How much less MPG after HO alternator install?

[MiniflexAlex 10+ year member]

Hello,

I'm planning on upgrading my alt, I currently run the stock 140A alternator.

I was thinking to upgrade to a 200+A alt, will I notice a change regarding MPG, if so by how much?

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[bgowdy 5,000+ posts]

why would you lose MPG?

 

[audiobaun 5,000+ posts]

I havent ever noticed any change with exception of the extra weight ive incured with my box and subs with a 250 amp alt from a 140 on chevy truck/98 xcab

 

[MiniflexAlex 10+ year member]

why would you lose MPG?

I would assume it takes more force to spin the alt, therefore the "drag" at the crankshaft increases...therefore I'll burn more gas OR I will lose a little engine power....maybe not noticable at all but I thought I'd ask //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Dirtrider4eva 10+ year member]

why would you lose MPG?

big alt requires more torque to turn the alt and produce power. ultimately more fuel,and less MPG.

also OP, prolly depends on motor too. larger motor and more power, less noticeable difference. id imagine in my little 1.8l going from 90 ah to 220 ah will drop it 2-4 mpg. but nothing drastic.

 

[MiniflexAlex 10+ year member]

I havent ever noticed any change with exception of the extra weight ive incured with my box and subs with a 250 amp alt from a 140 on chevy truck/98 xcab

yes, the added weight of the whole system has probably a bigger effect on MPG

 

[Kangaroux 5,000+ posts]

The amount of MPG you would lose from a HO alt is very small...well under 1 mpg.

 

[MiniflexAlex 10+ year member]

big alt requires more torque to turn the alt and produce power. ultimately more fuel,and less MPG.
also OP, prolly depends on motor too. larger motor and more power, less noticeable difference. id imagine in my little 1.8l going from 90 ah to 220 ah will drop it 2-4 mpg. but nothing drastic.

that's the theory I had in mind as well.

My passat has a boosted 2.0L engine with 200hp, the stock alternator generates 140A, If I'd go to an 220A alt I would almost double the output which very likely would lower the MPG...I was just wondering by how much...

DId you lose 2-4MPG or is this a number you would expect to see when you upgrade your alt?

 

[winkychevelle 10+ year member]

u wont notice just the alt it's the box and subs that get u. and really thats only a few mpg for a mild system

 

[SacTownBully84 10+ year member]

i put a dc power SP270 on my 2001 grand am w a 2.3 and when i demoed i could watch the RPMs drop 300-400....so i think it has to make a different.....cuz if it can drag 300 rpms down then why not?

 

[Dirtrider4eva 10+ year member]

that's the theory I had in mind as well.My passat has a boosted 2.0L engine with 200hp, the stock alternator generates 140A, If I'd go to an 220A alt I would almost double the output which very likely would lower the MPG...I was just wondering by how much...

DId you lose 2-4MPG or is this a number you would expect to see when you upgrade your alt?

i still have to get my alt.. no munz..

But heres what i do have. my car is rated for 31-34mpg hwy, 26-28 city. without system i keep a 32mpg average, with my system, (battery, 3 amps, 1 sub, 1 box) it drops to 28ish average. now when i put the alt and new box + 1 sub, im expecting 26maybes.

 

[bgowdy 5,000+ posts]

big alt requires more torque to turn the alt and produce power. ultimately more fuel,and less MPG.
also OP, prolly depends on motor too. larger motor and more power, less noticeable difference. id imagine in my little 1.8l going from 90 ah to 220 ah will drop it 2-4 mpg. but nothing drastic.

hm ok. i have the 4.3 v6 i just got a 220amp alt. so im going from 100a to 220a. i wonder how much that would change mine

 

[Instigator]

With the 4.3, you should expect .5mph loss, so nothing noticeable.

 

[subzero 5,000+ posts]

unless your belt is too tight or too loose. I noticed some seriouse extra drag/. alt and ac while bumping = bog down. Im gonna have a mechanic look at mine.

 

[maylar 10+ year member]

The alternator itself won't make any difference. It's the load that matters. 1 hp = 746 watts.