Background: Ive got an old JRSC kit with a 62.5 mm pulley, the TDR idler pulley bracket with raised edge pulleys, ac and ps in a 97 otherwise stock engined car. Im running mspnp and have an lc1 for wideband duties.

Issue: Ive never once made above 1 lb of boost. Ive searched for vac leaks, ran the car without the bypass valve, and have an obnoxiously tight belt on the car. Nothing works. My boost gauge and ecu both agree with the engine pressure so I know that that isnt the issue. The car felt almost like stock, just missing a little bit on the top end up until a couple days ago. The car sat for a couple days due to rain and people needing rides to work, and when I got back in it to go to work yesterday it felt like a completely different car in the worst way. At WOT I see between 10 and 7 in hg, and at idle I get around 20 in hg. I went through and tightened all the hose connections, checked the sparkplugs (they werent terrible) and put on a new belt and tightened it more. No luck, its still doing the same thing.

What in the world is going on?

Tl;Dr car has made no boost since installing mp45, sat for two days and now it maxes out at 7 in hg. all the common issues have been troubleshot.

 

Bypass stuck open. Has to be.

 

Ive capped the sensing line on the bypass on both sides and ran it like that and got no difference.

 

Check the rotors are spinning.

I think the 45 is the same as my 62 in that the nose pulley drives the rotors by a flexible coupler. I've seen the coupler break.

 

Before i installed it i checked it, they do spin and they are also pretty free spinning. Also i can hear the supercharger whine if i have the bypass sensing line capped (bypass gagged shut) and im pretty sure i feel it as a load on the engine at higher rpm

 

The bypass butterfly valve is definitely closed? I could see that getting stuck open.

 

Do you have a check valve in the idle control valve line? It runs (essentially) in parallel with the bypass.

 

Additionally, depending on how you have the MS setup, the intake idle control valve can have an inversion on the low end of pulse widths (mine does). If your idle closed pw is too low, the MS will actually open the valve when it thinks it is closing it. This needs to be tuned, presumably on a case-by-case basis.

 

Oh, and run a compression test (with fingers crossed).

 

I do have the check valve in, if i blow as hard as i can on the checking side there is a very slight leak by, could that cause a significant leak? I will certainly have to look at the tuning of the icv, because i didnt realize this was a thing (new to tuning)

 

How could i check to see if the idle pulse widths are inverted like you were saying?

 

You may be able to get a psi or so by blowing, so if you can get it to leak there it might be prudent to simply pull the trigger in a new one from TDR. You can build a tester fairly easily with some hose and a compressor if you have the means.

There is a fair amount of info on the idle control valve tuning out there, so I will not go into detail, but in summary:

Warm engine to normal operating temp
Use the idle control test feature in tuner studio to vary the pulse widths
Map where the idle hits the lowest rpm when decreasing the pw. Start at like 35-40 or so and work down. If you continue reducing the pw past this point (on an na6 at least) it will start to open again and increase the idle.

You can find the fully open point using the same technique, but by increasing the pw

On my car I seem to remember it being closed in the high 20s low 30s and fully open in the 90s. Dont hold me to that, I did it several years ago.

Oh, and compression test before buying anything. My hypothesis dies not address the WOT manifold pressure you reported. Hope that is an instrumentation issue or you may be pilling the head :(

 

Nevermind

 

Did you find out what was wrong?

 

If the bypass is actually opening and closing with vacuum, you have a major leak in your charge pipes or blower discharge manifold. My first guess is a faulty bypass valve / torn diaphragm not actuating the bypass valve butterfly.