why only 19 psi of boost

[turbowrenchhead]

Went to the track last weekend and I ran out the 93 octane through the shrader valve and put in 3 gallons of 110. I turned up the boost and all I could get out of it was 19 psi. It was a 80 degree day and 80% humidity. Early this spring I was running 23 psi of boost with no knock, then I put a bigger cam in it and gutted the intake out and replaced the fel-pro gaskets with stock steel shims. Is 19 psi all I am limited too?

 

[84wh1]

I dont see how your intake gasket can change your boost so I wouldn't think its that. Do you still have a Cat? If so, it might be plugged. Mine was, and all I could pull was 9-12 psi. Gutted the cat, then boost went up to 17psi . Your turbo boost controler on the driver side valve cover might be crapped to. Just a few thoughts, might help.

 

[cool 84]

After I had some headwork and intake work with the intercooler and headers and stock turbo, mine would also only go to 19psi. I had the wastegate locked shut. The turbo went a couple weeks like this until the shaft broke. Installed a new stocker with new feed line and the same thing happened. I think the poor thing couldn't flow any more air. You might also want to check exhaust restrictions.

 

[mark p. liner]

ON THE SAFE SIDE YOU SHOULD RUN AT LEAST HALF A TANK OF GAS. WHEN YOU ARE PULLING THE GAS WILL MOVE TO THE BACK AND COULD CAUSE THE PUMP TO SUCK AIR, YOU KNOW WHAT HAPPENS WITH HIGH BOOST AND NO FUEL.......BOOM

 

[TType85]

Isn't boost just the air that didnt make it into the intake?

What I mean is that now with the more efficent (supposedly) intake, and bigger cam, you are flowing more air probably more than the stock turbo can supply. The stock 84/5 turbo is known to basically blow up at low 13's so it sounds like you need a bit bigger turbo

It's all about the air flow.....


What did it run at 19psi though?

 

[turbowrenchhead]

One mistake on my part. The head gaskets were changed to steel shims. I can't believe I put the intake gaskets. It must be the heat melting my brain.
The turbo is capable of making more then 19 psi. It is knocking at 19 and I can't get it not to knock past 19 psi.
The intake and cam made a big difference in power. It pulls just as hard at 15 psi, then it did with the stock intake and cam at 20 psi.
The last time I had it at the track it ran a 13.62 and it was hot out. I know I can run better then that. I only got one decent run in. I am going again this Sunday and I will put six gallons of 110 in this time and some denautured alcohol.

 

[turbowrenchhead]

Oh yes, 84wh1 there is no cat. I have a atr test pipe. There are no exhuast restrictions.

 

[Turbo Riviera]

My feeling is that you need more octane, or more fuel pressure. I'm leaning towards octane. I can only get 17 psi on a hot air with a stock turbo on a 90 degree day before detonation on 110 octane race fuel. I feel that it would make some sense to step up in octane... I use VP C16. Some say that C16 doesn't make as much power as C14, or C15, but I think it's cheap insurance against broken parts.

At least go to 114 octane or more. I think you'll be pleased. Summer heat kills our hot air cars.

 

[TType85]

What MPH are you running?

your probably out of the compressors efficency range. It's probably just making hot-air at 19+psi.

With the more efficent intake/cam setup you are getting the air flow at 15psi that you were getting at 19psi before.

We all know the stock turbo really is getting out of its efficincy range above 19psi (on a stock motor). In other words you start getting diminshed returns, instead of 1psi giving you 10hp it may give you 5 or 3 or actualy hurt performance.

When Buick built these cars they didnt build them with the intention of running 20+psi of boost so they chose the turbo accordingly.

What typically will happen when you push it too hard (usually low 13s/high 12's with a stock 84/5 turbo is you spin the turbo past the RPM it's supposed to go and they self destuct. Who has a stock turobed 84/5 running faster than high 12s?

Whats all this rambling mean? Get a bigger turbo, or cool down the air some

 

[turbowrenchhead]

I can only get 110 octane around here. I don't know where I could get any higher octane fuel. Where should I look for the higher octane? I thought that with the alcohol injection would cool down my intake charge. It must to a degree because I can run 16 psi of boost on a 24 degree timing chip with 93 octane gas. Normally on 93 octane with no alky, I can run around 11 psi before it knocks.
I thought that if I put 110 octane in my tank that I could hit 25 psi of boost. But that didn't happen. It must only work in theory.
My mph was 98 that day.
Also turborivera, I bought a smc regulator that had a range of 0 to 60 psi. The regulator before that was 0 to 300. Way to touchy. This one works alot better.

 

[Buick From Hell]

*some* of the reason you'll only get 19psi:

--exhaust restrictions (scratch)
--intake restrictions (scratch)
--turbo bearing about to seize up! (possible)
--turbo maxed out (possible, not likely)
--wastegate opening (bingo?)

The key sentence that caught my eye: "It is knocking at 19 and I can't get it not to knock past 19 psi. "

If it's knocking (fairly badly), the ECM will limit your boost! My car would max at 14 psi until it was warmed up and started to knock, after which it would NEVER go past 12 psi!

Unless you're running a bleeder or some other bypass valve, it sounds like maybe your ECM is backing off the boost because of your knock!

 

[Nocooler]

Is the wastegate solienoid still in the loop?? If it is eliminate it - becareful you'll get as much boost as you want.

 

[Turbo Riviera]

I could be wrong, but I got the impression that Wrenchead was not necessarily at a physical limit of the turbo at 19 psi. It was more of a self imposed (smart idea) limit due to detonation.

Also based on prior threads I'm guessing that wrenchead's boost control is fully manual. No wastegate sol. hooked up.

What track are you racing at wrenchead? Most tracks sell fuel on the premesis. Not all do however. Ask the people that sell you the 110 fuel who might have it.

I was running 110 octane Sunoco purple in the tank of my '84 GN when I went 13.25 @ 101. I could not get any more than 15 psi out of a John Craig big turbo without detonation. I ran the turbo in excess of 20 psi (like an idiot!) and cracked a piston.

I could only get 17 psi on 110 fuel in my Riviera. Since then I've switched to VP C16 and I can get 21-22 psi without detonation. 20-21 works best though. I saw no gain going to 22. However, I get about 3 tenths between 17 and 20 psi.

Also, another way to find out where to get fuel is try the manufacturers websites. VP, Sunoco, Unocal etc. They should have a listing of all local dealers.

Hope that helps.

 

[Nocooler]

my bad....

I thought he was unable to get above 19psi....

 

[turbowrenchhead]

My turbo is capable of more boost. I am just limiting it to 19 psi cause I don't want any knock.
As for boost control the stock soleniod is still in place and I have a bleeder valve suplamenting it. I don't think the ecm is limiting it. If I give the regulator a little turn clockwise and I can have 20 or more psi. Turborivera told me how to hook it up. I followed his directions.
The track I race at is WIR at Kakuna WI. They do not sell any fuel there. The highest I can get my hands on around here anyway is 110.
I am going to the track on Sunday and I have 6 gallons of 110. It is going to be cooler out this time I hope. We have had 95 degree and alot of humidity latley. It was 77 out today with less humidity.