KG427KG427

iTrader: (1)

I have a 1991 v6 3.1 need a complete new exhaust I'm looking for best MPG. Don't care how loud it is or how much is cost. I drive 90 miles a day need




I got dynomax 202$ kit

83 Crossfire TA

iTrader: (2)

Long tube, small tube headers, as straight a moderate size run of exhaust pipe as possible (probably 2.5, or a stock iroc/ta 2.75", bigger will probably hurt you), probably single tailpipe without a muffler... Make everything as smooth as possible, especially transitions/bends....

LivinLarge

Why would larger size diameter piping hurt MPG? And wouldn't a well flowing muffler help or increase MPG?

305sbc

iTrader: (3)

Smaller diameter pipe is definitely much better for MPG improvement.
I would not go any larger than a single 2.5" I-pipe, then add a single-in, single-out turbo style muffler in back with a single 2.25" tail-pipe, - (or 1/4" smaller diameter than your I-pipe is).

The lower your cruise RPM is, the smaller pipe diameter you want for best MPG.

Wrapping your exhaust manifolds with insulator wrap like Thermotec will help warm the O2 sensor quicker on cold-starts and keep it hot even during low load conditions.

If most of your commute is at a steady speed on the highway, then it is very likely that a WAI - warm air intake will help your MPG as well, especially in winter.

Higher air pressure in tires gives a boost in MPG. The gains will level out at around 50 PSI for most car tire types.

For other ideas you can check out the ecomodder.com forum.

305sbc

iTrader: (3)

For 99% of street driving time there is no significant pressure in the exhaust system because such a small amount of air mass is moving through the engine, so no, the less restrictive pipe/muffler will not help MPG.
In most cases where engine speed stays relatively low, the reversion that large pipes allow will hurt the MPG.

Only if the engine is fairly loaded, as with climbing a hill or towing, or if you cruise at over 3000 RPM, then you may realize MPG gains from a larger exhaust. Most normal commuter type cars will not.

Ron U.S.M.C.

( Flowmaster American Thunder Exhaust System
In Stock 470$
Or
GMMG chambered exhaust system 700$
Or
MAGNAFLOW® - Street Series Cat-Back Exhaust System - Dual Split Rear Exit
1991 Chevy Camaro 500$ )

If your debating between these three than buy the cheapest one and invest the rest into a new rear end.(I have the American Thunder cat back and love it.)
A rear gear ratio plays a MUCH larger roll than your exhaust when it comes to MPG. If your stock your running 3.23 ratio that is "killing" your gas mileage. Invest some money in a 2.73 ratio and "that" will truly save you gas.You will be **** poor off the line but it will work.

2007xl50

If you don't want the car very loud Summit Racing has the Dynomax super turbo catback kit for your car $202.00. I have never really careed about MPG so I'm no help in that department, but wanted to give you the heads up on the catback

A rear gear ratio plays a MUCH larger roll than your exhaust when it comes to MPG. If your stock your running 3.23 ratio that is "killing" your gas mileage. Invest some money in a 2.73 ratio and "that" will truly save you gas.You will be **** poor off the line but it will work.

The above statement is correct in some ways, but there is no way I would go from the 3.23's to a 2.73 gear. The 3.1 is already gutless so going to 2.73's will make it that much worse. Also if you run 2.73's your MPG in the city will go down as the engine will have to work harder to get the car going and your going to push the gas more to get here going as well-that is why GM installed the lower gearing in the V6 cars. On the highway once up to speed then the 2.73's will help a bit, but really 3.23's are not crazy low gears plus all the money you are going to spend on a gear swap you could put aside for gas.

Ron U.S.M.C.

I agree that 2.73s in a 3.1 is a bad idea as far as around town but it sounds as if he wants to use a 3,500 pound v6 as a commuter thus the 90 miles a day.
Trying to cut gas mileage with a exhaust system although not a bad idea is minimal.The only thing that will help him while on the highway is a ratio swap.A 2.73 and 3.23 are two different animals.
Even though a swap would help him on the highway, as was already mentioned it will hurt your performance in town possibly cost you more in gas because of it.
I think you might be stuck with a car that's really not made for commuting long distances with out eating gas.

2007xl50

Agreed. I mean my DD is a 2013 Wrangler on 32's with 285hp under the hood, I knew MPG was going to suck, but oh well I wanted the Jeep so that's the price I pay. I drive over 60 miles a day.

The v6 3rd gens get very good MPG on the highway for what they are, hang out in the v6 section and you will see. Any old car that is about 3500 lbs, rear drive and is over 20 years old is not going to get the MPG that a new econo box is going to get. Yeah an exhaust is not really going to help with MPG so get the system that sounds best to you. Also if not done already a full tune up will go along way is the quest for MPG. My last truck got 2-3 mpg more just by doing new plugs and got alot more power back.

camarito

exhaust is not gonna give you a significant, if any, change in mpg, go for sound and price.
i drive 160+ miles a day and i drive My camaro at least once a week (15mpg average) the other days i drive a 2011 Hyundai Genesis 2.0t (26mpg average) they both have exhaust work and no difference in gas mileage what so ever

KG427KG427

iTrader: (1)

I have a 9 bolt 3.27 gear ratio so I guess it's not worth the money to change it since I already changed my rear end from drum to disc.
-----

Al drive shaft I heard can help MPG
Ported heads ?

Does anyone in California rebuild blocks, I want to rebuild a 3.4 block.

2007xl50

See you have to look at it this way. You are trying to spend money to save money-not really a wise move. If you want to do stuff to the car becasue you like the mods then cool, we all do that, but if you are trying to spend money on parts just to try and get better MPG then it's a waste of money. Save the money you would spend on parts and put that in the tank. It's kinda like when someone gets another car that gets better MPG, but spends alot more for it than the one they have-you just spend a ton of money that could have be put in the tank and then some.

Ozz1967

iTrader: (4)

I agree and disagree ith 2007x150. You can always do thing that improve efficiency. Dropping to better highway gears, better exhaust, better heads. Headers etc. There comes a point when you just can't get any better and you start getting negative returns. Exhaust won't make any difference. Not enough to spend the money on it anyway. Cruise control, 65mph (don't get caught up in the high speed drive of everyone else), proper tire inflation and a well tuned motor will get you the best results.

2007xl50

This is true, but I know I can't do 65 on the freeway LOL! The OP posted in the ECM sections about a chip for better MPG and he also stated over there that he has 18/19" Corvette Wheels and wide tires and I want to say a sound system in it. Like we said over there that the added weight of the wheels and tires will kill some MPG. I know when I went with the the wider 18" wheel over the 16" wheel on the 04 Dakota I had I lost about 2 MPG no matter what I did since they weighed more.

khulsebus

iTrader: (2)

A few years ago, I put a Flowmaster cat-back and K&N cold air intake on my 04 Hemi Durango. I went from a 20 mpg average before, 21 with only the intake, and then 26 mpg with the exhaust and cold air intake. the mid-pipe was the same single 3" as before, but instead of having a resonator and muffler with a small tailpipe i had only the Flowmaster muffler and dual tailpipes. Think of your engine as an air pump, the easier that it can get air in and out, the better it will run. That includes power and efficiency.

camarito

Definitely the extra rotating mass of the 18/19 corvette wheels will kill at least 1mpg easy, I can testify to that

2007xl50

Like I said, do mods because you like them, Besides maintenance stuff I don't see a point in spending a decent amount of money to try to save a little bit of it.