Alternator Delete VS starter motor

[bennelson]

Hey everyone.

My 1995 Chevy S10 2.2L (4 cylinder) 5-speed manual transmission is currently getting 31 mpg.

I only have a few basic mods on it. Swapped mechanical radiator fan for an electric (from the Metro!) put in synthetic oil, and have a partial tonneau cover.

I am very interested in the idea of disconnecting the alternator to improve fuel economy. I would then simply recharge the battery from the wall with charger I would leave built-in to the car.

Essentially, this sort of makes a hybrid, because some of the energy the vehicle uses comes from a source other than the gasoline.

Two things are stopping me from doing this. Daytime running lights, and using my starter after engine-off-coasting.

Daytime running lights would obviously wear down the battery much quicker than NOT having them on. Is anyone familiar with a simple way of disabling them? I have heard to put on the parking brake one click to turn DRLs off. I am a little afraid of clicking too far and adding drag. Maybe I could get in there and find the actual switch the is hooked up to, pull it out and modify it to some sort of manual override?

I do some engine-off-coasting, a lot of it coming up to traffic lights. If I coast to a light and am stopped there, then I have to use the starter to restart the engine to pull away once it's green.

I don't know how many times I could use the starter without the alternator. I think I might naturally want to turn the engine off LESS OFTEN if my alternator is disconnected.

If I disconnected the alternator, I would also replace the starting battery with another battery type, such as an Optima Yellow Top, or something similar. Starting batteries do NOT like to be deep cycled.

[johnmyster]

On my '98, there's a diode in the underhood fuse box. It's disguised like a fuse, but it's really a diode. I pulled it. No more DRL. The autozone.com wiring diagrams aren't good for everything, but they DO have really complete schematics for lighting. It may show you that there's a fuse, relay, or diode somewhere to pull or otherwise disconnect on yours.

Could try also an underdrive pulley on the crank. Slowing down the accessories by 25% couldn't hurt. They're generally $70 or so and you'd need a belt 3" shorter. Pretty common amongst the 4-cyl S10 guys. I'm also installing the smaller alternator pulley in order to keep it at full speed, though I rarely drive with AC, and rarely at night, so I could probably do without it. Thus, any gains I have will be related to slowing down the PS pump, AC, and water pump. At 3000 rpm at 70mph, I don't think they'll miss it. If I have good voltage with my efans, I'll probably go back to the stock alternator pulley.

I'm not a fan of the disconnected alternator deal. However, know that you can fit a group 78 battery in your truck by using a pair if channel-locks to tweak the inside edge of the battery tray. The 78 battery is about 1.25 inches longer than a group 75, but our trucks have about 1.2 spare inches to begin with. I did it in the parking lot of the store when I got my new battery last weekend. Alternator or no alternator, a bigger, higher capacity battery (for the same price) is just a better deal.

If I could get rid of these 235 width tires on mine, we could probably do a bit better...

Not to start a fire on here, but I think that the 10% gain reported by MetroMPG seems a bit lofty. I know my engine is tiny, but there's no way 10 percent of its power is going into the alt. If his alternator and belt drive is only 80% efficient, one horsepower is still 43 amps at 13.8 volts. I'd say my charging, ignition, ECMish, and lighting loads are probably in that ballpark. One horsepower.

On our trucks, you won't be able to kill the belt to the alt. However, the AZ wiring diagrams will show you that there is an external feed that energizes the coil. On mine, the ECM activates the alt. On yours, perhaps, perhaps not. However, you could put a relay in this line, and, for instance, run the alternator only with the brake lights, or only after starting, or manually with a switch when the lady demands AC.

[bennelson]

Hey John,

Thanks for the input.

NO AC on my truck, so that's one less thing to work about! Mine is the super stripped down model. No extended cab, no AC, nothing.

I actually think an alignment would help my fuel economy as well.

I did have my alternator belt break on my old Geo/Chevy Spectrum years back.

I was driving down to a class when it happened. I just had to get to the campus on time, so I couldn't stop anywhere. I drove home afterwards. By the time I got home, the battery was almost dead, but I must have driven 50 miles on it since the belt broke, restarted the car when leaving the campus, and it started raining on the way home!

The car DID run great, though, without an alternator belt!
Too bad the S10 uses a serpertine instead of a seperate alternator belt!

[bennelson]

Originally Posted by johnmyster

On my '98, there's a diode in the underhood fuse box. It's disguised like a fuse, but it's really a diode. I pulled it. No more DRL.

I dug through my Haynes repair manual, looking at the wiring diagrams listed in back and using the info you just gave me.

It appears that in mine there is a fuse that controls the DRL module. Or maybe its a diode that looks like a fuse like you said!

I pulled it. No more daytime running lights! Didn't appear to effect anything else.

Of course DRLs are a safety feature to make you more visible. My truck is white, so I am not too concerned about that, and of course I turn on my headlights whenever it is dark, hazy, or raining.

Great. Now I have to gas up, and reset my trip odometer so my next fuel log can reflect my new mod "disabled DRL".

[Daox]

From what I've read, alternators are only about 50-60% efficient (not including belt losses which I believe are only around 1-3%). Also, from what I've read you can be using up to 25A just at crusing speed. This calculates out to 300W of power needed, and at 50% efficiency we are looking at 600W of gasoline power which is the equivalent of .8 horsepower. At low speeds this could be well in excess of 10%. At higher speeds it definitly can be less than that (depending on many other variables).

Now you just have manual daytime running lights Ben.

[johnmyster]

Originally Posted by bennelson

The car DID run great, though, without an alternator belt!
Too bad the S10 uses a serpertine instead of a seperate alternator belt!

A pro ecomodder could buy a junkyard accessories bracket and machine slots for the power steering mounting points. Thus, They could raise and lower the PS pump to tension the serpentine. Since the PS is on the side with the water pump (and you have an e-fan) you could bypass the alternator with a nice, short belt. Straight from crank to PS pump, with an outside contact onto the water pump.

Another advantage you have on me is the stock 3.73 gears. X-cabs got 4.10 gearing. If my pinion seal starts to leak any worse, it'll be a good reason to find a junkyard 3.73.

[johnmyster]

Originally Posted by Daox

From what I've read, alternators are only about 50-60% efficient

I've seen those numbers too, but I think they're worst case scenarios. At full load, the switching diodes (rectifiers) get really hot, and become heavily loaded. My gut electronics feeling is that they'll be more efficient at typical loads.

Our trucks have 100 amp alternators. Little to no A/C, power/heated seats, big stereos, navigation, etc. Only one tail light on each side. Single headlights. No foglights. No rear window defrosters. S10 owners usually get good life out of their alternators compared to Buick/Olds drivers. Same alternator, but vehicles with more goodies, and drivers that like to use those goodies. I knew an olds driver who killed a 120 amp alt every summer. AC on max all the time fried the rectifier every single summer. I gander that our alternators are generally not hard pressed and can squeak out a more efficient living.

I suppose most of my driving is long highway trips. 1 or 2 hp saved doesn't sound like much compared to the 50 whp or so it takes to keep me going down the road. Maybe, but 10% is still a lot. Enough to make me consider having a row of deep cycle bats in my bed if it's really true. However, I like my $15 a month electric bill. As little as I drive, probably wouldn't pay off anyhow.

[Daox]

I would generally agree with you. I can't say weather those are optimal, average, or worst case numbers.

However, I'd like to clarify that it doesn't require anywhere near 50hp to keep you going down the road even @ 65 mph. From my general calculations using a conservative drag coefficient of .5 and a frontal area of 1.995m^2 (also conservative), you only need 19.7hp to keep you going 65 mph down the highway. Your Cd and frontal area are likely a bit better than those mentioned, so I'd estimate between 15-19hp to keep you going on the highway. Knock that speed down to 40 mph and you only need 4.6hp!

[johnmyster]

Originally Posted by bennelson

Great. Now I have to gas up, and reset my trip odometer so my next fuel log can reflect my new mod "disabled DRL".

On my truck, DRL puts the two high-beams in series so that they only see 6 volts each. Most headlight bulbs are in the 45-55 watt ballpark, right? So mine probably pulled 25 watts total in DRL mode.

Not much, but something. Don't think you'd ever notice 25 watts on tank by tank mileage. However, 2 amps saved on the charging system is significant if you go battery supported.

[johnmyster]

Originally Posted by Daox

However, I'd like to clarify that it doesn't require anywhere near 50hp to keep you going down the road even @ 65 mph...

...I'd estimate between 15-19hp to keep you going on the highway.

I admit, 50 whp is probably a bit high. Supposedly these things have about 90 whp max. I figure at 3k rpm about 50% of that is available if not more. At 70, it doesn't have much power in reserve. Not much at all. It's slow. So yeah, probably 25 to 30 nominal.

Okay, fine. You've convinced me that alternator loads are relevant. Crap. Looks like there'll be grease under my nails for some time to come. Time to look for deep cycle batteries. Can't yall wait until I finish my current projects before giving me more? I live far away from my junkyard and facility resouces so getting stuff done in the driveway takes forever...

Anybody got a manual PS box?