Thread: More airflow?

They certainly don't need it as such. But can be a good mod if you need to dissipate some heat from under the bonnet. What you need to be careful of is you don't create an air lock as can happen if air cannot escape.
If you are going to install a vent in the bonnet, then you also need to be sure the air being brought in has somewhere to go eg exhaust vents.
Personally I would install a bonnet scoop maybe GQ patrol type and some fluted type vents in the guards. Have also seen fluted bonnet vents. This will allow cool air around the engine and the warm/hot air to escape. Don't use marine stainless steel vents as these get quite hot and can burn someone. There are multitudes of fluted vents around.
If you are concerned with under bonnet heat this may help. Also consider exhaust wrap on the exhaust system. Also if you don't have them thermo fans. You can use Falcon twin fans or fit aftermarket fans easily. I have also seen a thermo fan fitted into the bonnet scoop, but IMHO that would be overkill unless you have an intercooler fitted there.
If you search here and on line there are lots that have done this mod.

More airflow of the correct type is better. Vents aren't required though, there are thousands of Rangies getting along just fine without them.

I have a D3 vent in the right side of the clamshell part of my bonnet, but only because I got it for free. It does vent noticeably warm air.

Originally Posted by BigJon

More airflow of the correct type is better. Vents aren't required though, there are thousands of Rangies getting along just fine without them.

I have a D3 vent in the right side of the clamshell part of my bonnet, but only because I got it for free. It does vent noticeably warm air.

MMM some thoughts come to mind now. Maybe could do some mods for the defender. Bonnet scoop and a couple of vents directed at the windshield might be good for cold days, but would be horrendous for hot days.

You don't want a scoop on top of the bonnet. Forcing air in there would create a high pressure zone in the engine bay, stopping airflow through the radiator. The sides of the bonnet are low pressure zones that will help with engine bay air extraction. The rear of the bonnet is a high pressure zone, which is why reverse cowl scoops work (Torana A9X, etc).

The only problem with side vents is that the hot air can come straight back in to your open front side windows. Letting the engine fan push the hot air out under the floor as per stock seems to be the best scenario.

I have wind deflectors, never noticed any hot air ingress. If it gets too bad there is always A/C.

Jon,
OK forgive my ignorance, but why do we see so many scoops that are not used for intercoolers or air induction into the engine? A few years ago it seemed every second RRC owner was doing this. Also even with an intercooler the air has to go somewhere when it has passed through, both Nissan and Toyota have under bonnet intercoolers where once the air has passed through goes' directly into the engine bay.
I get the pressure zones you are talking about, but would this depend on location of said scoop eg front, mid, back of bonnet. Also would vents in the guard help or detract?
I also know what you are saying about A9X, totally different application and if set up correctly should also have an induction tray to the air cleaner, but street cars often did not have these.
Cheers
Craig

Originally Posted by BigJon

You don't want a scoop on top of the bonnet. Forcing air in there would create a high pressure zone in the engine bay, stopping airflow through the radiator. The sides of the bonnet are low pressure zones that will help with engine bay air extraction. The rear of the bonnet is a high pressure zone, which is why reverse cowl scoops work (Torana A9X, etc).

Craig,Toyota and Nissan I/C's don't work,the reason owners fit liquid cooled when chasing power.It's been my experience the only thing under bonnet I/C's are good for is covering the motor with dirt,hence the chronic starter failure problems the donkey V8 has. Pat