Higher voltage

[good2win22]

Anybody know of any issues with stock electrical components receiving a constant 14 volts?

[Scoobum]

Constant...no. 15.x on mine at 70 percent throttle to WFO.

[Steve Wood]

No...not at all.  In a properly working system, the alternator should be putting out a tad over 14v.  Some items, such as headlights, are often rated at 13.5v, but that should not be confused with maximum allowable voltages

[good2win22]

Brad, I'm looking at running a charging system capable of constant voltage. Less voltage variables to the fuel pump.  Would make playing with the VE table a little easier

[Scoobum]

Steve posted...have a read. Guess my charging system is up to snuff. 14.1 at the back of the alternator.

[good2win22]

Thanks for the input Steve. I gathered as much. The charging system on my car is fine for a daily driver. When cold it puts out 14.2. When warm it drops to 13.5-8.  Under load at high rpm it will get down to 13.2ish. That's a factory gm alternator that I plucked for a junkyard. Just looking at some of these powermaster units that can be adjusted as high as 16 volts with a 200 amp load. Not sure if they can maintain 16 volts at 200 amps but having let's say a constant 14 volts would be easier on the tuning tables and I believe the fuel pump would like that voltage as well

[Steve Wood]

I assume you are checking the actual voltage and not that reported by the ecm.  It's not real and varies with temperature and probably the A-D conversion in the ecm.  Usually, the actual voltage has much less variation unless the alternator is tired.  Lot's of people hate the Powermaster brand across the forums for short life and other problems.

A little change in actual voltage to the pump is insignificant compared to the accuracy of the AF's coming out of the wide band which is roughly correct.  There is a reason why calibration grade or lab grade wide band sensors cost both arms and one leg

[good2win22]

I ran some leads to the back of the alternator and had the voltmeter sitting on the dash. Made a couple of 3 high gear pulls on some back roads to confirm.

[Steve Wood]

That sounds like a tired alternator in that case.  That's assuming the wiring is good-especially on the ground path.  Voltage drop tends to increase under load and exposes wiring problems.  I like to check up front and compare to the back end readings

[Scoobum]

Norbs built the one on my car. Puts out roughly in the neighbourhood of 5 million amps...

[Steve Wood]

plasma generator knowing Norbs

[Steve Wood]

Jason, whatever happened to this?

Somewhere in my shop I have a manual regulator for the alternator that allows you to to adjust the output voltage to the level you desire.  This is okay for racing, I am not sure it is good for a driver as it may be hard on the battery.

I have been thinking about your problem and I recall having a problem with the wire from the alternator to the battery.  I was having a larger than expected voltage drop between the alternator and battery.  I discovered a hot spot in this cable about a foot from the battery.  I did not cut the cable open to see what was going on-wish I had.  I replaced the wire and the voltage drop went away and it no longer had a hot spot in it.

The wire is pretty small from the factory.  I suspect that a 4 gauge wire, or maybe even a 2 would be better-particularly on a high boost race car.  The amperage vs wire length tables suggest that is way overkill but I have seen some cars that appeared to get a benefit from it.

A ten gauge wire should be adequate to the pump, but, maybe a good quality 8 gauge wire would be a help.  None of this copper coated aluminum crap.

Most of the fuel pump issues I have seen have been on the ground side beginning inside of the tank with the pump wiring.  Also, many try to add a ground to the frame which is the wrong place as the body sheet metal is the normal primary ground.

I bet that a battery mounted in the trunk  would cure some of these problems, or, make it easier to eliminate them but I think many use to0 small a cable to carry power to the front and from the alternator back.  Some more the lines of a 1/0 very expensive welding cable would be my choice...espec ially if someone else paid for it

[nocooler]

Just thinking outside the box. What about a capacitor in the + line to the fuel pump? I have no idea how big it’d need to be, but sized properly it should maintain voltage across the circuit.

I can say look at what the wideband is telling you. Back to back pulls should be consistent. If it’s not consistent and stable at wot then I’d worry about it. A voltage drop isn’t uncommon as draw goes up, but it should be consistent and repeatable. If it’s all over the place then I’d be looking into it.

[Steve Wood]

And the ECM provides a voltage correction to the injector pulse to maintain a constant injector flow-within limits, of course

[earlbrown]

I bought all the stuff needed to build some bad ass bigger/better battery cables but haven't gotten around to it.l   A couple months ago, I took my car off of 2 weeks slow charge, drove to a friends house (daytime, no headlights, or fan) and fired up the voltmeter.  At idle I was losing almost a full volt between the alternator and the battery. Then almost another full volt to the inside of the car  (cig lighter jack).


I roll my eyes everytime I see someone beefing up an alternator, or installing a 250amp welding unit to the 30+yo factory charge lead.   If the amps are there, increasing the voltage is a band-aid with consequences.



The factory charge lead is right at 67" long.


As science clearly shows, the factory charge lead was barely adequate when brand new.  100,000 heat cycles later, I.E. 'overheating', and it's a closed loop casualty that gets worse faster over time.

The cable I have in my mindbrain is an inch longer SAE/DOT wire on the starter lead to make mini-starter installs easier and route it a little further away. And some much thicker car-audio type wire on the charge lead since they genearally have much finer, and numerous, strands.  And for good measure, a nice thick pigtail that can reach the fenderwell to run, amps, distribution blocks, hotwires, headlights, fans, whatever.

On the ground side, same thing, standard pigtail to ground the body with that single crappy screw, block ground, an addional thick lead to reach the frame, and an extra pigtail for whatever.  Something like a ground lug for instance.