How many of you use an Air Shifter or Electric shifter using a RPM activated switch?

Ok here is my thing. I use an RPM activated air shifter in my footbrake car.

A lot of your dragsters and other door cars that use a delay box to shift on time. This is a feature built in the delay box.

My question is being a footbrake racer I do not use a delay box. So is there a timer you can buy or make to be able to shift on time instead of by RPM?

What are the pros and cons of shifting by RPM versus on time?

I have done it both ways. My Hot Rod car was very consistent on the throttle stop but also had a Biondo 450 delay box with this feature built into it. Oh how I miss that car. Dang Divorce!

Does anyone offer a shift activator for timed activation? Just throwing it out there. All comments welcome.