Alternator Delete VS starter motor

[aerohead]

If you could magically perform back-to-back tests,simultaneously,you could easily measure the difference.----------- One thing to consider.The alternator load may have been a design criteria for the cars powerplant design and may effect it's BSFC.----------------------------- By arbitrarily lowering the "load" on the engine,you could actually move it into a regime of lower efficiency.-----------------------------------------------I lost an alternator in Amarillo,Texas,in the CRX.It was going to be two days to get a part.I went to Walmart,bought a spare battery and battery charger.I drove,in two days,to Phoenix,Arizona,running constant-loss off the battery I charged in the motel room.I'd topped off the tank in Amarillo,and by Phoenix,I'd showed no measurable gain in MPG.------------------------------------ I have also purposefully removed the alternator belt and conducted mpg tests,and never showed any measureable difference.--------------------------- The CRX alt drops field exitation during acceleration,then resumes with manifold vacuum increase.--------------------- Also,cheap,adjustable,normally-closed vacuum switches can be adjusted to open-circuit the field,while under acceleration.----------------------- I've found the manufacturers systems so efficient,reliable and of little load,I no longer consider modifications to them for a daily driver.Just my opinion.

[modmonster]

here is my system. i have 144v of NiMH batteries hooked up to the power inlet side of a power supply, (where you would normally plug it into the mains). you can put DC into these even though they usually work on AC. the other side it comes out at 15.5v. i selected 15.5v with the trimmer pot because it was closeest to 14.5v that the alternator tops off at yet still gave enough voltage difference to get a decent amount of power. the power supply is from ebay and is for a computer or something? its rated at 350watts. i have a watts up meter in the line to tell me whats going on. i didn't drill through the fire wall yet i just tapped into the cigarette lighter port.

the car drew about 130watts, 8amps whenever the engine was running. when full lights were switched on this went up to 170watts. the voltage settled at 15.2v. weird thing was i couldn't EOC with it plugged in. the engine wouldn't switch off. this is why i will probably wire it straight to the battery.

i was pretty pleased with this first attempt. ill test it at the weekend when i need to drive somewhere.

[modmonster]

that should be 4.5% saving in fuel @ 55mph according to that handy spread sheet i found on this site. -who posted that?

17% saving at 35mph. load didn't seem to change with speed.

[modmonster]

ok ive installed it straight to the battery now so i should be able to EOC again. im doing some miles at the weekend so i should be able to test it then.

[teoman]

How did this work out for you in the end?

[oldtamiyaphile]

I think people might be over estimating how much power is needed to turn a starter motor. Assuming your car starts nice and cleanly, the starter load is almost not worth considering.

My supercap bank has a miniscule 90mah capacity. I was able to get four consecutive starts out of it in my Suzuki Swift (I immediately shut down the engine upon firing each time so the alt didn't have time to energize).

That's 0.3Wh per start. So a 60Ah battery is good for around 216 starts, assuming no other loads The starter is a big instantaneous load, but even with hard core EOC and city traffic it's total duty cycle is only maybe 60 seconds a day. It's actually 'always on' things like the ventilation fan that creates the majority of electrical demand.

I average 16mph, that's only a fraction faster than a NYC taxi. Over my 20km commute, I need the starter motor about a dozen times. Most of the time I bump start.