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Registered:
November 2002
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 Reducing under bonnet temperatures????
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Mon, 05 April 2004 12:36
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Hi all,
I'm interested to know what people have done to reduce under bonnet temps?
I already have my turbo manifold, snail and dump HPC coated which has helped alot.
BUT, the engine bay itself still gets too hot.
I'm thinking of fitting some sort of stainless or alloy sheet around the engine bay near the turbo and maybe some insulation type gear on one section under my bonnet. I don't like the idea of wrapping the manifold etc with anything.
What have you done? Got any pics?
It has to look right as well....
thanks,
Simon
TA22 GT
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: Reducing under bonnet temperatures????
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Mon, 05 April 2004 12:53
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Yep, put a big stainless shield over the turbo and manifold.
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Location:
Newcastle NSW
Registered:
June 2002
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Re: Reducing under bonnet temperatures????
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Mon, 05 April 2004 14:40
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im assuming youve got a TA22 have u taken of the deflector plates from underneath the bonnet vents? that does help vent hot air. 
OR
raise the rear of your bonnet 5-8mm this is more effective but has the downside of allowing the hot engine bay air into the cold air intake of your interior ventilation system 
and aluminium is a better material for heat sheilding as it transfers the heat away more than 5 times faster than stainless 
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Location:
Terrigal
Registered:
May 2002
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Re: Reducing under bonnet temperatures????
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Mon, 05 April 2004 23:05
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I got some head sheild material same as used on the Ford XR6 turbos. It works wonders! Was $50 for a sheet from ACL.
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Location:
South Australia
Registered:
July 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 02:29
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Don't those heat shields tend to end up reducing the lifespan of the turbo manifolds etc as they end up running alot hotter?
Aside from ceramic coating all the above mentioned parts that you have already coated, I would imagine getting some vents possibly in the bonnet to get some air flow out of the engine might help...getting a bonnet scoop is next to useless for reducing under-bonnet temperatures.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 02:34
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cut some speed holes...
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Location:
Brisbane
Registered:
May 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 04:07
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Heat wrap can reduce the lifespan of your manifolds, NOT heat shields. The former keeps heat inside the manifold, the latter simply deflects the heat and prevents it from affecting other parts of the engine bay.
I agree with Witzl, adequate ventilation is the way to go if you have heatsoak issues.
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Location:
South Australia
Registered:
July 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 05:23
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So if a heatshield simply deflects heat, then don't the underbonnet temperatures remain the same? I guess the theory behind them would be to change the distribution of the heat? Ie keep heat away from the intake side of the engine bay or something like that?
(just trying to learn something here  )
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Location:
Bundaberg, Qld.
Registered:
May 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 09:42
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| Alainve wrote on Tue, 06 April 2004 00:40 |
im assuming youve got a TA22 have u taken of the deflector plates from underneath the bonnet vents? that does help vent hot air.
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engine bonnet vents and extraction scoops are good. i remember the vents in the bonnet of my 260Z, you could see the heat coming up out of them when stopped at the lights etc.
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I supported Toymods
Location:
sydney.au
Registered:
August 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 09:57
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my drop vent carbon hood has made the temps drop SO much
the strutbrace used to be too hot to touch after a good fanging
now i can grab and hold it! 
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Registered:
November 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 13:18
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Thanks guys,
Given that my car is at a show standard and at full GT specs, raising the bonnet a little or cutting vent holes is not an option for me.
Maybe removing the bonnet vent deflector plates will make a difference.
Also I might try getting some of the alloy sheet TurboRA28 has used, but I will porbably sit it close to teh engine bay itself rather than over the manifold as too much work has gone into making it to cover it over
What about sticking some insulation type material under the bonnet itself, similar to that of a new commdore bonnet etc?
Cheers,
Simon
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I supported Toymods
Location:
sydney.au
Registered:
August 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 13:29
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running a aluminium pan under the cars sump area to lift air coming under the car through the engine bay is also a thought...
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Location:
Newcastle NSW
Registered:
June 2002
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Registered:
November 2002
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Re: Reducing under bonnet temperatures????
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Tue, 06 April 2004 14:08
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I spent way too much time and effort on panel alignment and getting a very straight body to justify raising the bonnet.
It just wouldn't look right.
Good idea about the bonnet seal, I'll definately do that.
I understand about the bonnet and sticking something under it. The main reason for this is to stop the paint gettign so hot just above the turbo manifold all the time. Before the ceramic coating was done I could physically see the bonnet buckle slightly through heat distortion.
Cheers,
Simon
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I supported Toymods
Location:
Perth WA
Registered:
May 2002
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Re: Reducing under bonnet temperatures????
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Fri, 09 April 2004 13:56
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After you raise the back of the bonnet or remove the rubber bonnet seal, check where the air is flowing while you are driving by doing some wool tuft analysis. Just sticky tape a piece of light wool onto the trailing edge of the bonnet. If it flies up - looks like air is coming out from under the bonnet. If it gets sucked into the engine bay, air is likely to be going in.
The area at the base of the windscreen is a high pressure area and at speed air may go INTO the engine bay. This may sound OK, but it may also reduce the airflow into your engine bay through the radiator / intercooler. I'm sure bug companies like Toyota would have not put in that bit of bonnet rubber sealing if it didn't do anything (they could save a few bucks).
I took it off anyway, because it does reduce underbonnet temps when the car is going slowly / in traffic (checked with underbonnet thermocouple over the turbo).
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Location:
Newcastle NSW
Registered:
June 2002
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Re: Reducing under bonnet temperatures????
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Fri, 09 April 2004 14:26
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nissan must have done some research on this as my Datto 280C has a similar setup stock to allow venting of the engine bay into the slightly lower pressure zone at the rear edge of the bonnet at the side so it acts more like a venturi to suck the air out not suck it in. plus the high air pressure inside your engine bay is more than enuf to overcome the high pressure at the base of your windscreen.
someones done their research
http://www.club4ag.com/faq%20and%20tech_pages/more %20on%20cooling.htm
i think the reason they put that seal in is to stop the hot air from reaching the cabin thru the vents there but if you dont mind a bit of hot air what the heck i say
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Location:
brisbane
Registered:
March 2003
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Re: Reducing under bonnet temperatures????
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Sun, 11 April 2004 10:16
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just put a gt4 bonnet scoop on it.. from the late model ones with the big hole in it
then fill the hole with a fine mesh
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Location:
Melbourne
Registered:
August 2003
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Re: Reducing under bonnet temperatures????
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Fri, 16 April 2004 11:29
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| Quote: |
The main reason for this is to stop the paint gettign so hot just above the turbo manifold all the time. Before the ceramic coating was done I could physically see the bonnet buckle slightly through heat distortion.
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Do you think your problem is convection or radiation?
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Registered:
November 2002
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Re: Reducing under bonnet temperatures????
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Fri, 16 April 2004 12:32
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Whats your point about radiation or convection??
How are you going to get convection from the turbo to the bonnet?
Simon
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Location:
melbourne
Registered:
September 2003
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Location:
Newcastle NSW
Registered:
June 2002
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Re: Reducing under bonnet temperatures????
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Fri, 16 April 2004 17:19
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shindeokure-
ever driven in the rain?
if they wanted to keep the engine bay dry the radiator and everything would duct around it and the engine would be enclosed in many shrouds and other crap 
and how exactly is the bonnet going to go thru the windscreen when its bolted down in the same way as any other bonnet?
not flaming just interested in your theory
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Location:
Melbourne
Registered:
August 2003
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Re: Reducing under bonnet temperatures????
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Sun, 18 April 2004 04:34
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| TA22 GT wrote on Fri, 16 April 2004 22:32 |
Whats your point about radiation or convection??
How are you going to get convection from the turbo to the bonnet?
Simon
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Ideas like raising the bonnet, venting it or removing seals will reduce under bonnet temperatures by removing hot air. This will lower the ambient temperature in the engine bay...
BUT
If you're concerned with the effect of concentrated heat on a portion of the bonnet above the turbocharger that's got little to do with hot air or convection (like a fan heater), it's got more to do with radiation (ie. like a bar heater).
The radiated heat from the turbo exhaust is heating the surrounding air *and* the bonnet. Removing the warm air will not stop the radiated heat warping the bonnet! You need to look at protecting against the radiated heat, maybe with reflective-backed insulation sheets on the underside of the bonnet or a turbocharger heat shield (which you didn't want to do because your manifold has wank factor).
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Registered:
November 2002
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Re: Reducing under bonnet temperatures????
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Sun, 18 April 2004 07:04
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I have just fitted the ACL heat shield. I agree thats the only way to really reduce heat from the bonnet.
And yes, in the end I did make a cover over my manifold.
Its made a huge difference.
Raising the bonnet etc is not an option and I'm sure anyone with a car of show standard would understand why I don't want to do that.
Simon
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Location:
Melbourne
Registered:
August 2003
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Re: Reducing under bonnet temperatures????
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Sun, 18 April 2004 08:40
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Personally I agree that realigning the body because your turbocharger is hot sounds like a lousy idea.
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..i'd also be worried about the bonnet going through the windscreen (unless you have a cf/frp bonnet).