Exhuast question..flowmaster
 

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.

RE: Exhuast question..flowmaster
 

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

RE: Exhuast question..flowmaster
 

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.

RE: Exhuast question..flowmaster
 

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.

RE: Exhuast question..flowmaster
 

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?

RE: Exhuast question..flowmaster
 

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:D

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.

RE: Exhuast question..flowmaster
 

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.)

RE: Exhuast question..flowmaster
 

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.

RE: Exhuast question..flowmaster
 

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.

RE: Exhuast question..flowmaster
 

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.

RE: Exhuast question..flowmaster
 

I have not tried that setup, but I have experimented with mine alot, anyone here can tell you that. Yes you need backpressure, but less than stock. I think that going to a single 3" pipe off the y-pipe into a muffler like you are talking about, then a single 3" out will be good. I expect some HP / Tq gains as well as some milage. Bigger than that you will start to lose milage. When I first did mine, my milage dropped by 2 mpg, but I did true dual 2.5, with an x-pipe (way overkill for these engines). SInce then I have been adding reducers. Now I have the same setup with the ens narrowing to 1.75" a piece. I think a tighter tube all the way would be better. So, I think you have a good setup idea, and would love to hear the results as that is what i think would be really good. The only change I owuld make would be dual exhaust out of the muffer or a reverse Y and dual pipes. I just like that look better.

RE: Exhuast question..flowmaster
 

smoke actually i'm assuming there are still two pipes to the muffler. I'm leaving those stock, installing a big block flowmaster with one 3" out the side where the factory pipe is now. The reverse of what your talking about. Did that to a 86 with a 305, but only had a single2" out, but had the smaller muffler. Sounded very loud, but did the job. I just don't want to open it up too much

RE: Exhuast question..flowmaster
 

I also have an 04 andI only had the one pipe running into the muffler. But the cats come after the headers and befor the Y so i would imagin that you could have it changed to the two pipes running into the muffler. And it dose sound like one hell of an idea if you are able to get the two pipes ran down.

RE: Exhuast question..flowmaster
 

I can see gaining mpg, but not so much around here. I could afford too loose SOME backpressure, but not alot of it. I know that the hills around here (with too much of a loss of backpressure) would cause more downshifting and therefore, higher rpms and less mpg. BUT, when I was down South with my truck I could drive it all day and it would never downshift unless passing or starting from a stop. And let me tell you that was soooo freakin nice for a change! All the roads were flat and open and (for the most part) the South has fewer red lights and stop signs per square mile compared to where I live. SO....I can see that a considerable loss in back pressure would not hurt and in some cases help mpg, unless you stomped the gas all the time. Around here, even in the country side it is up, down, up, down, stop, go, stop go, it BLOWS!

RE: Exhuast question..flowmaster
 

hey man you said you lost power and fuel economy... sounds like you might have an exhaust leak somewhere. the custom exhaust should boost both power and fuel economy. you should check for a leaking manifold or somewhere in your pipe