[MadUsa1]

In the JCW brochure they talk about a second flap in the JCW airbox, which opens at a certain RPM.

What is this flap and what does it open?

[sam_a156]

The flap opens an additional intake through a hole in the firewall. More fresh air...and more supercharger whine.

Supposedly the flap was added to keep the JCW conversion "civilized" during normal driving below 4500rpms. However, I - and many others - have done a "flap mod" that keep the flap open all the time. In fact, last time I cleaned the filter I removed all the mechanical parts and the flap altogether. Now it more or less equals the John Cooper Motorsport version of the same box. There is still another smaller intake hole under this one which normally is plugged. I have removed that too. Even with this mods, I believe that the JCW box is less noisy than some other aftermarket CAIs.

Cheers,
Sam

[MadUsa1]

so once the flap opens, air is pulled from behind the scuttle panel? this being the case is it worth fitting an intake vent on that side like this one:

http://www.playmini-racecar.co.uk/bo...ics/bonnet.gif

[sam_a156]

Yup!

I have read some discussions about the benefit of these, but there did not seem to be a consensus (or scientific evidence) if they are worthwhile or not.

[Nath316]

the simple equation can be seen in my sig

more air = more fuel = more power

However, it is recomended that the additional air is cold and from outside the car and not from under the bonnet where hot things live! hence the additional air intakes on cars

[sam_a156]

Nobody questioned the benefits of a CAI, but I'd also be interested in hearing if these vents that MadUsa1 pointed out are any good (I haven't found anything conclusive):

http://www.playmini-racecar.co.uk/bo...ics/bonnet.gif

[MadUsa1]

There's a review of the playmini track car in modern mini issue 18.

They claim the bonnet scoop lowers intake temps by 8 degrees C at 90 mph.

Probably marketing BS but might be worth a try, looks pretty awesome too.

[Nath316]

lol it may happen but surely that would depend on the ambient temperature

[Richard Crofts]

The vents under the windscreen are in a hole in air anyhow. Fitting a scoop typre vent to one will probably do nothing as this region of the car under higher speeds is cetainly not getting that much air hitting it....unlike the hood scoop or the grill.

Think about the line that air will take after it hits the bonnet....it will be pushed up so most of the air will hit above the hieght of any sensible sized scoop fitted on the scuttle vent...however others will argue differently.

PS I am not sayin there is no air available (there is defo as the Alta and GTT etc intakes use this area for a reason!) just that fitting a scoop will do litle IMO to ram more air in than the normal scuttle vent due to relatively small flow that hits that area.

[sam_a156]

What Richard Crofts is saying is making a lot of sense and it is in line with what I read elsewhere.

If there is a bit of a vacuum/turbulence (and there is a lot of turbulence with the aerodynamic features of our beloved MINI) around this area the OEM openings might even be more efficient.

[MadUsa1]

surely without the scoop the area behind the scuttle panel is a negative air space, where air is trying to escape, rather than enter the air intake.

This being the case, an intake in the scuttle area sounds like an utterly stupid idea, unless you fit an enormous scoop to that side to force air into it.

[Mike Edwards]

Hmmm... the area just in front of the windscreen (i.e. directly above the scuttle vents) is subject to high pressure once the car builds up any speed due to aerodynamic effects. This high pressure air will force its way through the scuttle vents - hence the use of this to feed the air box. Unless you do something like blocking the vents with a scoop...

[sam_a156]

Quote: Originally Posted by Mike Edwards (original)

:
Unless you do something like blocking the vents with a scoop...

LOL - well said

[MadUsa1]

Quote: Originally Posted by Mike Edwards (original)

Hmmm... the area just in front of the windscreen (i.e. directly above the scuttle vents) is subject to high pressure once the car builds up any speed due to aerodynamic effects. This high pressure air will force its way through the scuttle vents - hence the use of this to feed the air box. Unless you do something like blocking the vents with a scoop...

No, that's the wrong way around, the area above the scuttle is a low pressure area, because air is forced over the bonnet and then up past the windscreen.

The air flow going up the windscreen sucks air out of the scuttle panel, effectively pulling air away from the area you guys are using to feed the intake

The purpose of the vents in the scuttle panel is to allow air that has passed through the engine bay to escape.

[sam_a156]

Quote: Originally Posted by MadUsa1 (original)

No, that's the wrong way around, the area above the scuttle is a low pressure area, because air is forced over the bonnet and then up past the windscreen.

The air flow going up the windscreen sucks air out of the scuttle panel, effectively pulling air away from the area you guys are using to feed the intake

The purpose of the vents in the scuttle panel is to allow air that has passed through the engine bay to escape.

I guess we can argue to the end of the world which way the air flows without scientific/empirical evidence

However, a cold air intake takes the air behind the scuttle panel for the very reason that this area is not connected with the engine bay - and thus provides the CAI with cold(er) air. CAIs that take heated air from the engine bay can't really be called CAIs...

[MadUsa1]

The air passing over the scuttle panel from outside will indeed be fresh air, but most of this will be directed over the top of the scuttle and up past the windscreen.

The air that enters your intake will be air that has just gone through the radiator or intercooler and has passed through the engine bay, i.e. it will be warm air.

If you want cold air you need some kind of intake at the front of the car, just above the radiator for example, where the OE cold air feed sits...

[Mike Edwards]

Mad,

Go check the engine bay on your car to see if the panels and seals between the engine bay and scuttle compartment are still there...

(then, next time you're driving in heavy rain, watch what happens to the water near the middle at the bottom of the windscreen and compare this with whats happening to water at the upper corners)

[MadUsa1]

will do.

is air supposed to enter the scuttle panel from above or come through the engine bay into the scuttle area?

[Richard Crofts]

The scuttles vents (black honey comb ovals one each side) allow air (which is from outside the engine bay) to enter the cavities thats are blocked off from the bay. In the engine bay with bonnet open you will see a multitude of brake and other fluid lines on the bulkhead all divided off from the engine bay by black plastic panels with only the top being open. These are the areas directly below the scuttle vents on the bonnet. Therefore this area is fed with colder air than that available in the engine bay. However the main feed for cold air to the intake in the MINI is still the grill mounted vent/pipe that feeds through to the rear of the bay. The opened scuttle areas just allow the intake to grab a bit of extra air for the performance filter....and the scuttle zone is a bit colder than the air you could use in the actual bay itself. No-ne has ever claimed that this zone is high pressure air feed (ram action) for the performance filters, the onlyt claim by GTT and others is that its colder air than the engine bays and therefore is a better location to grab that little bit of extra air for the engine. Roland and other i'm sure will agree that the main feed of really cold air is probably the standard feed pipe from the front.

In my view the scuttle zone will be relatively low pressure feed when compared to say the front mounted intake, but it is all thats really available on the MINI due to very limited space near the front of the bay in the S. To mount the intake or have feeds from elsewhere is not relly practicle or will infact suck air thats too warm, putting hight boost cars at risk of detonation.