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MG MGF Technical - Air Intake.

Ive just finished fitting my Trophy TB, new ignition leeds and a new set of plugs. ALso i put back on my K&N. The car is now amazing. Words cannot describe it. It feels like all the flat spots on my MPI have disappeared!! What a worthwhile sunday afternoons tinckering.

One question though is that I never put back my origonal hoses underneath the car. Instead I connected another flexi hose to the housing of where my standard air box used to be. Is this ok?? WIll the air be getting through to my K&N?? The car feels ace at the moment so I am assuming so!!!!

Any sugesstions guys??
Chris Glen

The standard K&N setup (as used by many of us) relies on 'ram air', and there is very little of this at the side intakes, to produce a 'puddle' of cool air around the filter and experiments by Kinnor and some of the owners showed the best place to put the intakes was under the car.

Ted Newman

The problem I had with that before though ted was that when pointed under the car the sheer force of the wind was blowing the pipes all over the place. Is their a good way of connecting these??? Will the car be ok for the time being??
Chris Glen


Firstly, if i read your post correctly, you still have the old air filter box in the engine bay. This in itself will affect the performance of the K+N as there is a smaller 'air pocket' around the filter, you are basically after clearing a fairly large space around it, to provide easy access to quantities of air.

Secondly, as Ted rightly points out, the K+N 57i is designed to make use of COLD air fed directly from under the car straight to the filter. Cold air is denser and therefore contains more oxygen, causing a noticable increase in power. However, that said i understand where you are coming from with regard to sitong the air intakes under the car. The K+N recommended route is, not to put too fine a point on it, bl**dy stupid AFAIC, potentially damaging not only the K+N hoses, but alsot the Hydragas pipework! The solution is to get hold of one of Tom Randell's excellent K+N brackets, he is a regular on this BBS and hopefully will spot this thread and make contact. The bracket provides a solid mounting point for the pipes, suspended from the subframe. I have a picture of a fitted bracket if you are interested.



P.S. It has just occured to me that you could have connected the K+N pipes to the side resonance box instead of what i described above. If you follow the route through this box you will see that it draws air from the boot/engine bay partition wall below inlet plenum. Again, wihout the ram air effect from the pipes, the performance of the filter will be compromised.
Scarlet Fever

There's already quite alot of info on this subject, as I am sure you know Chris.

Working on a couple of alternative airbox designs (any luck your end with the fabricated 'box Andy?)- but here's another idea...

The thing about these enclosed airbox systems is that the preferred air intake site is actually the air vent, in the complete opposite to the 'ram ducts' that the K&N 57i uses.
Rob Bell


How much did the Trophy TB and the new ignition leeds and a new set of plugs set you back.

I am thinking of going down this route but was just going to get the Trophy TB. Do you think the new leeds and plugs will add much (my car is similar in age and mileage to yours)?

Having fitted the above all you need now is this Hurricane filter when the final kit is available ;)


I'd be interested in knowing just how easy it is to fit the Throttle bodies. Is it simple enough for a bloke with a socket set and a bit of nouse to work out?

They're about 112 quid arn't they!


The Trophy TB has arrived and has been fitted. The power pick up seems to be a lot smoother and the typical power lag between 3500-4000 RPM has been removed.

Fitting took about 40 mins, with no issues. I simply removed the access grill and did it all from the boot. I used an 8mm socket with extension)and a 8mm spanner to undo the four bolts holding the TB in place. A screwdriver (to remove the K&N air filter) and a pair of pliers to loosen the clip holding one of the hoses in place. The only tricky bit is a small clip holding a wire place. This was easily access when I had unbolted the TB. The clip looks like you should pull it off, but if you push down in the middle, the legs open up and you can pull it off.

After fitting I reset the Sensor (Ignition on (don't start the engine) push accelerator 5 times and ignition off - Thanks Deiter for that bit).

Can't wait for a long run to give it a good test. :-)
Stephen Ratledge

Does anyone know what would be the implication of installing a power boost value at the same time as a new throttle body. I'm told an improved fuel/air mixture would give a further improvement in throttle response but are we talking imminent HGF ......?!
I'm not so clued up on these things, can someone more knowledgeable advise on the implications.


ok guys sorry about the late reply. Andy. Ive taken off the old airintake box and so its getting the air from the resonance box i just modded an old flexi pipe to it. So their should be some air coming into the engine bay! (Hopefully)!!!

Tim I got the throttle body from Mike Satur along with the ignition leads and the sparks. The old throttle body just unbolts from the engine. All u have to do is remove the throttle cable which just slots into the throttle body. Two pipes and a cable need to be removed as well. Bolts are 8mm. easy peasy. About 20 mins to put it on. Intresstingly enough it took about 30 - 40 minutes to put in the new sparks. Clean the dizzy cap and the rotor arm and put on the new HT leads. Mad!!!

Rob im going to go down the local scrappys this weekend and look for a rover 820 box. Out of intrest is the rover box from the mark 1 or mark 2 car???

Mr Randell would love to hear from u if u have any brackets left for sale.

Cheers Guys
Chris Glen

After fitting the Trophy TB. I went out for a test drive. Boy was it good, I came back with my heart pounding and the adrenaline coursing around by system. Only two words can describe the difference it has made to my 1.8i.

Bloody brilliant!
Stephen Ratledge

Chris, the airbox was obtained from a Mk1 800 (the one without the grille). I should have made a note of the age of the car whilst I was there- but it was an early EFi. Still, once the bonnet is popped open it is pretty obvious what sort of airbox the car is equipped with!!!
Rob Bell

Brackets still available for holding the cold air pipes under the car.
10 inc P&P email for further info.

Tom Randell

This thread was discussed between 17/02/2002 and 19/02/2002

MG MGF Technical index

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