Ok, been having quite a heated discussion over on another forum.

Does a reversed bonnet scoop help with or make cooling worse? (assuming the car has an FMIC)

There have been many points brought up, including pressure points below the windscreen, pressure inside the engine bay etc etc.

Either way, I plan to conduct a simple test on my friends car.

I will stick a length of tape, with loads of lengths of string attatched just behind and above the reversed bonnet vent.

If the strings get sucked into the vent, that will tell us one thing, if the strings flail around, that will tell us something else, and if they don't move at all, that will tell us something completely different

 

surely you have better things to worry about

 

I'm just curious mate No better place to find out about such issues than on Scoobynet

 

im under the impression that a reverse scoop is normally fitted with a fmic and the idea of the reverse scoop is to let excess heat out of the engine bay particulary from the turbo area.

i cant imagine it doing any harm at all,in fact it would help.i once had a simalar set up on another car (non subaru) but the only proven way i found it worked was during winter when my windscreen cleared significantly faster

ps ive seen the 'wiggly string' test before.i believe car/plane designers still use it now!!

 

That's right, obviously with FMIC...

 

I have a FMIC with the scoop in the OE position. After fitting the FMIC the engine running temperature dropped slightly even during normal driving. Now this will be partially due to the FMIC cooling the air more than the TMIC. I also think that with the greater airflow from the scoop now going down over the back of the engine this will also cause a low pressure behind the radiator, so improving the airflow.

 

reverse scoop will effectively suck air out of the engine bay as the outside air passes over the scoop whereas forward scoop will force air into the engine bay.

Standard would be more effective with the top mount I would think (or subaru would have put them the other way around) but I can see how reverse might be better with a FMIC fitted.

 

Is a reverse scoop even legal?

The logic being if you get an oil leak in the engine, it could be sprayed all over your windscreen and you can't see and crash.

 

There's a deflective piece of duct that directs the air from the back of the fmic straight out of the bonnet, so there's not really an issue with anything getting inside the ducting. I only know this cause I built a model WRC car at Christmas

 

i have one fitted and going buy my engine bay temp sensor it drops as much as 25deg at speed, so yes i would say it works.

 

Indeed - good facts there Steve

Reverse duct will reduce the engine bay pressure and that will mean more air coming in through the rad, the fmic and escaping out of the vent over the windscreen.

They work very well if you have a fmic.