MSD Ignition and firewall mounted voltage regulator

[tooslow]

I have a MSD ignition complete with the coil , I have standard alternator with a firewall mounted regulator . I do not have ballast resistor installed because of the MSD coil.
Everything works , battery charges , runs fine
Problem
My expensive electric fuel pump surges with RPM , at idle its going slower , as rpm builds it increases cycles , plus lights dim at idle , My volt meter goes up and down so reg isn't working properly.
I think the electric fuel pump will be happier and last longer at a constant voltage
What are you guys doing for good voltage regulation ?

 

[67Dart273]

What are we working on here? A 1942 Supermarine Spitfire? Or a 1928 hemi Farmall?

And what kind of regulator do you have? "I assume" you are talking about Mopar, but maybe not??

69/ earlier or 70 / later?

THE MSD MAY BE CAUSING ELECTRICAL INTERFERENCE with the regulator

 

[tooslow]

What are we working on here? A 1942 Supermarine Spitfire? Or a 1928 hemi Farmall?

And what kind of regulator do you have? "I assume" you are talking about Mopar, but maybe not??

69/ earlier or 70 / later?

THE MSD MAY BE CAUSING ELECTRICAL INTERFERENCE with the regulator

 

[Mattax]

My expensive electric fuel pump surges with RPM , at idle its going slower , as rpm builds it increases cycles , plus lights dim at idle , My volt meter goes up and down so reg isn't working properly.
I think the electric fuel pump will be happier and last longer at a constant voltage
What are you guys doing for good voltage regulation ?

It also could be
the electric pump is exceeding the power capacity of the alternator at idle.
If the alternator can't supply all of the electric needs then system voltage will drop. It will drop even though the regulator is 'full fielding'.
When the alternator's supply voltage drops enough, the battery becomes the high voltage power source. The battery has tons of power, but only at 12.8 Volts at best.

It also could be something about the wiring arangement is choking the supply of current.

Electric fuel pumps, like most equipment, draws less current at lower voltage. That means less power and less performance.
You can see that on the graph from Walbro posted here: Holley/Demon Carb stumble

 

[coalman]

Dart273, on my car with the voltage surge, I didn't know the MSD could cause the above. Thanks

 

[tooslow]

thanks
I searched a little harder on here and found all kinds of good answers and things to fix
wiring grounds

It also could be
the electric pump is exceeding the power capacity of the alternator at idle.
If the alternator can't supply all of the electric needs then system voltage will drop. It will drop even though the regulator is 'full fielding'.
When the alternator's supply voltage drops enough, the battery becomes the high voltage power source. The battery has tons of power, but only at 12.8 Volts at best.

It also could be something about the wiring arangement is choking the supply of current.

Electric fuel pumps, like most equipment, draws less current at lower voltage. That means less power and less performance.
You can see that on the graph from Walbro posted here: Holley/Demon Carb stumble

 

[tooslow]

The car is a post 70 with the VR on the firewall
I am using an Aeromotive 1000 fuel pump. Ive seached and found great info on this forum , check grounds and wiring , clean them up anyway
question
What alternator should I use ? I read that stock Chrysler alternators do not put out enough current below 1500 RPM ?

 

[67Dart273]

Well since you did not post it, I had to look it up. A1000 is that what it is? specs no 10 wire and a 30A fuse. So that is a lot of current. Yeh. I'd say you need a larger alternator AND UPGRADED vehicle harness. You still have the stock factory wiring? Then forget it. You need to do an ammeter bypass, and I would for sure get larger alternator

"What else" have you not told us? Electric fans? Water pump?

There is no possible way to guess what all this "is."

 

[tooslow]

Well since you did not post it, I had to look it up. A1000 is that what it is? specs no 10 wire and a 30A fuse. So that is a lot of current. Yeh. I'd say you need a larger alternator AND UPGRADED vehicle harness. You still have the stock factory wiring? Then forget it. You need to do an ammeter bypass, and I would for sure get larger alternator

"What else" have you not told us? Electric fans? Water pump?

There is no possible way to guess what all this "is."

 

[tooslow]

I am learning ,,my first car with decent HP , takes more thought I am finding out, lots of mild street cars, Mopar guy I will provide all details
Post 70 dodge
446 ci
10.75 to 1
Ported AL heads
1.6 rockers
cam dur 246 @50 and 590 lift 108 lobe installed straight up
mech cam
727 trans
electrical
1000 amp battery
Dual fans
Aero 1000 pump
Mech waterpump
idles at 900 RPM could be lower but want to keep oil press up
I avoid driving thru town or stop lights , highway , back road car and Track Time car
Road America
Autobahn
Gingermann
I know the 727 sucks, no need to tell me for a road race app but its still fun and im saving the 5g's for a stout Tremac and pedals , another forum


standard new 2 wire alt with reg on firewall
MSD ignition
Why bypass the ammeter ? learning ?
Should I upgrade to 1 wire alt ?
I am going thru the wiring now , going larger AWG and eliminating connectors

 

[Mattax]

Why bypass the ammeter ? learning ?

I would have phrased it as "the car needs a different wiring strategy."
Why? Because the system was designed for the wire path with the ammeter to normally have no current flow. It was intended to only carry current for ignition during starting, and then for charging the battery. (If the alternator dies of course it can handle powering the ignition and even lights for a little while. That's still less than 15 amps.)
Now this car has electric fans and electric water fuel pump. So now that wire path is going to be used for these additional loads anytime the alternator isn't producing enough power. When this happens the battery is getting drained more frequently and more heavily. So recharging is going to be more frequent and longer at at higher rates than normal.

If that all wasn't enough, at low rpm its likely the alternator will be working at its max for long periods of time. So both it's field circuit and the output circuit are going to be maxed out.

Should I upgrade to 1 wire alt ?

1 wire is not an 'upgrade.' It's a useful arrangement in certain situations.

I am going thru the wiring now , going larger AWG and eliminating connectors

Connectors aren't always bad to have. They can be useful for troubleshooting and servicing. The trick is to use ones that can handle the load.

If those electrical items are going to be used, for an alternator I'd start by looking at a 'denso'. AR Engineering makes bracket to make it easier to adapt to the LA, and B engines.

For wiring, I'd look at a some sort of engine compartment power distribution.
This would include a circuit breaker or fuse box with relays for fan and fuel pump power. Also a relay for headlights.

 

[Mattax]

There are a few, rare options, and models with a wiring setup that could be adapted fairly easily.