My bridgy
Senior Member
Joined: Mar 2004
Posts: 558
From: MD
Originally Posted by Aurosting' post='876318' date='Jun 26 2007, 02:43 PM
I KNOW I WILL BUY ANOTHER REX SOMEDAY BUT FOR NOW ILL TRY BUYING A NEW CAR
why not just try to trade your bp engine for a diff. engine setup? why sell the car?
Senior Member
Joined: Nov 2003
Posts: 521
From: Hell (Colorado School of Mines)
I realize this has been beat to death but I'm bored.
Based on compressible flow fluid mechanics, for pipes with a low roughness, a pair of 2" pipes will have a higher pressure drop than a single 3" pipe, despite there only being half the flow through each pipe. Also, the true duals fail to utilize the pulse reversion that collectors use. These pressure pulses can be very high, as you can tell simply from how loud the car is. Duals rely only on the flow momentum to pull more exhaust out.
Just for the hell of it I ran some numbers:
At system conditions of 100%VE (for simplicity), 3000RPM, EGT of 1600°F, and using commercial steel pipe as a basis, the dual 2" pipes will have approximately 37% more pressure drop than a single 3" pipe.
The pressure pulses emitting from the exhaust ports will be upwards of 100PSI when the exhaust port opens. Even if only 10% of that pulse is reverted, that is still a 10PSI drop at the opening of the other port.
-Andy
Based on compressible flow fluid mechanics, for pipes with a low roughness, a pair of 2" pipes will have a higher pressure drop than a single 3" pipe, despite there only being half the flow through each pipe. Also, the true duals fail to utilize the pulse reversion that collectors use. These pressure pulses can be very high, as you can tell simply from how loud the car is. Duals rely only on the flow momentum to pull more exhaust out.
Just for the hell of it I ran some numbers:
At system conditions of 100%VE (for simplicity), 3000RPM, EGT of 1600°F, and using commercial steel pipe as a basis, the dual 2" pipes will have approximately 37% more pressure drop than a single 3" pipe.
The pressure pulses emitting from the exhaust ports will be upwards of 100PSI when the exhaust port opens. Even if only 10% of that pulse is reverted, that is still a 10PSI drop at the opening of the other port.
-Andy
