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View Full Version : To much flow? Is it possible?



Ironsam63
08-01-2007, 02:02 PM
I have an 89 SC 5 speed man. trans. No real engine mods exept for new cone air filter down by passanger fog light (removed light). 8.8mm wires and plugs and took out some useless weight out of the car (approx.30lbs). Heres my question, with original stock 89 exhaust (2 cats 1 resinator and 2 mufflers all clogged and rusted) I was running a 14.2 - 14.4 seconds on 1/4 mile at the track at 103-107 mph with radial tires at 18 psi. Now I took off all exhaust and have 2 1/2 pipes from exhaust manifolds at the engine going to 2 2 1/2 inch Flowmaster mufflers at the back of the car. ( no cats or resinator) The car sounds good and drives good under normal daily driving. But to me it feels like the engine wines out to fast and doesn't have the same throw back in your seat like before the new exhaust. Went back to track to see and I was right (h14s- L15s at 96mph). And at about 5 to 7 psi of boost the exhaust starts to sound " ricey". Can't afford bigger injectors, fuel pump, or chips just yet , so do I need more back pressure? If so, would something like the old resinator work? Don't want new cats. Thanks.

kenewagner
08-01-2007, 02:36 PM
Yes you can have to free flowing exhaust. I had a lot of mods and went to the size you have. I even had headers as well and added menthol injection. Car dynoed 6 more HP than a previous tuning. Dave Dalke was the tuner and commneted that the exhaust was more than i could use with stock heads, cam and low boost(13 to 14lbs) It will do you well once you have the correct modifacations done to match it as a system

Ken

watsonlk
08-01-2007, 03:13 PM
I have the same setup with manifolds, less one muffler temporarily.

Mine seemed to have more bottom end torque and didn't rev as quick, thus pulling harder longer in the 3k rpm range with both the mufflers.

Ironsam63
08-01-2007, 03:47 PM
So would it be to my advantage to install a resinator muffler before the back mufflers for back pressure until I can afford to match the engine with the exhaust?

scbird1
08-01-2007, 04:08 PM
I bet it would help. When asked on here it seems everyones opinion is to do the exhaust to save those head gaskets. The only real bad part of the exhaust is the back of resonator where it gets necked down to like 1 3/4. On a stock motor your going to lose low end tq. when you put large pipes on it. Like they say, bigger is not allways better. Oh and the head gaskets I found all of mine were due to electrolisis eating its way to the fire ring from the water passage. Changing the antifreeze every two years will curb that. If you up your boost well head lift can occur and take them out but I think you shoud match everything to a goal. Most will fall short and even cut performance when they dont go for the whole package. Sad but true.

Ironsam63
08-01-2007, 07:12 PM
But running the car this way doesn't hurt anything does it?

scbird1
08-01-2007, 10:47 PM
No should not be a problem as long as she is not running lean.

XxSlowpokexX
08-02-2007, 12:04 AM
your original time and trap speed were real good. My 89 auto in stock form could only muster a best of 15.4

If you like the way it sounds leave it alone..You may gain a bit by installing a resonator but not much if any