DASC boost loss issue. Need help.

[Christian]

I have a DASC on my Z3 1.9 with Technique Tuning software and a 3.4" pulley. When first installed it was producing around 10.5 to 11.0 PSI of boost depending on ambient temps. For the last several months boost has been 9.5 to 9.75 PSI max, even in cool weather. I'm looking for help finding the cause of the low boost condition. I'm very mechanically inclined, but have limited experience with superchargers so looking for help on identifying the issue.

- The internally stock motor has around 90.000 miles on it. I've autocrossed the car for several years. While it hasn't been tracked, it hasn't had the easiest life either.
- The supercharger has been installed for about 15,000 miles
- I'm spraying 50% water, 50% methanol through the supercharger. Per Eaton this should not damage the rotor coating for this generation of M62.
- Belt and dynamic tensioner have been replaced with improvement
- I smoked the vacuum system and found no visible leaks
- Replaced original PCV with PCV intended for boosted applications
- Supercharger turns relative smoothly and quietly when turned by hand. There is some resistance, but it seems similar to when it was new.
- No changes to exhaust system since boost loss.

An acquaintance who is an engine builder suspects the valve springs are weak and that the valves are floating at high RPM, making the boost blow right out the open exhaust valves.

I'm wondering whether the water/methanol mix has slightly worn the epoxy rotor coating (despite that Eaton said it was shouldn't) causing the rotors to not compress the air as much.

I think the car feels less powerful than it it used to, but I haven't had it on a dyno since the low boost condition. To confirm that it's not my imagination, I purchased a new, temporary boost gauge to replace my current boost gauge. I know it's a long shot, but perhaps my current gauge is faulty, and when I visually see the lower boost reading I imagine the car is less powerful when in actuality it's not. The new gauge should tell me. I hope to test it this weekend.

Any thoughts on other things to check?

[xxxJohnBoyxxx]

Make sure you have the bypass valve hose hooked to the DASC's manifold port. Also are you running a R-Pot valve to block lost boost from the injectors or did you elimate the injectors with a new set of 30# red top injectors when you installed Nick G's tuning and hardware?

I ran Meth through my DASC for many miles and never had a issue with rotor coating. The rotor coating issue was a screw up at Eaton and you should not have any issues with the coating.

If you don't run the bypass valve vacuum/boost source from the DASC manifold you will loose boost psi, I know this from personal experience.

John S

[Christian]

Originally Posted by xxxJohnBoyxxx

Make sure you have the bypass valve hose hooked to the DASC's manifold port. Also are you running a R-Pot valve to block lost boost from the injectors or did you elimate the injectors with a new set of 30# red top injectors when you installed Nick G's tuning and hardware?

I ran Meth through my DASC for many miles and never had a issue with rotor coating. The rotor coating issue was a screw up at Eaton and you should not have any issues with the coating.

If you don't run the bypass valve vacuum/boost source from the DASC manifold you will loose boost psi, I know this from personal experience.

John S

John,

Thanks for your input. I added the 30 lb injectors with Nick's stage III software (before I got the custom tune) so I don't need the check valve for the injectors.

Just tonight I moved the bypass valve vacuum line to the intake manifold instead of off the throttle body. Unfortunately it made no difference. I just ran the car. 9.5 lbs max boost on the limiter in 1st and 2nd gear.

I also moved the Ford SVO PCV valve so that it sits vertical instead of horizontal. i figured that maybe the ball valve wasn't sealing shut causing boost to leak into the valve cover. It was a long shot, but it made no difference either.

I'm going to piece together a diy boost leak tester later tonight or tomorrow and see what I find.

[xxxJohnBoyxxx]

Put a 3.2" pulley on that setup and I bet you will get 14-15psi boost in weather under 45degs F.