overboost

[garyk1970]

my car is overboosting (20+)psi.would like to get it down to 15 factory.and tune from there(have detonation over 10 psi)replaced some vaccum lines,check boost syl,etc.pulled computer and found a thrasher chip v7.0-

what can i do to set boost lower,another chip?(i dont have an oem thats good)

adjustable wastegate?

detonation has been the main issue.car has two fuel pumps :biggrin: ,second one kicks in at 4 psi,both working,not sure what they are.

replaced the two fuel filters :biggrin: ,no cat,new delco plugs,wires,coil pack,89 t/a fpr,gonna put a new o2 sensor in,ck maf when i get a scanmaster.its not fake knock,you can hear it.what else to check?

check out that fuel line...

 

[jurassic five 7]

Get rid of the two fuel pumps! Just get a Walbro 340 with hotwire kit.

Also go get a Turbotweak chip.

Forget two pumps, they could be bad and just crapping out.

 

[2QUIK6]

Unless your car is running 10's or faster, you don't need the 2 pumps. One could be bad and restricting the flow or allowing the flow from one pump to go backwards back to the tank depending on how its configured.
Get a manual gauge hooked up to the fuel rail and run it to the windshield so you can see it while driving and make sure your getting around 40-45# at idle with the vac line off the regulator.....then reconnect and drive it and make sure your getting 1# of additional pressure for each 1# of boost over the value you saw at idle with the vac line off.

So, if you had 40# at idle with line off....then at 10# of boost with the vac line connected, you should see 50# of fuel pressure.

Also, need to fix why your getting 20+# of boost...could be a number of things...maybe you already have an adjustable WG and it needs adj...make the wg rod longer...maybe you have an aftermarket DP with the puck hole in the exhaust side of the turbo too small...maybe a bad WG solenoid...maybe the "Y" vacuum fitting is backwards (the striaght leg goes straight to the turbo)...maybe a cracked vac line.

 

[garyk1970]

Unless your car is running 10's or faster, you don't need the 2 pumps. One could be bad and restricting the flow or allowing the flow from one pump to go backwards back to the tank depending on how its configured.
Get a manual gauge hooked up to the fuel rail and run it to the windshield so you can see it while driving and make sure your getting around 40-45# at idle with the vac line off the regulator.....then reconnect and drive it and make sure your getting 1# of additional pressure for each 1# of boost over the value you saw at idle with the vac line off.

So, if you had 40# at idle with line off....then at 10# of boost with the vac line connected, you should see 50# of fuel pressure.

Also, need to fix why your getting 20+# of boost...could be a number of things...maybe you already have an adjustable WG and it needs adj...make the wg rod longer...maybe you have an aftermarket DP with the puck hole in the exhaust side of the turbo too small...maybe a bad WG solenoid...maybe the "Y" vacuum fitting is backwards (the striaght leg goes straight to the turbo)...maybe a cracked vac line.

the car has two pumps because of its history.i guess the buick burned more methanol than what one pump could deliver??also has a 30 gallon s.s. tank.i think one pump old could be the problem.second pump is coming on at 4lbs boost(verified with a test light hooked to an extenion lead at pump and its getting voltage and you can hear it come on)

gotta get a fuel gauge.

oem wastegate and checked/replaced vaccum line/y

how to test boost syl?

has a thrasher chip v7.0?? boost???

 

[2QUIK6]

the car has two pumps because of its history.i guess the buick burned more methanol than what one pump could deliver??also has a 30 gallon s.s. tank.i think one pump old could be the problem.second pump is coming on at 4lbs boost(verified with a test light hooked to an extenion lead at pump and its getting voltage and you can hear it come on)

gotta get a fuel gauge.

oem wastegate and checked/replaced vaccum line/y

how to test boost syl?

has a thrasher chip v7.0?? boost???

The trasher chip won't make the boost go that high. The OEM wg is 13#, make sure its not a heavy duty one that's 18# or so...sounds like you replaced it already though.
Make sure the "Y" is installed correctly...(the single side goes to the wg solenoid..the red thing on the valve cover...the straight leg to the turbo, and the slanted off leg to the wg actuator.
The other cause could be an aftermarket downpipe and the wg hole in the turbo is not ported out enough, for a 3" DP, usually 1 1/16-1 1/8" is required...if the wg hole on the exhaust housing is less than 1" with aftermarket dp..that could be the problem...
What type of turbo?

On the pump, if one pump is bad, and the lines merge together as it appears they do in that pic, the pressure from one pump may bleed into the other and the fuel go right back to the tank...really hard to tell without a pressure gauge hooked to it...but whatever you do, LIMIT the driving in boost until you figure it out..to many times with knock loud enough to hear and you'll have a blown head gasket or worse on your hands.

For the boost..as a test you could run it "tuner" style and just run a hose from the turbo housing to the wg actuator...this should make your boost pressure equal to the spring tension in the actuator...13# for a stocker...if its still spiking then I'd look closer and the punk size and wg hole size in the exhaust housing.
If boost is spiking to 20#..thats also the lead cause for your knock/ping...it should not ping at 13# boost..if it does, then its the pump bad as well.

Also, get a scan tool, it is a must before ever going WOT in these cars if you want your car to last.

 

[garyk1970]

thanks 2quick6,im going to put the vaccum lines "tuner style" on turbo and wg and see if boost goes down,if so,i need to try another boost syl.

two pumps in tank,then only one line out to the two fuel filters,then one line contuniues to front/motor.

 

[garyk1970]

update

took a vacumn line and connected the vac port on turbo to wg actuator.boost is only 11 psi and car runs very good and no audible knock.:biggrin:

still need a scanmaster to see the numbers. atleast now i have a starting point. does this mean that my boost syl is most likely bad?

 

[2QUIK6]

took a vacumn line and connected the vac port on turbo to wg actuator.boost is only 11 psi and car runs very good and no audible knock.:biggrin:

still need a scanmaster to see the numbers. atleast now i have a starting point. does this mean that my boost syl is most likely bad?

It could be, it narrows it down, at least its not the wg puck size causing the problem. Could be the solenoid or the "Y" fitting not properly hooked up, or the wrong size orifice in the "Y" fitting...there were a few of those floating around a few years ago that were the wrong size...or a vac leak in the fittings or vac lines that go to the "Y".
If everything looks to be hooked up right, then I'd get a solenoid..if it ain't the problem then you have a spare.

 

[garyk1970]

thanks for your help, ill find my spare syl , y , vaccum lines.
whats funny is ever since i started keeping this car at the shop,its been very busy and ive had very little time to work on it.its a good luck charm for bussiness

 

[garyk1970]

Update

new turbo(ta 49),wgs,lines and y,turbo came with adjustable wg and was set to 11psi. installed new wgs and boosts to 22 psi + and stays there.
i also installed some 36 lb injectors and a custom chip(came with turbo).scanmaster not here yet,no audible knock.
guess i need to look at wiring and see if the computer isnt controlling syl for some reason.

 

[2QUIK6]

new turbo(ta 49),wgs,lines and y,turbo came with adjustable wg and was set to 11psi.

Can you lengthen the wg rod anymore?
Not sure how it could be set at a precise amount without trial and error on the car....the longer you make the rod, the lower the boost should go.

 

[garyk1970]

i lengthened the rod and got the boost down to 19 so far,gonna see if it has any left to get it down to 15-16 until my scanmaster gets here.

 

[garyk1970]

on the way to autozoo for new vac line. i noticed i have two different y's.

first on has BMC-A written on it and its orfice is smaller than #2

#2 has BMC-C written on it and its orfice is larger.

anyone know which is correct????

 

[garyk1970]

help...run the y with the bigger orfice??

 

[garyk1970]

installed the bigger orfice y and new h/d vac lines...all is good.thanks goes out to 2QUICK6.

 

[2QUIK6]

cracked vac lines will also let the boost pressure escape and not make it to the wg to open the puck. The larger orifice will alow more boost to get to the wg quicker and open the puck quicker.
Glad you figured it out. I was not certain which orifice was the wrong one, I just remembered some vendors were selling the wrong size at one point...couldn't remeber if they were larger or smaller than what was required.