Lose your belt= more MPG

[oilcan_boyd]

The alternator pulley recently fell off on my golf. While I am waiting for a new one I just removed the belt and have been charging the battery at night. One side affect I have noticed is increased economy. Another is very difficult steering.
So, if you don't need a/c, don't mind hard steering, and can charge your battery at home this is one way to improve fuel economy.

[Westro]

How much more MPG?

[oilcan_boyd]

I haven't had to fill up yet so I don't know exact numbers. According to scanguage it appears I'm getting another 5mpg around town. That might be a bit optimistic though.

For those that are serious hypermilers it may be worth investigating.

[andrewb_1985]

But how much are you spending in Hydro to charge your battery everyday?

[oilcan_boyd]

Originally Posted by andrewb_1985

But how much are you spending in Hydro to charge your battery everyday?

Good question.
I don't know. I only charge it each night because I like to be prepared. It doesn't need charged every night. It could run for quite a while without charging depending on how many accessories you run.

I was just recalling my wife's car when we got married. It was a 93 escort with no options. No a/c, no power steering, no nothing. It got 40-41 on the highway. I thought that was above average for that model.

[Westro]

Well the trend is towards electric driven power steering and water pumps, I'm just wondering how much fuel savings (potential) there is moving these systems off the belt driven.

[Erdrick]

A guy that used to get 100mpg+ out of a stock Ford ZE2 (is that right?) did this exact thing. He had a single set route that he used his car for though... and at each leg there was a fresh newly charged battery waiting for him.

Apparently the parasitic losses from the alternator are pretty great... and I don't mean that in a "good" way.

[oilcan_boyd]

If I was dedicated enough I would test and compare the differences...
but I'm not.

[04SlvrJetta]

makes you wonder if a simple system could be devised to make all accessories electric (that aren't already) and use a wheel driven charging system that engages only when needed and during braking or deceleration could be the key! Similar to hybrid technology, but likely very simple and inexpensive to design and build!

Sidenote...my son has regularly leaves "his" reading light on in the back seat. The other day I realized it was on and the car had not been used all weekend. The engine started just like always! Must be the stronger battery in the diesel because I know that would have killed the battery in gassers I have owned in the past.

[Got Bearings?]

The loses from your alternator are minor. Most of the gains are from the power steering... or lack thereof. I've seen someone do the math and it's something like 1 HP (or less) to run the alternator.

If someone can find a way to bypass the PS and keep the belt on the alternator, that would be ideal. Our cars are light enough not to NEED power steering. I've wrestled a few full size cars (4000+lbs.) w/o power steering its tough but doable. I had a Datsun 280Z in high school (probably less than 3000 pounds) and it was much easier to drive w/o power steering. The only issue was parellel parking and even that wasn't difficult.

On my Impala, I have an electric WP and it gained 10 HP right off the bat and .1 e.t. drop with no cooling issues. The problem with electric accessories (especially the WP) is when they fail, they go without warning and instantly. That's why I car a spare WP in the trunk.

[tasdrouille]

Loosing the alternator will give you ~5-10% better FE.

[Smokerr]

Originally Posted by Westro

How much more MPG?

If you have a plug in Hybrid, the direct cost is about 25-30% of what it would cost you in fuel.

However, in this case you have an enormously (relatively) large object and drive belts system with parasitic losses to fulfill a minor current flow function. Likely re-charge costs are so small as to be not worth a calculation (or the time spent trying to figure it out).

[Variant TDI]

I thought it was just conjecture, but I believed that I saw an economy difference if I forgot to unplug my Valentine overnight.

Maybe it was something.

[Got Bearings?]

Originally Posted by tasdrouille

Loosing the alternator will give you ~5-10% better FE.

Sorry I call BS!

1hp = 746 watts
watts= voltage*amps

So if we have an 120 amp Alternator:

Watts = 13.8*120 = 1656 watts
1656/746 = 2.22 HP to run an alternator

So it takes 2.22 HP to run a perfectly efficient alternator... but we know they do not run 100% efficent (drag, friction, etc...). They run more in the 60% range. For the sake of conservatism, lets say they run at 50%. That means the alternator takes 4.44 HP to run 120 amps continuously, which doesn't happen.

I highly doubt 4 HP would free up 5-10% MPGs.

[Chubber]

Originally Posted by Got Bearings?

Sorry I call BS!

(snip)

I highly doubt 4 HP would free up 5-10% MPGs.

On the other hand, the motor is rated at about 90 BHP. And during most of the operation of the motor (idling, steady running) it's using much less power, call it 50 BHP. So cutting 4 HP from 90HP is about 5-10% of the overall power, and a much higher percentage of the idling power if the alternator is doing lot's of charging.

But I agree that a few lines of code in the motor computer should be able to shut down the alternator unless the motor is turning 2000+ RPM and the accelerator position sensor is at 0%. If the voltage drops to lower levels, then adjust the accelerator percentage limit. Same thing with the AC compressor clutch. About a million years ago I rigged up a vacuum switch to not allow the AC clutch to engage if the vacuum in the intake manifold was low (WOT == high pressure == low vacuum). But because the CAFE standards don't count AC usage (though everyone uses them all the time in about 1/2 the country).