SF Alternator Upgraded Wire Size?

[Davidless]

Originally Posted by eschaider

When Detroit elected to stop using them, they were using 60 amp or so alternators. Reread Patrick's post #15. That is less than ten amps.

In so far as SPF and their decisions, the best source for why they chose to do what they choose to do is SPF. I have never heard of any replica manufacturer offering to help with any replica with a failed Amp meter that caused a fire and damaged the car. But hey, who knows? You could be the first who does, or you may never have a problem.

Detroit is very cost-conscious, so you can bet they would not introduce an electrical design change unless needed. You may never have an issue, but then again, for $99, you can eliminate the possibility of ever having a problem to start with ...

In the end, it is your car and your call. You need to do what you think is right for you.


p.s. Literally, any fire in that car will cost you more than $99 and the effort to swap gauges.

Thanks

[Blas]

Come on now, how about the simple answer like originality?

Blas

[patrickt]

If you are paying attention to your gauges, have an inquisitive mind and notice small changes and follow up on them, then an ammeter is fine especially if you have a shunt wire. Unfortunately, 99.99% of drivers do not fall into this category so harmless voltmeters and big red flashing idiot lights are needed. A few years ago a slightly wavering ammeter needle helped me spot a deteriorating ground connection on the voltage regulator. An idiot light would never have done that and I don't think a voltmeter would have done so either.

[eschaider]

I think you have all the necessary information to make a call for your own car, David. In the end, this is your car, and this is your call. Whatever you decide for you and your car will automatically be right ... for you.

[patrickt]

Originally Posted by eschaider

I think you have all the necessary information to make a call for your own car, David. In the end, this is your car, and this is your call. Whatever you decide for you and your car will automatically be right ... for you.

Until his car explodes in a fiery inferno, then he'll say "that damn patrickt, why did I ever listen to him?"

[eschaider]

Perhaps, Patrick.

However, it is an unmistakable fact that the final decision will be his. Moreover, who could possibly be a more appropriate 'decider' for a custom built vehicle designed by him for him, than him??

[sunman]

Ammeters went out with generators and points.
Amps up, volts go down.
You drop to less than 12 volts shut it off and check it out.
Unless your my ex… red lights on, gauges pegged, kept on driving.

[Davidless]

OK one more post...
I'm curious as to what the professional powertrain installers do in this case.

I think many are using high amp alternators (I know Prestige does)

The installers also charge alot for a turn key install and tune. I think one is charging 15G for the powertrain install and tune up, unless I'm mistaken.

David

[patrickt]

Originally Posted by Davidless

OK one more post...
I'm curious as to what the professional powertrain installers do in this case.

I think many are using high amp alternators (I know Prestige does)

They slap it in just as Blas posted. But, if you ask them, they will likely tell you: 1) a voltmeter is safer than an ammeter; 2) an ammeter looks cooler than a voltmeter; 3) if you want cool, with a modicum of safety, go with an ammeter that has been shunted.; 4) if you want the most safety, go with a car other than a Cobra. And they will probably say it in that order.

[cobragene]

My EM. Has separate circuit breakers in engine compartment for both fans and one for headlights, which doesn’t run through amp gauge, sounds like I would be better off with a volt meter? I did put a 250A fuse between bat neg. And frame, probably not necessity but haven’t had any issues. I am curious Patrick if that 10 or 12 GA shunt would burn out wouldn’t that be a fire hazard also? I guess a fusible link is safer because it’s short in length?

[patrickt]

Originally Posted by cobragene

I did put a 250A fuse between bat neg. And frame, probably not necessity but haven’t had any issues.

Alright, as a general rule you don't fuse the negative side of the battery. When you are cranking your engine, the initial draw of your starter motor will be several hundred amps. Yes, several hundred amps. But that doesn't last all that long, just long enough make a magic field for the starter to spin with. Now, my particular old school AC Delco starter draws a good 200 amps while cranking, but as the battery gets weaker, your amps will go up while cranking. So, keep that in mind if you blow your fuse. Chances are you won't, but if you do, you now know why.

Originally Posted by cobragene

I am curious Patrick if that 10 or 12 GA shunt would burn out wouldn’t that be a fire hazard also? I guess a fusible link is safer because it’s short in length?

If you burn up a 10 or 12 gauge shunt wire across your alternator there is something seriously wrong, like a bad fault to ground on the alternator to battery line. If that occurs, you want to have some sort of protection between the battery and the fault because the battery will keep pumping out electrons until the firemen come. The alternator stops pumping when the engine stops running. But even with a protection device (fuse, circuit breaker, etc.) between the battery and the ammeter (but after the starter solenoid) a serious fault to ground on the battery to alternator line is a very bad day in the making. FWIW, I have a 50 amp circuit breaker between the battery and ammeter/shunt and nothing between the ammeter/shunt and alternator.

[cobragene]

If you burn up a 10 or 12 gauge shunt wire across your alternator there is something seriously wrong, like a bad fault to ground on the alternator to battery line. If that occurs, you want to have some sort of protection between the battery and the fault because the battery will keep pumping out electrons until the firemen come. The alternator stops pumping when the engine stops running. But even with a protection device (fuse, circuit breaker, etc.) between the battery and the ammeter (but after the starter solenoid) a serious fault to ground on the battery to alternator line is a very bad day in the making. FWIW, I have a 50 amp circuit breaker between the battery and ammeter/shunt and nothing between the ammeter/shunt and alternator.[/quote]

Would you mind drawing a simple schematic of your shunt and fuse?

[patrickt]

[quote=cobragene;1520380]

Would you mind drawing a simple schematic of your shunt and fuse?

Circuit breaker in Yellow, Ammeter in Orange, Shunt Wire in Green.

[cobragene]

Thanks Patrick, you are a wealth of information. So you do have your fans and headlights running through amp gauge? I don’t but may change that. On the other hand it would be much easier to swap to a volt gauge?

[patrickt]

Originally Posted by cobragene

Thanks Patrick, you are a wealth of information. So you do have your fans and headlights running through amp gauge? I don’t but may change that. On the other hand it would be much easier to swap to a volt gauge?

I have both my fans and headlights on the alternator side of the ammeter. If I put them on the battery side of the ammeter then it would show a 30 amp charge every time I turned on all the fans and headlights. Having them on the alternator side of the ammeter allows the ammeter to still show zero, or maybe a one or two amp charge, when the revs are 1000 or more. At idle, with all my fans and headlights on, the ammeter shows a slight discharge. That disappears as soon as the revs come up and the needle then swings over to show a slight charge. This is perfectly normal behavior.

[cobragene]

After studying it the changes wouldn’t be that difficult. Does this look like it would work? Would seem to be a good idea to also put a breaker at the alternator, or would that be redundant?

[patrickt]

OK, as a guess, I would say your headlights will draw 10 amps, your pusher fans will draw 10 amps, and your main puller fan will draw probably 20 amps, but that's just a guess. Your main line between the alternator and battery should be at least 10 gauge. Your tap off to the pushers could be 12 gauge the tap to the headlights could be 12 and the puller fan could be 10 gauge. Having a fatter wire won't hurt anything, it's just a little harder to work with. Other than that, it looks good.