Different exhaust affecting MPG's? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Hentai · 06-02-2015, 06:08 AM

I'm just curious, Still a noob with mods.
Does changing the exhaust affect the mpg in anyway?

I just changed my stock exhaust with Spec D's and it seems like my mpg went down a little bit.

Thanks in advance!

churchx · 06-02-2015, 06:34 AM

Theoretically with all the rest being same more freely flowing exhaust and intake mods should increase MPG.
BUT!

I've seen often that MPG in many cases is more affected by lead-footness

. My brother's MPG on my car was 20%/4MPG worse for half a day he borrowed it. When i go for drive for fun with sideways-squealing-tyres, my MPG also rises by 3-4MPG above average of just 1st->2nd->cruising in 6th most of time, including in city, once 40 mph reached. In most cases aftermarket exhaust bolton mods are purchased/installed/accompanied by tune aiming to get most extra hp/tq gains .. i somewhat expect that for sake of more fun more power might make left foot even heavier

. I sometimes downshifted and ran at lower gears longer just for sake of sound. I doubt that even better sound of modded exhaust will make me do it less for more MPG

.
P.S.
If you care much about economy, IIRC there was thread about OFT tune oriented for that, with increased economy in lower rpm-s more common in daily driving. Though good ecu tunes in general may rise economy, due often running leaner then stock, or due more power providing needed just-enough acceleration at lower rpms/higher gears/less wide open throttle.

kch · 06-02-2015, 05:21 PM

Is the spec-D a dual canister style? There's been anecdotal evidence of lower MPGs using that style of exhaust. Allegedly, when you don't have anything in the stock muffler area, the rear bumper acts like a parachute.

tahdizzle · 06-02-2015, 05:39 PM

could it possibly be you're driving differently? :P

mav1178 · 06-02-2015, 05:44 PM

Quote:

Originally Posted by Hentai

I'm just curious, Still a noob with mods.
Does changing the exhaust affect the mpg in anyway?

I just changed my stock exhaust with Spec D's and it seems like my mpg went down a little bit.

Thanks in advance!

The only thing that can make your MPG lower is if your aftermarket exhaust lost the drag-reducing profile of the stock one, i.e. some type of aftermarket exhaust that leaves a gaping hole where the stock one sat.

Obviously I'm assuming you are not using the dash gauge and actually measuring real-world MPG, but if you do purely highway driving there could be a small difference in MPG at higher speeds with an aftermarket exhaust.

-alex

Hentai · 06-02-2015, 09:08 PM

Thanks guys, This is the exhaust I got
[ame="https://www.youtube.com/watch?v=xjSo6iiKGsA"]SPECDTUNING INSTALLATION VIDEO: 2013-UP FR-S & BRZ CATBACK EXHAUST - YouTube[/ame]
I got it installed by a good friend who owns a mechanic shop, and I help a lil bit myself
He said it shouldnt change at all or very little the first 200-400 miles,
just sucks how my mpg dropped about 3-4 ):

06-02-2015, 06:08 AM	#1
Hentai Member Join Date: Dec 2014 Drives: 2015 Halo GT86 Location: Las Vegas Posts: 74 Thanks: 22 Thanked 9 Times in 8 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Different exhaust affecting MPG's? I'm just curious, Still a noob with mods. Does changing the exhaust affect the mpg in anyway? I just changed my stock exhaust with Spec D's and it seems like my mpg went down a little bit. Thanks in advance!

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06-02-2015, 06:34 AM	#2
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,334 Thanks: 698 Thanked 2,086 Times in 1,436 Posts Mentioned: 53 Post(s) Tagged: 1 Thread(s)	Theoretically with all the rest being same more freely flowing exhaust and intake mods should increase MPG. BUT! I've seen often that MPG in many cases is more affected by lead-footness . My brother's MPG on my car was 20%/4MPG worse for half a day he borrowed it. When i go for drive for fun with sideways-squealing-tyres, my MPG also rises by 3-4MPG above average of just 1st->2nd->cruising in 6th most of time, including in city, once 40 mph reached. In most cases aftermarket exhaust bolton mods are purchased/installed/accompanied by tune aiming to get most extra hp/tq gains .. i somewhat expect that for sake of more fun more power might make left foot even heavier . I sometimes downshifted and ran at lower gears longer just for sake of sound. I doubt that even better sound of modded exhaust will make me do it less for more MPG . P.S. If you care much about economy, IIRC there was thread about OFT tune oriented for that, with increased economy in lower rpm-s more common in daily driving. Though good ecu tunes in general may rise economy, due often running leaner then stock, or due more power providing needed just-enough acceleration at lower rpms/higher gears/less wide open throttle.

06-02-2015, 05:21 PM	#3
kch Senior Misanthrope Join Date: Sep 2014 Drives: 2015 BRZ Series.Blue CWP Location: Seattle, WA Posts: 1,490 Thanks: 1,743 Thanked 1,169 Times in 645 Posts Mentioned: 20 Post(s) Tagged: 2 Thread(s)	Is the spec-D a dual canister style? There's been anecdotal evidence of lower MPGs using that style of exhaust. Allegedly, when you don't have anything in the stock muffler area, the rear bumper acts like a parachute.

06-02-2015, 09:08 PM	#6
Hentai Member Join Date: Dec 2014 Drives: 2015 Halo GT86 Location: Las Vegas Posts: 74 Thanks: 22 Thanked 9 Times in 8 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Thanks guys, This is the exhaust I got [ame="https://www.youtube.com/watch?v=xjSo6iiKGsA"]SPECDTUNING INSTALLATION VIDEO: 2013-UP FR-S & BRZ CATBACK EXHAUST - YouTube[/ame] I got it installed by a good friend who owns a mechanic shop, and I help a lil bit myself He said it shouldnt change at all or very little the first 200-400 miles, just sucks how my mpg dropped about 3-4 ):

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