Heat wrap VS Exhaust coating

[Critical_Mass 10]

Hi all,

 

Ive gota 6 branch that either needs heat wrapping in one of the various fabrics you can buy. Or get the manifold sent off to be coated in ceramic. Now, can anyone tell me the advantage of getting the manifold coated over just wrapping it in fabric. I know the ceramic will last longer then the fabric, esp if it gets water or any other fluid on to the heat wrap fabric.

 

Ive just got a quote for £150 +VAT and postage to get the manifold ceramically coated, which is 4-5x the price the fabric will cost. So should i hold out to get get it coated or just go buy some heat wrapping?

 

Pros/Cons of each? apart from the price and how long it will last? Is it worth spending that much more on getting it coated in ceramic, or should i save my money cos there isnt that much of a difference when it comes to how each one handles the heat?

 

Any opinions/advice/experiences welcome.

[ProdigalSon 1]

IIRC from a similar conversation I had with Darren at G-Werks, if it's a stainless steel (tubular) manifold then ceramic coating would be safer because fabric can restrict the natural expansion of the metal as it gets hot, and as steel is more stiff/brittle than iron it is more likely to fatigue and crack...

 

Also, the ceramic coating will be on the inside, so the steel will not really get hot at all :D You can see YouTube vids of F1 engines with this treatment, and the engineer putting his hand on the exhaust manifold while blue flame is coming out the back! :shock:

 

If you have an iron (cast) manifold, then fabric wrap will be OK, because the iron is more malleable and less likely to fracture.

 

I'm pretty sure I remembered that right - but willing to be corrected :wink:

[Critical_Mass 10]

IIRC from a similar conversation I had with Darren at G-Werks, if it's a stainless steel (tubular) manifold then ceramic coating would be safer because fabric can restrict the natural expansion of the metal as it gets hot, and as steel is more stiff/brittle than iron it is more likely to fatigue and crack...

 

Also, the ceramic coating will be on the inside, so the steel will not really get hot at all :D You can see YouTube vids of F1 engines with this treatment, and the engineer putting his hand on the exhaust manifold while blue flame is coming out the back! :shock:

 

If you have an iron (cast) manifold, then fabric wrap will be OK, because the iron is more malleable and less likely to fracture.

 

I'm pretty sure I remembered that right - but willing to be corrected :wink:

 

Yeah heard that myself too. Im considering getting some spray paint specifically for exhausts instead of the fabric wrap after ive just had a conversation with my mechanic - and it is a ss manifold. I bought the manifold for £160 (same ones they had at stanford hall on one of the stalls, if anyone saw them) but the ceramic + VAT and postage is looking more like £200.

[boost monkey 0]

Why are you planning to spray a stainless manifold? :scratch:

 

Also, ceramic coating is nice but on a road car is there much point? It's stainless so it won't rust and unless you're getting under-bonnet temps which are really high (although I can't see how as the VR engine sats so far foward that the exhaust has tons of ventilation) i doubt it will help.

 

I'd also be very impressed if you can notice the difference after it has been done too.

[JMC 0]

I looked into getting one of the G-werks SS manifolds coated about a year ago. AFAI can recall, Darren said there was a reduction in heat coming off it, but you would not want to put you hand on the pipework (so not quite like the F1 stuff). With ceramic there will always be issues around stability long term. SS and ceramic expand and contract at different rates - ceramic is brittle and will have a tendancy to flake off eventually. There has been alot of work done on adhesion promotion, but even so. As a geeky scientist I love the idea of this stuff as a way of reducing under bonnet temps, but as most people will say 'does the cost justify it?'.

[Critical_Mass 10]

Why are you planning to spray a stainless manifold? :scratch:

 

Also, ceramic coating is nice but on a road car is there much point? It's stainless so it won't rust and unless you're getting under-bonnet temps which are really high (although I can't see how as the VR engine sats so far foward that the exhaust has tons of ventilation) i doubt it will help.

 

I'd also be very impressed if you can notice the difference after it has been done too.

 

I looked into getting one of the G-werks SS manifolds coated about a year ago. AFAI can recall, Darren said there was a reduction in heat coming off it, but you would not want to put you hand on the pipework (so not quite like the F1 stuff). With ceramic there will always be issues around stability long term. SS and ceramic expand and contract at different rates - ceramic is brittle and will have a tendancy to flake off eventually. There has been alot of work done on adhesion promotion, but even so. As a geeky scientist I love the idea of this stuff as a way of reducing under bonnet temps, but as most people will say 'does the cost justify it?'.

 

In really only wanting to keep the heat under the bonnet down tbh, but I cant justify spending £200. I would spend that amount getting it done if there was a huge difference between the coating and the fabric in regards to dealing with the heat. Not bothered about it being ss and painting it as youre not gonna see it much. Just want to keep the heat into it. I hear leaving it unwrapped is something you dont want to really do.

[ProdigalSon 1]

One alternative would be to rig a 'chimney' for the hot air, a la Subaru. Basically a pipe that has one open end in the upper part of the engine bay near the exhaust manifold, and the other end down near the exhaust tunnel in the chassis at the rear of the bay. The science is simple - at even reasonable speeds, the air passing over the mouth of the pipe underneath the car causes a low pressure zone, effectively sucking on the end of the pipe, so that at the other end, the hot air around the exhaust is 'hoovered' up and dumped under the car.

 

If you have flared ends to the pipe then so much the better, but just to check it works, get some flexi metallised ventilation ducting from a hardware store, rig it and put a regular desktop fan blowing across the lower opening under the car (to simulate the car moving forward) - sticking your hand at the end of the duct by the exhaust, you should feel the air being drawn down, like an upside-down chimney.

 

It won't do much at low speeds, but may just help in ventilating the bay that much better, and for ridiculously little cost! That would save you having to shell out on expensive ceramic coating, or lagging your SS manifold and risking damage...

[JMC 0]

I hear leaving it unwrapped is something you dont want to really do.

 

Now that is interesting, and again there seems to be different points of view :? . When I got my G-Werks SS one, I bought some wrap as I wanted to make sure the heat was kept in. Darrens point of view was that he would not guarantee it if it was wrapped. Apparently the SS ones are not as thermally resilient as the cast iron ones, and if you wrap them they can get too hot and be damaged :shrug: . Is there the facility to add heat shielding above the manfold on the VR6's as this might be a way to keep temps down. The other big thing would be to add an external oil cooler if you haven't got one already - would cost you less than £200 and would have a big effect.

[Dec 1]

One alternative would be to rig a 'chimney' for the hot air, a la Subaru.

 

Good thinking! 8) ......but I'd use the pipe the other way around. It's mainly going to be radiant heat from the manifold, so sucking air away from the area wont do a whole lot to reduce overall temperatures. But ducting cold air towards the manifold etc could be beneficial.

[ProdigalSon 1]

Is there the facility to add heat shielding above the manfold on the VR6's as this might be a way to keep temps down. The other big thing would be to add an external oil cooler if you haven't got one already - would cost you less than £200 and would have a big effect.

I did think of the heatshield, but because the VR6 is a crossflow design, it's not as though the inlet manifold is being heated up by close proximity (unlike my nice counterflow 8v! :roll:). The requirement seems to be keeping the engine bay cooler overall, not just shielding one hotspot, if I understood Critical_Mass. An oil cooler is a great idea to keep the engine temp down, but depending on placement, the air that passes through the cooler will end up in the engine bay anyway, so won't keep the bay temps down.

 

One alternative would be to rig a 'chimney' for the hot air, a la Subaru.

 

Good thinking! 8) ......but I'd use the pipe the other way around. It's mainly going to be radiant heat from the manifold, so sucking air away from the area wont do a whole lot to reduce overall temperatures. But ducting cold air towards the manifold etc could be beneficial.

Getting air into the bay isn't too hard, which is why the radiator is up front(!) Getting all that hot air out is more tricky, hence the position I suggested. If the Corrado had wing or bonnet vents as standard, this would be less of an issue.

 

Doing both the 'blow' (direct cool air onto the exhaust manifold) and 'suck' (pulling hot air out and under the car) chimneys might just be the perfect solution :wink:

[Dec 1]

Yup, the sucking idea could definitely be good for removing convected hot air from the engine bay! and is nice and easy to implement, as you suggested! 8)

[ProdigalSon 1]

Yup, the sucking idea could definitely be good for removing convected hot air from the engine bay! and is nice and easy to implement, as you suggested! 8)

After a few more thoughts I've realised that you've got a good point, Dec, that most of the heat from the exhaust manifold is radiated unless you paint it black, when more heat will be convected away from the surface, and the chimney may become more effective. Any which way, it'll probably cost you about £20, so no great loss if it doesn't work that well!

 

*thinks of making a quick trip to B&Q himself* :lol:

[ProdigalSon 1]

When I got my G-Werks SS one, I bought some wrap as I wanted to make sure the heat was kept in. Darrens point of view was that he would not guarantee it if it was wrapped. Apparently the SS ones are not as thermally resilient as the cast iron ones, and if you wrap them they can get too hot and be damaged :shrug:

JMC, have you thought of padding the thin space between inlet and exhaust manifolds with some heatshield to stop 'direct' transfer of heat, then perhaps doing the chimney thing? I was going to wrap my exhaust (even though it's the stock iron jobby) as my inlet gets too d*mn hot.

 

However, I have a phenolic gasket for the inlet to isolate it from the cylinder head (prime suspect for heat transfer), which will get fitted in the summer, so the heatshield idea is a bit of a second thought. Still tempted to try out the duct idea though.

[Kevin Bacon 5]

Wrapping is far better at reducing "radiated" heat than ceramic coating.

 

Ceramic coating is just the latest fad that's filtered it's way down from Motorsport but it's not quite the same spec or technology :lol:

 

A for the chimney thing, not a bad idea if you can get it close enough to the manifold, but the car already has massive air flow underneath which carries heat away with it, plus the air blasting through the radiator goes over the gearbox and also evacuates hot air.

 

One thing you can do is cut a section out of the bonnet seal strip by the wipers and air passing over the car will also suck air out through the gap.

 

Bonnet vents do the same job, but more effectively, but they're not pretty :lol:

[boost monkey 0]

Apparently the SS ones are not as thermally resilient as the cast iron ones, and if you wrap them they can get too hot and be damaged :shrug:

 

afaik, this is because the wall thickness of the s/s system is a lot thinner; if you keep the heat in this reduced wall thickness, the metal is more likely to distort (damage) as the heat will be transitioning the crystalline structure of the material at an atomic level.

 

Obviously, it might not transition by much, but insulating a piece of thin metal which is consistently as 300deg C (ish) doesn't sound great for longevity.

[boost monkey 0]

if you ask me, the whole engine bay needs STRICT THERMO TECHNIQUE!!111one. :lol:

 

*marks Page 2 with Thermo Sciences Flag*

[boost monkey 0]

I would like to comment on the ceramic coating but I am not in a position to do so. The only applications I have heard of are on piston crowns (which obviously get hotter than manifolds) and even then I haven't had experience of them. Hence the absence of suggestions :salute:

[ProdigalSon 1]

*shamed by brother's strict adherence to the principle of 'If I have no experience of something, I won't offer an opinion on it'* :oops: :oops: :lol: :wink:

[boost monkey 0]

mainly cos I am normally wrong :brickwall: :shrug: :ignore: :drinking:

[Critical_Mass 10]

:lol:

 

OKKKK..... So forget the heat WRAP, lets talk about the stuff in the aerosol cans you can buy, better then wrapping? As it will allow expansion of the metal - or will this just flake off?