jfischer

I never said it was running well, only that it ran

And yes, a brand-new Diehard battery did keep it running for over a week - the alternator was shot. It was shot before he bought the new battery - that's why the old battery died in the first place. I measured the output of the alternator, and it was 0 volts.

RobbyRob

Alright then. Go out to your car and dis connect the alternater and leave it running. As a matter a fact take it for a drive and see how far you get. Make sure you tape up the end that connects to the alt. Don't want you to sort anything. Then tell me how far you get.

jfischer

Not gonna mess up my car, Robby. I've seen a Mitsubishi Eclipse do it for at least a week, that's good enough for me. The car is a POS, and I doubt the driver even had a clue why it was running so crappy. But it did run...

RobbyRob

If it ran for more then a hour the alt still worked. It my have not been given a full charge, But the car is not going to run a week on the battary alone.
If you think different just try it. Then you can give me some of the stuff your smoken.

crazypurgatory

OMG it all depends on the car.
Some cars take more juice that others IE pull more amps.
It's not necessary the volt's.
You can have a bat that has 12 volts and 5 amps.
And you won't be going anywhere.
Plus the Alt might be putting out a couple of amps even if it's bad.
And if you run A Camaro with a low bat the PCM will have a fit.
I think it is in the manual.
You might want to take a look I will.



Chris G.

breakmyfootoff

You would have to lose at least a little voltage if for no other reason that the alternator puts out somewhere around 12.7 to 13.0 volts to charge the battery and run the cars electronics. And low voltage does effect the PCM as well as the fuel pump and ingition. We're talking about spending 15.00 to try to free up 1 or 2 HP with the possibility of making it run worse, just take 10 or 20 lbs out of the car, same effect, no voltage drop, and free. Even taking off the power steering won't give much benefit as it provides very little drag when you're not turning the wheels. And if you want to translate that 1 or 2 HP into E.T., we're talking about taking about .01 seconds quicker in the 1/4 mile. You would not be able to see or feel any difference, hitting one extra bug on the way down the track would probably offset the performance gain from this mod.

jfischer

Agreed, if the alternator is working you will usually see closer to 14v at the battery. However, a brand-new Diehard battery probably has enough reserve to be able to run a POS car for quite a while, assuming no nighttime driving, no AC, no loud stereo, etc.

When I said a week, this poor kid was just driving it basically back and forth to work, during the day. If you're not running much of anything but the ignition, a brand-new battery will do this for quite a while. Throw in AC, a big stereo, headlights, etc and I agree it won't last very long.

I also agree that cutting out the alternator is a bad idea. While it's theoretically possible to gain a few HP by doing so, you won't notice it at the track and it's probably going to cause more problems that it's worth. I wouldn't spend any money myself to do this...

Silver

Ok so there is a market for an "alternator delete" pully. Will have drafts by morning.

ZeeVert

I personally would GUESS that it's not worth the effort to disable the alternator, especially for the effect on the ignition and control systems.

Please correct me if I'm wrong and please ignore efficiency issues, but here's some math to see what the potential savings could be...
HP = Voltage X Amps / 746Watts/HP

So for a 100amp alternator, the MAX power is:
HPmax = 13.5V X 100amps / 746 = 1.8hp

But an alternator almost never runs at max output and without the lights, stereo, fan, a/c, etc. on, I'd guess that the alternator is only putting out 10amps? to run the engine.
HP= 13.5 X 10 / 746 = 0.18hp

The alternator is an on-demand system... don't ask for any power, and it won't make any. So before we run off and build a cut-out, does anyone know what the amp draw is during something like a 1/4 mile run?

Z95m6

lmao.

crazypurgatory

Jezz talk about getting heated.
I have to remember to disconnect the Alt when I ever get to the dyno and do a run with a good bat with the Alt disconnect and a run with it on.
But unforchently for this thread it won't be happen soon.


Chris G.

RedRyder518

I also agree on the fact that if you don't have enough voltage the car doesn't run well. It may not be the same situation but last night my car run idling really low for whatever what reason, like around 600 rpm and my voltage was about 11.8 volts. The car started missing really bad and the lights were flickering. Once I took it out of drive and had the rpm's up, it all stopped.

Does this mean my alternater is on its way out or is that somewhat normal?

jfischer

If your alternator is good, you should be seeing closer to 14v when the engine is running.