Greddy Profec B

[samh]

My wastegate on my 86 930 was giving trouble so I decided to go for a Greddy Profec B boost controller and Tial Wastegate. Everything sent seemed straight forward enough and I have installed everything to the best of my ability. My question is concerning the line from the engine to the controller up front. The instructions show a three way tee into the fuel regulator back to the unit. Well I have tried this and I have also tried a direct tap in to the innercooler but no go. Each time I try to set the thing it does not controll boost at any level and goes straight to overboost. I know this vague, but if any of you have any ideas I would sure would appreciate it.

[beepbeep]

Huh??? FUEL regulator??? It has nothing to do with fuel...it works by measuring boost pressure and having a solenoid-operated valve modulate pressure going to wastegate.

Make sure you read instruction propperly and don't touch fuel lines.

There is a OEM hose going from intercooler down to wastegate bell, and you can connect everything BC needs to this hose.

I'll try to post a picture of how it works later...

[samh]

Thanks Beep, I finally reasoned that the controller has to feel the boost to operate the wastegate so I made a tap into the innercooler to achieve this. Still no go, goes straight to overboost just like nothing attached to wastegate. I have checked the connections dozens of times. I am beginning to think its a bad unit.

[beepbeep]

Just wait a moment, i'm just writing some more info with pics...i'l post it in 5 minutes.

[beepbeep]

I never used Profec B but almost all BC work in the same way.

You run a hose usually attached directly to wastegate bell into a solenoid-valve. That solenoid valve is operated by electronic box. Electronic box monitors boost with it's sensor. As long as boost is under pre-determined level, it opens a solenoid so air gets re-routed and instead of going into wastegate, it goes back into intake.

When boost raises to it's pre-determined level, solenoid shuts and boost goes into wastegate instead, which starts opening. Boost goes down, and solenoid shuts down, then starts oscilating just enough to keep your boost where you want it.

Check out this pic, it's from SAAB but APC works in the same way:

Solenoid open, wastegate shut:


Solenoid closed, wastegate open:


You can get absolute pressure signal to BC pressure transducer by tapping into intercooler, then you put solenoid between wastegate and intercooler, but make sure you re-route output-hose from solenoid into airbox (non pressurized area), and not back into intercooler, otherwise it won't work...we are talking hose "R" on diagram...

Good luck!

[beepbeep]

With other words, "C" has to be tapped into intercooler, "R" into filter-box and "W" into wastegate bell. In my opinion, reference-boost hose (not in diagram) to Greddy BC needs to be tapped somewhere else into intercooler and not just taken off the "C" hose... if "C"-hose is too long and you have T-orifice , you might get funny boost readings, so i suggest you to take it off some other place in the intercooler, preferrably after turbulators, which will force BC to regulate true boost as it is seen by engine and not just peak pressure in turbo compressor-housing.

further reading:
(There is slight risk that taking reference-signal after intercooler will involve certain delay-effects as there is big cavity to fill with air before BC senses it. It might lead to slight overshoot / funny behaviour in case modulation-frequency of BC and parameters of it's micro-controller happend to be a bad match to time it takes to fill intercooler-plumbing cavity but it's easy fixable by moving the hose and not inherently dangerous. I recomend you to give it a try...if it works you'll have Greddy holding exact pressure after Intercooler which is what engine sees, so it will keep it even if you change intercooler or tubing. If it doesn't you can just move the tap closer to compressor housing and obtain delay-free signal which has less chance of triggering unwanted oscilacions induced by complicated P-I parameters of such feedback-controled system. Calculating those is kinda out of reach of this post , so just go for trial-and-error )

Cheers!