DIY bonnet vents...how do I?

deviant · Postby **deviant** » Thu Mar 31, 2011 11:05 am

My turbo NA is suffering with some serious heat soak under the bonnet when I have been on track which makes hot starting and idle almost impossible. Normally I come off track and open the bonnet ASAP and leave it up until the next session but as soon as I drop the bonnet the heat just builds up super quick again and I have to hold 1800RPM just to keep it running.

I have got a better CAI kit on the way which should help with it sucking in cool air but I am also thinking a vent placed over the turbo area might help....the heat can just rise straight up through the vent and hopefull on the move air will be drawn past the turbo.

So how does one choose a vent and how do you install it? Would something like this suit: http://cgi.ebay.com.au/UNIVERSAL-BONNET ... 2561d67b4b

Am I risking omething like that melting / catching fire? The turbo is bright orange and almost white in a few spots when I come off the track!

I guess that to install it is 5 minutes with an angle grinder and 5 minutes with a dremel to tidy the hole and pop it in?

Hammer · Postby **Hammer** » Thu Mar 31, 2011 11:32 am

Read this thread - viewtopic.php?f=28&t=35048 - before cutting holes on your bonnet.

Placing vents in the wrong place could have the opposite effect to what you want.

mr2 spyder · Postby **mr2 spyder** » Thu Mar 31, 2011 2:25 pm

I made a bonnet mould for the early mx5[with pop up lights.with a vent behind the radiator. this was used on WAX 4u,s show drag car.I have a carbon section of the vent area. that could be fitted in place on a standard bonnet and riveted on. I could dig it out and email pics if you are interested?

deviant · Postby **deviant** » Thu Mar 31, 2011 2:57 pm

Hammer wrote:Read this thread - viewtopic.php?f=28&t=35048 - before cutting holes on your bonnet.

Placing vents in the wrong place could have the opposite effect to what you want.

Thanks for the link. Lots of reading to be done off of that and the further I went the more links I found!!

mr2 spyder wrote:I made a bonnet mould for the early mx5[with pop up lights.with a vent behind the radiator. this was used on WAX 4u,s show drag car.I have a carbon section of the vent area. that could be fitted in place on a standard bonnet and riveted on. I could dig it out and email pics if you are interested?

That would be great if you could do that! Cheers :beer:

dave2221 · Postby **dave2221** » Thu Mar 31, 2011 3:05 pm

i call them speed holes

mr2 spyder · Postby **mr2 spyder** » Thu Mar 31, 2011 3:38 pm

PMd. also have a fibreglass r34 style vent[3rowsof vents] if you are really serious about getting air out of there.? the carbon one has a lot deeper scoop to catch more air from under the bonnet. although this could be trimmed down. it worked well on wax4us.

deviant · Postby **deviant** » Thu Mar 31, 2011 4:45 pm

Responded to your email.

All the heat must be from the turbo area but I guess anything that can move air through the engine bay is going to help!

mr2 spyder · Postby **mr2 spyder** » Thu Mar 31, 2011 5:39 pm

wax4us was turboed and it keeps the intercooler cooler cooler.

rossint · Postby **rossint** » Thu Mar 31, 2011 9:55 pm

You should think about ducting some air onto the turbo as well in an effort to cool it down.

deviant · Postby **deviant** » Fri Apr 01, 2011 12:14 am

dave2221 wrote:i call them speed holes

Speed holes ayyyy...

rossint wrote:You should think about ducting some air onto the turbo as well in an effort to cool it down.

From what I can gather looking at other threads and the research people have done, right above the turbo is one of the worst spots aerodynamically for a vent...having said that the research I have read all seems to be about getting air through the radiator and out of the engine bay; a vent in front of the hump on the NA bonnet seems to be the spot to go for. No doubt it would not harm to have a greater flow of air through my intercooler and radiator but I think I seriously need somewhere for the heat from the turbo to go, preferably via the shortest route possible.

A scoop is surprisingly not very effective at getting air in to the engine bay so it needs to be a shaped vent of some sort that is going to be drawing air and heat out.

mr2 spyder has shown me a couple of very tasty ideas that I am mulling over which would put a vent in front of the hump....just need to be sure it is going to help with letting hot air vent out from the turbo area.

rossint · Postby **rossint** » Fri Apr 01, 2011 12:36 am

I'm talking about ducting cold air from somewhere like the bumper to the turbo to cool it, as well as venting to get rid of the heat under the bonnet. Probably not the best example but the scoop on the hood of my Forester is mainly to feed air through the intercooler but also has a small duct on one side that directs air straight onto the turbo.

bruce · Postby **bruce** » Fri Apr 01, 2011 10:55 am

Yup, the bonnet scoop in all WRXs, Libertys, Foresters have two sections - the main part for the cooler, and a section which leads down to the turbo (and I think something on the engine to duct the air to turbo).