Effective Bonnet Venting For Turbos

[toddlls]

id never thought about it that way. so the air coming in through the rad escapes throught the front of the bonnet meaning no air flows throght the rest of the engine bay?

and we also had the bonnet spaced up to clear the cooler piping so that didnt help.

No after air passes thru rad it then either travels down side of engine & downwards under the car by firewall or upward to the rear of the bonnet. My understanding is that it travels downward & under the car

[tk80]

mark and russ's 32 had the rear of the bonnet on their 32 raised and swore it helped. Anyone else think it actually works? or is the consensus rice?

**runs off to remove spacers from bonnet*

[Marlin]

it does work, but on my much lower powered car I elected just to remove the rubber seal rather than lifting the rear of the bonnet itself.

[Beer Baron]

I had a car (32 GTR) from japan with the rear of the bonnet spaced up. I thought it was a bit gay and everyone always thought my bonnet didn't close properly. when i got the chance I removed the spacers. temps definitely went up a bit. so yeah it's doing something. no doubt base of windscreen is a high pressure zone so maybe it's ingesting air through there and helping it force the other engine bay air (from the front bumper ducts) down the trans tunnel (which is where engine bay air escapes in a factory standard car with no bonnet venting)? I haven't studied it enough to know for sure but it's possible.

[tk80]

I had a car (32 GTR) from japan with the rear of the bonnet spaced up. I thought it was a bit gay and everyone always thought my bonnet didn't close properly. when i got the chance I removed the spacers. temps definitely went up a bit. so yeah it's doing something. no doubt base of windscreen is a high pressure zone so maybe it's ingesting air through there and helping it force the other engine bay air (from the front bumper ducts) down the trans tunnel (which is where engine bay air escapes in a factory standard car with no bonnet venting)? I haven't studied it enough to know for sure but it's possible.

function over fashion it is then.

i'll be the guy in the paddock with the riced up purple gtr. come and say hi.

[Beer Baron]

well the only other thing I'll say is russ and mark do test what they do. I'm sure if it wasn't working they would have put it back. I know average temps were noticeably higher when I removed my spacers without any other change.

if nothing else just give it a go. it costs practically nothing and takes only 20 min or so to remove and replace the bonnet. with some mates to help you can just fit one side at a time which is even easier. get a temp probe under there somewhere, or just log oil and water temps over a session, then do the same with/without the spacers. if results look good, keep it, if not back to standard and back to head scratching!

will definitely come say hi and then ask you if you realise that your bonnet is not shut properly... lol

[CameronBNR32]

how thick were the spacers you used? just washers on a longer bolt?

[Beer Baron]

from memory mine were about 15mm maybe 20mm and I think there were longer bolts too as I seem to remember when I removed the spacers the bolts were too long. washers and longer bolt are fine. if you find it's beneficial you can always machine up a neater looking spacer later on.