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Gas mileage

Posted: Sat May 18, 2002 3:43 pm
by Guest
I was wondering if chnging ur exhaust to 2.5 or putting different mufflers on ur car would alter the gas mileage or not..... is that a dumb question.

Gas mileage

Posted: Sat May 18, 2002 11:05 pm
by gar187er
yes it does alter it...depending on how much milage on your engine there is has a decent amount to do with it as well...the older the engine, the more drop in MPG youll see when you go 2.5"...i lost a few MPG when i went to 2.5", but thats also with an intake too.... :(

Gas mileage

Posted: Sun May 19, 2002 12:44 pm
by Guest
y would it make any difference

Gas mileage

Posted: Sun May 19, 2002 2:37 pm
by gar187er
the enigne was made to breathe or function under certain conditions, by changing you exhaust size, you essentially change how big the "lungs" are in your car...(i know guys keep the laughter to a minimum.....im tryin to relate it to something easy to follow).....the bigger the lungs, the harder ya gotta push to get all the air out.......get what im sayin??

Gas mileage

Posted: Mon May 20, 2002 7:35 am
by Guest
ahh, so u have to give it more gas than normal..... gotcha

Gas mileage

Posted: Thu May 30, 2002 3:42 pm
by 90_Black_GTZ
Your analogy makes no sense!  It takes more effort to push the air out?  Think about this.  If you try to breathe through a straw, then try to breathe through a section of 1" PVC.  Which way is easier to push the same volume of air out through?  

Better breathing should create better gas mileage under identical circumstances.

Gas mileage

Posted: Thu May 30, 2002 4:59 pm
by gar187er
not to sound like a D#$!, but so your saying no matter what size exhuast someone has whether it be 2.25" or 4"...it wont matter?

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Better breathing should create better gas mileage under identical circumstances.
Quote

the enigne was made to breathe or function under certain conditions



yes it does create better gas milage, but there is a point where it drops off....if it didnt, then we would all have 4" exhausts or larger....

Gas mileage

Posted: Thu May 30, 2002 5:44 pm
by Guest
You don't get 4" exhaust pipes because it hurts power, not because it hurts fuel economy.

Larger exhausts can lower fuel economy because, in conjunction with intakes and other engine work, it allows the engine to take in more air under the same amount of throttle.  More power is created because more fuel is added to this mixture.

There are a lot of other factors and the effect on fuel economy would vary from engine to engine.  Opening up the intake and exhaust can also increase the efficiency of the engine, so gas mileage can go up to a certain point.

Gas mileage

Posted: Thu May 30, 2002 6:24 pm
by Guest
This will answer all of you questions.

Go Here

Gas mileage

Posted: Fri May 31, 2002 8:19 am
by 90_Black_GTZ
... and that is the reason I said "under similar circumstances".  
If you have a Beretta with 2" exhaust, another with everything else identical but with 2.5" exhaust, both travelling down the highway at 60 MPH, the 2.5" will get better mileage.  Of course if the engine breathes better you have the potential to decrease your mileage because you are now burning more gas with a motor that will now accept more gas/air mixture, but again I was speaking to similar circumstances.  If you drive approximately the same speed, same drive to work every day, but with a bigger exhaust tube, then you will get better mileage.  There is a point of diminishing returns, as was stated earlier.  Again we can use the human body as an example, though not a great one.  If your lungs can only move a certain volume of air, no matter now big your intake is, you won't improve your endurance or strength.  If you run with a straw sticking out of our mouth, you will tire quickly.  With a good size chunk of PVC, you will go longer, but with the downspout from your house gutters, you won't be breathing any better because your lungs already reached their potential on the smaller tube.  
I saw quite a big difference in mileage on my 69 Firebird 400 when I went to a true dual exhaust.  That was even with an increase in power, I still saw a big difference.  Again in another 75 Pontiac I had.

Gas mileage

Posted: Fri May 31, 2002 9:58 am
by gar187er
yes but with those cars youre looking at alot more displacment then with a beretta.....

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If you have a Beretta with 2" exhaust, another with everything else identical but with 2.5" exhaust, both travelling down the highway at 60 MPH, the 2.5" will get better mileage


then why is it my gas milage went down a few MPG after going 2.5".....  ;)

Gas mileage

Posted: Fri May 31, 2002 10:02 am
by MAJ28
(I just thought it was wierd that Meineke says that bigger is better mileage.  When I went to get quoted on an exhaust they told me I'll probably lose HP,  I didn't feel like arguing... you guys know more about Beretta's then some shop.)
:0

Gas mileage

Posted: Fri May 31, 2002 4:31 pm
by 90_Black_GTZ
Quote (gar187er @ May 31 2002,08:58)
yes but with those cars youre looking at alot more displacment then with a beretta.....

Quote
If you have a Beretta with 2" exhaust, another with everything else identical but with 2.5" exhaust, both travelling down the highway at 60 MPH, the 2.5" will get better mileage


then why is it my gas milage went down a few MPG after going 2.5".....  ;)

If your mileage went down, enough for you to notice, then something is wrong.  More HP will burn more gas, but only if you are using that additional HP by loading the engine beyond what it was capable of before.  All other things remaining the same, there is no reason for a reduction in mileage.  

Yes, the displacement of those other cars was more, but so is their potential for creating HP.  The rest remains constant.

I'd do a check on everything, sensors, plugs, etc...

Gas mileage

Posted: Fri May 31, 2002 7:42 pm
by gar187er
trust me everything is fine, unless you count the busted turnsignal assembly, but that just happened.... :(  ya knwo how hard it is to find one of those?! at least around me its impossible....