Where to put bonnet vents on a turbo NA?

speed · Postby **speed** » Mon Sep 12, 2016 6:37 pm

So I'm getting a replacement bonnet with the idea to cut vents in, manly because I like the look of it but also to extract some heat from the turbo.

Really like the look of the one below but not sure if that will cause any negative effects.

Would appreciate your opinions and advice on something that both looks good and has function.

Hoping to not cut the frame because road car which will limit designs but happy to reinforce if that still keeps me legal.

Would prefer the louvered look as opposed to sticking vents on but open to suggestions.

Thank you!

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Magpie · Postby **Magpie** » Mon Sep 12, 2016 7:18 pm

Charlie91's bonnet did very well for him, however Charlie did cut out all the bracing from memory.

bruce · Postby **bruce** » Mon Sep 12, 2016 7:28 pm

Go the Singular vents, or copy them. U jigsaw the slots into ur bonnet and bend each one.

zossy1 · Postby **zossy1** » Mon Sep 12, 2016 8:19 pm

http://gwracing.altervista.org/how-to-l ... a-pro.html

Odd · Postby **Odd** » Mon Sep 12, 2016 9:58 pm

Have you investigated ceramic coating?
Seems logical to retain heat in the exhaust system and spit it out the back....rather than retain heat in engine bay and try to vent hood for it to escape?

davekmoore · Postby **davekmoore** » Mon Sep 12, 2016 10:59 pm

Here's your NA hood/bonnet pressures to help with where vents should go. Singular Motorsports used a similar pressure map to help them design their vents which are on my NB turbo. Their louvres/louvers also have what they describe as the correct aero design to act as extractors. I'll let you know how well they work as summer comes along and I get the rest of the car working properly and the motor pulling as it should in higher temps.

NA hood pressures.jpg

Bear in mind that at least one of the aims of the vents is to reduce under bonnet pressures so air can flow in through the radiator and out of the vents instead of building up more and more pressure with nowhere for the air to go, which then blocks the rad. Helping the air flow through will also reduce front end lift. People have experimented with vents, even "chimneys", directly above the turbo, but the consensus always seems to be to do something like the Singular ones. Theirs just aren't the cheapest option. This is the cheapest option:

IMG_7275.JPG

and it works. Loan of bonnet courtesy of lightyear.

Similar one with Mini Cooper centre vent and no shark bite available for sale @ $200 (the Mini bit cost $350):

IMG_9399.JPG

davekmoore · Postby **davekmoore** » Mon Sep 12, 2016 11:24 pm

....... and of course you could also try to copy what Mr Beavis will eventually get round to showing us with his venting/aero/cooling/downforce package, much of which I suspect won't even be visible unless the bonnet is up. Wouldn't be surprised to see an extra radiator/intercooler/motor in the boot either. To paraphrase another poster and David Bowie (on Lou Reed), Brendan is displaying levels of cool never previously believed to be possible by humans.

speed · Postby **speed** » Mon Sep 12, 2016 11:24 pm

Thanks Mark, Bruce, Chris, Odd and Dave for your responses.

Chris I really appreciate the link. Will have to do more reading and must get some of those pliers.
Do the minus numbers equate to lower pressure zone? I clearly have no idea.

Dave, I appreciate the theory and pics. Especially this part;

"at least one of the aims of the vents is to reduce under bonnet pressures so air can flow in through the radiator and out of the vents instead of building up more and more pressure with nowhere for the air to go, which then blocks the rad. Helping the air flow through will also reduce front end lift."

This sounds far more important then extracting heat from the turbo area.

I'd happily buy a vented NA Bonnet for $200 but obviously a NB one won't fit.

Most people seem to cut into the frame. Can I still vent it by getting "close enough" to the magic spots?
My very basic thinking is convincing me that close enough is better than none at all. Is this wrong?

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speed · Postby **speed** » Tue Sep 13, 2016 12:17 am

Just read Chris' post properly and checked out the links.
I now understand where the low pressure zones are. Not quite sure how to go from low pressure on top to high pressure underneath without some sort of ducting but I guess the low pressure on top is a start

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Postby **NitroDann** » Tue Sep 13, 2016 12:39 am

You just cut a hole.

bear2230 · Postby **bear2230** » Thu Sep 22, 2016 11:56 pm

Here is my Bonnet that I just finished. Just need a car to put it on

B1.jpg

speed · Postby **speed** » Fri Sep 23, 2016 8:41 am

bear2230 wrote:Here is my Bonnet that I just finished. Just need a car to put it on

B1.jpg

Looks good Richard, will have to come check it out. I've been meaning to come to see you for like forever now!
I now have a nice white spare bonnet to cut up

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Postby **beavis** » Fri Sep 23, 2016 7:15 pm

These pics might help.
Position the vents forward of the front wheels or you wont be adding much of a benefit. These vents work, they evacuate air from the engine bay, I have video of wool tufts fluffing in the wind so visualise it.
In this case the hole was cut with a grinder, and the sections that were removed formed the 'vanes'.

speed · Postby **speed** » Fri Sep 23, 2016 9:27 pm

Thanks Brendan. Will be sure to place in front of wheels. Now I'm not sure if I try to cut out shark gills or just the sections and stick a vent in underneath.
Would I still be fine to forget the middle one and just do the sides?
I figure it's better than none at all but then since I'm there...

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