I’ve been searching this forum for a while and have been unable to find answers to a few simple questions. Any comments would be appreciated.

1. It seems uncertain whether a particular dealer will void a warranty because of a reduction pulley. If the stock pulley is removed, can it be re-installed before bringing the car in for service?
2. I see a lot of discussion about pulley sizes…15%, 17%, 19%. To me these numbers are meaningless without knowing the boost produced by each pulley. What boost (in PSI) does a stock car run and what changes do the pulleys make? How much boost can the car take?
3. I don’t see much discussion about fuel management. If I simply put a smaller pulley on my supercharged NSX, it would run lean and probably blow up. Does the MCS ECU automatically compensate for more boost?

 

1) can the pulley be swapped back? what goes on can come off however while not difficult - it would be a pain in the *** to do every time you need dealer service.

2) the stock MCS is 10.5 lbs of boost a 15 pulley takes it to 14.5 lbs of boost.
Someone else will chime in on the boost change for the other pulleys.

3) Here I am a litttle confused being a MINI board and you reference a NSX.

which is it?

 

I'm asking whether changing pulleys, with no other fuel management mods, would cause a lean condition. My NSX isn't smart enough to compensate for increased boost. Does the Mini have this ability?

 

Most people will tell you that you can swap out for a 15% pulley with no change to the ECU. Others will tell you that changing the ECUs programming with the 15% will make things run much smoother and fix the A/F ratio.

 

The MINI is a bit rich from the factory, so in general a 15% or even a 17% will still be safe. But, a 19% will most certainly warrant new injectors to keep from going lean. Either way, the absolute safest way to tune these cars is by doing dyno runs and either replacing the software with aftermarket ones [Unichip, MTH, GIAC, etc] or by tuning it yourself [Apex-I]. The Unichip, it should be noted, is tuned on a dyno to maximize the gains for your particular car.

 

Yes, the MCS ECU has this ability (so i'm told). But keep in mind, can only give as much fuel as the injectors can.

 

From our findings, and using the stock redline, all of the pulleys are pretty safe. All of them will make the car run pretty rich, which is safe, but not optimum, so getting a chip of some sorts makes a pretty big difference. Since the Mini is a speed densitiy type ECU, it uses Air temp, engine speed and manifold pressure to deliver fuel. So the more boost, the more fuel. I would highly recommend staying with the stock redline for 17% & 19% pulley to keep the SC out of its redline.

 

Are you saying that, absent any chip modification, the car will run richer with your pulley than with the stock pulley? Is the rich condition only under WOT or also at cruising speeds? Am I correct to assume that a 15% pulley won't adversly affect my gas mileage in normal driving conditions?

 

No the stock car runs pretty rich, as to all OEM forced induction cars. With the pulley they still run rich. The stock setup is tuned rich to keep the combustion chamber cooler to keep the chances of detonation down. The stock car runs in the 10.5-1 AFR range and so do the smaller pulley cars.

This is all at WOT under boost, not at cruise or normal conditions. The engine under normal driving conditions sees a peticular manifold pressure weather or not the pulley is smaller or not. Since the ECU is tuned to be around 14.7 in these ranges there is no worries with worse gas milage or anything. You may see a slight decrease in milage because of more drag from the SC, but i have never had anyone complain. Most people will see a decrease in fuel mileage because there right foot seems to be a little heavier for some reason?????

 

10.5....that is rich. We tune my supercharged NSX to 12.3-12.5.

I'll have to underdrive the altenator to make up for overdriving the supercharger.

 

Yes it is, and even most of the chips i have seen bearly get into the 11's. So there is quite a bit of room to go with this car, hence the need for user tunable software.