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HEI power supply.

General engine tech -- Drag Racing to Circle Track

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In-Tech
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Re: HEI power supply.

Post by In-Tech » Tue Mar 19, 2019 10:18 pm

rfoll wrote:
Tue Mar 19, 2019 9:56 pm
In-Tech wrote:
Tue Mar 19, 2019 7:40 pm
Is this a comedy? It's pretty funny.
Does this mean you have all of the answers?
Simple problem, simple solution is all.
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl

rfoll
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Re: HEI power supply.

Post by rfoll » Tue Mar 19, 2019 10:33 pm

And a number of ways to solve it. I was really surprised that it was so difficult to find an amperage draw for a typical HEI. The MSD 6A will run on the feedback from the idiot light circuit. Were this my car I would do things different, but a low mile first year Malibu makes me give pause to clipping wires and disturbing the ignition switch. This car doesn't even have a single blemish in the factory bench seat.
So much to do, so little time...

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Re: HEI power supply.

Post by In-Tech » Tue Mar 19, 2019 10:50 pm

So take the two wires from the column and starter and hook to a relay and done. No cutting and easy to reverse if you want to.
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl

makin chips
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Re: HEI power supply.

Post by makin chips » Wed Mar 20, 2019 3:39 am

ProPower engines wrote:
Sun Mar 17, 2019 9:39 pm
I would tap into the ignition directly to power the choke and the distributor.
That way you will have a full 13.5 volts when running. the choke is the issue so I would fuse that but if you must fuse the ignition I would use at least a 40-50 amp fuse as the HEI coils draw a lot of juice and some coils I have seen draw 20 + amps.

HEI systems surge upon first power up, some as much as 25+ amperes.

HEI ignition systems should NEVER be fused. A larger wire gage really isn't needed to supply the HEI with adequate amperes to operate way past 8,500 rpms, after initial power up. 14 gage is just fine for that, but it is the power up current draw that requires the larger gage fed wire size.

HEI draw at idle, depending on the coil used, runs about 3.5 to 4.0 amps average at idle speeds, lowers considerably as the engine rpms rise. As the amount of charge time between firing intervals of the coil decrease, the loading also decreases. At idle, there is a large amount of charge time, so the ampere draw is higher, as rpms increase, time between charge intervals decreases, so does the amperage draw.

I have seen as low as 1.8 amps charge draw in a good HEI at above 9,000 rpms.

There are a few diversions to all this, dirty/corroded connections, too large a spark plug gap for the compression resistance, plug wires that have too much resistance, too low an input.

Where have you seen HEI coils that draw all this amperage? I don't claim to know all but I don't remember seeing any HEI coils that draw 20+ amps anytime other than during the initial startup surge.

makin chips
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Re: HEI power supply.

Post by makin chips » Wed Mar 20, 2019 3:40 am

Schurkey wrote:
Tue Mar 19, 2019 4:28 am
Woof. I knew that the HEI drew pulses of current, but I didn't realize they were that great.
Woof? We gonna start mooing next?

What had happened to this place?

Geoff2
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Re: HEI power supply.

Post by Geoff2 » Wed Mar 20, 2019 5:23 am

GM HEI module does NOT surge to 25 amps on start up. In the link I posted earlier in this thread is the complete cct diagram of the HEI. It uses the MJ10012 Darlington Pair [ not a gay couple from South Carolina ] in the output stage to pass the coil current of approx 5.5 amps. The MJ10012 is rated at 10 amps.
I think some are confusing surge with the surge of current when an incandescent lamp is switched on. When cold, the lamp filament has very low resistance, so a large current flows, as the filament heats up, resistance increases, current drops.

The coil is an inductor & when voltage is applied to it, current starts at zero & increases to the max current; & it is not instantaneous as in a surge, it takes finite time.

From GMs info on HEI: " A current limiting cct was added to the HEI module to limit primary current to 5.5 amperes rather than using resistance."

n2xlr8n
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Re: HEI power supply.

Post by n2xlr8n » Wed Mar 20, 2019 6:45 am

makin chips wrote:
Wed Mar 20, 2019 3:40 am
Schurkey wrote:
Tue Mar 19, 2019 4:28 am
Woof. I knew that the HEI drew pulses of current, but I didn't realize they were that great.
Woof? We gonna start mooing next?

What had happened to this place?
From my POV, Circlotron, Geoff2, Tuner, In-Tech (and some I forget) know their stuff with regard to ignition systems. They are the ones I'd take a class with.
He who is in me is greater than he who is in the world.

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Re: HEI power supply.

Post by rfoll » Wed Mar 20, 2019 12:35 pm

In-Tech wrote:
Tue Mar 19, 2019 10:50 pm
So take the two wires from the column and starter and hook to a relay and done. No cutting and easy to reverse if you want to.
I'm going to assume you say "column", you mean steering column. On a 1964 Malibu, the only wire in the steering column is for the horn. The only wires at the starter other than the main battery cable are the purple wire at the start terminal and a black wire with a purple stripe that connects to the coil for a full 12 volts when the solenoid is energized.
So much to do, so little time...

RCJ
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Re: HEI power supply.

Post by RCJ » Wed Mar 20, 2019 12:50 pm

I once traced the resistor wire back till I got 12 volts then ran a 10 gauge wire to the HEI.This worked fine for a while,till I was going about 130 mph and it melted the unchanged wire back to the fuse box.I repaired it as F-bird 88 has suggested.

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Re: HEI power supply.

Post by Tuner » Wed Mar 20, 2019 12:54 pm

makin chips wrote:
Wed Mar 20, 2019 3:40 am
Schurkey wrote:
Tue Mar 19, 2019 4:28 am
Woof. I knew that the HEI drew pulses of current, but I didn't realize they were that great.
Woof? We gonna start mooing next?

What had happened to this place?
baa baaa baaaa bah :roll:

rfoll
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Re: HEI power supply.

Post by rfoll » Mon Apr 08, 2019 9:34 am

Fail. I installed a relay for the HEI triggered by the original resister wire. It started right up and ran fine, but would not shut off. When I touched the resistor wire at the connection to see if it still had voltage, the engine shut off immediately, probably essentially grounded it out. My guess is some sort of feedback is keeping the wire charged. So I rewired it. There is a fused switched source at the panel and it works fine for the ignition on it's own, but had the same problem if I tried to use it to trigger the relay. Anyone have an explanation for me? I would really like to understand this.
So much to do, so little time...

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Re: HEI power supply.

Post by Tuner » Mon Apr 08, 2019 10:07 pm

rfoll wrote:
Mon Apr 08, 2019 9:34 am
Fail. I installed a relay for the HEI triggered by the original resister wire. It started right up and ran fine, but would not shut off. When I touched the resistor wire at the connection to see if it still had voltage, the engine shut off immediately, probably essentially grounded it out. My guess is some sort of feedback is keeping the wire charged. So I rewired it. There is a fused switched source at the panel and it works fine for the ignition on it's own, but had the same problem if I tried to use it to trigger the relay. Anyone have an explanation for me? I would really like to understand this.
Refer to the instructions for MSD CD systems regarding the use of a diode in the wire from the ignition switch to the voltage regulator, so the alternator regulator circuit does not back feed to the ignition switch and so the the ignition. The little diode is included in the bag of miscellaneous parts that comes in the box with MSD 6 etc.

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Re: HEI power supply.

Post by Circlotron » Mon Apr 08, 2019 10:53 pm

Yep, I had that problem once. Putting a diode in line with the alternator light was the suggested fix. I never ended up doing that because I discovered that the engine would stop when you pulled the handbrake on. Probably the brake warning light on the dashboard was enough to shut it down.

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Re: HEI power supply.

Post by rfoll » Tue Apr 09, 2019 10:31 am

Tuner wrote:
Mon Apr 08, 2019 10:07 pm
rfoll wrote:
Mon Apr 08, 2019 9:34 am
Fail. I installed a relay for the HEI triggered by the original resister wire. It started right up and ran fine, but would not shut off. When I touched the resistor wire at the connection to see if it still had voltage, the engine shut off immediately, probably essentially grounded it out. My guess is some sort of feedback is keeping the wire charged. So I rewired it. There is a fused switched source at the panel and it works fine for the ignition on it's own, but had the same problem if I tried to use it to trigger the relay. Anyone have an explanation for me? I would really like to understand this.
Refer to the instructions for MSD CD systems regarding the use of a diode in the wire from the ignition switch to the voltage regulator, so the alternator regulator circuit does not back feed to the ignition switch and so the the ignition. The little diode is included in the bag of miscellaneous parts that comes in the box with MSD 6 etc.
That was my first guess, but I wasn't sure if there could be enough power through the resistor wire to keep a relay closed. I would guess this tells me there is a relay in an MSD 6AL, and thus the reason for the diode.
So much to do, so little time...

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Re: HEI power supply.

Post by Tuner » Tue Apr 09, 2019 11:19 am

It is because the relay or the MSD box require so little amperage to activate. The resistor has so little current flow to resist the voltage drop is not much. Ohms law. Resistors resist amperage, not voltage. Voltage drops on the downstream side of resistance because amperage is reduced by resistance.

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