straightpipe vs. mpg
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: straightpipe vs. mpg
it might be worth swapping in a 'known good' O2 sensor
to see if the MPG improves
or going to a rear wheel dyno where they have a calibrated 'wide range' O2 sensor
to check the existing O2 sensor
to see if the MPG improves
or going to a rear wheel dyno where they have a calibrated 'wide range' O2 sensor
to check the existing O2 sensor
Veteran
Joined: Dec 2007
Posts: 419
Likes: 1
From:
RE: straightpipe vs. mpg
ICEMAN_CH: So what do you run? I am planning on doing my exhaust next month. I once thought of going 3" all the way, but from researching the site, seem to think 2.25 from manifold to the cat. Then the magnaflowcat I think is 2.25 out? The cat to the Super 44, and then 2.5 the rest of the way? Is that what most people do?
All Star
Joined: Mar 2007
Posts: 890
Likes: 0
From: South Carolina
RE: straightpipe vs. mpg
I'vegoing to haveLong tube pacesetter headers with a 3" y-pipe to a flowmaster 44 with 2.5 dual outs. It would probably be best to run 2.25 dual out but I wanted bigger tips. All I'm waiting for is the exhaust tubing to be delivered to my house.
RE: straightpipe vs. mpg
ORIGINAL: ICEMAN_CH
I know this is going to create an argument but here it goes. Backpressure is a bad thing that is commonly misunderstood. It used to be thought that backpressue would help to close the exhaust valve quicker giving you more time to fill the cylinder with air and gas giving you more perfomance. If this was the case why aren't we all running 1" pipes. The truth is you want the exhaust gas to have a constant velocity. This way exhaust gas can move freely and smoothly out of the system. If you throw a 6" pipe on for your exhaust then when the gas leaves the cylinder it's going to expand causing it to slow way downand rob you of performance. So you need to strike a balance. Something small enough that the gas dosen't slow down and something big enough that it can still move freely. If you get this balance correct then the momentum of the gas will actually create a negative pressure behind it (It sucks). This will create a negative pressure in the cylinder helping the exhaust valve close and increseing the amount of air into the cylinder.
ORIGINAL: Tarner
Why do you need back pressure anyway? What does it do, and how does that increase low end power and MPG?
Why do you need back pressure anyway? What does it do, and how does that increase low end power and MPG?