Those of you in the know and/or with boost gauges - how much boost do the JCW cars normally put out? No other mods. I'm getting 13-13.5lbs at WOT and only after the revs are up in the 6,000+ range. I've been told that it "seems a little low", and that I should be seeing 14-15lbs. Can anyone verify this?

Should I just shrug and get a 17% pulley?

 

where do you have the boost gauged plumbed into?

 

I think 13.5psi is good for a JCW...

Also, I don't think a 17% pulley would worth it on your JCW. If I had a JCW, I'd rather keep the engine as it is and work on suspension & brakes instead. There is a presige related to JCW and I would not mess with it lol

 

How much boost does a stock MCS put out?

 

It may be a good idea to check your bypass valve. There have been several problems of the butterfly valve being miss aligned and not closing properly. If the door is not closed you will loose boost.
Steve

 

Honestly, I don't know. It's the factory accessory boost gauge, and it was installed by the dealer.

 

Done. I had a DT bpv installed, and it made exactly 13lbs of boost - no more. I was getting driveability problems, so I had the stock one put back in for the time being. With the stock valve it'll hit 13.5.

Interesting too, because with the stock bpv, I could see a very thin sliver of light around the edges of both sides of the butterfly when it was closed if I held it up to light, and the DT valve is perfectly sealed - can't see any light coming past the butterfly.

 

That does seem low... The JCW's pulley is only slightly smaller than a 15% (14.2% reduction I believe). With my 15%, I'm seeing upwards of 16 PSI at 7000RPM at sea level. The stock pulley supposedly makes ~12 or so PSI. Does your car feel like its lacking in power compared to other cars?

Another possible factor is that the dealer bolluxed the gauge install and youre gettng false readings from it... Thats all I can think of...

 

70spop
Something doesn't sound quite right. If the DT BPV had a good seal on the butterfly valve and the stock BPV had some light showing thru you should have gotten more boost with the DT. Not the other way around. Was the work performed by a knowledgeable person? I think I would double check everything.
What type of driveability problems were you having with the DT BPV?
Steve

 

Temperature and Humidity can also raise and lower what you see for boost.

On a dry cold day in Florida, I can see 16psi. Normally its around 13-14.

 

Well, I'm only about 100-150 feet above sea level, and it's been both wet and dry lately with temps between 32 and 75 degrees. I haven't noticed any difference in boost with weather/temperature changes.

 

yeah im not seeing how boost levels will change with weather??? and ive been around forced induction for awhile.


13lbs seems a lil low, is your bypass valve still good?

 

Hello
How I verify if my bypass valve is good?

Best Regards

 

its kinda hard to get to, but take a zip tie and zip tie it shut, and then if you get all your boost (power) back then that is the problem.

 

I think so, too. If nothing else, a more completely closed bpv should have translated into a smidgen more boost - you'd think. The work was done by an independent BMW repair/race shop. The owner is also a factory certified MINI tech. After having the DT bpv installed, noticing driveability issues, and talking with Chad at DT about it, I had the dealer check out the intake tract for vacuum leaks and give the installation a once-over just as a second look. Everything was fine.

The driveability problem was that I was getting stumbling when I was between 0 and +4 boost. If I was accelerating slowly, the car would hesitate when the boost level hit that spot - felt like it was running out of gas. If I stabbed the pedal to goose the gauge needle past 5lb, it would accelerate fine. It did the same thing going the other direction, too. If I was on 5+ boost and then let off or held the pedal steady, I'd get the stumbling when it dropped down into the 0-4+ range. And steady cruising on the freeway pretty much felt jerky all of the time, like the engine didn't know whether to go or not. I don't think it was the bpv yoyo-ing, because the needle stayed pretty still. Almost seems like a fuel delivery issue, but then why would the car accelerate steadily all the way to redline on higher boost?

I've got an appointment to have the car dyno-ed tomorrow evening, so I'll get a better idea of what kind of power it's (not?) making, and maybe get some ideas of what might not be working properly.

I haven't driven other cars recently for comparison - heck, I don't know if I even know anyone with a stock pre-'05 JCW to compare it to. It just feels weak compared to how it accelerated in the past. It still feels basically *strong*, like it has no problems pulling up hills in 5th or 6th, but that "shove you back in your seat" feeling in 2nd and 3rd is missing. I shelled out the bux for it, and I want it back. The car definitely feels like it's working hard when accelerating in 2nd and 3rd.

 

Oh, I tried that when the DT bpv was in the car. Made no difference, other than being very slightly quicker on boost because the butterfly didn't have to close. Total boost and driving "feel" where unaffected.

 

belt slipping?

 

Kinda wondered about that, but I've never heard of that being a problem. I mentioned it to a SA, and was told that if the belt was slipping, it would probably be more of a slip/grab thing, and that it would be REALLY noticeable, and show up on the gauge as an erratic needle. Dunno, though. If the belt's tight enough to keep the sc spinning, but loose enough to start slipping when a certain resistance is reached....:impatient

 

to be honest, ide just buy the pully tensioner tool (cause its not to exspensive) and buy a belt and just replace it

 

I Live in Salt Lake City utah, and my 2004 JCW would only see 13 psi on the very best day, usually 12psi. Now when I go to Las Vegas I see anothe pound of boost because of the elevation. How High about sea level are you?

 

'Bout 100-150 feet. On Saturday, I was at sea level for a little while - we did a run along the coast.

 

off subject of boost, but would it be worth it to get the JCW intake and exhaust then get the kit, my dealership has those parts laying around and I can get them for $1100 w/o labour though.

 

Might be a little more expensive than going aftermarket for the same parts, but sure it'd be worthwhile- a better breathing intake and exhaust are always good.

 

Temp and humidity can change your boost levels due to the amount of air the s/c can stuff in - colder dense air = more boost.

Ask just about anyone with a boosted car in Florida the difference they will see come May when it gets hot as hell and humid.

 

+1 - Tampa is right.