Finally got the 383ci w/T72 to track, couldn't get more than 13 lbs boost!

Spooled

New Member
Joined
May 27, 2001
Hey guys, I finally got the car to the track. Got it down to 1.51 short, 10.42 @132 1/4 on 13 lbs, 26 timing, 11.4 AF ratio. However, on my blitz dual solenoid boost controller, I went up on the ratio (which should provide more boost) and I couldn't get it to go over 13 lbs! I would think my turbo should be capable of 30 lbs. The turbo is a craig T72 Q trim. I think the problem has to be one of these three things. No enough air into the turbo, out of the turbo, or through the turbo. I've got a full 3.5" discharge with a 3.5" dynomax bullet muffler so I don't think that's the problem. I've got a 4" elbow on the compressor inlet with a big KN filter. The filter is collapsed in the middle and thats making it easier for the turbo to suck it shut but even when i try to compress it by hand it doesn't totally collapse so i think air would still have no problem flowing through it. So I'm thinking it must be not enough exhaust through the turbo. I'm going to check for exhaust leaks today...but i'm pretty sure there aren't any. I'm wondering if there could be something wrong with the boost controller. But again, I don't think that's it. The wastegate is an ITS progate. I know when you look at a compressor map, my turbo isn't the most effecient, but I would think it should still make a hell of alot more than 13 lbs! I guess i'm just looking for any ideas. Norb, did you have any problems with that boost controller (since I bought it from you). I really wanted 9s but couldn't do it on 13 lbs. There was a badass GN there with an ANS performance sticker in the rear window that did a bumper dragging wheelie. Well, thanks for the help. Any thoughts are appreciated!
 
Nope worked good, just didn't like that you couldnt dial in the exact boost. You must have some ofther problem. The car is flying though! try taking the air filter off?
 
I haven't tried it yet. I contemplated it on my last pass but decided that wasn't what it was when i tried to compress it with all my strength and thought plenty of air should still flow when compressed. I'll try it but I really don't think that's it. I checked for exhaust leaks today...found two very small ones where my crossover pipes connect to the headers. They'er very small...nowhere near the size I'd think I've have to find to only get 13 lbs. I'm really still stumped. Anyone ever had a problem like this????
 
I dont have any advise on the boost controller part of it. Do you know what size spring is in your wastegate? If it has a 15# spring in it, might be worth unplugging your boost controller and seeing how much boost you can get on only the spring.

Just a thought.

Keep us posted bro. Even though it wasnt what you were looking for, 10.40's on the first time out isnt bad at all! (y)
 
I was talking to Guido last night on the phone and he mentioned that he has heard that you can only effectively double your wastegate spring pressure with a boost controller. Just to let you guys know, with my blitz Dual SBC controller set to 0 (which is suppose to be only the spring controlling boost), it's roughly 7 lbs boost. So it's funny that it almost works out to that theory...spring is 7 lbs and I could get like 13.5 at the track. Has anyone ever heard that before? I really don't see why that would be the case...but hopefully it is! I'll be on the phone to ITS tomorrow!
 
You can go more than double with a boost controller.

Done it MANY times. The wastegate spring does have a BIG role in maintaining the boost.

If the exhaust backpressure if pushing too hard on the wastegate puck, the boost controller will not do you any good.
 
sounds to me like it is not the boost control. because you are
getting 7psi with no control and 13.5 psi with.
first if you set a base boost level with just the vacume line
to 15psi with the controler you should be able to get on a
average of +7-8 psi more with the controler. but you need to set
the base psi so if you want 30psi try and get the base close
to 20 psi.
 
Thanks guys....I talked to ITS today (because I have their Progate). They said you can go more than doube but it depends on exhaust backpressure. I ordered their 15 lb spring. We'll soon see!
 
try using a separate air souce like a compressor and regulator or bottled air co2 to feed the wastgate for more pressure. Try running the boost sensor built in the blitz to the top of the gate, this will give you open loop control. ( no feed back from engine boost) and give you a constant pressure on top of the gate
 
Spooled...

Hey.. How you doing? Sounds like you've gotten it back on the road! Cool.
I ended up keeping my building. Might be able to look at your car if your still in need of some fabrication.
Let me know!
~Scott
 
Hey Scott..that's good to hear. How is the business doing? I think the fab work is pretty much done. I put my new spring in....actually ITS sent me TWO springs. One was big and the other much smaller in diameter. I'm not sure what the smaller one is for. I'm going to call them tomorrow and find out. Going to try and get back up to Morocco and blow off some mid 9 second passes!
 
Update...called ITS today. The guy said the second small spring can go inside the cap with the big spring to give 20 lbs. Seems awfully weird because there's no groove for the spring to sit in. Seems like it could "fall over" pretty easily. I'll try the 15 lber and see if I can get any more booooost. I'll let yall know. Thanks for all the help!
 
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