I'm planning on putting a flowmaster on my truck, 5.3L. My plan is to put a big block flowmaster ( don't want it real loud, muffler shop suggested this ), and instead of two pipes with crome tips and all that, I'm planning on changing out the factory tail pipe with one plain jane3" in the same location. I'm sure there's better performing setups, but what are your thought those of you that have done the exhaust changes. I'm looking to add hopefully another 1.5 mpg to my already 18.5. Only other mod at this point is a lower end K&N cold air kit.

 

and what about exhaust back pressure. do you still need that on these new computer controlled engines

 

Yeah the vortec does need back pressure. I think some people said they noticed there 1/4 mile times went up just a bit. My dad has the set up you're after but it'son his 87-88, sounds great mild at idle but over 2k rpm's it sounds damn nice. I'm sure it'd sound just as good on a vortec with 600,000 less miles.

 

I disagree. Not to creat an argument but because of the simple fact that I lost both gas mileage and torque when I put my exhaust on. YES you need backpressure. If you wanna stay at 18.5mpg leave the factory exhaust on there.

 

I think we all need to come up with ideas to have exhaust and keep most, if not all, the back pressure. I say a single in, dual out muffler with 2" pipes or smaller. Remember in the 70s and 80s when people would put little dual pipes on there Chevys and Fords. Maybe that will work? Either that or just replace the muffler with something louder, like a Flowmaster, and keep the pipe stock. Any ideas?

 

Gas mileage isn't affected by an exhaust sytem...I think you're seeing a loss in MPG because it sounds so good to get on it now that you're flooring it more than when it had a stock exhaust. Thats my 2cents

As quick02 said All the votecs need backpressure for torque however if you put on a high flow exahust system, you will lose torque but you'll see an increase in HP.

What you're proposing, z71twotone, won't affect anything but the sound.

 

Okay bro your right. I forgot you knew so much about these which is why your asking for advice.

(For anybody else who cares to know, yes you will probably lose gas mileage and torque by adding an exhaust system. Take it from someone who used their vehicle for work purposes everyday for half a year and then added exhaust to it. I promise you I'm right.)

 

I am going to have to say i have never had dual exhaust cause me to loose gas milage just from the trucks i have put it on. So its more depense on the truck. With all my mods and bigger tires i have gone up from 18 to about 19.5 or so. And after exhuast mine did not change any. That is if i drove it the same as before the exhaust.

 

You're the first person to say you lose MPG when installing an exhaust. everybody I've talked to who's done it gains MPG's. just an observation, you don't have to try to prove it to me.

oh yeah, and "bro", look at who's post you just responded to, not the one asking for advice.

 

I'm not worried about losing mpg's. i doubt i will, that's not my issue, nor is the back pressure. a high flow muffler with one 3" out will not rid me of exhaust. an engine is an air pump, get it in faster, and out faster. there's enough restriction at the headers to still have back pressure if I cut the pipe off at the cats. have you ever looked at those? anyway, i'm just looking for everyones opinion. has anyone tried this set up. bigblock highflow muffler, 1 3" out, 2 2" in.