starter relay needed? ????

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swifter

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So were in our final stages of wiring the drag car and got a question-we run a pos. Cable from battery up to starter-the momentary switch on the dash is 30amp-do i still need a relay.since were going from the switch to the neutral safety on the shifter down to the starter. Thanks Steve
 
I would think so, relay will keep the high volts away from your wiring to your dash switch, a must do I believe.. but lets see what our racing techs say .
 
Always run a relay on anything high voltage/ amperage. it takes the load off your switches and controls - other wise running 90-125 amps thru the ignition switch will heat it up and cause intermittent connections on anything that gets power from the ign switch
 
I lost you on how the NSS fits into your plans. Don't run anything but a small relay coil current thru that.

You could probably control the starter solenoid directly w/ a 30A manual switch. I might guess it draws ~20 A. The main starter current (>100 A) will still flow thru the thick cable from the battery I assume. You must have a relay to use the NSS, and probably not safe (or allowed) to not use it. You can use a standard 40A "automotive relay". They do so in modern Mopar cars.
 
What you are thinking of doing is IMO fine, but kinda defeats the whole purpose of having a relay. The oem relay is under the hood, between the battery and the starter, to provide as short a wire run as possible, to deliver as much current as possible, with as little heating as possible.The starter solenoid does draw a considerable amount of juice.
By bringing that current into the cabin, you are creating a much longer wire loop, and bringing an unfused high current wire through the firewall, and into close proximity to all kinds of sharp metal edges.Better it would be to trigger the oem relay with the momentary.That could be a 14 or 16ga wire and easily fused. Your ignition sw will love you for it.
All your other high current devices should be similarly relayed, with the relay wired between the device and the battery with as short a wire run as possible, and outside of the cabin, and either fused or fuse-linked. The trigger sides can then be run off a switch in the cabin and through the Ig,sw. and a fused source.
High current devices include;pumps,fans,solenoids,A/C clutchs,capacitor discharge ignitions and high-powered headlights.
Look under the hood of any modern EFI vehicle. You will find a power control center where all those relays are mounted. The factory is keeping the high-current out of the cabin.
Just trying to be helpful
 
I don't know of any aftermarket NSS (shifter mount) that will handle the juice without relay

the facotry NSS cannot be wired without one as it goes to ground

You must have a NSS under race rules
 
What r u guys talking about???? What load???? We have a 00 xable from batt to starter all we r doing is pulling the starter solenoid in. Im confused-the factory used a #14 ga. Wire. Thanks steve
 
If your neutral safety switch can handle the amperage , some of those micro switches on aftermarket shifters are pretty light duty and would be fine to provide a ground for a relay, not so sure about current passing through them, even though it may only be 20-30 amps.

One thing with using a relay you know you will be OK , I like the idea of overkill when it comes to wiring so I don't have to worry about something failing .

A lot of guys running drag cars have the battery in the trunk and use a ford style solenoid near the battery so you only have you main cable hot during cranking and mount a relay at the rear to energize the solenoid.
 
swifter said:
What r u guys talking about???? What load???? We have a 00 xable from batt to starter all we r doing is pulling the starter solenoid in. Im confused-the factory used a #14 ga. Wire. Thanks steve
Click to expand...

The load of the starter solenoid. Mopar solenoids draw a fair amount of amperage. The shifter mount NSS I've see are micro-switches, and should have a relay. You don't have to use a mopar relay, just use a good heavy relay.

Maybe I lost somethin in the thread. Wat you using for nss?
 
u are right swifter, the big positive wire is direct to starter. use a 12 wire to pull in and go
 
I guess i didnt think the solonoid pulled that much power, i apologize if u took me the wrong way im very grateful for the help ALWAYS-i guess i still dont understand the stock wiring then, any Mopar ive had barely had a 14 or 12 ga. Wire to the solonoid from the relay, so i understand what am i not getting? ??
 
Well theres something Im not getting either. Theres already a relay there, and its already in the right place; so...What would be your thinking on not wanting to use it?

Hey,waitaminute. That circuit is only energized for a couple of seconds at a time.A 14 wire will never get hot. I still agree with post #6 though.
 
This is a full out drag car -no street and it is gutted and we are rewiring from nothing-sorry if i didnt say that.steve
 
Thanks Aj-i fully understand post #6 -good explanation but since this is a 8 circuit race car we r extremely cautious about any sharp edges and routing of wires.steve
 
It is hard to explain, but I will put down a few things for you to do additional study on by looking up and reading about.
A starter solenoid is an inductor. It draws several amps. it slides the bendix, and closes large contacts that turn on the starter motor. To turn on an inductor is easy, the current starts at zero, and builds in time to what is limited by the circuit resistance. You can measure the resistance of the solenoid and use Ohms law to estimate the current.
The interesting part is turning off the solenoid is the hard part! When that happens the current is high, the inductor stores the current, the voltage increases, the switch contacts may weld, keeping starter engaged. It is the inductive kick, similar to the operation of ignition coil.
So that is a reason to use a relay that is designed and rated for the purpose.
A relay coil typically draws tenths of an amp, the circuit is easily wired with a NSS as an interlock at the low current.
 
swifter said:
I guess i didnt think the solonoid pulled that much power, i apologize if u took me the wrong way im very grateful for the help ALWAYS-i guess i still dont understand the stock wiring then, any Mopar ive had barely had a 14 or 12 ga. Wire to the solonoid from the relay, so i understand what am i not getting? ??
Click to expand...

I think you'll find that wire is at least 12. The "tractor" or universal starter buttons are fine, as long as the wiring is large enough, that is not the problem. Problem is the NSS cannot handle it, and a stock switch is in ground circuit.
 
The nss handles it just fine in the factory circuit. Hes only wiring the momentary and the nss on the signal side of the relay, just like the factory did. He is merely changing the location of the relay, and the caliber of the relay.
OP; To pull a quote from post 6
"What you are thinking of doing is,IMO, fine"
 
Hotwire harness for hemi uses a 30 amp relay for the starter , Seems to be the norm for that circuit.
 
Took all the advice and wired in the stock mopar relay to remove any load on N.S.S.-ran ground on relay thru the N.S.S..thanks guys-steve
 
AJ/FormS said:
The nss handles it just fine in the factory circuit. Hes only wiring the momentary and the nss on the signal side of the relay, just like the factory did. He is merely changing the location of the relay, and the caliber of the relay.
OP; To pull a quote from post 6
"What you are thinking of doing is,IMO, fine"
Click to expand...

I'm talking about he was trying to figure a way to remove the relay. From his last post sounds like he's on it.
 
Yep on it-after I thought about it, didnt want to take that much amperage thru the neutral safety -f.a.b.o comes thru again - Thanks -steve
 
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