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MG MGF Technical - Air intake via engine hood

Hello, I am a new member to the BBS. A few words to introduce myself first: I own a 75th LE, late 1999 built, equipped with a Trevor Taylor FXtreme sportexhaust, no other changes. The car has 56'km on the clock and runs perfectly. no problems yet. I am aged 35 and live in Munich, Germany.

Now here comes the question:
Is any reliable information available on the air-flow at the engine hood? Esp. the flow at the 'intake'-spots would be interesting to me. I am about to construct or more likely, to build an idea, on how to get more air faster into the engine. I need a spot on the MGF that provides enough air-flow to get the idea to real. So any comments on this matter are very welcome.

Thanks for your answers !

martin p.
Martin Poehlmann

Most of the air flow is from under the car and a little from the side vents. The air escapes through the vents in the boot lid (engine hood?). Using these vents for cold air into the engine could cause cooling problems rather than solve them. On the other hand if you are thinking of cutting a hole and fitting a scoop then it should work.

The supersprint side air vents from Mike Satur improve air flow a little as far as I know. I had an idea of having a scoop moulding for the side vents but I have no skills in this area.

You could always fit a K&N with the cold air pipes (or alternative cone filter). This will give +8BHP more on an MPi and +15BHP on a VVC.
Tony Smith

Martin, the biggest problem with an airscoop on the boot lid is the variable aerodynamics of a car whose roof can be raised and lowered- altering the location of high and low pressure areas over the rear deck.

I would guess that with the hood raised there would be a high pressure area right over the bootlid vents- a pressure area that'd disappear with the roof stowed away.

Carl has noted that air flow is OUTWARD from the engine bay through the vents, as air in the engine bay is higher than the fast moving air over the upper surfaces of the car.

So if you want to make an air scoop for an air filter assemble (for example), the intake system would need to be sealed from the engine bay.

IMO it would be a better to start with a scoop working in the more predictable air flow from either the side or under-side of the car.


So Martin, what exactly are you planning? Sounds very interesting!

Rob Bell

I thought of constructing a double air-intake that fits with half the width of the two vents and is, when lid is closed, directly attached to it (no gaps). Sorry, cannot describe this better. These intakes lead into a round double hulled airbox with an intake and an outlet on the downside, about 20 cm diameter and 15 cm in height (depends on the available space), putting in the air from downwards into the airbox. The airbox itself is, as mentioned, double-hulled. That means, you have a gap of about 1 cm between the 2 hulls and the inner hull is about 2 cm shorter than the outer. The air will flow in thru the intake and is lead in between the 2 hulls. The lid of the airbox has a conical center, leading downwards to the outlet.

The intake spot is depending on where the most and constant airflow can be found at the car, so the boot lids were only an idea, cause I thought it might be an adequate spot and also for construction it would be easy to do.

I will do a drawing this weekend and post the link here, just to give you a better idea of what I mean, esp. on the airbox.

If you think, this all in all is some kind of stupid idea, tell me so, I will then litter it.

Martin Poehlmann

Carl has a closed box system for his K&N on a web site somewhere (Dieter???). The only thing I ever worry about is sucking a load of water into your engine.

I remember some of the the early MKII Astra GTEs had this problem when the car was driven through a ford too quickly, or somewhere else very wet. The water went through the bonnet air vents and through the enclosed filter, result, new engine required.

Any thoughts?

If you have a little cash spare get a supercharger fitted (only 4,500 quid :-), the supercharger should suck air from wherever you want it to.
Tony Smith

I understand what you mean Tony. The system should not pull water, thats basically.

I did a fast drawing now on how I see the Airbox. Have a look at

So i need to find a spot on the car to get the (cold) air in or for a solution to seperate water from air. Any ideas ?

Martin Poehlmann

Has anyone thought of air intakes on the FRONT bonnet? Cut a hole or some slots in your bonnet, remove the spare tyre and replace it with a huge scoop ducted either under the body or thru the door sills. Lots of lovely cold air!
Alister Louis

This thread was discussed between 17/05/2001 and 21/05/2001

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