Regular readers will remember, GBMINI had the JCW air filter installed last year (as part of the “step-up” kit that takes the original JCW kit) from a claimed 200hp to 210hp.
This is one of my most favourite mods to GBMINI – I love the way that the supercharger sounds gets loud when you are heard on the throttle and revving over 4500, but remains quiet when driving “normally”. There is an obvious drop in MPG since the upgrade, which I attribute to my changed driving style – I “drive for the whine” often now!
If you have an MCS with no JCW upgrade, you can still get this air filter – I recommend it 🙂
There was a thread on MINI2 a while back where someone had the new air filter installed but the dealership was not ready to reprogram the engine computer. However, the air filter worked properly anyway, opening the extra air intake valve at 4500 rpm.
At the time, this seemed surprising … but I have recently learned that the extra intake valve is not controlled by the engine computer at all, but by some special electronics developed for and installed with the air intake:
The electronics is in the little box center of the pic, mounted on the back of the new cowl which is installed to provide the opening for the extra air intake. The electronics determines when 4500 rpm is reached, and powers the extra valve to allow more air flow; there is some hysteresis so that the valve is not closed again until revs drop below 4000.
What I don’t know is if there is any feedback signal sent to the engine computer to indicate when the valve is opened – but I would guess “no”. The existing sensors allow the engine computer to determine air/fuel mixes, and presumably they will provide all necessary indications of how much air is flowing into the engine.
The engine computer still needs to be reprogrammed for the “step-up” kit, to take account of the bigger fuel injectors which are also installed – I don’t know if reprogramming is needed when the JCW air filter is installed “standalone” on a non-JCW MCS.
M&I / GBMINI 
Is the flap moved with a simple solenoid? It could be easy to wire it to an interior switch for those times you would always like it open.
I have been thinking of installing the Dinan CAI. Any opinions or observations on that device?
+++RB
Sorry – I don’t know the answer to either question!
Hi Ian,
** I don’t know if reprogramming is needed when the JCW air filter is installed “standalone” on a non-JCW MCS. **
I can confirm that it is not needed. I just installed the JCW air filter assembly on my wife’s non-JCW 2005 MCS and it works great without any programming. You can really tell when the motor hits 4,500 RPM and the extra flap opens as the wine from the supercharger becomes very apparent. It’s awesome!
I agree with you in that this is one of my favorite mods as well (albeit a bit expensive for a CAI). I love the fact that the car is quiet while cruising and then screams when you step on the throttle. Whohoo!
BTW, the installation was straight forward and easy enough (it took me about two hours as I was taking my time in order to make sure that everything was done properly). The only hard parts were trying to get the vacuum line hooked up (as it’s in a very hard to reach location) and trying to get over the uneasiness of cutting into one of the computer harness’ wires (i.e. the white/red wire on pin 113 which I imagine is what carries the signal that the black box attached to the new cowl uses to determine when the engine hits 4,500 RPM).
— MIKE
Interesting info Mike – thanks! Glad you also love the noise 🙂
General note: told this week by Scott at MINI Peabody that a replacement air filter for the JCW will run you $160!
** General note: told this week by Scott at MINI Peabody that a replacement air filter for the JCW will run you $160! **
Ouch! That’s ridiculous. MINI should be ashamed of themselves on that one. I bet that we can find a K&N filter cheaper that will work just fine.
how much will the air box kit cost and how much power will be gained
Official pricing is $450 plus install, but I’ve seen it advertised much lower on the various MINI forums. Claimed HP increase is 6-8.