Wrapped headers
Discussion
Hot weather again so under bonnet temperatures on my Monaro are higher than I would like. It’s always been a problem but I keep forgetting to do anything about it. One option is to get the headers wrapped or coated but the latter is a faff and can take ages.
Heard mixed reviews on whether wrapping exhaust headers is a good idea on a road car. Any practical experience or advice?
Thanks.
Heard mixed reviews on whether wrapping exhaust headers is a good idea on a road car. Any practical experience or advice?
Thanks.
Considered wrapping on my racing car but read some horror stories about the long term effect on the exhaust material from being insulated and running hotter than usual leading to cracking and earlier failure etc. As well as some stories of underbonnet fires caused by hot air managing to find its way out at a certain place in the wrapping and causing a lot of heat in a small area.
I didn't investigate it in too much detail after this but it seemed plausible and it put me off enough that it might lead to some unintended consequences.
Coating sounded like a better option, but like you say a bit of a faff and more expensive.
I didn't investigate it in too much detail after this but it seemed plausible and it put me off enough that it might lead to some unintended consequences.
Coating sounded like a better option, but like you say a bit of a faff and more expensive.
wormus said:
Hot weather again so under bonnet temperatures on my Monaro are higher than I would like. It’s always been a problem but I keep forgetting to do anything about it. One option is to get the headers wrapped or coated but the latter is a faff and can take ages.
Heard mixed reviews on whether wrapping exhaust headers is a good idea on a road car. Any practical experience or advice?
Thanks.
Wrapped or coated headers can reduce local radiative heat problems, but won't make much difference on general under-bonnet air temps. The real solution is to make sure the hot air can get out, and that it can be replaced by cool air coming in somewhere. In certain cases, specific "chimneys" have been used to vent hot air off the exh manifolds and cats up and out the bonnet. In that case, the exhaust line is usually encased in a heat shield and the top of that shield vented up and out a suitable bonnet ventHeard mixed reviews on whether wrapping exhaust headers is a good idea on a road car. Any practical experience or advice?
Thanks.
Heat wrap is largely crap, and wrapping metal parts to keep heat in will lead to premature ageing/cracking/failure of the metal
How badly will depend on how many hot/cold cycles and hoe often it is used etc.
But as Max says...allowing the heat to escape is the easiest option. That may require bonnet venting of some sort, placed in a low pressure area to help draw air out.
Modern cars like sealing their cars up everywhere, tight panel gaps including around the bonnet area
How badly will depend on how many hot/cold cycles and hoe often it is used etc.
But as Max says...allowing the heat to escape is the easiest option. That may require bonnet venting of some sort, placed in a low pressure area to help draw air out.
Modern cars like sealing their cars up everywhere, tight panel gaps including around the bonnet area
k all for under bonnet temps. I like the idea of those chimneys though.Pericoloso said:
Are those "chimneys" an Aston part or added later ?
Std/OE partsThe header and cat assy'd are clad in the usual metalic (sand filled) formed heat shield material, and have the chimney stuck on top. When the bonnet is shut, hot air thermo-syphons up the chimneys off the mani/cats and out the bonnet vents and cold air is pulled in a matching set of holes in the engine undertray that align with the lower skirt of the downpipe cladding.
Stopping after a good thrash in a hot climate, you could easily grill bacon on the bonnet vents!
ETA:
iirc, the chimneys were not carried on to any other Aston vehicle beyond the original Vanquish, as testing proved they were not actually needed. They were put in place on that car as a "just in case" because there was a concern raised about heat soak damaging the bonding glue used for the aluminium chassis. However, later test and measurement proved that the ally chassis was actually just as good at conducting away engine bay heat, so the actual bond temperature was effectively low enough to not be a concern.
( that's my memory of it, but bear in mind it's nearly 20 years ago now, so i might be wrong..... ;-) )
iirc, the chimneys were not carried on to any other Aston vehicle beyond the original Vanquish, as testing proved they were not actually needed. They were put in place on that car as a "just in case" because there was a concern raised about heat soak damaging the bonding glue used for the aluminium chassis. However, later test and measurement proved that the ally chassis was actually just as good at conducting away engine bay heat, so the actual bond temperature was effectively low enough to not be a concern.
( that's my memory of it, but bear in mind it's nearly 20 years ago now, so i might be wrong..... ;-) )
Going back to the original question about first hand knowledge of exhaust wrap problems. Two specific cases come to mind.
1)Early 90s we tuned a Pinto engine in a Capri with twin Webers etc. Took heat wrap off and gained 4 bhp at wheels, we have seem similar on Pinto engined Escorts on a few occasions since.
2) late 90s Std Race spec MGB GT, running std cast iron ex manifold. Customer heat wrapped ex manifold and down pipes. Towards end of season he decided to fit his spare engine so he could finish the season with fresh power. He contacted us and informed me the 'new' cylinder head was faulty as the manifold studs didn't line up with the ex manifold. Turns out the ex manifold pinged in about 6mm when it was levered off the head! Replacement ex manifold solved the problem and the customer went on to win his cllass championship.
As Max Torque says, keep the exhaust heat separate from the inlet manifold and carb, a physical barrier seems to work best. Ally plates work well. Always make sure, if they were std fitment, to keep the carb heat shields where they should be and not in a spares box.
Peter
1)Early 90s we tuned a Pinto engine in a Capri with twin Webers etc. Took heat wrap off and gained 4 bhp at wheels, we have seem similar on Pinto engined Escorts on a few occasions since.
2) late 90s Std Race spec MGB GT, running std cast iron ex manifold. Customer heat wrapped ex manifold and down pipes. Towards end of season he decided to fit his spare engine so he could finish the season with fresh power. He contacted us and informed me the 'new' cylinder head was faulty as the manifold studs didn't line up with the ex manifold. Turns out the ex manifold pinged in about 6mm when it was levered off the head! Replacement ex manifold solved the problem and the customer went on to win his cllass championship.
As Max Torque says, keep the exhaust heat separate from the inlet manifold and carb, a physical barrier seems to work best. Ally plates work well. Always make sure, if they were std fitment, to keep the carb heat shields where they should be and not in a spares box.
Peter
I have bonnet vents added to my V8S and it dumps out a tremendous amount of heat and drops the engine bay temperatures dramatically. I previously had the headers wrapped, and it did cool things down quite a bit and muffled the engine too. But it doesn't last long and eventually falls off. I added ceramic paint (on the outside only) and that didn't seem to make much difference apart from making things look a bit smarter.
My old E30 engine conversion liked to overheat at low speeds, track days, pulling off the motorway after high speed etc. I wrapped the manifold but that didn't really help much even though subjectively you couldn't feel anywhere near the heat coming off them.
What did solve the problem for everything but track days was putting back as much of the factory plastic bits around the radiator as would still fit. That really was night and day. Bigger rad fixed the track days problem.
I have to say all my messing around with that car did give me a newfound appreciation for factory plastic bits in general...
What did solve the problem for everything but track days was putting back as much of the factory plastic bits around the radiator as would still fit. That really was night and day. Bigger rad fixed the track days problem.
I have to say all my messing around with that car did give me a newfound appreciation for factory plastic bits in general...
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