Msd
 

hi, I see how MSD wires their relay 8961 into two step and clutch switch.
how does it switch from high side to low side?? the instructions in book doesn't tell you anything . I tried calling all three numbers, and no answer. do you have to install a switch , to select high side and low side ? just curious, as going to install the relay in a clutch car. like to know before hand. thanks

Re: Msd
 

Re: Msd
 

The red wire from the two step, connected to and energized by the 8961 Relay controls the high/low function when used with a clutch switch.

http://www.jegs.com/InstallationInst...1/121-8961.pdf
(See Figure #6)

Hope this helps!

Re: Msd
 

The high side on the 2 step is always active. The low side is activated when power is applied via a switch.

Re: Msd
 

hi, ok, if the line lock sets the low rpm, how do you do a burnout? won't have enough rpm to spin tires, prob slip clutch? I do my burnouts on high side, then switch to low side for launch now. I want to use their relay and rewire my system.

Re: Msd
 

I think that if you want to control leave, burn out and high side rpm you would need a 3 step......or a switch to turn off 12 volts to the 2 step module with the line lock energized for your burn out

If you put in a switch there will be no RPM limiter for the burn out...

Bob

PS: Remember to turn the switch back on after burn out!!!!!!!!!!!


Are you running an automatic or stick???????????????????????????//

Re: Msd
 

I may have missed something here, but aren't you using the line-lock/low-side limiter for your burn-out's?

If you need a burn-out, launch AND over-rev protection, you'll need to follow Bob's advice and get a 3-step switch to work with your MSD and relay (although unless you'll be controlling a high-amperage circuit, you may not need one).

MSD has all of their wiring schematics, cross referenced by unit number, on their website, as well as a very handy smartphone app, to help if you need it.

Re: Msd
 

I just use my right foot to control burnout RPM...seems a whole lot simpler and less stressful on the engine.
Then the switch on the clutch pedal runs the low side limiter.

Re: Msd
 

Jim, I understand your point about wiring the line lock and low RPM two step together being a problem for burnouts but if the RPM is too low for clutch lockup wouldn't the simplest solution be to just add another inline switch to override the two step during burnouts only? Just switch it back on after the burnout?

Re: Msd
 

Why not use a 3 step. Burnout/launch /top end MSD # 8737 about $100 I have a new one sell it for $60 plus mail. Fed387

Re: Msd
 

If you add a diode in the latch circuit it will drop the two step out when the clutch releases,


I'll try to attach a wiring diagram.
Gary

Re: Msd
 

This uses an MSD relay and a second bosch style relay to ground the brake light circuit. This lights the "brake" light on the dash when the linelock is activated.


When holding the shifter button for the burnout as soon as the clutch is released it drops out the two step so it goes to the high limit.


With clutch depressed the shifter button will latch the circuit so you can let the shifter switch go before launching.
Gary

Re: Msd
 

hi, ok, a switch is in so can switch between high and low side, thanks .

Re: Msd
 

Re: Msd
 

If you use a 3 step or even just a 2-step you need a toggle switch in line on the output of the relay that you turn on AFTER burnout. The line lock still works in the burnout and with that switch turned on now the line lock and rev limiter work with the foot pedal switch but only after activated by the line lock button. I use the same method in both my stick and auto cars. I have a youtube in car video also. As far as the 3 step MSD 7al 3 box goes, launch and burnout have their own rev limiters but LAUNCH always takes precedence over burnout if both are active at the same time, which they always are in my car on the launch because linelock controls burnout for me and foot pedal controls launch. If you don't want or need a burnout limiter just pull the chip out.

Re: Msd
 

With the 2-step I don’t use a toggle switch and don’t see the need for one. If I knew how to draw a wire diagram to show you how I did it, I think it would help. My sketch here sucks but I hope you get the point. Both switches have to be activated to complete the circuit(clutch pedal down and line lock pressed) and if either one is released it brakes the circuit and switches back to the high side. In the past we used a toggle switch but was forgotten about to many times. We also run cameras in our cars and that’s how we figured out that we weren’t flipping the switch. I’m no electrical engineer so maybe my way is a little sketchy but it has worked flawlessly for 3 years.
Brett

Re: Msd
 

It's called series wiring the 2 switches. Both switches must be activated to apply voltage to the 2-step. It will work them same way with using the brake light switch and line-lock for automatic cars.
Dan

Re: Msd
 

I use a 3 step burnout, starting line, high side. I rev up to about 7500 in the water and let the clutch out.