Fibreglass Bonnet Vent Ideas For A Circuit Car

[nelsonian101]

I have a FGXR8 fibreglass bonnet (with bulge/no vents) I want to add vents to for my daily driven circuit car.

Always have had problems with summer circuit overheating. Will be shrouding my radiator this year and experimenting with less coolant percentage and additives.

From my understanding, the vents ideally need to let the air out after it passes through the radiator at speed on the track.

The one below is from a HO Interceptor. I am considering putting some old XR6/Focus RS style vents where these front side holes are, or also adding some more slots to the front/sides.

Any ideas appreciated.

[Boganspeed]

I can't see the law being too pleased about all those holes.

I'm guessing they'll let the heat out alright though.

[arronm]

[nelsonian101]

I like it!

Is there any mesh underneath and is it ever driven on the street like that?

[arronm]

No and No

[AdamIan69]

You could try removing the rubbing seal under your bonnet on the windscreen side, then space the bonnet of the hinges 5mm or so. You could even cut a piece out of you spacers/washers so you would only have to slide the spacer in and out for track days. You would never have to remove bonnet hinge bolts for a spacer change again.

[nelsonian101]

I have already removed the rear rubber seal and have done many circuit days with and without it.

From my understanding, the pressure difference between the bottom of the windscreen and engine bay forces air INTO the engine at speed. Not out. This would be hot air at the circuit on a 30deg day. I.e. a venturi effect that you don't want at 200kmh.

This is why older cars had rear facing scoops though for a different reason. To get air into the engine intake, not out.

Opposite would be true while stationary in a road car I guess.

Looking at the vent position of Fords top circuit cars like the GT40 and RS Focus have vents toward the front just behind the radiator.

This is the plan but may also put some at the rear of the bonnet bulge too.

[Dagabond]

No and No

Does it even exist anymore...last time I saw it it was sideways into a fence...

[AdamIan69]

The way I see it Nelson if what you say was true, when you use the windscreen washers at 200kph the water would enter your engine bay and not hit the windscreen. Also if that were the case when my mates car blew the top radiator hose while at speed, the coolant would not have hit his windscreen via the gap at the rear of his bonnet and firewall. But I am no engineer.

[ScatterBrain]

I have previously done testing on my car and the pressure in front of the windscreen is 0.1228psi higher then that under the bonnet at 100kph. The only time removing the rubber strip is beneficial is if the under bonnet pressure exceeds that of the windscreens, Which generally only happens when the car is extremely low or it has a stone tray limiting flow out under the engine.