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

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.

ClubGP wrote:

quote:

ORIGINAL: seen97
So, if you think you can always watch for KR, I guess you be ok, since THAT is the primary use of the solenoid, it forces the BBV open when KR is present. Well, its not my engine.


Actually, it doesn't...

It will open the bypass for traction control, or if the PCM goes into abuse mode (calculated torque exceeds programmed limits) It will also force the bypass open in reverse... But it doesn't open the bypass just because of detected knock.

PRJ .

I just removed my solenoid and from what Paul said, it's not terribly important anyway. My tune pretty much negates half it's function and I don't ever hammer it in reverse. Screw the bugger - at least for now

Cody,

Most of the time the actuator holds the bypass valve open by throttle-body vacuum, what we used to call manifold vacuum: low load, high vacuum. As you apply more throttle, the vacuum drops and the actuator allows the bypass valve to close, giving you boost.

NOW - The other port is not for vacuum! It is for blower-pressure bled out of the manifold by the Boost Control Solenoid, which pushes the diaphragm back in the same direction that the inlet-vacuum was originally pulling it, thus increasing the bypass and lowering boost pressure...

What is the name of this part? It's located above the thermostat housing and is it supposed to be leaking any air? I have it circled in the picture.


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That is the BBV or Boost Bypass Valve and no it should not be leaking vacuum continuously.
If it is indeed leaking or hissing, check all the vacuum connections and make sure none of the hoses aren't leaking before replacing the valve.

Alright, thanks. Gonna go through vacuum hoses tonight. Already had to change one dry rotted one last night.

It's a good idea to replace ALL the vacuum hoses and start with new ones. Sometimes they will look OK but if you look real close you'll see the ends cracked slightly where they attach to any nipple.
I just drove my car to the auto parts store and had the guy come out and look at the hoses to be able to give me a certain amount of each size hose and I replaced them right there. Cost me less than $10.00 IIRC.
Sometimes it's hard to identify the diameter of the hoses if you don't work around the engines everyday.
I was lucky and I got a knowledgeable guy to set me up with what I needed.
All I brought with me was a sharp razor knife to cut the old ones off if they were stuck on the fittings and a pair of good wire cutters to cut the new hose to size.
It really doesn't take much hose to replace the ones you can get at.
Some of them end into factory reducers and if you have a leak or see a crack on one of them be careful with them and try and find the necessary fittings at the parts store so that you can somewhat duplicate the reducers and get a good tight fit.

The hoses are next, but the boost bypass is leaking air off to.

If you do find that you need a new BBV do a search on this site. There was some issue about finding new replacements, but I can't remember what it was exactly. It may have just been a cost issue, but then again my memory fails me at the moment.

I've been looking online, but haven't found one.

Did you search this site for some additional info.

There may be another name it is found under from GM or other vendors. As I mentioned, I remember the topic coming up a while back but don't remember the outcome.

It's in this database somewhere.

GM P/N is 89018120. Monsterparts has no listing. I found this though, has no pic, but the pricing is the same as what GM shows under the P/N.
http://www.gmpartsgiant.com/parts/gm-actuator-kit-89018120.html

Is that seriously an M112 Blower on that thing?!!!

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/what-is-the-part-number-of-the-bypass-valve-actuator-t5880.htm?highlight=boost+bypass+valve


Take a look at the LINK above for the BBV P/N and it can be had from www.monsterpartsonline.com for cheap. If you can afford to wait for it, otherwise order from your local dealer.

EDIT: Based on Abaddon's post, maybe it is no longer available from Monster. Sorry if I confused the matter. And I think the part identified in the link above is the electrical actuator or solenoid. That is the least expensive part which is attached to the same bracket as the BBV. This is why I couldn't remember clearly from before as it was a bit confusing as to what GM Parts actually calls it compared to what the FSM calls it.

Ok, thanks again.

Be careful, there are different P/N's for different year cars.
I would verify the part number by going to my local dealers parts dept and ask them to look up the number for me.
The local dealer in my neighborhood is good like that and I ask for a printout with the picture of the part and part number, then I can go on-line and try to find what I need.

I located a used one for about $30.00 a year or 2 ago when I needed one but there isn't a P/N on it.

EDIT: If you should find and confirm the correct P/N for the BBV will you post it for reference and addition to the P/N List.
Thanks,
Rick

I'd sure like to find a good one for my '96.
Without paying attention, I braced against it with my Right hand as I leaned into the engine compartment and broke it off it's base.
Then later I found the top came off it. Thank goodness the vacuum hoses held it in place so it wasn't lost.
In both cases I used JB Weld to put it back together.
It works, but looks like hell.
Hard to believe it's a difficult part to find, and costs that much new.