Most liked posts in thread: Bypass valve DELETE!!

Backing off the stop set screw and wiring tie shut the valve along with plugging the vacuum port controlling valve operation was the first way I discontinued the operating BPV. I did not notice any discernible difference in the IATs, timing,coolant temperatures or total boost but I did read boost start in at a lower RPM range. I lost about 2-3 MPG when I did monitor it at 60 mph 0 wind level highway pulling steady at 16-17inHG.
The mid range RPM surge or "Yo-Yo" was reported by BMW/MINI very low percentage of MINIs but got forum attention mostly I believe on nam? At that time 03 -04ish I read every TSB available pertaining to this concern and surprisingly the BMW/TSB reports compared to forum reports were extremely low? This would mean in reality a handful of MINI actually experienced the effect? You would think that most MINIs were still under warranty and that being a warranty concern more reports on TSBs? I will say in the last few years that on some that felt they were experiencing the "YO-YO" effect a good tune seemed to solve the feeling?

 

Early on...

in 2002, BMW was putting out ECU file updates like Moms passing out candy on Halloween. I think the problem was pretty bad and widespread, though not universal. BMW/MINIs history was more to give new ECU files as released, but not issue TSBs or the like. Whether you wanted it or not, they'd slap a new ECU firmware version on you car when you went in for your "free" service!

Like Jan said, it was poor programming of the ECU that lead to the problem, but as tunes were harder to come by then, and I don't think any (or very, very few) were doing dyno tunes, the only way to supress it was tweaking the BPV or the like. Anything that shifted how the valve opened or responded to vacuum and RPM could move the transition away from the problem spot. These tweaks included:

1) Wire Tie. (Ryephix 1, buy our buddy Ryan)
2) Stiffer Spring. (Ryefix 2 or DT BPV, developed by Ryan again, now sold by DT)
3) Relocation of vacuum tap (Vacuum Gain System, from Andy at Ross-Tech)
4) Flow restrictor in vacuum line (M7 would give you an orifice if you wanted one, it would slow the transition from open to closed)
5) Worked over BPV (Like what I did)

Anyway, cause of how all the stuff interacts, any one solution didn't solve everyone's problem. Eventually BMW/MINI got the tunes improved to the point where it's become close to a non-issue. Yet some of the solutions live on. Me, I'm still running my worked over BPV and the VGS....

This was a perfect example of how not to do nested feedback loops and showed how coupling of negative feedback systems can lead to instabilities up the wazoo! Each feedback mechanism in isolation would seem to be stable, but when allowed to couple, you'd get yo-yo.

And that concludes the MINI history lesson for the day....

Matt

 

When my wife and I couple our feedback mechanisms, we get yo-yo too.

Weird.

 

When do you plan on taking it to the track?

 

opcorn:

 

Doing it this way....

you will only get a bit of benefit in the very first gear that you roll onto power in. This is the only one that will have the valve open at all. Once at high RPM under load it will be closed.

Matt

 

When are you taking it to the track for testing?

 

Any updates on this bypass valve delete? I own a 2002 kompressor and wanted to do this but no one with my car has ever did this! Im trying to research all the benefits and disadvantages to this modification.

I have read many disadvantages to come from deleting the bypass valve. I read that it can cause compressor surge? I'm not sure how that would work on a supercharger but when the throttle is closed suddenly in full boost it does make sense to have some sort of problem right?

I would appreaciate any help

 

No because this is why.
This whole area has no boost
INTAKE FILTER--> THROTTLE BODY --->

Then from
SUPERCHARGER ---> ENGINE--->
is all compressed but when u let off the throttle it stops feeding in compressed air that is still pushed through the motor. It will more likely cause lean spots off the throttle. Compressor surge happens on my turbo because the compressed side of the turbo is where the throttle body is. Since there is never any boost on our throttle body(sc mini) then it shouldn't surge pressure anywhere.