Hi, I just bought a 2008 cabrio JCW (1st gen). Beautiful car that was well taken care of and garaged. 50K miles. Car is essentially a garage queen and 100% stock. The problem is it doesn't feel like a 210hp car. it feels healthy, revs fine, I can hear the supercharger whine but just feels slow. It feels more along the lines of a 150hp. also the boost buildup feels more like a turbo, not the instant super charger torque I was hoping for.

I've owned lots of cars in the past and have built several cars including supercharger and turbo installs and all associated mechanic / maintenance work. I've also tuned ECUs on my cars. I would love some advise on where to start in the debug effort.

Here is what I know so far:
- Max boost is around 12.9psi per OBD2 monitor. This is consistent from run to run
- No CEL / codes
- BPV spring feels healthy. Tugging on it I feel no gap or play.

I've tried to do a bit of searching and reading. What else should I look for?

Here is the car

 

The JCW utilizes an 11% overdrive pulley to up the boost earlier by over-spinning the supercharger (as compared to a standard S). Boost on the supercharger builds slowly until around 3,500rpms. There's no lag like a turbo but the revs must be up before substantial boost is achieved. 12.9 is a bit low. My 15% pulley pulls around 14-15lbs. of boost but it has also been tuned. Do you know if your little guy was ever tuned? If not, I highly recommend it. Mine was worth an additional 18hp.

 

No the car has never been tuned. 100% factory. The JCW tuned kit has an 11% reduced SC pulley relative to the S?

I logged a couple of pulls to compare boost build-up to RPM at full throttle. Here is what I get:
RPM / boost psi
2100 - 7.5lbs
2500 - 8.7lbs
3000 - 9.4lbs
3500 - 9.7lbs
4000 - 10.4lbs
4400 - 11lbs
4800 - 12.2lbs
5200 - 12.6lbs
6000 - 13lbs
6200 - 13.2lbs

How do those look? I'm at sea level.

 

The JCW pulley is 11% smaller than the pulley that comes standard on the Cooper S. Therefore, the JCW supercharger spins faster than the S and creates more boost. 13.5 may be the max for an 11% pulley? Maybe there's someone on the forum that can guide you on the expected boost for a stock JCW. I would think that your RPM max would be around 7,000 which would up your total boost reading a bit. You might also want to check for leaks around your SC boots or air plenum, though an air leak would normally throw an OBDII code. The boots, in particular, can sometimes not seat fully on the underside of the SC when reinstalling, or alternately have a small crack/split producing a leak that's not visible until they're removed and examined.

 

Check the boots going to the intercooler just for cracks and leaks.

Stock boost:: https://www.northamericanmotoring.co...-pressure.html

 

Thank you both. I'll check the boots for leaks.

ECS, I read that thread earlier. Unfortunately people are reporting numbers all over the place. There seems to be no consensus on what a factory JCW should be boosting.

BTW, I read somewhere online that others have experienced the dealer "forgetting" to install the JCW map, resulting in low power. Any truth to this? seems a bit far fetched.

 

Your JCW is probably Factory installed since it’s a 2008, but you can run your VIN through a decoder to see if it lists option 3AL If so, you should also have an LSD and the JCW brakes.

 

If this helps any -
I was on an open four lane road yesterday with my 05 JCW, so I thought I'd watch, "carefully" what the boost (Autometer) did.
The only thing that I watched was the boost gauge, no tach, no road (!), no MPH.
At "about"...3000rpm, I slammed the throttle to the floor.
The gauge went to solid 17psi, held for a second or so, and slowly dropped, until I took my foot off the pedal, then dropped very quickly.

The engine is a stock, JCW, 211 hp (dyno sheet verified with JCW exhaust), with a stock header and a Miltech catback exhaust with 20,285 miles

Mike

 

RB-Mini, verified factory JCW

Mike, Thanks for rubbing it in . I'm assuming this is 211 BHP? what was the whp on the dyno? stock tune? a plot would be great.

 

Nice nab. I was trying to get that car earlier in the year and got corona virused from traveling. It is a factory JCW, all option but rear fog light. Even had the additonal add on
alarm from the dealer.