Borrowing a trick off of the grand prix's, I added 2 3amp diodes into my alternator voltage reference line. I picked up about a extra volt.. resulting in less volt drop when I have things on, and much better fuel pump opreation.

Being turbo'd I need alot of fuel so the extra voltage to my fuel pump really gave me the extra fuel pressure I was looking for.

How do you do this? Does it work on alterators for '84's?

Forgot to ask, do you have pics?

[This message has been edited by ktthecarguy (edited 08-30-2009).]

Can it be done to any alternator? This is internal right?

not internal, the alternator at least on grand prix'es has a wire called the "sense" wire. It connects to the alternators internal regulator. This is the voltage reference for the internal regulator. Regular old semiconductors like diodes cause a voltage drop of roughly 0.7V on a circuit. Put a couple in series on the alternators sense wire and you will convince it that the system has less voltage than it really does.
Personally, I think it's a bad idea. It can be very dangerous to charge a car battery with ~16 volts. The electrolyte will gas out and If you do this to a sealed battery like any of the Optimas it's very likely to explode. Besides, the internal regulator controls the alternators output current so even by fooling it to think the voltage is lower you won't get any more current out of it in the long run. You might even get less current because the new regulators are digital and "know" when the voltage is abnormal. Yes the extra voltage does make some things run better though... I know lots of people have done this so it might not be as bad as it sounds...but i wouldn't do it.

You have to be careful.
Diode add .7 v per unit. Use 1 at a time or you can go over volt.
Short story: Put diode in the sense line (S pin CS alt. {see cs alt} A pin SI alt.)

I don't recommend it unless you know how to check. Battery overcharge is not fun. Battery charge volt can be tiny window. Go outside of window and you can shortage the battery life. How much dependence on thing.

Warning: Sucky wire don't help. Use diode can be bandage for alt, alt wire, or bad ground. Now you have bad wire and high alt. 3 diode add 2.1 volt at the alt. Mean alt main as 16.something if alt/wire/ground is good and can be bad for battery. If you are not make 16 v either you did something wrong or more likely your wire/alt is weak/bad.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

[This message has been edited by theogre (edited 08-30-2009).]

Zooomer and I had a conversation about this and it should not be done on daily drivers. It was for OFF ROAD use only, and targeted to drag racing so consistent levels of power made the fuel pressure stable, so consistent times could be run. This was only a short time of running.

As with any modification that goes wrong for the end user, they dont come back to a posting how bad it went in the future...

Anyone overcharging a battery should be very careful. If you smell acid, its too late, the plates are cooking in the battery.

People with unstable and low fuel pressure should get the proper fuel pump that matches their application of HP and torque. There are plenty of mathematical formula's that relate to this.

http://www.fastfieros.com working with Kinsler Fuel Injection in the past on fuel pump output levels. http://www.kinsler.com/Cat_...201234_screen58.html

[This message has been edited by FastFieros (edited 08-30-2009).]

quote Originally posted by FastFieros: Zooomer and I had a conversation about this and it should not be done on daily drivers. It was for OFF ROAD use only, and targeted to drag racing so consistent levels of power made the fuel pressure stable, so consistent times could be run. This was only a short time of running. As with any modification that goes wrong for the end user, they dont come back to a posting how bad it went in the future... Anyone overcharging a battery should be very careful. If you smell acid, its too late, the plates are cooking in the battery. People with unstable and low fuel pressure should get the proper fuel pump that matches their application of HP and torque. There are plenty of mathematical formula's that relate to this. http://www.fastfieros.com working with Kinsler Fuel Injection in the past on fuel pump output levels. http://www.kinsler.com/Cat_...201234_screen58.html

The fuel pump problem can be better addressed with thicker gauge wires. I could hear my pump surge with the turn signal and discovered during a pump upgrade that the ground wire was frayed. I further discovered that there was room for improvement when the 730 ecm was installed and fuel pump voltage could be monitored which turned out to be lower than battery voltage.

For some reason I could never get the alternator to charge like I wanted, and after some research on battery charging there was no obvious issues with this trick unless you make over 15.5 volts... and in my case I never ever made more than 14 even when dead cold everything off. It now keeps me in the high 14's cold and mid to low 14 warm or with things on. So I am nearly 100% sure the battery will be the last thing I need to worry about while using this.

Is there a problem with a wire somewhere? Maybe, but I did not detect significant voltage drop in many of the big alternator wires, so short of rewiring all of my B+ type wires in my car I figured I would try this for awhile.

Diodes need to be installed with the stripe facing the alternator.

quote proper fuel pump that matches their application of HP and torque

Thats fun and all, but I dont feel like running 2 fuel pumps so I can max out my 50# injectors when I can just make the voltage correct. When I go to 60#s here soon, I will most likely be able to get away with it using my delphi proto pump, a 044, or possibly one of the real walbros I have laying around here at the shop not having to use 2 pumps.

I like the idea of tricking the alternator into putting out a higher voltage for strip use. For normal driving on the street I would put a switch in parallel with the diodes so that the trick can be used only at the dragstrip or when you want to open her up.
As TheOgre has said charging a battery at too high a voltage for too long will cook it. Running too high of a voltage will also decrease the lifespan of all of your lights, instruments and other items. Again good idea but one that I would use only at the strip.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
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" ON THE LOOSE WITHOUT THE JUICE "

Well, what I suppose may be unclear here, is that I am not "overcharging" anything, I am just bringing up my voltage to where I SHOULD be, which is mid 14's.

Volt measure how? Dash volt is probably wrong.
Check at battery and check again on main output of alt. They should match or be very close. (.1-.3 volt)

Alt <14.6-7 either alt is bad or alt wire/ground is weak.
Test alt. Take it to store and bench test. On car test will not work is you case.
Ground is thru alt mount. Clean it, the alt, and the block.
Alt wire have splice for Sense wire. (see my post above.) If splice is bad then you won't get good volt.
SI alt uses shitty plug on side. A/B plug can be bad and look ok. (CS uses Metipack for that reason.) Replace it and solder the connection.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

[This message has been edited by theogre (edited 08-30-2009).]

One or more diodes of the rectifier bridge may be cooked.

[This message has been edited by pmbrunelle (edited 08-30-2009).]

You probably already know this, but I've found that almost all low voltage problems are wiring/ground related. First thing I do is make sure huge beefy ground straps are in place between block and chassis, and battery and chassis. I also run heavier gauge wire b/t alternator and battery, and battery and power distro center.

Usually, just making sure that the grounds are uber-low loss makes a HUGE difference in my cars..

Not to mention the Alternator is not meant to charge the battery only maintain the charge. It is capable of putting out over 17 volts but only for a short time. That's why you should never jump start another car with your car running.

quote Originally posted by aaronkoch: You probably already know this, but I've found that almost all low voltage problems are wiring/ground related. First thing I do is make sure huge beefy ground straps are in place between block and chassis, and battery and chassis. I also run heavier gauge wire b/t alternator and battery, and battery and power distro center. Usually, just making sure that the grounds are uber-low loss makes a HUGE difference in my cars..

I do, and the lazyness factor I put into my daily driver turbo car is awe-inspiring. My next swap will get overkill on the ground/wiring department.

I have been scanning voltage with the pcm and logging it. It shows and holds voltage perfectly around low 14's 95% of the time I am driving it, only on start up does it get near low 15's. My AUX pod gauge is stupidly wrong, at 14.4 it shows the voltage off into the red quite a bit, and in the middle it shows about 12 volts actual.

quote Alt <14.6-7 either alt is bad or alt wire/ground is weak. Test alt. Take it to store and bench test. On car test will not work is you case. Ground is thru alt mount. Clean it, the alt, and the block. Alt wire have splice for Sense wire. (see my post above.) If splice is bad then you won't get good volt. SI alt uses shitty plug on side. A/B plug can be bad and look ok. (CS uses Metipack for that reason.) Replace it and solder the connection.

I imagine this alt is bad, it is a fiero alternator... cold it typically made good voltage, about 14.1-2 or so, but the second it got warm it would drop to low 13's.

Ground for the alt goes through 2 places on my swap, both very clean and good ground points. Chassis ground is within a few inches of the alt, and main battery ground is just around the corner from that, all in good shape.

Alt wire and splice were done quite well, and I also moved the reference to the starter bolt just before I did this, with a SMALL gain in voltage overall, but still quite low when warm. Wire is actually from a GTP so its significantly newer and a bit more gauge than a fiero wire. A few crimps were done but they were also braised with solder.

my connector is sorta rough, but it seems to be clean where it matters and I added some electric grease to help and it didnt.