I have the 2007 MCS with 35K miles and just installed the JCW CAI and JCW factory exhaust. For some reason sometimes turbo just cuts the boost at around 4K rpm. Usually it happens on freeway on-ramps when in 4th or 5th gear (auto trans. in manual mode) There are no CEL lights showing up. It seems as the ECU recognizes that more air is being taken and cuts the boost.
Any ideas on how to fix it?

 

How much boost is being cut during these engine speeds specifically?

 

Being under warranty, I would take it in and let the dealer resolve it.

 

mine does it. but mini wouldnt fix it "because they couldnt get it up to speed".....

 

You can check to see if your car has the latest software. in 2008 Mini had a reflash for most of the early cars. Everyone was infering that it was a de tune to maximize engine life. I myself got reflashed when I first got my car and noticed a marked decrease in my power.
I was so mad.

You should get a code reader and see if there are any codes being stored but not causing a cell.
When I had my Unichip I had a simillar problem and a code would be held in the computer (P115d) but only cause a cell after a hundred miles or so.

 

Ah, you phrased it much better than I did... my car does this as well, but apparently only on very cold days. Sometimes it'll choke up at redline as well. I wonder if it is due to a my modifications and being tuneless, but I don't know. The transmission shifts fine, and the motor sounds and runs smoothly except in that scenario.

 

I don't know since I don't have the gauge. From 4K it drops to 3K or something like that, it's really annoying especially it doesn't do all the time.

 

I don't think they will do anything under warranty since (I am guessing) they can say it's the MCS and it's not suppose to have any JCW parts anyway unless you the car has the tuning kit.

 

The won't deny your warranty for the parts you have.

I see you're in SoCal...take it to SouthBay MINI if its near you. Have always had great service from them on both of my modded MINI's when I lived in LA.

 

I am sure my 2007 has the original software. This was the exact reason I didn't want to reflash it, I didn't want to loose any power. I know there is an internal code which indicates that the CAI takes too much air and because of that it drops the boost. So you guys think I will have to reflash with the new software or live with it? The car didn't cut the boost with the stock CAI though. Can it be related to the JCW factory exhaust (2nd catless)? It wouldn't make any sence.

 

Well if nyou get the JCW package from the dealer they do tune for it, so You may need a tune to make it work properly.

Also JCW cars have a bigger M A F Sensor. I think that flows more air than the MCS one. However I dont know if it comes with the kit or only the factory JCW?

 

Factory JCW only methinks...

 

I am wondering if I can just install the JCW MAF sensor, would it fit?

 

You have no need for it. And not to mention, your car probably wouldn't run right with it.

Just take the car in...they can find out real fast for you what the problem is. The car stores a ton of data that can only be read by BMW/MINI's equipment...I can almost gaurantee you that there is something stored in the DME related to your interuption of boost. Also...I'm real confused how your car could be dropping 1000 rpm upon acceleration. Even if it dumped all boost, your revs would still be climbing...granted in a slower fashion.

I'm assuming it feels somewhat like a stumble? Kinda like the car falls on its face? It could be the 'superknock' that is very common with these motors.

 

Yes you're right, it feels like rpms just stop climbing, they don't really decline, it just feels like it. What is superknock?

 

Basically its a really bad ping/dentonation. Usually happens under load in the higher gears like you mentioned, and only occurs intermittently.

The car will cut boost, pull timing, and dump fuel during a single occurance. If you look as it happens you can sometimes see a puff of smoke out the back as it happens. It won't throw a CEL or code that can be read by a reader...but it stores a BMW specific code in the DME, and its literally labeled "Superknock".

I really think theres something else going on, which is not caused by your intake. You're JCW intake really can't be taking that much more air in than stock, to where the car will cut boost. I've run with no intake...just an open MAF, and even then the car ran fine.

 

Sucking in bugs, birds and all huh

 

Lol if you're referring to make filterless shenanigans...it was actually by accident and I had no idea. The filter portion of my DDM intake had slipped off and I didn't even realize it for a few days!

 

I don't feel that the JCW intake and exhaust are your issue. Just take it to the dealer. The dealer should not even look at the different intake or exhaust. They are not a warranty issue. I also have the 2009 JCW exhaust and with ALTA intake piping, intercooler and high flow after market air filter and it is not an issue at all other than the MINI runs much better.

Your problem is elsewhere.

It could be a CAT issue or a fuel delivery issue. Without havring a boost gauge or a scan tool it's hard to tell for sure.

 

So that what that is... i've gotten it bout half a dozen times since i took it in for scheduled maintainance. i wonder now if was changed when the reinitialized the windows. i thought someone had deployed a parachute on my boot the first time it happened.

 

Ok I swaped out the JCW CAI with K&N CAI yesterday and I no longer seem to have a problem. No more boost cutting, it pulls and pulls, I tried in all gears: 3rd, 4th all the way til 5K rpm, 5th around 4K rpm, nothing and as an add-on now I can hear what's going on in the intake. I have no explanation for it since it pushes even more air than the JCW CAI but it is working great.