Ok, over the past month i've noticed that my boost has been going down, this is the situation. A month ago when i would punch it boost would rise to 10 psi, then as i neared redline it would go up to 17. It would go up at around 6000 rpm. Now, i only get about 6-7 psi at redline, and spike 10 if i rev the engine in neutral. For some reason i think it might be the diverter going bad... what do you guys think?


Before all this happened, i would get about 10 psi at 2k and it would rise steadly to 17-18 at redline. Stange stuff.

 

A very simple reason...

You got a bad Bypass Valve, if you call me at the office tomorrow I will be happy to walk on you thru the procedure on how to check it's function.

peter
Team M7
562-608-8123 (9:30-6:00pm pacific time).

 

Have you checked the simple stuff yet, such as your belt tensioner, belt condition...? The way the intake is built, it seems unlikely you'd have a leak anywhere after the supercharger, but check your fittings in and out of the box too...

I'm not a real supercharger expert, but these things just came to mind. Oh, out of curiousity, maybe someone else knows, where is the boost sensor located?

 

Ah... M7's post didn't appear until after I posted... but it looks like that's your leak!

 

Ok i know its the bypass valve, I bypassed the bypass valve for one run down the street and instantly had 18 psi! Woohoo! Does anybody make an upgraded valve?

 

If there were a malfunction in the Bypass Valve, would you have to take off the SC to fix it? Is the Bypass Valve on the SC or is it mounted elsewhere?

 

Check out Detroittune, give Chad a call. Peter, You're like a doctor for the mini

 

The valve is situated under the right hand intercooler horn (as you look at the front of the car) so you do not need to remove the supercharger. Here are diagrams of my valve that was out of alignment....

Before adjustment....


After adjustment....

 

Well looking at those pics of that bypass valve looks like i got myself a project.


Is there any notice in difference after you adjusted that?

 

Yep certainly did ive done a few MINIs now

 

can you give a detailed description on how to do that for the DIY-er? Or, point a newbie to it if it has already been posted?

thanks!

-jac

 

You want to look for the yo-yo chronicles thread. There is lots of detail about removing them in there. One recommendation. Use some removable threadlocker on the bolts when you put it back. I did not and noticed my valve actually fell off after a couple of weeks when the bolts backed out. THat will put a hurting on your boost level.

 

Hmmmm....just a minute....

You stated that before you began a period of lost boost, your (aftermarket) boost gauge reflected normal operation. Thus the following can be deduced:

1. You (or someone) installed an aftermarket boost gauge in your MCS. This is usually done by tapping into a vacuum line, usually the one that attaches to the fuel pressure regulator.

However, the SC BPV is also actuated by a vacuum line. You might want to determine exactly in which vacuum line the "T" was installed to support the boost gauge and check to make sure all the fittings in that area (line) are tight. Tie-wrap if necessary.

2. You state that your boost was fine, then suddenly was lost. Therefore, the MCS was initially operating normally...and then something happened.

With apologies to all who have identified the BPV as the culprit, this is not the M.O. of a mal-adjusted BPV; they don't "all of a sudden" go out of alignment. They are incorrectly adjusted at the supplier's plant then sent to the Tritec assembly plant, so you would have noticed an non-standard boost level from new, not "suddenly" after a period of normal operation.

3. You also state that you bypassed the BPV and everything was then working correctly. I assume you tie-wrapped the BPV butterfly-lever in the closed position.

This does not conclusively prove that the BPV misalignment is the source of the problem. Again, incorrect vacuum at the BPV could also cause your loss of boost and tie-wrapping the BPV closed would also negate the effect of vacuum loss. In fact, that you tied your BPV closed and the boost loss disappeared proves that mis-alignment of the BPV butterfly IS NOT the cause of your sudden boost loss (the alignment is the same whether the BPV is activated by vacuum or forced closed).


Before you remove the BPV, check your vacuum fittings.

Theo

 

Just to help stir things up even more. A few more sources for boost pressure loss:


Holes/cracks in your intercooler from debris coming in the scoop.
both s/c boots
T Map hose
MAP hose
inlet duct
vacuum hose of inlet duct
throttle body area

 

Trying to long distance trouble shoot is always a guessing game. In my experience with this exercise there is usually some un-revealed symptom that if communicated could narrow the possibilities for a solution. The general rule is to look at the last change made and work backwards from there. As mentioned already look for leaks in places where clamps or slip-fits are involved.

A by-pass valve can suddenly hang open or develop a catch. It has happened to me. Usually the faulty BPV manifests itself as a flat spot in the low-mid rpm range. The “vacuum” line on the BPV routes back into the BPV body and exits to one side of the butterfly valve. I had a small piece of paper from a carelessly placed part label make its way into that hole and disrupt flow on one of the three BPV’s I’ve had (number four needs to done next); fortunately a puff of compressed air was all it took to dislodge it. Your chances at winning the lottery are better than that ever happening again. Checking for a sticking plunger is as easy as actuating the arm on the BPV and feeling for resistance.

Any of you that do not know where or what parts are on your vehicle needs to purchase a shop manual. It will save you money and frustration from fear of the unknown.

 

The problem is the actuator, It has broken internally somehow. I'm going to replace it and run a vac/boost line directly to the nipe on it. My boost gauge is not the problem, its been on for 20k miles without a problem, and i checked its vac line. I tied into the fpr vac line for a boost signal.