Ford Mustang Forum - View Single Post - Help with Exhaust/Performance problem
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post #8 of (permalink) Old 02-14-2006
SHELBY GT 500 Member
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Originally Posted by ts3096
Losing the "punch" is from switching to the larger tube, you lost your exhaust gas velocity at low rpm. When the motor is at low rpm, the exhaust is not restrictive, rather it needs the smaller tube to maintain exhaust gas velocity. The motor still makes the power upstairs because it is pumping more EG and is less restircted with the larger tube. Its a trade off that everyone faces, low end torque or high end power. If you want to get your "punch" back go with the restictors, but you risk losing the power increase at higher rpm.

As for your loss in MPG, it is probably from lost exhaust efficiency at low rpm where you do your normal driving. The restrictors will help with that, but with some hp cost.

I think your best bet is to equip the motor to use the 2 1/2" pipes. If you don't already have it, but a CAI on it. It will help the motor intake more air, creating more exhaust, making the 2 1/2 pipes more efficient. It won't make a dramatic difference, but it will help.
The problem is the cam,heads, etc you open up too much, and the cam can't support the flow. You've moved the velocity out of the range of the engine.

Woe to him who builds his palace by unrighteousness,his upper rooms by injustice,making his countrymen work for nothing...Does it make you a king to have more and more cedar?Did not your father have food and drink?He did what was right and just,so all went well with him. He defended the cause of the poor and needy,and so all went well...But your eyes and your heart are set only on dishonest gain,on shedding innocent blood and on oppression and extortion. Jer 22:13, 15-17
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