

french gravel traps well thats another matter!

[R59]

You're not digging yourself into a hole again are you Graham?

The subject of turning off engines with red hot turbo's - does the heat wrap make matters better or worse? Does it keep the heat in the exhaust side of the turbo, making it hotter for longer, drying out the bearings?

Or does it help dissipate the heat, reducing the above effect?

Something that's always made me wonder about the merits of wrapping turbo's, other than to keep their "exterior" cool in the event of a fluid (flammable type) leak.

Rob.

[phoenix]

Originally Posted by graham bahr

over the last two years i have had many indepth conversations with turbo technics who have built my turbos, and emerald who make and set up the management ecu's that i use, i have learnt much and lots of effort has been put into development, the one thing neither company have suggested or spoken about as a way to improve things is heat wrap.

Well either you listen to people - or you find out for yourself. The choice is yours, of course................

I am a true believer in empirical data.


BUT I never suggested that you wrap the exhaust after it leaves the turbo as there will be no positive effect, so long as your tailpipe is the correct diameter.

[Cameron Winton]

Very dubious about heat wrapping. The exhaust side of a turbo is a turbine. Turbines convert the momentum of a fluid into rotational momentum of the turbine. The momentum of an engine's exhaust gases is created by the exhaust stroke. So temperature has nothing to do with it. The only feasible advantage is that by running the gas at a higher temperature is that it will have lower density & viscosity hence losses in the manifold could be lower. However, the momentum imparted is dependent on mass flow therefore any advantage gained from reduced losses is probably more than offset by the loss of momentum imparted onto the turbine.
Perhaps the empirical data discussed was down to different environmental conditions or the heat wrap reducing under bonnet air temps giving a lower intake charge temperature.

[graham bahr]

looking at the just how small the internal bore of the turbo is just before the exhaust gasses meet the turbo, compaired to the bore of the manifold branches i would say is an area reduction of about 80% which would substancially speed up the gases just like a carb venturi, i am now in even more doubt that wrapping the manifold would do any good, and still we have the problem that heat wrap cant take the heat produced by turbo manifolds for more than a very short time period

[Al Weyman]

I thought and as I have read, the whole idea of the wraps is simply to reduce underbonnet tempratures thus assisting a cooler intake charge. In the same way as the chevy race intake manifolds have appertures to allow cooling. Also agree with Rob about the heat soak to the starter motor as I am suffering that at the moment even with a brand new Hitachi super magnet mini motor.

[dtype38]

Agree with Al, but I can't be so sure that there isn't some real gas momentum characteristics going on somewhere. Absolutely, if you are drawing carburettor air from underbonnet and you have a fairly restricted underbonnet airflow (eg dirt track racers and the like) then keeping underbonnet heat in the exhaust will make a noticable difference to power. There is, however, a physical difference in the exhaust itself caused by hotter, lower density, higher velocity gas. To be honest, I can't be arsed to get out my fluid dynamic text books to work it out, but intuitively I'd guess that it increases the resistance of the exhaust to gas extraction due to higher frictional losses but increases the gas momentum (same mass flow, more speed). The former is bad that latter is good. So in back to back tests I'd be looking for a wrapped exhaust to improve mid range torque (cos of increased extraction from the higher exhaust momentum) and lower top end power (cos of increased flow restriction due to the higher velocities).

Spookily enough, I fitted a much higher flow head to my car (same cams, no turbo) and wrapped my manifold and exahust. I got masses more mid range torque but no more top end power..... If only I could be bothered to take the wrap off and retest, we might have a conclusive answer

PS anyone think their car sounds noiser/quieter with the wrapping on?

[dtype38]

The carb and cam discussion which was ongoing from here has been separated into a separate thread called "Carbs and Cams".... or it might be "Cams and Carbs". Whatever!

[graham bahr]

Originally Posted by dtype38

PS anyone think their car sounds noiser/quieter with the wrapping on?

as tubular headers transmit noise quite readily i would of thought they would quieten things down in the engine bay a bit, i might of even noticed it, but then was it sycalogical ( this thing needs a spell check!!!!)

[Al Weyman]

Spell check would help you grahame as you have to at least start it off with the right letter (P)

[dtype38]

Or even wouldn't help him Al

Anyway, I wasn't thinking about the engine bay, more the area where the man at the track sticks his meter.