So my co-worker and I just had a wild idea. how hard would it be or better yet can I unplug the voltage regulator during and autocross run without hurting anything?

Benefits would be the altenator is free-wheeling vs stealing a couple HP. Should help acceleration too????

Why not pull the belt? Should take 2 minutes.

Because pulling the plug is 2 seconds. and I got the belt the right tension so I would rather leave it.

I doubt it steals enough HP to make it worth it. Well, 2 seconds, it might be worth it, but might end up being worse because of the voltage change, and not providing as much power to the coil?

Ok, but how does unpluging the regulator decrease the work the engine does to turn the alt? They don't have a clutch like an AC compressor. Don't they spin the same no matter what the VR does?

The more amps you are pulling the harder the alternator has to work, and puts more pull on the engine.

You would save about .00001 HP.

But hey, we need all the help we can get.

Paul not sure that is true. How much power is requires to spin an altenator making 15 or 20 amps which is charging the battery, running fuel pump, CD ignition box brief brake lights (anything else)? Oh, gauges ! Next to just spinning the alt under no load which I agree is .0001 hp.

OK, maybe .1 HP. Will you ever feel it?

Make two autox runs. One with the alternater hooked up and one without.
Did you turn a faster time without?

On a stock car I would doubt it.



BTW, Joe I layed up one of your passenger door last weekend. It's curing in the sunshine.

Paul

QUOTE (URY914 @ Mar 24 2005, 07:00 AM)

OK, maybe .1 HP. Will you ever feel it? Make two autox runs. One with the alternater hooked up and one without. Did you turn a faster time without? On a stock car I would doubt it. BTW, Joe I layed up one of your passenger door last weekend. It's curing in the sunshine. Paul

Car is far from stock BTW

Joe,

I don't remember the wiring schematics at the moment.
but its sort of like a racing kill switch... The alternator current has to have a method of winding down throught a resistor and ground in order to not burn out the diodes.

but yes it can be done.
I once started the project (never finished it) on an old car.
we had a hidden switch in the engine bay underneath the regulator panel.

What I mean by a stock car is that is would have more effect on a lightweight car (mine) or a modified car (yours).

Big fat heavy stock car you wouldn't notice that much.

The actual HP loss is easy to calculate.

Ignition is about 3 amps. The fuel pump is about 4 amps. The injection system is another 3 amps. Let's say that's all that's running. 10 amps @ 14v is 140W. 746W in 1hp. The alternator is roughly 50% efficient, so it's consuming 280W, or 0.38hp. More than Paul's guesstimate, but still not enough to make any difference.

The stock alternator running full bore will consume about 2hp.

You don't need to pull the regulator. Just pull the field wire (the one that runs through the G bulb in the dash). Put a switch there, and the alternator will be disabled when it's off. No current generated, so no worries about melting any diodes in it.

That's a good idea. Pull the Gen bulb and see if the alt is charging @ the battery.
If it works then I'll put in a switch. Certainly can't harm the altenator if I am just simulating a burnt bulb. So the excitiation voltage goes throught the bulb just like my 928. Cool!
Hey if you aren't cheating you aren't trying. If you aren't trying you aren't learning what not to do next time.....

QUOTE (Joe Ricard @ Mar 24 2005, 01:45 PM)

That's a good idea. Pull the Gen bulb and see if the alt is charging @ the battery. If it works then I'll put in a switch. Certainly can't harm the altenator if I am just simulating a burnt bulb. So the excitiation voltage goes throught the bulb just like my 928. Cool! Hey if you aren't cheating you aren't trying. If you aren't trying you aren't learning what not to do next time.....

Just like your 928, and pretty much every charging system made in the last 50 years.

Still, you're not going to do enough good to offset even this minor effort, IMHO. Less than 1/2hp is awfully small.

QUOTE (URY914 @ Mar 24 2005, 08:00 AM)

Big fat heavy stock car you wouldn't notice that much.

URY - who you callin' FAT?


Joe, losing five pounds by cutting out the fried foods and the soda would have a greater effect.



I've got a Weight Watcher's meeting in fifteen minutes, gotta go!


John


P.S. and watch the after dinner snacks too

Well maybe, pulling the belt would probably be better allowing the engine to spin up faster. 1978 lbs and a 12 lb flywheel it's just gotta be worth something and it won't cost Nuthin. Thats the best part

On a injected car... losing the alt is a kick in the pants. It is certainly more than 1hp when you turn the alternator off. I used the switch method in the past. Very easy. I switched it at the regulator plate. Turned the alt off right before timed runs in PCA time trial series (3 laps)


B

Thanks Brad, Thats what I am looking for. 44 IDF's 86b cam and ported 2.0L heads already are a kick in the pants. This is the kinda thing that will keep me ahead of my son when he co-drives

QUOTE (Brad Roberts @ Mar 24 2005, 02:05 PM)

On a injected car... losing the alt is a kick in the pants. It is certainly more than 1hp when you turn the alternator off. I used the switch method in the past. Very easy. I switched it at the regulator plate. Turned the alt off right before timed runs in PCA time trial series (3 laps) B

Hm...

If so, then the stock alternator is considerably less efficient than most.

OR, a completely different effect: D-Jet has very poor adjustment for battery voltage fluctuations, which have a substantial effect on mixture due to changes in injector opening times. Counter-intuitively, a lower battery voltage means a richer mixture. With no alternator, system voltage will be 12.5v (more or less) rather than 13.5-14v, since that's what the battery is putting out by itself. This is why a bad or marginal voltage regulator can have a significant effect on mixture with D-Jet. Perhaps the "kick in the pants" you're feeling isn't caused by losing the alternator drag, but rather by a richer fuel mixture across the board caused by the lower system voltage.

well a little richer is always better at WOT. My carbs take good care of that 12.5 to 1 air fuel. the Mallory box keeps it lit.

I semi checked this:

A Optima battery will hold a 13+ volt charge for upwards of 15 minutes. We run 4cyl race cars with NO alternator and Optima's (or whatever racing battery we decide)

I'm pretty sure Jake tested this on the dyno..

Lose the fan belt on your stock 2.0 You can imediately feel the difference when it happens.


B

QUOTE (Brad Roberts @ Mar 24 2005, 02:28 PM)

Lose the fan belt on your stock 2.0 You can imediately feel the difference when it happens.

I'm sure not having to TURN the alternator would make a difference in HP output.



I would respectively suggest that reduced load or for that matter no load on the alternator would make for a marginally insignificant effect to HP output.



John