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GTP down on boost.... can't figure it out...

97AutoXVette

97AutoXVette

New member
3.5 pulley and I am only seeing 3ish PSI at WOT.

I recently redid all of the vacuum lines and just checked them again. Seem to all be fine.

I also removed the boost bypass solenoid a few weeks back so it is not that (plus the tune is showing me 100% commanded for the solenoid. so it should be seeing full boost...)

Any suggestions? I have the right size belt and everything... :th_scratchhead:
 


Ok, what is left?

The actuator isn't being controlled by the soleniod you removed. Vac lines are good. The only thing left that can control it would be the actuator.
 
Yepp.. I can check that after work (not really sure how to check that completely though)... The rotors/gears just don't suddently go bad do they?
 
ordered a new Bypass Actuator. Did some searching and seems to be a probably cause. I will update after I get it installed this weekend.
 
Well, installed the new bypass actuator today. That means new vacuum lines (check all of them), electronic boost solenoid removed, and brand new Eaton actuator. Just got done logging some pulls with HP Tuners.. Still seeing 4 lbs of boost max :confused:

What else should I check?? No check engine lights, no issues of any kind.. Just really low boost. Everything else is normal. Thanks in advance!
 
does it sound like its getting full boost? and feel like it? if so try a new map sensor, its what the pcm reads boost from.
 


I'd say it sounds like it is getting into boost okay but doesn't quite feel like it. any recommendations where to pick up a map sensor? I am going to search around.

Again, no leaks or noticeable issues of any kind, plus plenty of new parts. Maybe it is just in the MAP.
 
Scottydoggs said:
i swap a jy one on if you got a yard near by.
Click to expand...

Yes indeed! going to grab one here early this week. Out or curiosity, The car mainly reads air and adds fuel based on the MAF readings right? Wondering if this "potential" MAP issue can do damage to the car during normal driving and while under boost.

I hadn't noticed any issues in AFRs yet so...
 
not sure if it has anything to do with fuel, but it reads the boost. its got a vac line to it from under the supercharger snout.

dont think any harm will come from driving it.
 


Sounds good. I actually removed it from the engine mount about a month ago and mounted it to the firewall with a new vacuum line running to it and the sensor running to it as well.
 
Yepp. I do not have a boost gauge but I am maxing out around 120ish kPa and then I convert to psi and subtract off atmospheric. After thinking about it more, I think my MAP sensor is fine. Duty cycle on the injectors is down, low MAP readings, no knock, and what feels like a lack in power.. At this point, I am stumped again. Guess I can pull the plugs, but no check lights and it runs/idles perfectly smooth...
 
Fivefingerdeathpunch said:
Do you have and acutal boost gauge or are you just going by what you see for MAP Kpa?

Figure 140-160 kpa is 7-9 psi I think.
Click to expand...

I can also throw the data log I took today up on HP Tuners if you'd like. Not sure it will tell you more than I did in my previous post though. Let me know. Def. up for recommendations and advice at this point.
 


here is another thought.. I removed the electronic boost solenoid completely. I then hooked the vacuum line running from the fuel pressure regulator straight up to the bottom of the BBV.. Was that a bad idea? I thought it was a direct connection when the solenoid wasn't limiting boost.
 
Fixed it.... I feel so dumb. Thanks for the help guys. I ran the vacuum lines wrong when I removed the boost solenoid. It's back in and everything is working fine now.

Now, back to this KR issue!!!

FYI, peaked at 173 kPa = ~25.1 psi

25.1 psi - 14.7 (atm) = 10+ psi of boost on the 3.5 pulley. That was after seeing up to 9.6* of KR. Poly mounts are going in this week. We'll see if that helps with the KR at all.
 
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