Car runs bad with open exhaust!

[Tim Barnum]

Ok ,I ran my car at the track and it ran 11.05 at 120mph the first time out with 16lb boost threw the exhaust. Then when i took my car back to the track with the exhaust open it ran 14's and cutout. I didn't put 2 and 2 together until yesterday when i was working on the car in the garage and capped the exhaust off because it was too loud to here the lifters and now the car is running like new and has awsome power again. What could be the problem? All of my other turbo cars ran better with open exhaust. Any thoughts? Just let me know. Thanks Tim Barnum

 

[TurboDave]

Originally posted by Tim Barnum
Ok ,I ran my car at the track and it ran 11.05 at 120mph the first time out with 16lb boost threw the exhaust. Then when i took my car back to the track with the exhaust open it ran 14's and cutout. I didn't put 2 and 2 together until yesterday when i was working on the car in the garage and capped the exhaust off because it was too loud to here the lifters and now the car is running like new and has awsome power again. What could be the problem? All of my other turbo cars ran better with open exhaust. Any thoughts? Just let me know. Thanks Tim Barnum

Turbo cars will ALWAYS run better with open exhaust.

ASSUMING you do the necessary tuning to compensate for the huge flow difference (depending on exhaust system design).

 

[Chuck Leeper]

OPEN EXH??

Tim, as Dave has said,, look at the improved exh flow and tune for it.. I see that you have 2 cars listed and say 1 has been taken apart.. Did you put the 4" exh off 1 onto the car you are having problems with??? If not, what's on the problem child??
Opening a dump w/ a GOOD, 4" sytem may make LITTLE difference.However an open dump w/ a "stock style" exh, surely would.. You went lean when the exhaust was opened.. You fattened it back up when you closed it...
Did the boost go up when you opened it up???

 

[Tim Barnum]

The problem car runs 3" non mandal single exhaust. The boost does try to go up with the dump open but, it doesn't go any faster with more boost it just cuts out and runs rough. I'm running 16lbs boost. The o/2's are at 758 and no knock and the egt is under 1450 at w.o.t. Thanks Tim

 

[azgn]

what kind of fuel are you running? the extra boost may be putting you into detonation?

my car picks up 2-3 lbs of boost with an open dump

 

[TurboDave]

Originally posted by Tim Barnum
The problem car runs 3" non mandal single exhaust. The boost does try to go up with the dump open but, it doesn't go any faster with more boost it just cuts out and runs rough. I'm running 16lbs boost. The o/2's are at 758 and no knock and the egt is under 1450 at w.o.t. Thanks Tim

Wait a minute, these numbers don't add up. You're saying that the WOT O2's are 758, but in the same sentance the EGT's are under 1450 Your EGT's say your running very rich, and your O2's say lean

No knock?? I'd say, verify your knock sensor is working also.

 

[Tim Barnum]

I think i found the problem. The cam is flat on the #5 cylinder. Now how much fun is that going to be to replace? I also found out that the valve springs are 145lb units on the flat tappet cam. Well, Does anyone have a good suggestion for a cam that will last in a street / strip car? I'll also need to change the springs to 110lb units or so. Thanks Tim