Cookwithvette

It seems I need to rewire my alternator and up my voltage tables. Fully warmed it up for the first time this year today and as soon as those fans kicked on it went dead lean. :crazy: I was left scratching my head for a minute before I realised what was happening. :lol:

In case you're wondering what on earth I'm rambling on about, lower voltages introduce a lag in the opening of the injectors. The computer has a table of voltages that should tell it what to do at whatever voltage.

zwede

Maybe time to upgrade the alternator? I see no difference in the voltage reading on my C950 when the fans (I also have the spals) come on. I used a 12SI alternator out of a 1980 'Vette. The 12SI series charge much better at low rpm than the older 10SI. Easy install. I just had to bend one bracket slightly as the 12SI is 6" diameter where the 10SI is 5.5".

Cookwithvette

That is a possibility. My current alternator is a Powermaster 100 Amp but I don't know what it puts out at lower rpms.

I'm going to re-wire things first before I get to alternator swappage. Right now the output is all being run through a single 10g wire and I'm not sure if the previous owner left the sensing wire alone. If I remember correctly, 10g is only good to about 55A so I'm due for some extra capacity anyway.

The 12SI sounds like a good idea. Thanks! :cheers:

BacaBill

I didn't think ya had to worry about injectors on a '75 :D


[Modified by BacaBill, 12:44 AM 4/18/2004]

Shark Racer

Cook- just a thought, but if you're running 1-wire alternator instead of 3-wire, the alternator won't kick in at lower RPM. However, I don't think the 100A is enough to run fans and all the EFI components anyhow...

-Steve

Cookwithvette

BacaBill, Well.... normally you wouldn't have to. :lol: I have this knack for making things complicated.

Steve, I'm running a three wire. I suppose it's possible 100A won't be enough.

50-Fans
20-Heater fan
20-Wipers?
15-Lights
10-Fuel pump
10-Stereo
_5-ECU

I've been poring over the electrical system lately with a fine tooth comb for the big wiring project next winter. I also plan on switching to a serpentine setup which will require another alternator... Looks like I'll go beefier.

I should add that the voltage difference was really minimal. It went from 13.86 steady to around 12.8~13.0.

Hmmm.... I just realized, I'm running the ECU and fuel pump off the battery... a big :nono: . Dang, I really need a distribution block.