I have a question about my r53 after adding the Alta 15% pulley.... I installed a boost pressure gauge and ran my car hard to see what kind of boost I got stock and then changed the pulley. I again ran the car hard only to find that I had gained about two pounds of boost in first gear and little or none in any of the other gears. My bypass valve spring broke about a year ago and I replaced it with a small flashlight spring and it worked great again but I'm wondering if the spring is too strong? As far as I can tell the spring keeps the valve open to let the air into the supercharger, not to the intake? Not sure if this is the problem or not.

 

I am almost certain there's a power pulley on mine - is there any way to tell what kind?

 

You should be able to see the pulley on the front passenger side of your engine just below the edge of the belt tensioner. Only way I know how to tell is if there is a brand name on the face of the pulley.

 

I will check

 

I would say it's either the spring or a vacuum leak to the bypass valve, but.... the spring wouldn't be too strong, it would be to weak, the spring holds the butterfly closed, vacuum to the diaphragm compresses the spring to open the butterfly, and the spring tension controls the point of vacuum in which the butterfly will be fully closed, a weaker spring means the butterfly will stay open to a lower vacuum point or higher boost point (since vacuum and boost are polar opposites)
You won't know without swapping it to see.

 

If you want it check the spring... Just ZIPTIE it open or shut and compare it...
The real test is look at your boost gauge... It should should zero boost at low rpm,and close as you approach 2200-3000.the intent if the bypass valve is to get the engine off boost at low rpm when boost is not needed...thus saving fuel.

 

Exactly what I thought.... I used a vacuum tester (the kind u pump with ur hand) on the valve after I installed the spring and the valve opened and shut pretty good.... Ill have to check about the vacuum leak... It does shut the boost down when I let off the gas no matter what rpm its at. Thanks

 

I do know that when the spring broke, the valve stayed open and the car will actually go into limp mode because it senses that the supercharger isn't getting air.... I just couldn't think of why it's not giving me the boost and I knew that I had messed with the bypass valve...

 

What size belt did you use with the pulley? Also, is your crank pulley stock?

 

K060535 gates. Which is what I already had on there.... Not sure why but when I changed my belt last year before the pulley, the parts store gave me a belt and it was too long.... I took it back and they said yes that was the right one for the mini s so I'm pretty sure I got the JCW belt from them... But I used the regular MCS puller to get the old pulley off and the new pulley was a lot smaller than the old. Yes my crank pulley is stock. I also have the stock intake.

 

60535 should be good size for the 15%.

 

That's what I found everywhere I looked...

 

What about the condition of your belt tensioner? Just trying to rule out belt slippage.

 

Not really sure how to check it but I did not change it. As far as I know it is the original. When I put the belt on I can see the first hole on the tab plus some. I took my stock air box out a while ago and drove around and it gave me more boost in first and second gear... May just need to get a CAI?

 

Boost is rpm dependant....not GEAR dependant...You should see similar boost at the same rpms is different gears....
And you drove around without a airfilter? Great....quick way to destroy a motor and the SC.....little bit of grit...
Filter look nasty? The stock filter gets nasty pretty fast
If the belt hasn't jumped off, the tensioner is likely OK...
You would see it jump or squeel lots at all rpms....

 

I understand that but I'm only seeing what I'm seeing.... Extra boost in first and second ( about 7-8 psi) and little to no extra boost in any of the other gears (5 psi) even when revved out. As for tearing up the motor and supercharger, I drove down the street and back... Pretty sure it'll be just fine. New air filter in it though, the old one was very dirty. Very rarely squeals and IF it does it is very short and more of a chirp when I shift gears. ( mostly first to second)

 

So I guess I'm gonna try the cold air intake.... My brother is going to make one for me.... Ill update when I get it. Probably the end of this month....

 

Look around your intercooler boots...any oily residue?....they can crack with age...maybe you have them leaking?
Then again, your choice of springs on the bpv might not be perfect...
You still get the same 5 psi if you ZIPTIE it shut so you are always on boost? And do you trust the gauge? Can you feel it in the back of your pants....the gauge matches?

 

I do have some residue on the intercooler boots....
I'm sure it's not the best spring choice... I'll give you that much.
I didn't zip tie it shut so I might go ahead and try that when I check for leaks.
Not real sure about the gauge.... I did drive the car right after I put the gauge on a couple days before the pulley mod. I just didn't feel that "completely different car" feeling that everybody was talking about. My 0-60 is still the same.

 

Sometimes when the IC boots tear, they howel or whistle, sometimes they don't....most folks get about 7years or so from the OEM units, which are the easiest to use, by far. The rubber does tends to stiffen with age, and they tear...sometimes just a bit of a leak sometimes lots...and sometimes a code,but an oily residue is the clue since you are getting the PCV condensate on the outside of the joints.
I'd look at them next,especially since it is a free 5 minute check if you have a torix bit.

 

I guess I should be more clear.... There is oily residue on the INSIDE of the IC boots.... None on the outside. I will check for small tears in them tho. I have taken the front end of this car apart more times than I can count tho and I cleaned out the intercooler and boots several months ago.

 

Inside is normal... Heck the entire intake tract... The PCV vapors condense... Pretty normal...heck, it keeps the SC lubed...
Oh well... Was hoping to find you something easy!

 

Sorry, guess that's common sense! Lol Thanks for your help tho... I'm taking it apart right now. Trying to see if there is any vacuum leak to the bpv.

 

As far as I/C boots, one of the things I like to do after cleaning and right before re-installation is to spray a little parts/carb cleaner on a rag and wipe the inside of the boot where it mates with the metal, (don't spray the boot, it's actually not good for the rubber) just a little bit from a rag will make the rubber slightly tacky and get you a good seal.

But I'm actually leaning toward a weakening tensioner, here's why...
Normally you would think a loose or improperly sized belt would be more apparent in lower gears or at quick revs in idle simply due to the speed in which the RPM increases, but a tensioner that is just starting to weaken might do the opposite, quick RPM gains may not be effected as where slower RPM gains may be more effected by "belt bounce".
Just a thought.

 

Thank you ZippyNH!! I just put my car back together after taking apart the bypass valve and quickly cleaning the throttle body while I had it off. I ZIPTIEd the bpv shut to give it all boost and OMG my car woke up! When I took it apart I made sure to see how the spring was doing that I put in there a year ago and it looks like it has weakened because there was a tiny slit of opening in the bpv and the air was probly slipping right through.... Now my boost gauge shows about 11psi.... THATSWHATSUPP!!