Your experience foot brake vs. 2 step regarding ET

[FireSale]

Here's my take. If you floor the pedal on a two step set at 3000 or so, the butterflies go wide open and the pump shot from a double pumper is expended with the car on the line. If you rev until you just hear the stutter kick in you still have throttle travel in reserve and get the pump shot when the engine goes under load at launch. I haven't raced enough to tell the difference but I feel more like a racer when I mash the pedal on the last yellow...I mean green light...

Dale

[HandOverFist]

Originally Posted by FireSale

Here's my take. If you floor the pedal on a two step set at 3000 or so, the butterflies go wide open and the pump shot from a double pumper is expended with the car on the line. If you rev until you just hear the stutter kick in you still have throttle travel in reserve and get the pump shot when the engine goes under load at launch. I haven't raced enough to tell the difference but I feel more like a racer when I mash the pedal on the last yellow...I mean green light...

Dale

Kind of how I used to think about it as well Dale, but according to those in the know the engine does not care about that pump shot because of the airflow with all the butterflies WOT. I see them leave fine so it must have merit. -

[Eric Merryfield]

On a two barrel beast like the Gremlin, there is a noticeable difference. With two step the extra accelerator pump shot, can help with reaction time, and car launches tamer, a tick quicker .01 for same launch RPM 60 foot. 1/4 mile no real difference. However the car launches much harder off footbrake and mashing it, and you can adjust your RPM up and down as needed for reaction time.

My fuel injected cars/trucks seem to really like 2 step. Test with dakota a couple of years ago was .02 quicker in 60 foot and .03-.04 quicker in 1/4 mile.

For real accurate data, you would want to datalog the throttle position just to make sure you are at 100 WOT especially if you have wheelstand or hard landings going on also.

[impstocker]

I find this a interesting subject as I have never raced a "real automatic race car" I learned to race with my 68 Impala stocker with the Jerico 4 speed which I just floored the pedal to the desired RPM set on the 2 step (usually 5500 - 6500) So in building my 65 Impala I wired 2 step through a Brake pressure switch with a on/off toggle to activate the system. I assume with a 2000-3500 rpm range I will mash pedal on 2 step.

I will also be running the Holley version 396/325

Building motor now, can't wait to race. This "bench racing" gets played.

Will Lamprecht
1965 Impala I/SA almost finished.