Need Input, Possibly Changing Exhaust, Backpressure Issue?

blueroo

Well-known member
When I install the rear sway bar on my car there is a chance I will need to reroute my exhaust. It currently exits directly in front of the right rear tire. I was wondering if I'd loss too much back pressure by doing a dual exhaust setup with the "double hump" crossmember and a Flowmaster 40 Series Non-Delta Flow on each side.

Would I lose to much back pressure though? If so, would adding a resonator at the end of each pipe help and not cause me to lose too much sound?
 
Bort62":30c5hjom said:
There is no such thing as losing too much backpressure...

^its about the velocity. i think as long as you dont go too big with the exhaust you should be ok. most guys on here use 2" or 2.25" i think.
 
Back pressure is a mith... You want as less as possiable... the less back pressure the better.
If back pressure was good then Drag cars wouldn't be running 2 1/2 to 3" exhuast and they would be running mufflers.......
Tim
 
I run dual headers through true dual 2.25 pipe and turbo mufflers dumping out the factory valance. Sounds great and its a big improvement over the old but new single pipe and flowmaster 40 2.25. No loss in hp but a good gain in motor breathability.
 
You want velocity in the header... once you are out of the collector you don't care. You want as little restriction as possible.
 
We need a butt dyno "shootout". :lol: Whoever can guess the closest numbers consistently, wins...
 
Whew - I saw all these replies to this thread and I thought some idiot had jumped in here talking about how you needed backpressure to make torque.

Glad it was just the usual suspects :)
 
addo":3eb07e0i said:
We need a butt dyno "shootout". :lol: Whoever can guess the closest numbers consistently, wins...
Great idea! Losers get shot in the butt, of course.

Of how about a Butt-Dyno Burnout Contest? Kinda like a bunch of dogs scootching their butts along the ground. I'm not gonna enter, but I'll bet the video would be a hit on youtube.
 
Actually, back pressure isn't a myth.
Although it usually isn't a property that will drastically change performance in the exhaust system, it could be under the right conditions.
In a nutshell, back pressure can be said equivalent to the outlet exhaust pipe pressure, which in this case is the ambient air pressure. At sea level, P_amb ~ 96.9 kPa.
The back pressure comes into play when you are looking at the mass flow of air, and the existence of shocks. If the incoming fluid pressure of the exiting gases from the beginning of the collector happened to be say, 150kPa, using an isentropic relationship for the inlet pressure/outlet pressure with respect to the Mach number, the outlet Mach number would be much lower than the inlet. This means the mass flow is less due to shocking, which means more work required by the piston to push out the gases. This situation is obviously idealized.
In reality however, the actual inlet pressure is much much greater then the exit pressure, which in turn minimizes the chances of shocks in the flow. So it doesn't typically come into play in regular exhaust systems. The addition of a megaphone type outlet could change it though.
Because most flow properties are directly related to the was flow, length of the pipe can also be neglected, assuming the pipe is of uniform diametre .
 
AZstang66":po3csxt8 said:
Actually, back pressure isn't a myth.
Although it usually isn't a property that will drastically change performance in the exhaust system, it could be under the right conditions.
In a nutshell, back pressure can be said equivalent to the outlet exhaust pipe pressure, which in this case is the ambient air pressure. At sea level, P_amb ~ 96.9 kPa.
The back pressure comes into play when you are looking at the mass flow of air, and the existence of shocks. If the incoming fluid pressure of the exiting gases from the beginning of the collector happened to be say, 150kPa, using an isentropic relationship for the inlet pressure/outlet pressure with respect to the Mach number, the outlet Mach number would be much lower than the inlet. This means the mass flow is less due to shocking, which means more work required by the piston to push out the gases. This situation is obviously idealized.
In reality however, the actual inlet pressure is much much greater then the exit pressure, which in turn minimizes the chances of shocks in the flow. So it doesn't typically come into play in regular exhaust systems. The addition of a megaphone type outlet could change it though.
Because most flow properties are directly related to the was flow, length of the pipe can also be neglected, assuming the pipe is of uniform diametre .


Oh great, here we go...

I must have been at work too long (going on 12 hours) because I can't even understand what you just posted, and I am an engineer!
 
Back
Top