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Sev7n007 08-12-2009 07:18 AM

Boost controller and B.O.V?
I am about to purchase a manual boost controller and after market B.O.V on my 1999 95 b235e. The only thing i have done to it is a tdo4h swap.(striaght bolt on, no ecu programming) I am very early in my tuning but this part just popped out of knowhere for a good price. I would have rathered upgrading intake and exhaust side before even adding it. Just curious cause the controller is coming first.
I guess i have two questions in this thread. The first would be, has anyone else experimented or knows specifications of how much boost could my setup handle safely? Personally I just want to be able to add 5psi to what i got now.
The controller i have manages both waste and blow off valve. I like the idea of not having to replace stock springs on my wastegate. I really do not want to try and push the envolope on this setup. Just want to get a little more out of it if needed. I am looking to purchase another motor to build up to something that could handle a bigger beating.
The second question is the implementation of the after market B.O.V? (Which is a external dump.) The stock setup recycles back into the intake. I was thinking of just plugging the intake from where the bypass tube merges back into the system. And just using the normal bypass valve mounting point to the compressed side of the intake before the throttle plate. Finally the question. Is this the only reasonable way to do this with least intrusion to the stock setup, or has someone gone about this totally different.
thanks again.

dan-the-kid 08-12-2009 07:19 AM

Neither will work.

Both with flip out T7. Sorry.

Sev7n007 08-12-2009 07:42 AM

Don't understand? Why wouldn't it work? I'm not trying to do anything more drastic with boosting just want to delay wastegate opening if that is what is regulating my psi. If it's really a flow issue i could understand, meaning it is not taking in enough in order to put out more. And opting out the bypass valve in direct replacement of a external dump valve to regulate intake pressures?

PoisonBeef 08-12-2009 08:30 AM

T7 uses a mass air flow meter so when you dump charge air to atmosphere it "loses" it and notices. It then gets mad at you.

not sure how the boost controller will do, but the ECU will be confused.

Adub 08-12-2009 08:34 AM

The reason it wont work is because T7 (your engine management system) will definitely not like the BOV and the boost controller, which are managed by the system itself. Your car has a MAF, which measures air flow, not pressure, there for it will be looking for the recirc'ed air coming from a bypass valve. Now, there would be no harm in running an aftermarket bypass valve, but the car would still definitely not agree with the boost controller.

...edit.. got beat to the point.

dan-the-kid 08-12-2009 08:48 AM

Its a similar reason for the MBC.

Since the car uses a BPC(boost pressure controller), like a mbc but controlled by the ECU. If the ECU is telling the BPC to allow an X amount of boost pressure, but you have your MBC set to some other amount, the engine management (T7) is getting different MAP readings while thinking the boost pressure is set by the BPC, when its not.

In layman terms....


PoisonBeef 08-12-2009 01:25 PM

You could t7 sweet your ecu for just a little more than your bov and mbc.

Sev7n007 08-12-2009 01:41 PM

Interesting . . . . .
Thanks guys for explaing that to me it slipped my mind that the "air flow meter"
has already pre - calculated what is in the intake. Never the less couldn't I adjust the B.O.V to vent a little air just to stop compressor surge? Could i also delay the wastegate from opening? (Make it put up with a little more pressure before venting.) Hey, I just figured it's a mechanical compenant, which maybe monitored by bpc. ( was actually thinking of installing the controller in series between wastegate and bpc. Not trying to bypass anything)
I get the point that if i choose to vent too much air out of the intake ( Blow,off,valve) upon the next time the plate opens it will run rich for an instant. ( vice versa for the wastegate)
I am not trying to aggressive tune the vehicle with the manual controller. I just want to see what i can get away with, before the systems looses stability.
If anyone thinks there is a way that this theory could be done don't be shy. Also if there is noway the bpc will allow anything out of it's desired mapping and it's very sensitive please get back to me. Thanks again guys trying to understand my system. This vehicle is turning me into a full manufacturer lover over night.
going to take another look and the "wis"

Tweek's Turbos 08-12-2009 02:22 PM

Most everybody is off to the Saab owners convention starting tonight. I wouldn't put anything on the 9-5 untill at least after next week.

Sev7n007 08-16-2009 07:52 PM

Maybe the better question is?
I think the better question is has anyone implemented a external B.O.V, and used a manual boost controller successfully on this system?

Palmer 08-16-2009 08:04 PM

No, because of the way the system works. T7 and a BOV are mutually exclusive.

Same deal with the boost controller.

Sev7n007 08-16-2009 08:18 PM

I was hoping that the system was a little more forgiving. Although i do like the uniqueness of the system.

Palmer 08-16-2009 08:20 PM

It's not, but it's still pretty amazing.

Look into "t7 suite" With an investment in time, and a few supplies, you can tune your ECU yourself.

lekonna 08-16-2009 09:16 PM

you can use the bov if you really want the silly sounds, just move the maf meter to somewhere before the throttle on the pressure side and vent from there. though i would't recomend it. The transitions get all bugged with the t7. the original by-pass will work just as well stopping any surges.

as for the boost controller, what you'll end up is a t7 apc error and a check engine light. The T7 will monitor the airmass it requests and the airmass it gets, if there is a big difference it will default to error mode with lower requests.

Sev7n007 08-18-2009 07:08 AM

ok thanks everyone

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