i had pretty much the same problm with my car.

i took it to supercheap got a free check with a little hand held machine, and it told me that pretty much the altonator was F#$ked.

the idle Amps was about 11 when it should be 13.2 or above, so when i droe around it was only reaching 13 when it should be way above that when reving the engine. i had to buy a new altonater about $120

Quote:

Good excuse to drop a nanger when you take off

I agree with go_the_datto and lumix6 this sounds like the alternator is functioning correctly.
An alternator works by keeping the battery voltage at roughly 14.2V.
If you turn on your lights this will use power and the alternator replaces it.
The more current that the accessories on your car use, the more current that the alternator will try to produce to replace it.
The more current that the alternator produces, the tighter the alternator becomes to turn and this is why your revs drop and also why your car stalls at low revs when you take off.

( Just means your engine doesn't have enough torque for this down low!
No big deal!)

One thing I like is what Niscoupe pointed out about a bigger pulley slowing the alternators revs down.
This could also help in your case 1200rallycar.
By the bigger pulley giving more leverage to the alternators rotor, it would require less torque from your engine to turn it.

Either way the problem you are experiencing
is no big deal. Just means a few more revs are required when taking off.

That sounds quiet normal to me.
Weve all heard after a lot of cranking of an engine the alternator making a slight whistling sound as it is putting charge back into the battery and the revs drop off a little, sounds to me that the alternator is working well and drawing a bit of load off the engine

Jeez a 100amp alternator will cover 1200watts....thats a hell of a lot of power! Maybe the AE86 had a decent sound system in it :)
On our rally car using 6 driving lights, tail lights, dash lights fan, fuel pump, heater fan, computer etc, we could only reach a maximum peak of 800 watts. We use a alternator rated at 85 amps and that is ample. In fact we used to use a 55amp alternator with no problems until we upgraded last season. These things do soak up hp and even with the kind of hp we have you certainly notice the difference when everything is turned on. A poor little A12 would certainly struggle with a whopper like 100amp!
Alternators are designed to reach maximum output at not too much above idle, so revs shouldn't be an issue as far as charging goes.
If you are using a high revving motor it actually pays to replace the standard alternator pulley with a larger pulley to slow it down. A major cause of alternator failure is due to over revving. I have never stopped to work out what revs a standard alternator would be doing when the engine is doing 8500rpm but it must be PLENTY!
When I had the A12 I used a 4" (100mm) pulley on the alternator and never had any problems.

a friend of mine who rallied an ae86 sprinter told me once the minimum size they could run was a 100 amp alternator from a commodore.the car was fuel injected,so they needed to run all the electricals,but maybe the alternator isn't big enough.remember,the alternator is rated at a certain rpm,so maybe it isn't charging enough at the revs you're running.

The alternator will be putting a fairly signifiant load on the engine when the lights are on. The more power you draw from the alt. the harder it is for the engine to turn it. At low revs this could be enough to stall your engine.

Chris

Sounds to me like your alternator is not up to the task. If you can't start the engine with the spotties on, then it's battery or wiring.

It could be a bad earth on the 12V feed to the high beams, possibly a bad relay.. But an ammeter inline with the 12V feed to the battery side of the relay (Which I expect you have for these spotties) will tell you the story. With the engine running and the high beams on, does any of your wiring get hot or even warm? They shouldn't even get warm, if they do, look for a bad earth or get thicker wire..

Chris.

ps. Make sure that your ammeter can cope with 20A + otherwise you'll cook your ammeter. I've done it, it doesn't look or smell nice.

yeah i just upgraded to a GT40RT and it needs a resititor, you will get alot better spark and easy starting etc, while your doing that upgrad your leads to TOP GUN

actually i was thinking of upgrading the coil anyway to a bosch GT40 or something, whats the deal with putting those in, do i keep the ballast resistor or do they have in-built one, is there any other issues and which is the best to get?