I just went to a 7531 box and have a lot to learn about it. I've always used a progressive to ramp nitrous in and had great success that way. I was always comfortable that since it pulsed both fuel and nitrous the same that my tune-up was coming in clean.Good question, as we are always needing to kill power on the Launch due to less than tight track conditions.
Here are the options as I see it (to reduce power @ Launch)...
I will leave out the obvious items such taller & wider tires, higher rear gear, higher 1st gear, better suspension or suspension adjustments (shocks, ladder bar or 4 link adjustments, tieing the front end down more or less, etc.), weight changes, tire pressure changes, etc.
(1) Use NO 2 Step, i.e. leave off of the wood with no 2 step (Example: our Converter goes to 4300 Motor with no 2 step);
(2) Build in a 7531 Box Launch Retard Timing Retard & Ramp it for whatever works (Example: motor is @ 33* with 1st stage @ 18*, 2nd stage @ 12* but we set the LR @ 10* total on stage 1 & 2* total on 2 stages & Ramp for 1.0 seconds);
(3) Build in a 7531 Box soft rev limiter "dots" to maintain ERPM & DRPM on the Launch (will depend on car's actual ERPM & DRPM);
(4) Tighten the Converter by sending it off, or at least add thicker John Deere Hy-Guard fluid to lower the stall speed by about 200-300 rpms;
(5) Make sure there is NO Delay in the Retard "on" setting in the 7531 Box (we actually have .20 set as "on" & .05 set as "off", but we needed this because our ERPM & DRPM were actually lazy up to .40 seconds);
(6) Set a Gear Retard to calm the car down once it launches & is down track (I have not used this option yet);
(7) Use a smaller / weaker n20 tune (n20 jetting);
(8) Use a progressive controller to ramp in the power over time or rpms;
I think there is a fine line between getting down the track with power to the ground, and running a tune-up with less power. Trial & error. But as an example, and not that this is impressive at all, but on a loose track, leaving as low as 2* total timing for 1.0 ramp, we still went BEST 144 to the 1/8 on 29.5 x 13.5 tire with old school ladder bar car @ 3350#. Our 60' at 1.26 was worse on 2 stages than our 1.23 best on 1 stage.
Good luck, and I'm sure I did not cover everything.
Good Info on using the 2 step as a launch "softening" tool. I was always going the other way thinking the lower launch rpm would be easier on the tires....
good newsKroid yes its back together!! I plan on making some shake downs in Hattisburg Ms in march we found out a lot of things that were wrong with the car, the chasis shop in Michigan had set the rear suspension up total wrong!!!! When they lower the car it tru the IC completely out of wack an the angle of the upper ARM were screwed up as well and with all of the going on the rear was binded up!!! He also had preload in the right side upper arms with pulled that side of the car down, when we took it a loose that hole side snaped up!!!!! The new shop said John force couldn't drive it like that...Loi I was lucky