I can get as much as 22+ on the highway and 16-17 bombing around the city. If I get into race mode or just want to hear my exhaust, I have been as low 10. Just try to keep your shifts at about 2000 rpm for mileage

 

x2

I never need to go beyond 1,800 rpms on my truck when accelerating...

I think it hasn't seen 2,200 rpms in acceleration... well since, probably 8 months... maybe more?!

Actually... that's a really good question... I've stumped myself.

I'm sticking to 8 months though... it's gotta be.

But doing 65 mph, I'm looking at 2,500 rpms... while crusing... but thats not accelerating... and that is with 4.10s stock tires/rims.

 

Honestly I believe it When I straight piped mine, im layin on the skinny pedal alot harder and just watch the gauge go bye bye. If I dont do so, it dont move as fast

 

haha... I tend to stick my foot into the gas on the Dak... it just sounds oh, so awesome.

But when downgear into 4th or 3rd... it sounds like a real diesel jakebrake.

 

Backpressure is needed!! Take your exhaust off at the manifolds and run the truck, I will guarentee you will loose torque. Backpressure is good unless its a turbo, and then you want as little as possible. And for the top fuel cars, they run zoomies for weight, and the fact that the exhaust is so hot(the flame is white b/c it is burning the hydrogen out of the surronding air) mufflers wouldn't stand up. And the blower takes 400+ hp just to turn it, so a extra 10 or so is useless. Horsepower and torque are related, but you can loose one without the other, I've seen it in dyno testing personally. I put magnaflows on my truck today, and instantly felt more torque than with the straight pipes, Backpressure is good to an extent.

 

i think your forgetting a key thing here
if i remember correctly a super40 is NOT a straight through flow design
thats where your losing horsies and milage. borla and magnaflow however are straight through flow designed and would increase both because of this.
i run a magnaflow and my milage went from 16 - 17 to 18-19
now with my chip cai and exhaust i get 22mpg regularly ( speed limits followed )

( 3.73 ratio )

 

When you take off everything, but the manifolds you're going to lose proper scavenging. You no longer have your exhaust pulses equalized and no longer have them "pulling" the one behind.

At low rpm you need a small pipe to maximize scavenging, and at high rpm you need a big pipe to minimize pressure drop (backpressure increase). Your exhaust pipe can only be one size, so it's a compromise. For a given engine, one pipe diameter will make the most overall power (i.e., have the largest area under the curve on a dyno chart).

So, the loss of torque has nothing to do with backpressure, and everything to do with gas velocity. So you need exhaust components that are not restricive (manifolds/headers, mufflers) and that are sized correctly for your application.

To further dispel the "backpressure is necessary" theory, try this if you want. If you have access to a vehicle with open headers, make a block off plate that will bolt to the collector. This plate should have only a 1" hole in it for the exhaust to flow through. That will give you PLENTY of backpressure, and zero scavenging. Then you can report back on how much low end power it has.

 

What can be done to increase fuel economy, other than the exhaust of course. My research is leaning me towards swapping my FM Super40 out for a 50 series. This will quiet the drone a little on the interstate and give me a more moderate sound overall. I do a lot of hwy travel. Didn't expect the Super40 to be so loud inside.

What else can be done to increase my fuel economy if I stick with a Flowmaster.....air intake?.....ride a bike?

 

that sir made me laugh a lot, high point of my day

 

Back pressure is not needed on a 4 stroke, thats what valves are for. but 2 stroke on the other hand is a whole other beast where back pressure is an absolute must

 

option 3 the bike

Exhuast aint gonna give you a big enough if any improvement in MPG's to justify.

 

No the blockoff will create TOO much backpressure, so of course you will loose power. And the exhaust doesn't have to remain one size, the best torque will be made by step tube headers. Any exhaust other than header dumps will create backpressure to an extent. I did alot of dyno testing on Nascar engines. With extensive study into the exhaust and intake. Step tube tri-y headers were the best, and a 3" x-pipe true dual system was the best over 3.5" and 2.75" h, x, y-pipe. Backpressure is caused by lack of exhaust velocity and lack of scavenging from improper exhaust sizing lack of mufflers and lack of a balance pipe. Smokey Yunick did alot of testing with exhaust and found a 8 into 1 system was the best setup, and that would create a high amount of backpressure.

 

I never noticed much of an increase in mileage when i put my magnaflow cat back on. I was pulling 19 straight highway all summer at 65mph. Then I put on intake (Gotts), efans, larger tires and my troyer tunes came in. I went for a 500 mile + road trip one way and pulled 22 mpg at 70 mph with no wind on boxing day so winter blended fuel. On the return trip at 80mph against the wind a week later pulled 17.5 mpg.

 

from everything I've heard, E-fans are your best investment if you're looking for an MPG adding mod(i think generally +1.5, but don't hold me to that). there's write ups on here on how to do it for around $100 bucks using fairly quality parts

 

Very possible - but can you confirm, Josh? Maybe he should clear the computer with a battery disconnect and let it relearn from scratch.

Slowmaster 40's are drone boxes. That's the only selling point, they make NOISE. There are much better performance exhausts out there.