Well after reading this entire thread to this point(the debate has been great!)

im going to toss in my 2 cents worth:smile: I have an 03 jcw until last week the only hp mod was a madness cai. 1st point: Break-in I had concerns about breaking in with full synthetic oil. I've seen/read about people shifting at 2k until they reached the 1250 mile point and then were puzzled because they had oil consumption problems between changes DUH! I believe 1 reason I dont suffer this issue is the fact that I drove mine to 4500rpm nearly every gear change, I let it decelorate from 4500rpm in gear dozens of times in the first few weeks and varied my rpm consistantly in the first 1250 miles.
2nd point: ECU Adaptability I have driven the same route to and from work since I bought my mini before and after the JCW kit.
I average 30-32 mpg on a 148 mile round trip 32+ on the way there 28-30 on the way home heat/traffic effects the drive home more here in Florida.
and if you cant tell I drive 99.9% of the time with the mpg up on the tach.
After the multiple hurricanes this year we had some make-up races that we ran (ASP #58-SCCA SOLO II) along with an evolutoin driving schoolso I ended up racing 3 weekends out of 5 with 2 being Sat/Sun meets. I always run 3/4 tank 100 octane 1/4 tank 93 octane to race on. And then after the racing I refill up with 93 and reset the milage /MPG for the commute. I had always noticed a small change after racing in fuel economy but after a few days it returned to normal. After all of the racing in consistant and consecutive days also add in 47 runs at the evo school my milage dropped to 25mpg and took 2 weeks to raise back to 32mpg driving much more conservitive than usual.
I added the 03 to 05 JCW upgrade, the latest ecu software version, and the recall work on the emissions.
35mpg! on the ride home in the heat and traffic. But..... even tho I was missing the howl of the Madness CAI the butt dyno was not happy with the upgrade either
Now.... 2 weeks later ive been driving the car harder the mpg is down to 27mpg the bottom end tourque is stronger yet smoother than before, I had to take it easy this morning in some very bad fog, the best I could muster was 30mpg! Also the responsiveness on the bottom end is much improoved no jerk, the traction control is not as over-reactive, I normally would disable it to pull out in traffic or blind spots to avoud eating the steering wheel when it engaged. Now it is working much better. The ears still miss the howl but im going to give the jcw intake a few more weeks to settle in and test on the auto-x course.
My experiences hav prooven to me that driving hard every now and then dont equal driving hard all the time or on consecutive days, also the change in the parameters is slow requiring days to make a noticable difference accounting for a good 10-15 hp on my car in "like" conditions.
What do you guys think?

 

^ you've nailed the point as to why I reset the adaptive logic prior to any Dyno pull - to rule out any variability due to adaptive logic getting in the way.

 

Sorry for the long post but I have been wondering about some of the same things myself, and stumbled on this thread and rambled for a bit

I think I may be one of the lucky ones as far as the JCW kit goes I ran a 14.7 1/4 mile in all stock trim. 60ft times a sloooow 2.6-2.8 before I added the CAI and limmited slip now with the upgraded kit im thinking low 14s - 14.0 what do you guys think possible?

 

I used to enjoy reading this thread, so I thought I would try to re-capture some of the magic and see what kind of perspective we have currently.

I had a dog; it only could manage 125 hp on a Mustang dyno. That was 35,000 miles ago. Today it’s not a dog. I’ve done a few bolt-ons but the real improvements didn’t come until after improving flow in the intake system (I’m not talking about a CAI), fixing leaks and getting a properly adjusted bypass valve that works. The list of leaks included the fuel injectors, which were causing all sorts of sloppy, slug like behavior. There were quite a few more things that needed fixing, but telling all would make this post way too long. This is the way it was with my car, its performance potential held back due to faulty components and poor fitment of intake parts.

Earlier there was a discussion about whether sensors may play a role in the case of the dog. I did have a suspect air mass sensor, but changing it had little comparative effect. From my experience I tend to believe it has more to do with the hardware stuff. A properly functioning bypass valve sure makes a difference. Complete seals in the intake system help insure adequate performance and fresh plugs with a clean air filter make a car and its operator happy. Over the past two years I’ve noticed differences in the quality of castings among parts. Not that new is better than old or visa a versa, just that some are way off. Recently, I had an intercooler output duct that was absolute crap. I’ve seen intake manifolds with different shaped entries. Larry Widmer (TOO) told me he received a head that was cast way off center, and he has seen others that had some variation from what he would call good. One of the local MINI techs told me he's seen faulty head and block castings. I've taken a peek inside a few stock blowers, one had resistance when spun and showed signs of wear-in on the edges, the others spun freely and had very little lobe marring. An O5 model was one of the spin free blowers and the new coating was flaking in non contact areas just like the old style lobe finish can. Of course, not all dog MINIs have malformed parts, but something like this may play a part.

 

Wow, this is the best reply yet. You seem to have an owners and a Tech perspective of the various production problems the MINI have.

Although you did mention that you had a "dog" your knowledge seems to go beyond that of a typical concerned owner.

I, for one, would like to hear more.