Anyone notice a MPG increase from Magnaflow catback?

[Mark42]

Anyone noticed a MPG increase from installing a Magnaflow cat back? Found the v6 2.5" w/3" tip Magnaflow 15693 at an affordable price and might just order it. I read about the hp increase, and if it gives a MPG increase too, that might just convince me to order one.

[FlyingDutchman]

I went from avg of 14ish mph to high 15s low 16s around town. Def a noticeable increase

Idk about highway, never bothered to check... this is with an LT1



**edit: i drove very easy though.

[deadtrend1]

very unlikely that you will notice a difference in MPG, and I doubt the HP gain from it will be seat of the pants significant. MPG may probably be worse in the beginning since its hard to keep your foot out of it when you get a new exhaust. Probably plateau and be the same or slightly a tenth better.

[maroman88]

very unlikely that you will notice a difference in MPG, and I doubt the HP gain from it will be seat of the pants significant. MPG may probably be worse in the beginning since its hard to keep your foot out of it when you get a new exhaust. Probably plateau and be the same or slightly a tenth better.

agree lol... since i put the catback on my vette i went from 14.9 to 11.7 wen i checked this morning!

[MyFirstZ]

i dont wanna know. I just ask for 25$ 93oct when i go to the gas station. If i knew i probably would cry a little

[JL8Jeff]

What size is the stock I-pipe on the V6 cars? If it's less than the 2.5" then you will definitely see an increase in mpg. It might not be big but even a .5 mpg increase is nice. Winter is not the best time to compare mpg though, every vehicle drops a couple mpg during the winter. I average around 18-19 mpg daily driving in the summer with my LS1 and it drops to around 15.5-16 mpg in the winter. My old 4Runner would average 20 mpg in the summer and 17 in the winter. I picked up a solid 1 mpg with the 4Runner after installing a 2-1/4" cat-back which replaced the stock 1-3/4" exhaust. So bigger pipes will help mpg in the long run. The initial change in driving style may hurt as you enjoy the new sound and get on it more often.

[Savage_Messiah]

What size is the stock I-pipe on the V6 cars?

2.25"

Here, this is a great deal: http://www.fullthrottlev6.com/forums/showthread.php?t=59092

[sweetbmxrider]

says the sale ended brah

i didn't notice any mpg increase, but i didn't have the proper equipment to measure for it so i guess this is really just an opinion.

[ws6 jim]

I agree with Jeff based on the sizing beforehand and the amount of back pressure a vehicle has to begin with.
Everyone buys a cat back for sound foremost, power and mpg is negligible and a fringe benefit.

[Mark42]

Yeah, the pipes are 2.25 OD from the cat back on the single outlet system. So a 2.5" is a nice increase in area, but not too much for my stock v6.

All the other systems I had on other cars gave about 1-2 mpg increase on highway driving, but they were all custom systems.

I remember reading a doc from Magnaflow claiming 10hp and up to 3 mpg on the V6 cat back, but now I can't find it. The 3" version (same configuration) used on the V8's gives has a dyno sheet on their website showing 18hp and 15 torque gain. If the V6 does half of that, I would be impressed. They do claim:

Question: How much horsepower can I expect to gain?

Answer: It's different for every car, but typically expected gains are in the average range of 10%.

Replacing the muffler/exhaust with a MagnaFlow will help your engine increase power by being able to expel exhaust gases quicker. This creates less workload for the engine, makes it run more efficient, and results in better power.

"Average Range" being the operative words......

I sent Magnaflow an email asking for the V6 dyno sheet(and any mpg info), seeing as they claim every design is dyno tested to ensure HP gains. We will see what they say.


They also had this interesting bit of info on pipe sizes:

http://www.njfboa.org/forums/attachment.php?attachmentid=3824&d=1266185898

I was surprised to read this on the Magnaflow site. Its classic "old school" exhaust sizing, where today it seems that many people think you can't get big enough pipes. Nice to see some rules stand the test of time.

[sweetbmxrider]

yeah if you research around, you will see its pretty well known. surprised you didn't find that out here :-?

[Mark42]

I'm surprised that no Magnaflow V6 owners have chimed in. Thought there were lots of them on this forum, especially after reading how many feel the Magnaflow is the best cat back for the V6.

Would be nice to hear from someone with the Magnaflow.

[Savage_Messiah]

I gained a couple mpg... I have the 3" though, not the 2.5

[LTb1ow]

Well if a good catback gains MPG, then NO catback means major MPG gains!

You should do headers too, I hear they can add MPG.

[Mark42]

I gained a couple mpg... I have the 3" though, not the 2.5

Something about the 3" system is confusing me. I've seen pics of Magnaflow 3" system that has two bullet mufflers and dual tips, but this system is not listed on the Magnaflow site. The 3" system listed is the same single muffler configuration as the 2.5" system.

Also read posts from 2006-2007 where people said the Magnaflow was loud and had a drone.

Was there an older 3" system with two bullet mufflers that is no longer offered?

Well if a good catback gains MPG, then NO catback means major MPG gains!


:rofl:

[CHRIS67]

I had a 4.3 Sonoma that had Magnaflow exhaust, a cold air intake, throttle body spacer, under drive pulleys, and a JET stage I chip. If anything my MPG went down because I drove more aggressively with the HP increase. More HP = more fun!! If you’re looking to save on gas the best thing you can do is keep those tires inflated to their recommended pressure, keep the car tuned, and keep a light right foot.

[JL8Jeff]

The 3" system would be more for trying to get maximum top end power which you're not looking to do. I think you would be better with the 2.5" system for your purpose. Even the V8 systems are necked down to 2-3/4" at the I-pipe connection so the rear portion of the system is most likely the same for both with just a different inlet size. My 2000 SS has the Random Tech cat-back and there is no drone or resonance at all. The muffler is a straight through with perforations to feed the passenger side tailpipe. You might want to look at actual muffler designs to help determine what might work best for you.

[Mark42]

The 3" system would be more for trying to get maximum top end power which you're not looking to do. I think you would be better with the 2.5" system for your purpose. Even the V8 systems are necked down to 2-3/4" at the I-pipe connection so the rear portion of the system is most likely the same for both with just a different inlet size. My 2000 SS has the Random Tech cat-back and there is no drone or resonance at all. The muffler is a straight through with perforations to feed the passenger side tailpipe. You might want to look at actual muffler designs to help determine what might work best for you.

Hey Jeff! Thanks for the informative post. I have been looking at all the exhausts available and decided the 2.5" V6 cat back by Magnaflow is what fits the bill. The pipe size is perfect for a stock motor, and its all stainless so rust should not be an issue, and if the system fails, it is warranted for the life of the system. The muffler on this system is a straight through design, so it should be low restriction. I also like that all the packing is stainless steel too, so it should not burn, compress or blow out like fiberglass packing does over time.

I agree with your assessment on pipe sizes, way too often a system is fit to the car that is too big for the HP/CID, resulting in an actual loss of performance rather than the anticipated gain. From what I see on various forums, this system is perfect for my application.

Hopefully, this Maganaflow will not be too loud, or drone at highways speeds.

Thanks again.

[Mike]

the reason you aren't getting a ton of feedback from the magnaflow v6 owners, is because many of them don't care about mpg, or didn't pay attention to their previous mpg... i had a 3'' borla on my old 3.4 car, and while i never drove the car with stock exhaust, i do know that the car averaged 3-5 mpg more than the factory claims...

the 3.8 is obviously a more efficient motor than the 3.4 was, so you should be able to expect the same or better, but i don't know where your car is in comparison to the factory claims....

besides, it will sound good, gain a little power, and gain a little mpg, and the tips usually look better.... add all that together and its worth picking up.

[Mark42]

the reason you aren't getting a ton of feedback from the magnaflow v6 owners, is because many of them don't care about mpg, or didn't pay attention to their previous mpg... i had a 3'' borla on my old 3.4 car, and while i never drove the car with stock exhaust, i do know that the car averaged 3-5 mpg more than the factory claims...

the 3.8 is obviously a more efficient motor than the 3.4 was, so you should be able to expect the same or better, but i don't know where your car is in comparison to the factory claims....

besides, it will sound good, gain a little power, and gain a little mpg, and the tips usually look better.... add all that together and its worth picking up.

I suspect you hit the nail on the head!

Alright then, you guys forced my hand! It is becoming painfully obvious that I will have to find out if there is an MPG increase or not for myself. That requires procuring said exhaust system, so I have. It should be here Friday. After its installed, I will post my findings. This is all being done in the name of science, and no way reflects my desire to own a Magnaflow exhaust nor is the MPG issue being used as an excuse to purchase said exhaust...... :lol:

[sweetbmxrider]

so what is your current mpg and will all conditions be replicated to ensure accurate data? just want to keep it factual.

[Mark42]

I've been keeping record of fuel, miles and modifications since I bought the car this past summer. My driving is pretty much the same from week to week, so I will be able to post accurate results.

[Mark42]

Oh man! Look what came today! This is sooooo much nicer than I had read or anticipated. I can't believe I got this for under $300 new.

http://img.photobucket.com/albums/v437/mark42/1998%20Firebird/HPIM6490.jpg

The build quality of this system blows away anything I had bought from Flowmaster or Dynomax over the years.

Come on warm weather!

[sweetbmxrider]

weird how from what it looks, the outlets are on the same side. the magnaflows are nice though.

[BonzoHansen]

Looks good Mark. You'll love it.

weird how from what it looks, the outlets are on the same side. the magnaflows are nice though.

The Banks Engineering 3" catback system on my 3rd gen had both outlets on one side. When I called Banks and asked they told me it flows better like that, not making the gas make additional turns. It also sounded awesome.

http://img.photobucket.com/albums/v359/SIBLY/Cars/th_1982TA_1.jpg (http://smg.photobucket.com/albums/v359/SIBLY/Cars/?action=view&current=1982TA_1.jpg)

[JL8Jeff]

I completely forgot that the Magnaflow V6 exhaust had the outlets on the same side of the muffler and one routed back to the passenger side. That exhaust should be perfect for what you're looking for. But don't try to compare your current winter gas mileage now to what it does if you install it later on when the temps are closer to 60 degrees out. I think I'm getting my worst mileage of the winter right now looking at my readings.

[sweetbmxrider]

yeah i figured they would just use the same system as the v8's

[Mark42]

I completely forgot that the Magnaflow V6 exhaust had the outlets on the same side of the muffler and one routed back to the passenger side. That exhaust should be perfect for what you're looking for. But don't try to compare your current winter gas mileage now to what it does if you install it later on when the temps are closer to 60 degrees out. I think I'm getting my worst mileage of the winter right now looking at my readings.

Looking inside the muffler, it is straight through. There are two perforated pipes welded into a V shape with a mini-two pipe collector at the input side, and each leg of the V angles to an output. It literally splits the input flow into two output pipes. You can look right through, but you have to look at an angle to see through each leg.

Heard that winter gas gives lower economy, but I never tested it. I'll take your word on it. Hate working in the cold with hand tools, so I'll wait until March or April to install it. Also have the aluminum drive shaft to install too.

[BonzoHansen]

Heard that winter gas gives lower economy, but I never tested it. I'll take your word on it. It does. I still watch my fuel usage like a hawk, its a good indicators of issues. I lose ~5% on winter gas. The snow tires I used to run cost me another ~5%.

[Mark42]

yeah i figured they would just use the same system as the v8's

Magnaflow built the V6 system specifically to enhance V6 performance, rather than selling the V8 with a few V6 mounts tacked on. For a stock 3800, the 3" V8 system is reported to cause a loss of bottom end torque. I always thought the Magnaflow was too expensive for my budget, but when I could get it for less than $300, I just couldn't pass it up. Thats even cheaper than some of those "aluminized" steel cat-backs.

[Mark42]

It does. I still watch my fuel usage like a hawk, its a good indicators of issues. I lose ~5% on winter gas. The snow tires I used to run cost me another ~5%.

Wow, I didn't realize winter fuel could cause as much as 5% economy loss! That is the pits....

That could also account for the 0.5 - 1.0 mpg fuel economy loss since changing the rear gears early in winter.

Update: Found this on the Chevron website:

Oxygenated gasoline reduces fuel economy an average of 2 to 3 percent because oxygenates contain less energy than non-oxygenated gasoline.

They go on to say other winter factors increase the loss of economy. I'm surprised I was not really aware of how significant the impact of winter is on fuel economy.

[sweetbmxrider]

Magnaflow built the V6 system specifically to enhance V6 performance, rather than selling the V8 with a few V6 mounts tacked on. For a stock 3800, the 3" V8 system is reported to cause a loss of bottom end torque. I always thought the Magnaflow was too expensive for my budget, but when I could get it for less than $300, I just couldn't pass it up. Thats even cheaper than some of those "aluminized" steel cat-backs.

seems like win win with magnaflow then 8-)

[JL8Jeff]

They go on to say other winter factors increase the loss of economy. I'm surprised I was not really aware of how significant the impact of winter is on fuel economy.

Yes, winter seems to cause a loss of 2-3 mpg regardless of the engine. I've watched my mileage drop that much with 4cyl, V6 and V8 vehicles.

[Tru2Chevy]

Yes, winter seems to cause a loss of 2-3 mpg regardless of the engine. I've watched my mileage drop that much with 4cyl, V6 and V8 vehicles.

Yup, I go from 17-18mpg to 15-15.5 in my Jeep from summer to winter.

- Justin

[Mark42]

MPG Update time!

very unlikely that you will notice a difference in MPG, and I doubt the HP gain from it will be seat of the pants significant. MPG may probably be worse in the beginning since its hard to keep your foot out of it when you get a new exhaust. Probably plateau and be the same or slightly a tenth better.

FYI... the average MPG has risen 1.5 mpg. Thats a 6% increase over the average of 25 mpg. I bet your happy and relieved that its quite a bit better than your prediction of "very unlikely that you will notice a difference in MPG.....be the same or slightly a tenth better".

I went from avg of 14ish mph to high 15s low 16s around town. Def a noticeable increase

Idk about highway, never bothered to check... this is with an LT1
**edit: i drove very easy though.

Yep, I am getting similar results with the V6.

Just as I expected, there is a very measurable increase in fuel economy. Seeing as there were a few trips on rt80 that were bumper to bumper, I expect the long term MPG to be even better.

Magnaflow claims a 2-3 mpg improvement (iirc).

[Mark42]

Rather than starting a new thread, I decided to find this old one and update so all the info is in one thread.

The "winter" gas is pretty much gone from the fuel tanks in these parts. I also learned its not just a Summer/Winter blend. The fuel is modified to match the degree days throughout the year. So late winter/early spring gas is different than mid winter gas, and different than summer gas.

Anyway, to the point of the post.....

To recap, the mods to the car are: 3.73 gears w/Truetrac posi, PCM tune (PCMflorless.com), Magnaflow V6 exhaust, 180 Thermostat, and low restriction intake.

My last 4 tanks have averaged 26 mpg. That includes some traffic backups due to accidents in the commute that I thought would ruin the numbers, but didn't happen.

So keep in mind that changing gears like I did (3.08 to 3.73) is not going to blow your fuel economy out the window (like so many posts said). When you drive with a light foot, and keep your speeds under 67 (I cruise at 65 mph @ ~ 2300 rpm when possible) the fuel economy should not be impacted, depending on mods done.

I have to admit, that the week I was off from work, and working on the car, I was hammering the throttle often, doing 0-60 tests, peel outs, etc and also just doing around town driving, and short trips such as taking the kids to school. The fuel economy for that week dropped to 20 mpg. Apparently WOT sucks the fuel. :mrgreen:

So, what did you learn?

- The claims that changing gears will drop fuel economy 3-5 mpg in our V6 are proven bogus. Especially if other mods off set the change, like PCM Tune and Exhaust.

- The 2-3 mpg improvement claimed by Magnafow is probably closer to 1-2 mpg, and along with the PCM tune, offset any loss of MPG due to the gears. Claims that the exhaust will only give a "tenth" of a mile per gallon are most likely bogus.

- Yep, winter fuel does give lower MPG than summer fuel.

- WOT sucks fuel. So if you are wondering why your car does not get good economy, its probably due to your right foot, and not the cars mods.

[WildBillyT]

Rather than starting a new thread, I decided to find this old one and update so all the info is in one thread.

The "winter" gas is pretty much gone from the fuel tanks in these parts. I also learned its not just a Summer/Winter blend. The fuel is modified to match the degree days throughout the year. So late winter/early spring gas is different than mid winter gas, and different than summer gas.

Anyway, to the point of the post.....

To recap, the mods to the car are: 3.73 gears w/Truetrac posi, PCM tune (PCMflorless.com), Magnaflow V6 exhaust, 180 Thermostat, and low restriction intake.

My last 4 tanks have averaged 26 mpg. That includes some traffic backups due to accidents in the commute that I thought would ruin the numbers, but didn't happen.

So keep in mind that changing gears like I did (3.08 to 3.73) is not going to blow your fuel economy out the window (like so many posts said). When you drive with a light foot, and keep your speeds under 67 (I cruise at 65 mph @ ~ 2300 rpm when possible) the fuel economy should not be impacted, depending on mods done.

I have to admit, that the week I was off from work, and working on the car, I was hammering the throttle often, doing 0-60 tests, peel outs, etc and also just doing around town driving, and short trips such as taking the kids to school. The fuel economy for that week dropped to 20 mpg. Apparently WOT sucks the fuel. :mrgreen:

So, what did you learn?

- The claims that changing gears will drop fuel economy 3-5 mpg in our V6 are proven bogus. Especially if other mods off set the change, like PCM Tune and Exhaust.

- The 2-3 mpg improvement claimed by Magnafow is probably closer to 1-2 mpg, and along with the PCM tune, offset any loss of MPG due to the gears. Claims that the exhaust will only give a "tenth" of a mile per gallon are most likely bogus.

- Yep, winter fuel does give lower MPG than summer fuel.

- WOT sucks fuel. So if you are wondering why your car does not get good economy, its probably due to your right foot, and not the cars mods.

Throw in a vacuum gauge. Try to keep it as far from 0 at all times- that'll give you the best milage.

[NastyEllEssWon]

Throw in a vacuum gauge. Try to keep it as far from 0 at all times- that'll give you the best milage.





yup that worked well in my supercoupe. kept it away from 0 or going into boost whenever possible to do so and ended up getting mid to upper 20s. its all in driving habits :nod: it also makes things easier when trouble shooting for little things

[Slow-V6]

I was running my stock 3.8 with a 4.10 rear end. I had Whisper lid, WS6 ram air hood with ram air box, MSD Coil packs, headers, 3 inch y-pipe w/o no cat, 3 inch S pipe, 3 inch I pipe, and a Flowmaster 80 series with 3 1/2 inch tips! It sounded so mean. I was also getting around 28 miles per gallon in the city and 32-34 mpg on the Highway! I would drive up to Jersey from VA beach with only using 1/2 tank of gas. It was 260 miles to my parents house! When I did the built motor I was still getting 25mpg in the city and around 30 mpg on the highway!

[JL8Jeff]

Here's an interesting one for you. The 2001 Silverado Z71 I bought a month ago has pulled down 14.8 mpg on the first half tank which was daily commuting and not getting into overdrive or above 50 mph, then another week of daily commuting and a 130 mile highway trip(65-70 mph in overdrive) averaged out to 14.8 mpg as well! :-? My last tank with daily commuting came out to 14.8 mpg. I just changed the plugs, put in a 160 t-stat, a ported TB and took off the mud tires and put on some BFG AT's. Already it rides quieter and actually coasts when you take your foot off the gas. I think the worn mud tires were really hurting it big time. I'll see what this next tank does before doing some tuning, the LTFT's are running around 8 so I should be able to adjust the fuel curve and spark to get better cruise conditions. I need to see what the first set of changes did first though.

[BonzoHansen]

Jeff, tires can make sure a big difference in MPG. Width, compounding, etc.,

[JL8Jeff]

I actually went 1 size up on the tires from 285/75 to 295/75 but I'm sure the tread pattern is going to be the big difference. I can really feel it and hear it in normal driving and the block size on the Mickey Thompson Baja MTZ tires is huge compared to the AT tires. But looking at the LTFT on the scanner after the ported TB vs stock is showing how much better the air is flowing in. I also cut back the EGR tube that sticks into the intake like I did on the SS and that is probably helping airflow as well.

Mark, that makes me wonder what the EGR setup looks like on the V6 cars? If the tube sticks into the intake as bad as it does on the V8 cars you might want to look into trimming that tube back to allow better airflow.

[Slow-V6]

I actually went 1 size up on the tires from 285/75 to 295/75 but I'm sure the tread pattern is going to be the big difference. I can really feel it and hear it in normal driving and the block size on the Mickey Thompson Baja MTZ tires is huge compared to the AT tires. But looking at the LTFT on the scanner after the ported TB vs stock is showing how much better the air is flowing in. I also cut back the EGR tube that sticks into the intake like I did on the SS and that is probably helping airflow as well.

Mark, that makes me wonder what the EGR setup looks like on the V6 cars? If the tube sticks into the intake as bad as it does on the V8 cars you might want to look into trimming that tube back to allow better airflow.



It goes in about a 1/2 inch. I removed mine from my old V6 to save on weight.

[Mark42]

Will make this update short and sweet.....

Now that construction is done on RT80, and no more winter gas, the fuel economy is now 27.45 average compared to a best average of 26 when the car was bought last summer.

So, even though a few trips showed a best of 27 mpg average for the one 15 gallon trip last year, now I am showing a weekly average of 27.45 for regular commuting (without construction backups/delays), including some strictly around town driving.

I will be doing some long highway drives from NJ to LI all through the summer. Will be interesting to see what the MPG is for those long highway trips. Bet the car averages better than 30 mpg.

Again, I have to admit that the PCM tune and Magnaflow exhaust have offset and/or exceeded any loss due to changing from 3.08 to 3.73 gears.

Your mileage may vary... :mrgreen:


so what is your current mpg and will all conditions be replicated to ensure accurate data? just want to keep it factual.

Hmmmmm. See above. AND, its time to start posting your MPG and driving habits. OK?????

And all you guys should do the same. Its not hard to write down the mileage and gallons. It helps everyone because it gives them a reference. If enough folks post their milage, maybe this thread will become a sticky.

[LTb1ow]

My mpg is more painful when you write it down.

[NastyEllEssWon]

the fuel economy is now 27.45 average compared to a best average of 26 when the car was bought last summer.



youd think the six cylinders would get better mileage than the v8's :?: damn gm

[WildBillyT]

youd think the six cylinders would get better mileage than the v8's :?: damn gm

Yeah, and the milage went UP after a gear swap. :mrgreen:

[Mark42]

youd think the six cylinders would get better mileage than the v8's :?: damn gm

Well, that is the average for that cars use. The type of driving the car gets is documented earlier in the thread. How does your driving compare to the V6 Firebirds use? More highway, less highway?

If you question yourself about your driving habits compared to what is in the thread, then you will have the answer to your inquiry about 6 vs 8 economy.

Let us know how it turns out for you.

Good luck,

Mark.

[NastyEllEssWon]

Well, that is the average for that cars use. The type of driving the car gets is documented earlier in the thread. How does your driving compare to the V6 Firebirds use? More highway, less highway?

If you question yourself about your driving habits compared to what is in the thread, then you will have the answer to your inquiry about 6 vs 8 economy.

Let us know how it turns out for you.

Good luck,

Mark.





i got upper 20s in the past few ls1 cars ive owned. id label the driving style as ''Spirited'' :nod:

[Slow-V6]

On the Highway my LS1 and V6 were pretty close. Best I got about 27 mpg in my T/A and the best ever in my V6 was 33mpg! Around town the best I can do in my T/A is 300 miles per tank! I use to avg between 380-420 miles per tank in my V6 around town! All of this is by using skip shift in my T/A and 1st-3rd-5th in my V6! Normal driving in my V6 I never took it above 3000 rpms! The car sounded mean as hell up to 3000 then it started to sound like a V6 after that!

In Virginia the track was 75 miles away from Virginia beach. I use to cruise up there in my V6 with the other T/A guys. We would fill up before leaving Va Beach, then I would make 5-10 runs there and when we got home I would still have between a 1/4 -1/2 tank left. All the LS1/LT1 guys would have to fill up when we left the track!