Exhaust vs MPG

[gp90se]

anyone whos gone to a larger exhaust or mandrel bent (downpipe to mufflers), , what happend to your MPG?

[Kalgorn]

I haven't done an upgrade like this but your MPG will go up with a better flowing exhaust.

[19Cutlass94]

Mandral bent pipe flows 35% better than non mandral bent pipe. Thats quite a bit. Better flow = better mpg.

[frusciante fan]

what they said. don't think you'll get 10 mpg better, but it will help some.

[DaveFromColorado]

Mandral bent pipe flows 35% better than non mandral bent pipe. Thats quite a bit. Better flow = better mpg.

 

that's not entirely true ... it depends on the angle of the bent, if you had say a 10 degree bend, I don't think the difference would be that great.

 

Anyhow, every time I've opened up the exhaust on any of my cars, I've always found my gas milage to take a dump with it.

 

--Dave.

[GutlessSupreme]

I've been told that if on an N/A car, your mpg are probably going to decrease because of less back-pressure. Obviously would be the opposite on a turbo car, unless you go so big that you have boost-creep.. but you know all about that.

[mfewtrail]

I don't know if my exhaust on the car changed the mileage that it gets or not, it might have actually increased it a slight bit(but I never really bothered checking what kind of mileage I was getting years ago before I had a custom exhaust on the car). My most recent calculations = 33mpg pure highway driving out of my 1993 GP SE(3.1, I have a 2.5'' mandrel bent exhaust system on the car w/ one flowmaster, no cat/nothing else....also have a K&N drop-in air filter) at speeds of 60-65mph. I average about 27mpg overall with mostly highway driving and little mix of city driving thrown in there. The motor has over 190,000 miles on it as well, runs like new/gets damn good mileage for lugging this heavy car around.

[gp90se]

my bone stock regal with stock paper air filter and stock exhaust got 34mpg doin 75mph for 380 miles. might throw on 2 1/2 mandrel bend and see what it gets

[Dan94Z34]

I know on the old V8's, i you put long tube headers and dual exhaust on it, it would get better fuel mileage and run cooler. Dont know about the newer stuff though.

[19Cutlass94]

yeah the older cars were like that, but the newer cars, you can only go so big, thenit just hurts everything. Theres like a happy medium between size of the pipe, power and mpg

[pwmin]

all i know is that when i put the mands downpipe and exhaust (2.5" middle outlet) on my riv, i got better gas mileage. i had three systems: one with a 28" long, 6" wide magnaflow and straight out theback, one with the long muffler and another magnaflow 5x8(iirc), and another with the long muffler and the stock mufflers in the back and i got better power and mpg with the two muffler setup as opposed to the 1 or 3 muffler setup. then again, that was an L67.

[Lee]

In the last month my car has registered 33 mpg a couple times. This is while doing my 35 mile one trips to work, x10. Do I believe that this car is gettting 33 mpg....duh, NO!!!

 

I'm figuring it has to do with how good my fill up/top off tank events are going. I've had this car for 9 years and it ain't never done better than 29/30. My normal average is 27 mpg. Do I believe any of you are getting 34mpg at 75 mph, NO!!!

 

Unless the greenhouse effect is increasing mpg, we are all full of it.

 

We should start an honest poll where each person monitors their mileage, (accurately), over at least six major fillups(2000 miles), then use those numbers.

 

Anyone want to do it? My miles rack up pretty fast.

[z284pwr]

http://home.earthlink.net/~z284pwr/beretta/gas.txt

 

There, I think I'm allowed to say how much gas mileage I was getting.....that is about 95% city driving in the old hurt 2.8 Beretta GT. It now gets around 25 MPG with my own Haltech tune on the freeway, good enough....beats the ~15 the TGP is lucky to get

 

Edit - can you guess where we first installed the Haltech Yes, I sucked at tuning the thing at first if you can't tell......

[Kalgorn]

10 MPG?

 

I bet when gas hit 2.03 you were like "holy shit that's expensive". And now look at it...

[gp90se]

Lee, I did 330 miles (Boston to Jersey) and filled my tank up with 9.72 gallons of fuel

 

I didnt believe it, but I wasnt gunna argue. I am the only one who drives the car and the only 1 who fuels it.

[Bolt_Crank]

when I took my mufflers off... I kept the cat and resonator on, I gained like 4MPG in city driving...