Boost won't go above 6 psi, HELP!

[mongoosetoo]

85 Buick GN trans, rear, and engine, all of it transplanted into an 87 Cutlass. everything mechanical is new; engine, trans, turbo (stock rebuilt), rear.

Anyway, I suspected the boost was low, and my led boost indicator is on the blink. So I finally installed a mechanical guage. The highest pressure I ever see is 6 PSI - that ain't right is it??

What do I check? I've already gone through the vacuum hoses, they look correct and all are brand-new.


Thanks, Brew

 

[Jerryl]

Do you have the correct "Y" orifice and is it hooked up correctly?
Leaking waste gate puck?
Exhaust leaks?
Seriously plugged cat (unlikely but worth a try)

 

[HOTSIX]

I second that motion.

Maybe during the transplant you messed up the vac line routing ? I had that problem with mine after doing the heads and intake. I presume your WG rod is nice n tight ?

 

[mongoosetoo]

Y orfice?

Are you talking about that little vacuum y that has one side sort of restricted? What is the hose routing for it?

My waste gate is good, I put a vacuum pump on it and it functions well. The rod is fine also.

Thanks, Brew

 

[mongoosetoo]

I just went out to the garage and checked the GNutlass vacuum routing. After comparing it to the hose charts on this site, I think I tossed the factory Y and put a non-restricted one in it's place.

I have the dual vacuum line waste gate, about three or four inches from the WG, there is a Y that splits off. Is this the Y you are talking about? One line goes to the waste gate solenoid from there and the other goes to the compressor. Di I hook this up correctly?

Which way does the restriction go? And does anyone have a restricted Y for sale? Or at least know where I can get one? I suppose I could make one if someone could tell me the orfice size.

Also, the cat is hollow, so no restriction there!

Thanks, Brew

 

[Jerryl]

I just went out to the garage and checked the GNutlass vacuum routing. After comparing it to the hose charts on this site, I think I tossed the factory Y and put a non-restricted one in it's place.

I have the dual vacuum line waste gate, about three or four inches from the WG, there is a Y that splits off. Is this the Y you are talking about? One line goes to the waste gate solenoid from there and the other goes to the compressor. Di I hook this up correctly?

Which way does the restriction go? And does anyone have a restricted Y for sale? Or at least know where I can get one? I suppose I could make one if someone could tell me the orfice size.

Also, the cat is hollow, so no restriction there!

Thanks, Brew

Sounds like you found your problem.
Restrictor goes to the WG actuator. Hole size is around 0.040.
See pic for "Y" http://www.engraver1.com/help/intakeETC.gif

Look at the bottom of this page for Y hose install
http://www.gnttype.org/maint/quickref.html

Try this page for "y connector" install
http://secure.johnsperformance.com/...t_id=4435485.23679*Hy8d9&product=Engine-Parts

Or contact www.gbodyparts.com for the connector.

 

[1QUICK85]

Sounds like you found your problem.
Restrictor goes to the WG actuator. Hole size is around 0.040.
See pic for "Y" http://www.engraver1.com/help/intakeETC.gif

--------------------------------------------------------------------
Restrictor goes to the compressor housing.......the little port on the turbo.

 

[cool 84]

Sounds like you found your problem.
Restrictor goes to the WG actuator. Hole size is around 0.040.
See pic for "Y" http://www.engraver1.com/help/intakeETC.gif

--------------------------------------------------------------------
Restrictor goes to the compressor housing.......the little port on the turbo.

Correct. You want to restrict the overall volume of air to the actuator and solenoid so it has to be to the compressor side.

 

[mongoosetoo]

Thanks, I'm sure that's the problem. Also one last note, what kind of boost pressure should I expect from the stock turbo?

Thanks, Brew

 

[Jerryl]

...... what kind of boost pressure should I expect from the stock turbo?

With or without knock? :tongue:

Depends on your car, i.e. WG rod setting, exhaust, etc. In terms of "just plain boost numbers", some have been able to get it up to a very inefficient 19-20 max.

 

[1QUICK85]

I wouldn't go above 13lbs. of boost without a knock guage, A REAL boost gauge(you got it), bigger fuel pump(hotwired), adj. fuel pressure regulator & fuel pressure gauge and some good 93 octane. Even then you may not get much more boost out of it without knock. -Nick.

 

[HOTSIX]

You can still get the restrictor from a GM dealer.

 

[mongoosetoo]

Here's what I did...

I thought if the orfice could be adjustable then I could play with it until I get it right. So I brazed a tiny plumbing valve to a brass tee and hooked it up.

When I tried it out it I saw 6 psi or 22 psi, but could not get it anywhere between those two numbers so I chalked it up as an hour of my life wasted away. Then I used another brass 5/16 Tee and put an old mtotorcycle carb jet in it and drilled it to .040". I installed it and I'm up to 6.5 to 7 psi now.

I think I'm about done experimenting. I think I'll just slap down the cash and buy the right thing. I mean I know the system can produce more because I saw it go above 20 (I took my foot off it when it did), but on the other hand, 6 psi is just not acceptable. I'll get the correct tee and install it and repost.

DOES ANYONE HAVE ONE TO SELL? I'm in Ohio. Thanks, Brew

 

[Jerryl]

Here's what I did... ..... When I tried it out it I saw 6 psi or 22 psi, but could not get it anywhere between those two numbers so I chalked it up as an hour of my life wasted away. Then I used another brass 5/16 Tee and put an old mtotorcycle carb jet in it and drilled it to .040". I installed it and I'm up to 6.5 to 7 psi now.

Now you may need an adjustable WG rod to increase your boost. Try this link.
http://www.gnttype.org/techarea/images/Adj_wastegate.JPG

 

[1QUICK85]

Shouldn't need adj. wastegate to see stock boost levels. He needs the "y" connector. I have been there, I too could only get about 6lbs. of boost running without the "y". -Nick.

 

[Jerryl]

Shouldn't need adj. wastegate to see stock boost levels. He needs the "y" connector. I have been there, I too could only get about 6lbs. of boost running without the "y". -Nick.

Yeah, you are correct. The orifie may need to be smaller.

 

[MoeJr]

Stock boost psion an 84/85 setup I believe is 10-12 psi

 

[mongoosetoo]

I'll braze the T fitting shut and drill around .025. It'll be a couple weeks beforew I get to it - going on a trip for work.

Thanks, Ya'll\