Transbrake Lock Out using MSD Grid

Although I use a delay box that has a transbrake lockout feature, I dislike how the feature works when activated and the method needed to re-set it when the car is not actually making the run.

Using the MSD Grid Output Switch and a 20 amp rated relay with N/C contacts, this what I did.

For the relay wiring, I attached the wire from a fused +12v source to terminal #30 and attached a wire from #87a to the Transbrake PB on my steering wheel. Relay terminal #86 to ignition ON +12v and the Grid Brown /White Output Switch wire to terminal #85.

In Grid programming for the Output Switch I set the RPM ON to 4000 and the RPM OFF to 8000. The Activation Point is 0.01 and Duration is 7.00.

This is how it works. The +12v going “TO” the transbrake PB on the steering wheel is going through the N/C contacts (#30 + #87a) of the relay. This +12v is what is applied to the delay box PB1 or Trigger when the transbrake PB is pushed. As long as the engine rpm is less than 4000 rpm this +12v is present. So if you use the TB PB to back up it’ll continue to work normally after released and pushed again anytime later.

On the starting line with the throttle matted and engine at launch rpm, the delay box times out and removes the +12v Transbrake / Launch output ( or if no-box racing releasing the TB PB), starts the “Time From Launch Timer” in Grid. With the engine over 4000 rpm, 0.01 after Launch the Output Switch turns ON activating the relay. The N/C contacts that provide +12v to the TB PB now open. This removes the +12v at the TB PB for a Duration of 7 seconds as long as the engine rpm is over 4000 rpm but less than 8000 rpm.

Besides working in both delay box and no-box, this wiring method is “Legal” in all N/IHRA classes because it is wired going “to” the TB PB and not from it.

The way I read this,(if correctly understanding) the "time from launch timer" setting in Grid can be used as a transbrake release DELAY function without having a Delay Box wired into the car...

Please correct me if I misunderstand...


Dan

quote:

Originally posted by Mad Dog:
The way I read this,(if correctly understanding) the "time from launch timer" setting in Grid can be used as a transbrake release DELAY function without having a Delay Box wired into the car... Please correct me if I misunderstand...

Any Delay period would happen “prior to” the Removal of +12 from the Launch input to Grid. Grid is only capable to output a timer function “After” the release of Launch which starts the “Time from Launch Timer” that controls the Output Switches.

Grid offers as many of these Output Switch RPM / Timer outputs as you may need. They are available in the MSD 7760 3 Stage Delay Timer module that attaches to the MSD 7740 CAN-bus hub.

There's no need for a trans brake lock out to be so complicated. Just use 2 buttons. The chances of applying 2 buttons by accident, and the same time are less than some type of electrical malfunction when using all this other stuff. There's an added bonus also. Have you ever staged then somehow not got the perfect pressure on your button? With 2 buttons you can get the perfect pressure, placement ect. on your "real" button before you stage. When you're staged just press the other button to apply the trans brake.