launch rpm air cylinder and 2 step questions

I looked through archives concerning this but wanted some answers to direct questions.

I race TD with 540ci/big chief/871-20#/MSD 10+, car runs very consistent and goes rounds. Has very consistent 60's of less than 1 sec. I use air cylinder to launch car at 4200 rpms. I check/reset air cylinder at the beginning of each raceday because of air changes. (somewhat concerned about temps rising throughout the day and changing the launch rpms but hasn't seemed to have any adverse effects yet)

I recently put data logger on and found that the rpms are creeping up about 500 rpms while waiting on tree to drop.

Seeing posts about using 2 step in addition to air cylinder has me intrigued about being able to make my car even more consistent.

So I would like some feed back on how this works for others and how much higher should the air cylinder be set above the two step?

What are the negatives to this setup?

I found the posts about how to setup relays for backing up, so not worried about that part of the setup.

Thanks in advance for the info.

 

RPM Creep

I don't use a pneumatic launch control but I deal with hydraulics and pneumatics in my job, if your cylinder is extending causing your rpm to rise I would look at the valve. It may need overhauled/replaced.

My 2 cents
Corey

 

I had a two step and air throttle on my Hemi TD. According to the data logger it was VERY stable while on the step. I showed a high-to-low spread of 19rpm. No trick to wiring it, just activate the step and the throttle from the same circuit as the brake. As you are aware, some guys recommend a diode. I didn't have one and had no problems. The only reason I took it off is because our local track wasn't good enough to hold a launch using the TBrake so I had to start foot braking.

As for the opening, I opened it to about 1/3 throttle thinking it would be a little rich, but not drown the engine. I didn't want it to go lean. EGTs did not change at all on the step. I think that will be a personal preference on your part. It certainly was on mine.

Hope this helps. I thought it was a pretty simple system. The two step holds a static RPM, and the air throttle limits the blade so the engine doesn't load up.

-Brian