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MG MGF Technical - Closed airbox

Hello all,

I recently bought a secondhand K&N airfilter + a Rover 800 airbox. For the "frequent visitors" here, it was the induction system of Fabrice from Liege, Belgium.
The idea was to have a closed induction system based on the K&N57 filter with "ram-air" for a little extra power.
Also see :
"The 100mm flexible hose is ducted towards the left hand side air intake, as per the original airbox instructions. At the other side of the 'Y' piece are inserted the original air ducts from the K&N 57i kit. These are suspended under the subframe using one of Tom Randell's K&N brackets" (thank you Rob!)

But I don't think this works. Pressure can only be build up when "the entrance of the forced-in air, is bigger then the exit". When driving at high speeds the air would be fored in the airducts under the car but would be able to escape through the hose on the other side of the Y-piece. Unless there would be a valve closing that "exit"

So I was thinking to loose the Y-piece and duct a big hose from the airbox under the car using the Tom Randell bracket. Until this morning when I drove into a big puddle of water on the street... and realized that the engine would suck up water and debris, damaging the filter and possible the engine.

Is this "ram-air" worth it ? How much extra power it gives?
And if yes, any ideas how to make some kind of valve that opens when the ram-air gets big enough and closes when there is a pressure drop on the ram-air side ?

Kind regards,
Geert Maes

No, in this case there is no effect for using the air vent at the side, air is not forced in by the movement of the car. The ram-air effect is very slight anyway, and the real benifit is that you get cold air, not pressureized air.
Will Munns

Geert, I think you could be right there. But I am not sure how much of a contribution you'd get with the 'ram air' from under the car.

When I put my kit together, I felt that the disadvantages outweighed the advantages and therefore only mounted the intake behind the LHS grille... Less of a problem in terms of road debris and water.
Rob Bell

There is, as far as i am aware, no ram-air effect from the side air intake, it is pretty stagnant. This can be proved but taping streamers to the outside of the intake and have someone videoing them from a car next to you - you will see that some air goes in and roughly the same amount of air comes out!

The beuty of an enclosed system is that it requires a staganant source of cold air, and the side air intake provide this.

Scarlet Fever

Okay, thanks for the information.

So I will only put a hose from the airbox to LHS grille.

I think your right, Rob. Too much disadvantages, the pressure raise from ram-air can't be that significant. And to optimize it I would have to use smooth tubes and put them in smooth curves inside the engine-bay to prevent to much turbulence of the air.
The fact that the engine will get cold air is much more important.

I wonder why the engineers at MGR in the first place didn't use the LHS grille as an air intake? The original filter and resenator box are close to it and still they use a tube to get the air somewhere else inside the engine bay...

Kind regards,

Ps. Rob, on your website, there is a triangular bracket for mounting the airbox to the fuelfilter but it's only for a 1,8 MPi. Do you have one for a VVC already ?

I'm not sure why MG didn't use the LHS air vent for the standard air intake - perhaps it was down to drive-by noise regulations? Not sure - would be good to find out...

Regarding the VVC bracket, no I am afraid I don't have the dimensions; I was hoping that someone with a VVC would send me their bracket dimension once they'd worked them out. So if you make your own triangular bracket, let me know Geert! :o)
Rob Bell

I have done this mod on my VVC. However, as my local scappie didn't have any Rover 820s in, I raided a Diesel 800 Series instead. The airbox is fundamentally the same except there is no hole in the lid.

On Rob's site, the fitting instructions utilise this hole, so I found an alternative way of mounting the box. As it has it's own mountings in the form of nuts set into the base, I made a bracket that would allow me to use them. Looking at each of the points where the engine bay access panel bolts go, I found one to be in the perfect position for my bracket so exchanged that bolt for a slightly longer one and put it through the bracket upwards, allowing a nut to be put on when the panel was refitted. (I hope that makes sense - Needs a diagram really - I'm working on it!) It also has the advantage that the lid of the airbox comes off without any removal of bolts, brackets, etc. The bracket can't be seen (unless you are a contortionist) from the boot and no holes have to be drilled anywhere. Plus the bracket cost 70p from Wilkinsons!

I too look one big pipe from the left side intake to the box. Bearing in mind that I hade been driving around with my K&N bolted directly to the throttle body previously (with the complete original airbox system entirely removed), the difference between hot and cold air was amazing. Even the fuel consumption is better with my car always getting over 300 miles to a tank and thats with lots of town driving and heavy footed country laning to and from work each day!

Rich Stone

Rich, if you have any pictures/ diagrams of your solutions, I'd love to put them on my site as an alternative solution to the way that I did it.

Also good to hear that you found such a dramatic improvement in performance! :o) Nice one
Rob Bell


You've got mail on drdocbob hotmail !!!

Got it, thanks - you've got a reply! ;o)
Rob Bell

I think they shot the e-mail pigeon somewhere over the Channel, Rob.
I didn't get it yet.

Could you send it again to geert dot maes at vandewiele dot com, please.

They get confused in the channel tunnel! LOL - recieved it yet?
Rob Bell

got it!
Thanks !

This thread was discussed between 19/01/2004 and 22/01/2004

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