Boost Bounce ????

[Buick Beginner]

Gentlemen,
I don't think I'm the only one to experience this condition, but I can't find anything on correcting it. When I run the car at WOT my boost climbs quickly to 17 PSI, (like it's supposed to), but then it bounces off 17 drops down to around 13 to 15 and stays in that range for the remainder of the run. Seems like I've read something about correcting this with a manual boost controller or a Delta Gate or something. Any help is appreciated. - BB

 

[WarpSpeed]

That sounds like what happens when the Y is in backwards. I think the Y leg(The most angled one) goes to the compressor.

 

[FJM568]

Some chips are programmed to run lower boost in the higher gears due to more load on motor in those gears...

You can run the so-called "Grainger" valve to adjust boost to a certain level and hold it there, but you lose the ecm ability to pull out boost when knock or detonation occurs...

I believe some of the aftermarket boost controllers that some of the Buick vendors sell, might do what you are looking for...

 

[Buick Beginner]

Thanks

I'll check my "Y" tonight. - BB

 

[Russ Merritt]

Dude, the straight one goes to the compressor, the angle goes to the wastegate! Adjust the wastegate rod a little tighter, sometimes more spring tension helps stabilize boost press. MAKE SURE THERE ARE NO LEAKS IN HOSES AND ZIP TIE ALL CONNECTIONS, ESPECIALLY THE SOLENOID VALVE!!!

 

[TurboDave]

When does the boost drop? At the 2-3 shift? It's supposed to ya know.

 

[Buick Beginner]

Hi Dave

Thanks for joining in, no actually the boost drops as soon as it hits 17 psi, or if I crank the WG rod back to 15 psi it will bounce off of that. Typically it's about 3/4 of the way through 1st gear when it hits 17 psi, then it just bounces off 17 down to about 13 and seems to stay around 13 to 14. This ocuurs before the gear change. - BB

 

[FJM568]

Do you have a scantool hooked up when it does this???

It sounds to me like the ecm is pulling back boost due to knock or detonation...Drive it until you get less than a half tank of gas, then put in a gallon of xylene or even some high octane race gas and see if the boost still drops off...

 

[TurboDave]

Re: Hi Dave

Originally posted by Buick Beginner
Thanks for joining in, no actually the boost drops as soon as it hits 17 psi, or if I crank the WG rod back to 15 psi it will bounce off of that. Typically it's about 3/4 of the way through 1st gear when it hits 17 psi, then it just bounces off 17 down to about 13 and seems to stay around 13 to 14. This ocuurs before the gear change. - BB

Ahhh, then what you are actually describing is not so much a boost sag. What you're seeing is a boost spike.

Your actual boost setting of 13-14 is what it's going back to after the innitial spike up to 17.
What we need to do is figure out how to cure "boost spikes". Gotta get to work right now, but will be back later this evening.

 

[Buick Beginner]

I'm Listening

Teach me Master Jedi. - BB

 

[Buick Beginner]

Found Something Out

Well, I don't know if this is connected or not. I was over at a buddy's house this evening who is also running an '87 GN and i was just looking around under his hood and noticed that on his waste gate solenoid, one tube had a vacuum line on it which ran to the compressor and the waste gate. The other tube sticking out of the front, had a small filter on it. Now wait a minute. My second little tube sticking out of the front has been capped with a rubber cap. My buddy says, "No, it is supposed to have a foam filter on it." I removed the cap thinking, "I wonder what effect this has on boost?" I got out on the open road on the way home and nailed it from about 10 mph. To my horror, I watched my boost gauge shoot up to 23 pounds of boost and my knock dectector went beserk! Can someone please expound upon this situation? Apparently the previous owner/abuser installed the cap and not a filter. What gives?? - BB

 

[Russ Merritt]

You need a new wastegate solenoid! The cap is there because someone knew it was junk. It stops the boost press from escaping the valve, hence opening your wastegate, controling boost somewhat (just not letting it over boost) get a new solenoid, wastegate hoses (7/32" hose at autozone) and zip tie all connections, and you should be all set

 

[TurboDave]

Re: Found Something Out

Originally posted by Buick Beginner
Well, I don't know if this is connected or not. I was over at a buddy's house this evening who is also running an '87 GN and i was just looking around under his hood and noticed that on his waste gate solenoid, one tube had a vacuum line on it which ran to the compressor and the waste gate. The other tube sticking out of the front, had a small filter on it. Now wait a minute. My second little tube sticking out of the front has been capped with a rubber cap. My buddy says, "No, it is supposed to have a foam filter on it." I removed the cap thinking, "I wonder what effect this has on boost?" I got out on the open road on the way home and nailed it from about 10 mph. To my horror, I watched my boost gauge shoot up to 23 pounds of boost and my knock dectector went beserk! Can someone please expound upon this situation? Apparently the previous owner/abuser installed the cap and not a filter. What gives?? - BB

The previous owner unwittingly capped it off, and in doing so, rendered the solenoid useless. The get some boost back he probably had to shorten the wastegate rod A LOT. With the solenoid back in control, you'll have to lengthen the rod back out to a reasonable length.

 

[Buick Beginner]

Solid Boost Now

Gentlemen-
Just wanted to keep everyone in the loop on the boost bounce saga. If you have followed the posts up until now, you have read about my interesting discovery of the missing little filter on the waste gate's solenoid. After the horrifying overboost situation, I began cranking the waste gate rod out and I eventually ended up twisting it around 12 full rotations. The boost is now solid at 17 pounds in first gear and 15 pounds in second and third. Just thought I'd let everyone know. Again, thanks for all the inputs.
- BB