quote:

Originally posted by markemark:

quote:

If using a high amp alternator be sure to use at least a 2ga wire

Agreed on the 2 gauge minimum. If tying the alternator wire to the starter (my preferred method) using the same size wire on alternator as battery to starter is a wise choice.

So, how does the shut off switch work if the engine is running and the alternator is charging?

quote:

Originally posted by Goob:

quote:

Originally posted by markemark:Agreed on the 2 gauge minimum. If tying the alternator wire to the starter (my preferred method) using the same size wire on alternator as battery to starter is a wise choice.

So, how does the shut off switch work if the engine is running and the alternator is charging?

2 gauge from battery to starter and continuing to the alternator does Not run through the Master Cutoff.

quote:

Originally posted by Goob:

quote:

Originally posted by markemark:

quote:

If using a high amp alternator be sure to use at least a 2ga wire

Agreed on the 2 gauge minimum. If tying the alternator wire to the starter (my preferred method) using the same size wire on alternator as battery to starter is a wise choice.

So, how does the shut off switch work if the engine is running and the alternator is charging?

Four post master disconnect switch.

quote:

Originally posted by SP 124X:

quote:

Originally posted by Goob:

quote:

Originally posted by markemark:

quote:

If using a high amp alternator be sure to use at least a 2ga wire

Agreed on the 2 gauge minimum. If tying the alternator wire to the starter (my preferred method) using the same size wire on alternator as battery to starter is a wise choice.

So, how does the shut off switch work if the engine is running and the alternator is charging?

Four post master disconnect switch.

My Master Cutoff removes power to Only the relay board stopping all electrical functions. The starter, alternator, ignition, EFI ECU and digital dash remain powered. Legal.

Although I agree that a 2-gauge cable is OK from the alternator, it is overkill and not necessary. In my opinion, it would add unnecessary bulk. An 8-gauge cable is completely acceptable.

Powermaster rates their alternators at idle using a pulley ratio of 3-1 at 800 rpm, or 2400 rpm alternator speed.

Mr. W

Smaller the wire the larger the voltage drop per foot. 8 ga for less than 5 feet is fine. 5 to 10 is like 4 ga recommended ect, ect. Do not get me wrong LOTS of cars use a 8, and work fine.....

quote:

Originally posted by markemark:

quote:

Originally posted by SP 124X:

quote:

Originally posted by Goob:

quote:

Originally posted by markemark:

quote:

If using a high amp alternator be sure to use at least a 2ga wire

Agreed on the 2 gauge minimum. If tying the alternator wire to the starter (my preferred method) using the same size wire on alternator as battery to starter is a wise choice.

So, how does the shut off switch work if the engine is running and the alternator is charging?

Four post master disconnect switch.

My Master Cutoff removes power to Only the relay board stopping all electrical functions. The starter, alternator, ignition, EFI ECU and digital dash remain powered. Legal.

You need to review the 2023 NHRA Rulebook

Section 21, Page 29
General Regulations 8:4
MASTER CUTOFF

Absolutely not legal or safe.
A track official or your crew MUST be able to go to the back of the vehicle and STOP ALL OPERATION with a SINGLE SWITCH.

quote:

Originally posted by Goob:
You need to review the 2023 NHRA Rulebook

Section 21, Page 29
General Regulations 8:4
MASTER CUTOFF

Absolutely not legal or safe.
A track official or your crew MUST be able to go to the back of the vehicle and STOP ALL OPERATION with a SINGLE SWITCH.

Read the rule Dave. It states “must stop all electrical functions”. The relay board that is powered through the Master Cutoff in the rear of my car controls ALL electrical Functions. No power to Relay board NO Electrical Functions. NO ignition on, NO fans, NO fuel pump, NO starter……NO Nothing!

Nowhere in the rule does it state that power is removed from the vehicle, Because it’s NOT.

BTW, I’ve been through this rule on multiple forums.



8:4 MASTER CUTOFF
Mandatory when battery is relocated, or as outlined in Class
Requirements. An electrical power cutoff switch (one only) must
be installed on the rearmost part of each vehicle and be easily
accessible
from outside the car body. This cutoff switch must be
connected to the positive side of the electrical system and “must
stop all electrical functions” including magneto ignition. The off
position
must be clearly indicated with the word “OFF.” If switch
is “push/pull” type, “push” must be the action for shutting off
the electrical
system, “pull” to turn it on. Any rods or cables
used to activate the switch must be minimum 1/8-inch diameter.
Plastic or keyed switches prohibited. Switches and/or controls
must be located behind rear wheels on rear-engine dragsters.

quote:

“must
stop all electrical functions” including magneto ignition.

Which part of that is hard to understand?

The vehicle must completely shut off, by that switch. Period.

Allowing for different electrical layouts, like relays and whatnot, it still doesn't answer the question....how do you isolate alternator output from continuing to power the systems?

Your wording was vague at best.

quote:

My Master Cutoff removes power to Only the relay board stopping all electrical functions. The starter, alternator, ignition, EFI ECU and digital dash remain powered .

Your statement contradicts itself.
Making this way too hard.

Let me make it simple....
If someone moves the master switch to the off position while the vehicle is running, does it stop?

^^^^^^^^^^^^^

Without discussing if turning off the master disconnect would instantly kill all functions and the engine would instantly stop, the drawing above still doesn't remove the fact that there is still power going to major areas of the vehicle and could cause a fire (short circuit) on its own.

I been using a 1 wire 100 amp gm alternator for 20 years. Use large pulley and continuous cycle solenoid to kill everything by switch. Back when they used to tech, always passed.

Over time, eyes start fading so 4 years ago added cheap digital display for votage down track.

Used a small pulley in old days for a short while, 3 spd and 5.14 gears made alternator sound like a turbo and wore bearings fast.

quote:

Originally posted by markemark:
^^^^^^^^^^^^^

Great, that sort of clarifies your wiring strategy.

But, what happens when the starter solenoid sticks and you need to stop it?

quote:

Originally posted by Goob: what happens when the starter solenoid sticks and you need to stop it?

Okay.
Sure made a simple deal complicated, in my opinion.

quote:

8:4 MASTER CUTOFF
Mandatory when battery is relocated, or as outlined in Class
Requirements. An electrical power cutoff switch (one only) (one only) must
be installed on the rearmost part of each vehicle and be easily
accessible
from outside the car body. This cutoff switch must be
connected to the positive side of the electrical system and “must
stop all electrical functions” including magneto ignition. The off
position
must be clearly indicated with the word “OFF.” If switch
is “push/pull” type, “push” must be the action for shutting off
the electrical
system, “pull” to turn it on. Any rods or cables
used to activate the switch must be minimum 1/8-inch diameter.
Plastic or keyed switches prohibited. Switches and/or controls
must be located behind rear wheels on rear-engine dragsters.

Adding another disconnect is against the rule.

quote:

Originally posted by Wild Wild West 2:

quote:

8:4 MASTER CUTOFF
Mandatory when battery is relocated, or as outlined in Class
Requirements. An electrical power cutoff switch (one only) (one only) must
be installed on the rearmost part of each vehicle and be easily
accessible
from outside the car body. This cutoff switch must be
connected to the positive side of the electrical system and “must
stop all electrical functions” including magneto ignition. The off
position
must be clearly indicated with the word “OFF.” If switch
is “push/pull” type, “push” must be the action for shutting off
the electrical
system, “pull” to turn it on. Any rods or cables
used to activate the switch must be minimum 1/8-inch diameter.
Plastic or keyed switches prohibited. Switches and/or controls
must be located behind rear wheels on rear-engine dragsters.

Adding another disconnect is against the rule.

On my car I have the PUSH OFF mechanical master power switch in back of car. I also added an electrical master cutoff down line that I can operate from inside the car. Note the mechanical in the rear of car is right at battery NOTHING works if it is off. Electrical switch inside will only work if master mechanical is on. When I did that I checked and was legal like that.

Yes, it must kill battery, motor, fuel pump and everything.

Also there has been some discussion here in the past about having one Electrically operated Master Switch. Some say you can not do that but some new high end dragsters are made that way from factory and they are approved.
The advantage of the switch inside is for me to be able to kill power immediately from inside car. Usually I leave master switch in back on all day at the track and and use inside switch to kill power between rounds. Sometimes mere seconds can make a big difference. The disadvantage is it is something else that can fail.

The solenoid only isolates alternator from battery in mine. Everything forward of master switch is cut off with master. Solenoid activated by master switch.

Digital voltmeter comes of ign/fuel/water/fan power supply. Had issue with Alt doing strange stuff downtrack. Now is min of 14.5 day and 14.2 night with lights on after shift.

Have been running sep ground to Alt case for years. Went to tighten belt and Alt case was welded to head.