Dual Exhaust
 

Question for you guys....

Want to put dual exhaust on my 98 5.7 4x4, looking at flow master mufflers. They offer a wide variety of sizes and styles, like 2.25" in 2.25 out or 2.25" in and 3" out. 2 or 4 chamber, etc. Want to do a cat back system. Just wondering what is the best application for the best performance. Any experience or help would be greatly appreciated.

All Flowmaster system for that truck I found were really a single exhaust. I got the 2.25 in/out with tailpipes out each side, cause that is what my wholesaler had in stock(impulse buying you know). If you want dual tailpipes, Flowmaster makes an American Thunder with 2.25 tailpipes out each side, or two 2.25 pipes out one side. The other system is a 3.00 out the pass side. None are any better for performance then any other. You will find a decent performance gain, and a mileage improvement. The Flowmaster system was the best mod I have done to my truck from a performance standpoint. You will find it a little loud if you pull a trailer at highway cruise, and if the engine lugs a little, it tends to echo a bit, but I really have no regrets

Ive got a set of flowmaster 2.25 in and out on mine and am truely impressed, I also at the same time threw on a high flow air filter I get about 20 mpg.

So did you guys use 2 mufflers instead of the 1 stock set up? Or did you use the 1 flowmaster with 2 pipe exit? Is it worth going to two mufflers or is 1 sufficient? Seems like from a performance point, 2 would be better.

Wow, 20 mpg, I have to do what ever you are doing...

all I did was exhuaust and k&n filter charger, and of course baby the throttle, I get on average about 350 miles to the tank if I wait till 1/8th of a tank, pretty sure its a 25 gallon tank, better than my old dodge v6

On my 96 C1500 5.7 I originally had the dual inlet muffler, and what I ended up having a shop in town do was remove the dual inlet single exit muffler and replace it with two 40 series flowmasters with two 2.5" pipes and 3" tips out the rear

So you went with two mufflers. Now were your two flowmaster mufflers the 2.25" in and 3" out? Or were they the 2.25" in and 2.25" out with only the tips at 3"?

Did you have the same gas mileage result as 97silv5.7?

On my 97 2wd 5.7L I have 2 Flowmaster 40 series with 2.25" in /out.....Sounds great rumbles a little in cab but not annoying.

On my 99 Tahoe 4x4 5.7L I have a 2 inlet 2 outlet flowmaster. Sounds great too, not as loud as the 97, exhaust sounds great and only heard in cab while on throttle. With stereo on I don't hear it.

My mufflers were 2.25" in/out with the tips being 3".

Thanks guys, I know what my next project is....

How are you figuring your fuel mileage? If it were completely empty:
350miles/25gallons=14MPG

If you actually had 1/8 of a tank left:

25*(7/8)=21.875 gallons used

So, 350/21.875=16MPG

The way I learned to calculate fuel mileage is this. (assuming your speedometer/odometer is accurate)

Fill up and drive till almost empty--fill up again and divide miles traveled by gallons used to refill tank.

I think this is the only accurate way to calculate it (again, assuming speedo/od is accurate.)

IMHO, peedo/odo problems are why so many people have inflated MPG claims.

I tend to do what you said but go by half a tank and fill up, then take how much the tank took and divide by miles. Even if I am a lil off I still do better than the dodge that I used to have.

Just for your information, there are some great deals on flowmaster mufflers on ebay. I've found them for as low as $35 a muffler.

i put on 2 1/2 inch pipes on my v6[4.3] with turbo's on it also.
made a world of diff on mine. i went over 500 miles on 3/4 of a tank of gas from dayton tn to jacksonville fl.but i also dropped my tailgate and didn't run ac.
has 25 gallon tank.

I run a Force II Catback, nice mild tone at cruise, really comes to life when you get on it, I dont mind a single exhaust

Force II

:metal:

I Got 17 MPG with a tent on top and 4 passengers, this from a recent trip to CA. (I ran premium fuel)

Most cat back systems are single muffler (3 inch inlet, and dual 2.25 out) and if smog is going to be an issue most states will not allow dual mufflers. Check with the local laws to be sure. It is a B*t*h to put all that on only to remove it later. Just my 2 cents. I run a flowmaster 3in inlet and 2.5 dual out with 5 inch tips, a K&N air filter w/ a stage 2 chip on my '96' and all I can say is "wow". Hope this helps :burnout:

Rich