Bonnet Vent - Placebo Effect or Reality?....

[RedRobin]

When I changed my bonnet to an OSIR carbonfibre one (with no real justification!) I had the opportunity to get the first one in the UK with a vent. The vent is above the turbo area - A well-known hotspot but, although the steel bonnet would get warm/hot all over after a good run, overheating was never a problem. I've had the vented cf bonnet for a few months now but have felt (unscientifically) that my car has tended to feel she's flying quicker since. I put it down to cold weather possibly delivering cooler air.

I've noticed that after a long run, heat can be felt from the vent but the rest of the bonnet is cool to touch. This has got me wondering if this minor mod of a vent actually has a more significant benefit than I realised it would have. Does it also contribute to expelling air from the whole engine area and hence more efficiently draw air in from the grills and intake?

Does anyone have any knowledge about the effect of vents please?







Thanx

[The Wheel Man]

I have no idea to be honest.  I would say that it makes sence for the air to be passed through easier and these is no 'dead end'.  How much this would make a difference to intake temps would only be solved with a roalling road session..... probably. 

[topher]

You'll probably find that a non-vented carbon fibre bonnet is cool to touch too, and I look forward to seeing you and Hurdy not only admiring each others rear ends but also caressing each others front ends on Sunday to compare

[RedRobin]

You'll probably find that a non-vented carbon fibre bonnet is cool to touch too, and I look forward to seeing you and Hurdy not only admiring each others rear ends but also caressing each others front ends on Sunday to compare

....You're a voyeur!! ONLY hot females have permission to touch my end!!

[maxamus]

Get a room you guys 

[vw_sales]

In my opinion the performance must be increased with the vent in place.

Its like a computer, the colder you keep its working parts the better it will run.

Surely the same can be said about the engine/turbo.

??

[SteveS]

In my opinion the performance must be increased with the vent in place.

Its like a computer, the colder you keep its working parts the better it will run.

Surely the same can be said about the engine/turbo.

??

thing is with a computer, the hotter the bits the worse the power efficenty, not actually directed at the metal and moving parts... a car has those, so mayb not as similar as it seems.. but yeah if its keeping the engine cool, and i would have though carbon fiber is better at that then steel anyway. it can only be a good thing..

[RedRobin]

....Yes, logic definitely suggests strongly that coolness and air flow is generally improved and consequently there may be some performance benefit. But it won't compare to what a front-mounted intercooler (FMIC) should deliver.

If Hurdy will let me touch his front end on Sunday, I'll check if he finds a carbonfibre bonnet stays cooler. I guess that a steel bonnet will soak and retain more heat than a carbon one and consequently keep the engine bay relatively warmer - But the differentials won't be substantial I expect.

[Hurdy]

You'll probably find that a non-vented carbon fibre bonnet is cool to touch too, and I look forward to seeing you and Hurdy not only admiring each others rear ends but also caressing each others front ends on Sunday to compare

Ooh err missis :embarassed:

[Ridg]

the only  benefit i can see the bonnet having is the weight saving over the standard one, is the MK5 GTI bonnet actually made of steel and not ali?

regarding air flow, i can't see it really making anyodds as the vent faces backwards, which is only going to allow air to escape (eg not cool air being drawn in) and becuase the car's going to be moving forward this air would have been pushed back through the standard vents anyway