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Tune-A-Can Exhaust - Higher MPG?!

 
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  • 4 Post By wingman55
  • 1 Post By Gkon
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  #1 (permalink)  
Old 19 Jul 2017, 11:59 am
wingman55's Avatar
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Default Tune-A-Can Exhaust - Higher MPG?!

SO, ever since I have installed my Tuna Can Exhaust, . . .

See thread here:

QUIETER but still cool Exhaust!

. . . I've noticed better gas mileage. According to the dash readout I am getting around 27.4 to 27.6 MPG for everyday driving. That's about 1 to 1.5 MPG better. According to calculations I am getting around 28 MPG. <-- Hmm. Not sure about that.

I've always heard that engines need at least SOME back pressure to run good, and it would seem that adding that small amount of back pressure has boosted the MPG.

At any rate, I am still amazed at how quiet the exhaust is at highway speeds, but when I listen outside the car at idle, and revving it, it still has that nice, low, but not ridiculously loud, rumble...
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2004 Limited Edition Platinum Series, Graphite Metallic, Standard Turbo, automatic, RBQ radio with Sirius Radio & 6 CD changer, VentShades, chrome exhaust tip, door spears, grille inserts, door lock pulls, bright pedals and steering wheel spokes. Red spoiler from a donor PT. Known as: "The RATMOBILE" I bought it Apr 28th, 2016 with 62,400 miles on it.

Last edited by wingman55; 19 Jul 2017 at 12:02 pm.
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Old 19 Jul 2017, 12:22 pm
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Default Re: Tune-A-Can Exhaust - Higher MPG?!

Quote:
Originally Posted by wingman55 View Post
SO, ever since I have installed my Tuna Can Exhaust, . . .

See thread here:

QUIETER but still cool Exhaust!

. . . I've noticed better gas mileage. According to the dash readout I am getting around 27.4 to 27.6 MPG for everyday driving. That's about 1 to 1.5 MPG better. According to calculations I am getting around 28 MPG. <-- Hmm. Not sure about that.

I've always heard that engines need at least SOME back pressure to run good, and it would seem that adding that small amount of back pressure has boosted the MPG.

At any rate, I am still amazed at how quiet the exhaust is at highway speeds, but when I listen outside the car at idle, and revving it, it still has that nice, low, but not ridiculously loud, rumble...
Better back pressure and better gas mileage always held true for my motorcycles, so I don't see why it wouldn't help with a car.

I love that tuna can.
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Old 19 Jul 2017, 12:51 pm
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Default Re: Tune-A-Can Exhaust - Higher MPG?!

it's possibly due to you driving differently with the quieter exhaust. when i drive my mustang normal i get higher mpg than when i try to keep it quiet with my mom in the passenger seat.

it could also be possible it's just a coincidence and the average is slowly going up due to the car running summer gas instead of the winter blend crap. the civic was 24.3-24.8 all winter and now it says 25.5-25.8

i have never seen increased gas mileage from increased back pressure. it makes no sense. i get MUCH better gas mileage and acceleration with the mustang uncorked vs with the flowmasters. increasing efficiency increases efficiency. no way around it.

i would think if you removed the can, your MPG would continue to increase even more.
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Old 19 Jul 2017, 02:33 pm
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Default Re: Tune-A-Can Exhaust - Higher MPG?!

Quote:
Originally Posted by wingman55 View Post
SO, ever since I have installed my Tuna Can Exhaust, . . .

See thread here:

QUIETER but still cool Exhaust!

. . . I've noticed better gas mileage. According to the dash readout I am getting around 27.4 to 27.6 MPG for everyday driving. That's about 1 to 1.5 MPG better. According to calculations I am getting around 28 MPG. <-- Hmm. Not sure about that.

I've always heard that engines need at least SOME back pressure to run good, and it would seem that adding that small amount of back pressure has boosted the MPG.

At any rate, I am still amazed at how quiet the exhaust is at highway speeds, but when I listen outside the car at idle, and revving it, it still has that nice, low, but not ridiculously loud, rumble...

It is possible that your tuna can baffle increase the efficiency of your exhaust system. But it's not very probable.

One of the areas I'm schooled in is industrial ventilation. And a well-designed exhaust system can increase efficiency. On a hot gas emissions system like an automobile, you could even reach a point where the exhaust creates a pressure drop at the source. This mean that if designed right, at ideal speed, RPM's and ideal everything else, it theoretically possible for a car's exhaust to suck on the engine rather than create backpressure.

But while possible, the likelihood is very low that adding a tuna can baffle somehow blindly provided an efficiency gain. My guess would be as Rob said. Your improve exhaust sound has likely modify your driving.
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Old 20 Jul 2017, 10:09 pm
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Default Re: Tune-A-Can Exhaust - Higher MPG?!

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Originally Posted by rob302 View Post
it's possibly due to you driving differently with the quieter exhaust. when i drive my mustang normal i get higher mpg than when i try to keep it quiet with my mom in the passenger seat.

it could also be possible it's just a coincidence and the average is slowly going up due to the car running summer gas instead of the winter blend crap. the civic was 24.3-24.8 all winter and now it says 25.5-25.8

i have never seen increased gas mileage from increased back pressure. it makes no sense. i get MUCH better gas mileage and acceleration with the mustang uncorked vs with the flowmasters. increasing efficiency increases efficiency. no way around it.

i would think if you removed the can, your MPG would continue to increase even more.
Nope. I never drive it in winter, so it's never had winter blend, and I don't drive it any differently, at least that I am aware of. Just normal driving to and from work, and the occasional trip on the highway, like last night. I drove to Utica, doing about 70 on the Thruway, 110 miles round trip. It now reads 28.2 mpg. (Of course highway is better, but I didn't baby it, or do anything different.)

So, I don't know. I kinda agree with GKON where he suggested adding a baffle to his motorcycle helped.

And, don't forget: the tuna can forces more of the exhaust out of the passenger side pipe now, whereas before, hardly any came out of that side. It was mostly for show. With that said, maybe, just maybe, it is actually extracting the exhaust better?

So . . . That's all I know.
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2006 Limited Edition, Inferno Red, 5-speed, Bassani dual exhaust, Chrome backup light bezels, taillight trim, fuel door, antenna mount, Ventiports, door spear covers & hood prop. Silver painted lower front grille. American Racing 383 Casino wheels, w/Chrysler emblems, '02 engine cover, PT Cruiser mudguards, cargo mat. EGR Window Visors, dark gray lock pulls, dual horns, Fuzzy Dice, flames and MOPAR emblems added to front door logos, gold Chrysler emblem on rear hatch. Upgraded to RAK radio with 6 CD changer, Cassette Tape and RDS info. Name: "FIREBALL" I bought it Aug 10, 2015, with just over 35,600 miles on it.

2004 Limited Edition Platinum Series, Graphite Metallic, Standard Turbo, automatic, RBQ radio with Sirius Radio & 6 CD changer, VentShades, chrome exhaust tip, door spears, grille inserts, door lock pulls, bright pedals and steering wheel spokes. Red spoiler from a donor PT. Known as: "The RATMOBILE" I bought it Apr 28th, 2016 with 62,400 miles on it.

Last edited by wingman55; 20 Jul 2017 at 10:27 pm.
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Old 21 Jul 2017, 12:11 pm
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Default Re: Tune-A-Can Exhaust - Higher MPG?!

Quote:
Originally Posted by wingman55 View Post
...And, don't forget: the tuna can forces more of the exhaust out of the passenger side pipe now, whereas before, hardly any came out of that side. It was mostly for show. With that said, maybe, just maybe, it is actually extracting the exhaust better?

So . . . That's all I know.
If anything, it's restricting the exhaust. In order for more flow to come out of the passenger side pipe, it has to be prevented from flowing out the (path of least resistance) driver's side pipe.
[nerdmode]
Actual extraction can occur, if you design for it. Exhaust gases leave the combustion chamber at the speed of sound- it's essentially a shock wave traveling down the exhaust pipe. When that shock wave meets the end of the pipe, it sends a low-pressure reversion wave back the way it came. If that reversion wave meets the exhaust valve as the valve is opening, the low-pressure wave actually sucks the escaping gases out through the exhaust valve. This process is known as scavenging, and its arrival is determined by (among other things) the length of the exhaust pipe. The shorter the pipe, the quicker the reversion wave meets the exhaust valve, and the higher the rpm that the scavenging occurs.

If you shape the end of the exhaust pipe in an increasing diameter cone, the reversion wave gets "smeared"; instead of coming back up the pipe as a distinct, low-pressure shock wave, it arrives over time as sort of a low-pressure zone. The scavenging effect is reduced (the gases escaping through the exhaust valve don't get sucked out as hard) but the rpm range over which the low pressure event occurs is increased (instead of scavenging happening exactly at 4,500 rpm, it occurs between, say 4,000 and 5,000 rpm.

And that's probably more than you wanted to know about exhaust extraction.
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Old 21 Jul 2017, 03:28 pm
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Default Re: Tune-A-Can Exhaust - Higher MPG?!

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And that's probably more than you wanted to know about exhaust extraction.
Nice write up but you totally left out the Thermal dynamics. Heat has more to do with your explanation or at least plays a major part. And you also might have mentioned CFM and how simple bends in an exhaust pipe can have a large effect of the engine output.

But its not really needed and the explanation of all of this would be several pages and several thousand words long!
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