Follow up to my first question...loosing boost

[coach]

I seem to notice that my boost is changing when the car shifts. It will climb, then drop when it shifts, and then fluctuate from there. Last night it was cool and the faster I went in 3rd WOT, the more boost I made...WTF!!! DOES ANYONE KNOW WHAT GIVES??? It is driving me nuts... Please point me to somethings to try and I will eliminate one by one.

Thanks
Coach

 

[coach]

Can I run the RJC boost controller with an external waste gate? I think my boost controller might be giving me fits.

Coach

 

[DailyDrifter]

Yes you can run the RJC BC with an external gate, I have a Turbonetics MBC installed inside the car so It can be adjusted without popping the hood. I would look for leaks in the vac lines for the gate. Or the gate itself could be malfunctioning(SP?) What are you using to control the boost now? are you just using the spring in the gate?

 

[coach]

Right now I have a Turbonetics controller. Pull up on the knob twist it and push dowm to lock in place. It seems to have way too much adjustment for what I need. One turn and I am in the mid to high 20's. It should be more fine tuneable than that. My downpipe is a GN1 PERFORMANCE. I do not know the gate size, but I think it is a 46mm. The vac lines to the gate and controller are all zip tied. I would not think that is where I am loosing it. Is the RJC controller more tuneable?

 

[DailyDrifter]

Yeah those BC's are touchy, Not sure about the RJC. Maybe someone with an RJC will chime in. Its funny you turn that thing a little and its like 5 psi +/- , its a good boost controller to test headgaskets.

 

[ijames]

What scantool are you using? What happens to the O2 volts or afr from before a shift to after the shift? If you are running a little rich already (for safety, or with pump gas, or whatever) and the motor goes a little richer at the bottom of a gear the boost can fall off then recover through the gear.

 

[coach]

I run a scanmaster. I get no knock at all ever. I am going to mess with this controller a little longer, then I am changing it. It is way over priced for what it is anyway. I think I am going to go with an RJC. Is it possible it is the turbo itself? I bought it used and it has no play in it at all. It seems to spool real good. I run an open dump and There is no pitch change in the sound when I am at WOT. It is beginning to really pizz me off!!! When it does get to 19-20, holy crap is it strong, I wish I could feel it for a full 10-12 secs.

 

[84BuickGNYorkPA]

Coach,

IMO if the boost is climbing then you may need a bigger wastgate hole in the turbo housing, or you have a issue with the wastegate itself not opening up far enough. But when you say that the boost drops after you shift.... not sure... I would also take a close look at the external wastegate.
I prefer my adjustable boost knob over my RJC boost controller, only because I can reach under the dash during a run and turn the wick up or down while running and watching the boost gage.

Chuck

 

[coach]

The thing that erks me is when I first installed the downpipe/wastegate combo with the boost controller, it would go to 15 pounds and sit there all day. I installed this 49 and it has not been consistant since. I do not think I have any leaks.

Coach

 

[84BuickGNYorkPA]

Do you think that the wastegate hole in the turbo housing is big enough? If it is to small then I could understand the boost creep you are seeing on the top of the gears. Maybe when the car shifts gears the lower RPM is controllable with the wastegate, and the boost comes back to the intended setting, as the rpm rises and the hole is maxed out because of air volume the boost creep comes back.

Chuck

 

[grocerygetter]

or it's the other way and the thing is leaking at the base of the turbo. Check for soot.
That may be combined with the wg hole needing to be enlarged.
You can check sealing pretty easy...just pull the dp off and look at the puck, you should see a deifined carbon ring. Take a pic and post it.

 

[ijames]

Does that wastegate use the hole in the turbine housing or is it plumbed in before the turbo, and has a flange that just covers the hole in the turbo? A 44 mm wastegate should be plenty, and the only dp/external gate combo I've read about with flow and creep problems is the old Hooker Headers dp which had too small of a tube for the wg. What all did you change when you bolted on the 49?

 

[bison]

Do you think that the wastegate hole in the turbo housing is big enough? If it is to small then I could understand the boost creep you are seeing on the top of the gears. Maybe when the car shifts gears the lower RPM is controllable with the wastegate, and the boost comes back to the intended setting, as the rpm rises and the hole is maxed out because of air volume the boost creep comes back.

Chuck

+1. Open the hole up to .110 and see if the problem is still there. You should get more creep in 3rd than other gears. 1st and 2nd are so fast you barely have time to even see creep unless its data logged.

 

[coach]

My first post was about the boost peaking and then falling off. I still notice that when the weather is hotter, but the other night when it was real cool, I noticed it was climbing the faster I went and would fall after the shift. My problem is it never did this before. It would peg 15 psi and stay there like the gauge was broke. It did not fluxuate at all. I changed the stock turbo to a 49 and added 42.5 injectors in place of the stock and a new chip from Eric. That is it. WS6 and I did the install and it went real smooth. No hang-ups or trouble with anything. I zip-tied every line and super glued the boost gauge line. I believe my gate to be a 46mm. It is a GN1 and comes in two sizes, 38 and 46. I would have to check with Archie to be absolutley sure.

Thanks
Coach

 

[bison]

My first post was about the boost peaking and then falling off. I still notice that when the weather is hotter, but the other night when it was real cool, I noticed it was climbing the faster I went and would fall after the shift. My problem is it never did this before. It would peg 15 psi and stay there like the gauge was broke. It did not fluxuate at all. I changed the stock turbo to a 49 and added 42.5 injectors in place of the stock and a new chip from Eric. That is it. WS6 and I did the install and it went real smooth. No hang-ups or trouble with anything. I zip-tied every line and super glued the boost gauge line. I believe my gate to be a 46mm. It is a GN1 and comes in two sizes, 38 and 46. I would have to check with Archie to be absolutley sure.

Thanks
Coach

Id still verify the hole is .110 or more. If its not then its most likely the problem. If the spiking problem is worse when cold this is further evidence.