do you like my bonnet vent?

[mitzitech2007]

uploaded/50343/1221922758.jpg

this is my plan for a bonnet vent to help get some cold air into a custom air box i am planning to make but the question is do you think it looks good?
:thinking2

[Nick Mann]

It doesn't look ugly, but I don't think it looks good. I personally am not a fan of vents, simply because of the loss of stealth, but I understand the functionality of it! It looks like it may be too far back and not offset enough though?

It looks better than some vents I've seen on VR4s!

[Physician]

Beauty is in the eye ...............

I think it looks OK but it's certainly a good idea to get more airflow - the standard system sucks :)

[mitzitech2007]

its not fitted yet. all i have done is rested it where it would best fit the airbox and took a pic then blurred around the vent!

[Davezj]

persanally i am not a great fan of bonnet scoops unless they are symetrical.

i take it by the placement of the vent you are going to use the original air box. if so i don't see any benefit of getting air from the bonnet instaed of or as well as the front grill of the car. the standard turbos boost to 0.55bar in a auto prefacelift and getting a bigger opening to the out side will not make any difference to the boost level as this is controlled by the wastegate of the turbos. the standard air box does a good job as it is.

However if you are fitting the bonnet vent just to get more cold air under the bonnet to cool the under bonnet temp then yes i can see the benefit.

you might want to lift the rear of the bonnet slightly to give an escape route for the extra air as well or remove the black rubber stip alog the back of the engine bay under the windscreen, as this will have the same effect as the bonnet lift, and still look stock.

[Nick Mann]

the standard turbos boost to 0.55bar in a auto prefacelift and getting a bigger opening to the out side will not make any difference to the boost level as this is controlled by the wastegate of the turbos.

Yes but no but.....

Easier airflow can allow for several beneficial side effects. The obvious one is that the turbos are not working so hard to achieve the 0.55 bar boost, which means better efficiency on the turbo, which means less heating of the air travelling through the system. Colder air in the piston equals higher density, which means more fuel and therefore a bigger bang.
A bit more tenuous would be that if the wastegate opens more for the same inlet pressure (Turbos working less hard) then there is a slightly easier gas flow through the turbo, allowing a free-er flowing exhaust.
Maybe a bit more tenuous would be that the higher efficiency of the turbos could potentially give boost pressure at lower revs than previously. This is potentially a huge performance increase without increasing maximum boost pressure, but as to how much just giving a better scoop would make I am not sure.

Hope that I have explained that well enough? I'm not saying there will be huge advantages, but there should be improvements to be had by removing restrictions in any part of the air flow system, even if the ultimate pressure achieved is the same.

[mitzitech2007]

i have to agree with nick there should be a performance increase as im already running a boost controller, de cat and cat back system so hopefully should pickup better, im also hoping to make a custom air box to help keep air temp down and more direct/less restrictive air flow. i might still use the original box its just i dont like the idea of the air intake resting on top of the radiator with all that hot air at lower speeds about!

[pitslayer]

needs to be more over to the right as we look at it now, similar to what i want to do with mine

[ANTHONY]

very similar to the ones Derek had on his old car but he had two either side but more towards the wings. but i do like it

[bradc]

http://www.autospeed.com.au/cms/A_2159/article.html
http://www.autospeed.com.au/cms/A_2160/article.html
http://www.autospeed.com.au/cms/A_2162/article.html

Just thought I'd put that out there

[elnevio]

http://www.autospeed.com.au/cms/A_2159/article.html
http://www.autospeed.com.au/cms/A_2160/article.html
http://www.autospeed.com.au/cms/A_2162/article.html

Just thought I'd put that out there
Good stuff brad. It's amazing to think that what may seem intuitively right, can have the opposite effect!

[bradc]

Basically for venting hot air out you want vents at the front such as on an EVO where the vents are always towards the front.

If you want to get extra air in, put the vents towards the back like Subi's

[mitzitech2007]

thanks for the input guys. not sure if moving the vent to the back will make the nessary pipework underbonnet counter effective cos it will need to be a bit longer than it is now making a bigger restriction. but like i said its good to know cos i havent started making holes in my bonnet yet!!!

[Turbo_Steve]

The best place for cold air induction is below the bumper line: this is the highest pressure area on the car, and the reason why the radiator and intercooler are fitted here. FOr best results, it should be surrounded by a flat surface that gently grades into the inlet duct.

That said, induction should ALWAYS have a pressure relief valve at a higher point in the system: this ensures you don't end up pumping any deep puddles into your engine.

Did quite a lot of measurements myself on a a jury rigged system and found this area to have the highest pressures. Shortly afterwards, BMW bought out the M3 with the induction inlet....exactly where I had put mine.

Haven't experimented with undertrays: that was a very interesting article, brad!

Found that positive inlet pressure cause the turbos to spool 300rpms earlier, and that I was able to advance the ingnition by 4 degrees lower in the map.

[GalantOnly]

The real vents should look like that...

[Davezj]

the gains being talked about do seam quite small, for all the hassle of cutting holes in bonnets, etc.

however i do undrstand you have to start somewhere with the mods and cold air induction is probabley a safe one.

[mitzitech2007]

thanks for the input got given a mushroom filter from a friend so have made a cardboard template air box for the regular mounting location using this filter its a £30 item from halfords so once ive made it out of alloy or something similar and tested it will let everyone know and also list dimensions etc so anyone could also make one.