Systems and gas mileage

[BLD 25 10+ year member]

Hey, do decent sized systems reduce the gas mileage much? I have an 03 intrepid ES with one 12DVQ infinity sub and an mtx 250d sending about 400watts or a little over to it. I noticed my mpg sucks, especially at night, and the system is enough to get the lights to flicker. Would a cap help?

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[phantom240 5,000+ posts]

Nope.

 

[aeronautica86 10+ year member]

all the energy used by your system has to come from somewhere, and in a car, it comes from the combustion of gasoline and oxygen in the engine. Only thing that will help is turning the volume down.

 

[sundownz Pro Seller]

Every 100 pounds of equipment tends to decrease gas mileage by 1 MPG, that is the generalized rule. Alternator draw is relatively minor -- 200 amps is under 2 horsepower if I recall the conversion right.

 

[phantom240 5,000+ posts]

... i figure im losing about 8 hp with my entire system and my fat ***. Thats why when people ask why i put so much money in performance parts in a car that has a heavy *** system, i just laugh. My mileage is gonna **** once i finish my dual alternator setup. //content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif

 

[SUB_URBAN 10+ year member]

every 100 pounds doesnt affect my gas mileage that much, but my suv is huge already.

 

[BoomBoomBoy 10+ year member]

Unless you have a wall of woofers, the system you have won't make much of a difference. As far as the number of watts your system uses, it won't make any difference. The resistance your alternator presents to the motor is constant and that's what uses up hp. The amount of alt output is entirely dependent on the alt's capacity.

As far as a cap goes, I drive an Accord with a stock 80A alt. My system total watts is 700. At night my headlights dimmed with the beat of the music. I added a surplus (not fancy) .75 farad electrolytic cap and if helped a lot. Kept my voltage from sagging.

 

[BLD 25 10+ year member]

thanks for the help guys.

 

[phantom240 5,000+ posts]

Unless you have a wall of woofers, the system you have won't make much of a difference. As far as the number of watts your system uses, it won't make any difference. The resistance your alternator presents to the motor is constant and that's what uses up hp. The amount of alt output is entirely dependent on the alt's capacity.

Not true. If you knew how an alternator (generator) worked, you would know better. An alternator only produces as much current as being drawn at any one time. It doesnt produce 80A if the demand for 80A isnt there. Therefore, as current draw increases, the harder it has to work and therefore produces more resistance. Having a dad that specialized in electronics in teh navy FTW.

 

[baseballer1100 5,000+ posts]

Everything affects my gas mileage.

 

[CBFryman2 5,000+ posts]

200a current draw is going to take about 5hp from the engine.

adding 200lbs of system is going to increase mass less than 1%.

Mileage wont be affected that much, you can save more gas by learning to controll your foot.

 

[TreyE 10+ year member]

yea i took my system out which was like 200+ lbs and i get way better gas mileage now...i also have a 2004 GMC Envoy tho

 

[BoomBoomBoy 10+ year member]

Not true. If you knew how an alternator (generator) worked, you would know better.

You're right:

http://www.alternatorparts.com/how_much_horse_power_does_an_alternator_make.htm

 

[CBFryman2 5,000+ posts]

I thought they where a little more efficent than that now at cruising speeds. I geuss I was wrong.