RPM dip doing onto stop, w/ racepak graphs

[triplezero]

Originally Posted by Lenny5160_v2

This setup is pretty similar to mine, although you have more power and are 200 lbs lighter.

Shifting on time would cost a lot of MPH. I wouldn't do that. I'd probably go up a bit on the cruise RPM to 4300 or so.

I go on the stop at .500 to get things moving. You seem to have a similar thought. Moving that timer would be a good thing to try, but I don't know which way might be helpful in this case.

Do you have a crossover hose on your carb bowl vent tubes? Maybe some fuel slosh.

Intermittent issues are always the worst.

I'd like to go to a higher cruise but with a higher cruise I'll have to run more numbers and then I'll be coming off the stop and shift right away, so I was thinking if I do go higher cruise then try to move the first number from .4 to .3 or .25 to help keep the second number under 2.4 seconds and keep the run at the shift.

Yes, on the crossover tube.

[Lenny5160_v2]

Originally Posted by triplezero

I'd like to go to a higher cruise but with a higher cruise I'll have to run more numbers and then I'll be coming off the stop and shift right away, so I was thinking if I do go higher cruise then try to move the first number from .4 to .3 or .25 to help keep the second number under 2.4 seconds and keep the run at the shift.

Yes, on the crossover tube.

I don't think you need to worry about the stop/shift relationship with a higher cruise RPM. It still needs to load the converter and then run up to the shift point. Not much will change there.

[J&S Racing]

I chased that creep for a long time. Ended up being the converter

[JP1738]

I go on at .30, cruise at 4250-4300 with a CO2 stop and a really fat 30 year old carburetor. That set-up has been pretty good to me in 1/4 mile SST. 383 sbc at 2830lbs (6.30s W/O at that weight), usually 137 mph depending on weather and track.

I change mine to shift on RPM when I run 1/8th mile SST or any S/G, but I use the same .30 on and cruise speed, just add numbers on the back end. Just changing the shift to RPM usually gets me close to 6.90 given I have to go around 7.25 to the 1/8 to get me 10.90 in the 1/4 when shifting on time.

It does dip a bit, but not enough to hear or affect much. I can see it on my Mega 400 RPM playback but the resolution is not very fine. Might be worse than I think it is but I think I'd rather just not know. Ignorance is bliss.

Despite being slow, I'm more of a "get me close and figure it out before the finish line" kinda guy. Also never really had a T-stop ratio, I just try to get it close.