air throttle GPM

We have a chevy with a D rotor psi @100% and automatic. Launching with 4100rpm on the 2 step and blades set to 23psi the car intermittently drops cylinders too cold and won't come up on the two step. I installed a 2 step leanout and it helps but has not cured it. It looks like anything more than 3.9GPM on the two step loads it up. The egts average 7-800.
With a lean main jet It went fast but had crispy plugs and high egts. That was 14.1 gpm at 8000. I richened the main .015 on the next hit and it fell on it's face again on the starting line when the fuel flow increased.I did not lean the 2 step when I changed the main.
Any thoughts on how much I can dump on the two step before it's dangerous?
Also does 14.1 gpm at 8000 sound lean. The chevy seems a little thirstier than the hemis I compare.

thanks Mike

 

I use 2 dump solenoids while on the 2 step... 1 has no jet in it at all ( equivalent to a .130 jet) and the other has a .030 I run 13 gpm with a roots 50% over so Ide say your lean with a screw

 

If you're not leaving with the blades at WOT I wouldn't dump any fuel. The fuel flow @ 8000 seems fine, that's roughly 15.8x at 9000. I'd say your stage temp, 700-900 are way too hot, 600-650 is ideal to me. Numbers 1 & 2 will kick fuel out regardless, you could almost put those on 30# nozzle checks as they're always cold with 2 step/converter/screw. I use a .900 Waterman and a 2 Step, no fuel bleeds, and I only have 3.5xG through the meter. My two step is at 4000 and the blades are around 4500 without being governed. Id either close your blades more and adjust your stage circuit, or bleed off .5g via a normall closed Whitey Valve. You could always put them at WOT and bleed off an appropriate amount of fuel.

Brandon Booher
NHRA TAD #34

 

2 step

Brandon, it sounds like your blades/barrel valve must be closed more than mine since your gpm is that low without a leanout.
I've got several different issues with the airthrottle. It makes a dogleg on the rpm graph when the pedal is matted. It takes almost .5 to get through that and hit the 2 step. If the tree is slow it's fine. On a quick tree the rpm doesn't get there and it leaves like a pig.
I was thinking about opening the blades further or giving it more timing on the brake so it will hit the 2 step harder. That's the only reason i've been leaning it out on the two step.
The car will 60ft hard if it gets to the 2 step even with colder egt's.
Almost everyone in ADRL is leaving with the blades wide open but the belt carnage is not acceptable to me. We have 17 hits on a 11mm that we bought used so far.
Also, my fuel system puts a lot of fuel in the hat. 2-86, 2-87 with checks on 2 of them.I wonder sometimes if it's loaded up so bad it needs time to cleanout at stage. The driver cleans it out once before staging but it never really seems clean until it's WFO.