Am I running out of turbo

[Double-L]

I have been told I am at the limit of my turbo so I thought I would throw this out and see what you think and what you would do or change, My car is mostly a street car, It rides like a Caddy, Has ice cold ac and gets good mileage but I do like to race it, Here is my build-
1987 grand national
3.8
J&E 30 over with total seal filed rings
Champion Stage 2 aluminum heads
1.65 shaft mount rockers
Comp part # 69-400-8 Cam
Girdle
Balanced
Eagle Crank
Eagle H-Rods
Hemco plenum
Accufab 70mm throttle body
Front mount Intercooler
73lb injectors
Meth Injection
Walbro pump,hot wired
200 4r with all the good parts
PI 5 disk converter,lockup at 126 mph
3.42 gear
LT1 mass air meter with translator
4" cold air intake
66 BB turbo, Cottons
TA performance headers
ATR 3" down pipe
Turbonetics delta gate mark II 6psi
Turbonetics boost controller

16 psi pump fuel
20psi race fuel

The best it has run on 100 octane and alky is 10.40 at 133, At 20-21 pounds of boost, Coming off the line at 5+ pounds off the foot break, One problem is it comes off the line hard but after 60 ft. it spins the Hoosier slicks just enough for the front to drop, my 60 ft in in the 1.50's, I have ready to put on a HRparts rear sway bar, small starter and a set of aluminum pulleys, I know I have missed something but hope this helps

 

[Red C5]

I don't think you're out of turbo. Why only 20psi on race gas?

Peter

 

[Double-L]

Well we always use pump gas just put that in for a race, We will turn it up but a friend said if we are spinning the tires now more boost isn't going to help and another Buick guy said that is about the limit on that turbo anyway

 

[Red C5]

I'm no expert but there is no way that 20 psi is the limit of a 66 bb turbo. The thing probably starts to come to life at 22-24 psi and I'm sure probably does very well into the mid 30psi range. But I'm sure someone more knowledgeable will chime in. If you're breaking loose you need better tires or work on the suspension.

 

[machinegun]

i dont see a tire size / type / compound

i think you need to look at the spin issue and once resolved then can look at the turbo

 

[RED LS1]

You have the glorified version of my brothers combination. His is iron heads and 212 cam. Also XFI.

I hope to see his run past 125 like yours does

 

[Double-L]

We know that we have to get the traction under control before we can do anything else, That is why I got the rear sway bar and taking a little weight off the front, We are also going to try some lead in the trunk, The tire is Hoosier and the size is as big a 15 inch as you can get under a 87 GN and the compound is soft, I have tried other slicks to, I have two air bags, Adjustable rear shocks, Took the front sway bar off

 

[V6RACER]

73lb injectors
Meth Injection
Walbro pump,hot wired
66 BB turbo, Cottons

I would think you would run out of fuel before you run out of turbo..

I went 8.85 on a Precision 67/68

 

[Double-L]

Well I knew I forgot something, We have a bigger fuel pump and was thinking of adding bigger fuel lines to if what we do helps with the traction

 

[TurboDave]

Man oh man! If you got people advising you that you're out of turbo with a 66 at 20# of boost, you really need to find a different circle of advisors!!!!!!!!!!jj When you get it up over 27+ lbs of boost then maybe, just maybe you'll be pushing it near it's limits.

You just need to get your traction issue under control..

 

[Double-L]

Well Cotton is one that said I am at the limit of that turbo, I was asking if it would be worth it to put a F1 wheel in or just go with one of the new ones and sell mine as far as performance ver price when and if I get the traction worked out or just enjoy the car as it is, After I put the new parts on it, HRparts said that very well may take care of the problem

 

[bison]

I'd say you were out of turbo if you were trapping 136+

 

[bison]

Man oh man! If you got people advising you that you're out of turbo with a 66 at 20# of boost, you really need to find a different circle of advisors!!!!!!!!!!jj When you get it up over 27+ lbs of boost then maybe, just maybe you'll be pushing it near it's limits.

You just need to get your traction issue under control..

He will be out of turbo on his engine at about 25psi if he's going 133@20psi. It's good for about 70-75lbs/min on an engine like his. The 66 compressor is not happy at over 2.5:1 pressure ratio/5700 rpm on a 233ci. I did some tests about 3 weeks ago with the t66 and the t72. The 66 was a gtq the 72 was an old 76 p trim and guess what? The 72 walked all over it from 5600 up to the point I ended the testing at about 6300. The 66 only made 25psi/650whp@5500. It wouldn't make more boost. The 72 made 678whp@5550 but carried it wayyy further. At 6200rpm the 72 with the little old p trim made about 80whp more. That is huge in a car that will be trapping at 6000rpm/140mph. Not much difference in peak but crazy difference out the back. Backpressure may have been holding the 72 back. It used 810hp worth of fuel. 93/alky. The key to the Op's success with the 66 is a converter that flashed to about 5300-5400 and couples hard by 135mph combined with a tall slick of 29". A ptc 17 blade would do it.

 

[Double-L]

He will be out of turbo on his engine at about 25psi if he's going 133@20psi. It's good for about 70-75lbs/min on an engine like his. The 66 compressor is not happy at over 2.5:1 pressure ratio/5700 rpm on a 233ci. I did some tests about 3 weeks ago with the t66 and the t72. The 66 was a gtq the 72 was an old 76 p trim and guess what? The 72 walked all over it from 5600 up to the point I ended the testing at about 6300. The 66 only made 25psi/650whp@5500. It wouldn't make more boost. The 72 made 678whp@5550 but carried it wayyy further. At 6200rpm the 72 with the little old p trim made about 80whp more. That is huge in a car that will be trapping at 6000rpm/140mph. Not much difference in peak but crazy difference out the back. Backpressure may have been holding the 72 back. It used 810hp worth of fuel. 93/alky. The key to the Op's success with the 66 is a converter that flashed to about 5300-5400 and couples hard by 135mph combined with a tall slick of 29". A ptc 17 blade would do it.

Pretty much what my friends told me, If I can get my 60 ft. down and the traction there I should be pretty close, This is a street car that you can race, If I wanted a race car you could drive on the street it would be a lot easier to make it go fast, If I decide to go faster I was asking Cotton would be be better to change the wheel in the 66 or go with something like a Precision 67 66 CEA BB, He said at any boost you are close to the limit on the 66 but not many street cars runs 133 in 1/4 spinning the tires so turning the boost up would give me little help

 

[TurboDave]

Interesting information guys, thanks! 20# just didn't sound like that could be working that turbo so hard, but after paying closer attention to the data on the engine and Bison's info, it now makes a little more sense. My appologies to Jack C. He's likely forgotten more about this stuff than I'll ever remember!

 

[bison]

Interesting information guys, thanks! 20# just didn't sound like that could be working that turbo so hard, but after paying closer attention to the data on the engine and Bison's info, it now makes a little more sense. My appologies to Jack C. He's likely forgotten more about this stuff than I'll ever remember!

Yup. Manifold pressure and mass flow are two totally different things. You can have 40psi boost and only 60lbs/min of flow. You can have 20psi manifold pressure and 65lbs/min mass flow. The higher the mass flow the more power. Turbos don't make power they support it. If they made power everyone would be slamming on 76 turbos and making 900whp. It just doesn't work like that. Your engine has to swallow it or it's just a measure of how much of a bottle beck the top end of your engine is. You do have a pretty big window though. This is a great example of a tight combo. When you hear of guys that are having all these boost control issues trying to run a turbo that supports 800hp on an engine that flows 50lbs/min of air you can see the glaring mismatch of components. So their solution is to go with large pucks or external wastegates. Lol.