FAQ: Boost Bypass Valve/Boost Control Solenoid Questions (No Boost)

AA wrote:

Mark, I think I understand now. Btw, I did read every word you wrote - about 5 times over. The part that threw me off was this: "And as a reminder for everyone, the boost Bypass Valve is vacuum-operated, but the vacuum circuit itself is controlled by the Boost Control Solenoid valve."

This statement led me to believe the BBV and BCS behave similarly or identically. I never read "overboost" until your last post (that might have helped clarify). But thanks for all the info.

Sorry about that, Aaron. You're right, that earlier post wasn't clear...

When I suggested re-reading, I should've specified that I was referring to my "long" post, with the green stripe, that said: "Most important, the Boost Control Solenoid switches the "control" backpressure between the blower output and the bottom of the Bypass Valve actuator, not the main vacuum from the throttle body to the top of the BV actuator..."

Not a prob - it's complicated stuff to absorb (for me anyway). The important part is, it's written here for anyone who wants to read into it and learn - and hopefully, perhaps with your help, we can understand better!

My GTP has a little crappy LED boost guage. Still better than the Riv i guess, but at full acceleration it was only reading halfway, and the car felt sluggish. My Riv's valve stuck once a while ago and ran lousy so i checked the valve linkage first. It was fine. I'm then thinking i have a vacuum issue, but a quick test showed it's fine. So i suspect it's the vaccuum switch that feeds the bottom of the vacuum "ball", or the "ball" itself. To test this i unhooked both vacuum lines from the ball and let the linkage fall down to the intake, (bypass closed).

It idles great, maybe even better, and i have full boost on the guage with just a tap of the pedal. Plus, it a tire smoking good time. I left work with the mileage computer (another feature of the GTP) reading 16.8 average. I beat it up driving home to see how it was going to run, and have fun with it, and was reading 17.0 when i arrived 12 miles later. I can feel a little loss in torque in the mid range but it feels much more powerfull and responsive as a whole.

My question is, is it the switch, or the "ball" Or, what i mean is, whats more common of a part to fail. I'm guessing the ball because it's a moving part with vacuum on both sides of the diaphram, but just a theory. I could take the parts off my riv to test i guess, but i'd rather not touch the Riv.

What, if any, is the downside to leaving the bypass closed? I can say right now, 12 miles in, i LOVE IT.

BTW, this GTP is a $500 winter rat, that i'm on winter #2 with and including maintenace , repairs, even DMV and tax still have'nt broke into four digits yet. All i really want in the end is whatever drivetrain parts that are left for the Riv. The blower is still tight at 163k. I do wish the Riv had HUD though. It's addicting.

Ball-part #524 in the top end breakdown (sticky)
switch-part #546 " "

Vista Cruiser wrote:

I do wish the Riv had HUD though. It's addicting.

"

Sorry I can't help you with the real question, but just wanted to let you know if you look around online you can find aftermarket heads up display units that tell you just about everything the built in one on the GTP does. I have one in my Riv and I actually like it better than the one in a friends Grand Prix GXP V8 edition.

I assume by 'ball', you mean the bypass valve actuator...
That's easy to test, just pull the other end of the vacuum line off at the throttle body and suck!

yeah..but dont swallow the balls!

Eldo wrote:

I assume by 'ball', you mean the bypass valve actuator...
That's easy to test, just pull the other end of the vacuum line off at the throttle body and suck!

Yes, and Yes, it moves, but i don't think it's moving enough. Maybe if i held a vacuum on it, then see if it backs off (leaks). The more i think about it though, i want to leave the bypass closed, and have a tire shreading winter. I'll just think of it as a test and a learning curve for the Riv. In the Spring i'd be happy to walk away from it with the blower under my arm.

I hate this GTP. I feel like i'm driving some bimbo's car. I was never going to drive it again after last winter, and gave it to my daughters to drive around out in the woods. So all summer they had a blast cranking tunes and beating the shit out of it. The exaust was shot and i was'nt spending $700 on an exaust for a $500 car. But then i got a free exaust from Impala LTZ 3.9. So i thought, one more winter? What the hell. The only effects from the woods was a wheel bearing, i packed and painted the fist size rot hole under the gas door, and it looks like brand new. Now if someone would be nice enough to slide into it, i'll get full value. In reality it's so rusty, it's ready to break in half. Good thing it has the big GTP rocker covers on it. They cover up all that air behind them.

There are some things about the GTP that really sucks that Buick did'nt offer though:
1-hidden antenna
2- HUD
3-mileage computer/boost gauge
4-performace trans switch

I know, i'm just pissn' in the wind.

MY GOD MAN! YOU ARE OBSESED WITH VACUM! CHIN UP MAN CHIN UP!

Unless the spring in the actuator is extremely stiff, you should be able to suck it to the end of its travel, then hold your tongue over the end of the hose to see if it bleeds down...

If you want to beat on it, the boost control solenoid should still back it off if reach overboost, as long as you leave the other hose connected to the actuator.

1- Mast antennae usually work better than glass mount ones. But the others are cheaper...

2- I've never tried a HUD, but the option would have been nice.

3- TOTALLY!!!

4- That's what the floor-shift is for

Kyle, more info on aftermarket HUDs please! A quick google search revealed... not much. Maybe I'm just searching the wrong terms.

I, too would like to see some information about HUDs.

Have you done a search for"HUD" or "HUDS" ?
This topic is titled Blower By-Pass Valve

Just an update. Having the bypass valve shut ROCKS!

No ill effects after 1000k. Having such quick throttle response is great. I'm going to have to do the same thing to the Riv because after this amount of time in the GTP, the Riv will feel like a slug to me with the bypass opening.

I'm also thinking about making a switch to leave it normal, but being able to turn off the vacuum so the bypass stays closed when i want it to.

My one warning is to keep an eye on the motor with a scan tool. Watch for KR. You are using boost at throttle positions when the PCM is not expecting it.

The ONLY thing you gain from this is throttle response. Really, it's costing you gas milage and putting your pistons at risk. The WOT performance hasn't changed any, and your shift points and other settings are far out of whack because your throttle positions are no longer where they are expected to be.

Basically, you are screwing around with your tune.

Yes, it's fun to have great throttle response, but in all reality, you could just drive with a heavier foot and have the same amount of fun, with the added advantage that the computer is treating the rest of your drivetrain properly.

I agree with everything your saying Derek. Never heard a knock yet in this car. Always use super, and have always driven this car in the winter. I have a Tech two at my disposal, but never felt the need to take a snapshot. I know exactly what it sounds/feels like when it runs out of retard. The real damaging kind at least.

It does run better at WOT because my accuator is broke, and i'm not taking the one off the Buick, or buying one either. This GTP is a 165k rat. An experiment if you will. It will be off the road forever by mid April. Whatever parts i can use for the Riv i'll keep. I may build this engine for later use in the Riv. If so, i'll get new pistons, maybe a set with a CR bump. Don't know. I'll search out or post that some other day. If it blows up..........ohh well. When i bought this car, ($500) i wanted one winter and a spare blower. I'm on the second winter, and the blower is still tight. So i'll happily beat this thing.

Cool, it's all good then! I just don't want someone to read this and think it's a safe thing to do. Have fun!!!

Does the 97 GTP (winter rat) have a GenV or Gen3 Blower stock.?

Rick, Gen V blowers weren't around until '03 or '04.

Ah shit, I knew that. It was 2004 with the GTP.

Even though, I have a "NEW" (never used) one with Nov. 2002 barcodes on it that no one can explain. It does have some witness marks on the housing where it would be bolted down, as though it was bolted to a test stand, and has absolutely no indication that it has been run on an engine. There are no dirt markings in the intake, absolutely no wear markings on the rotor blades or combustion markings anywhere you would expect them to be. It appears that this unit was installed on a flow bench with nothing but clean air run through it.
This leads me to believe it was only used in R&D.
Hopefully I didn't buy some research and development reject.

But I did know that production vehicles didn't come out with the GenV till 04 on the GTP.

This could be merged where appropriate but I wasn't sure where best to put it yet.

I'm about to swap the BBV off my genV onto my old genIII to see if it solves my lack of boost problem. I just noticed that the ports are turned differently and wanted to document it.

Did you give the actuator the suck test?

Eldo wrote:

Did you give the actuator the suck test?

If I positively knew what it was really supposed to do, I would. Both ports should be sealed and pull the diaphram, yes?

I'm actually more confused now than I was before I tried this actuator. Hooked up the same way, this holds the BBV closed (retaining boost) during idle which isn't right. I cannot adjust the position of the actuator to correct it. So it stays closed and obviously remains closed when I blip the throttle. I can see it trying to move it down though but it can't because it's already down.

The bypass solenoid opens and closes the passage of manifold vacuum/boost to the lower half of the actuator, right? Or is there more to it than that. I see there's a third port on the solenoid that just vents to the atmosphere...

This thing seems too complicated for what it is!

Because I was curious as to how yours is working, I went out and started my car and watched the BBV.
At idle the vacuum goes to the upper part of the diaphragm and raises the rod all the way, then when I blip the throttle the valve starts to go in the opposite direction (down) and then returns.
I can not get the lever arm to contact the base of the supercharger while parked, with engine running,as that would require much more vacuum to be applied to the bottom side of the BBV.

For shits and grins I would like to read the actual vacuum that is being applied to each side at the same time and see how it all works with the solenoid in place.
Just need to tee into 2 different lines and have 2 vacuum gages reporting the info.
Unfortunately cannot do it now as it has just started raining and the sky turned Black.
May be a fast passing storm, let me see if I have enough vacuum tee's in stock. I know I have at least Two vacuum gages that are accurate.

Also, I have a Gen V BBV on the Gen V supercharger that is waiting for install.
I also have a spare BBV for the gen3 in a box that I bought good used, low miles, just in case I found myself in the need.
If you need me to take some vacuum readings off this for you or if you find you need to buy a BBV or borrow until you can get your GenV install completed, let me know.

Rick, by chance, do you have a spare boost solenoid? Obviously that must have some sort of plunger mechanism in it to work and with that, a point of failure other than the electric portion.

I'll search around a little to see if there's any good info on the workings of the solenoid.