Nitrous Pro Mod Trans/Ratio

[TOL]

Am I correct in assuming that most of the nitrous Pro Mods (Outlaw or otherwise) still use a 4-speed CS-2 for quarter mile stuff?

Can someone please give me a ballpark idea for the trans ratios, and rear gear, that are common for say a 706 Buck motor with either a 34.5 or a 36 rear tire? A rough baseline would be very helpful.

Why is a CS-2 used as opposed to a CS-1 by the nitrous guys? Is it weight, or strength, or less rotating inertia, or?...

[Jason Bunker]

Thats a good set of questions, why has nobody responded?

[T/S 3477]

CS2 is the tranny of choice--I believe it is lighter than the CS1 and it is reliable. Most of the nitrous cars are using the Goodyear 1022 tire (34.5"), 4.10 rear and 2.20's-2.30's for the 1st gear tranny ratio.

[The Professor]

If you are running a 5.0 bore center motor with 3 stages I would suggest a 2:25 or 2:30 first gear and 4:10 gear if it a 4.840 bore center motor I would suggest a 2:35-2:37 1st gear with a 4:10 or 4:30 gear. The goodyear 1022 is probably the best tire to run. The 1230 or 1430 is usually used for cars that run alot of 1/8 mile racing and takes a lot of horespower to turn and adds about another 40lbs to the car.

[TOL]

Thanks all.

Professor, this is a half water Donovan 4.840 HC700. Two stages currently, contemplating a third. Curious why the ratio difference between 4.840 and 5.000. Is it to do with bore strength?

If I may, in general terms, what are people doing for N20 control & timing? Stages 1& 2 right at the hit, and stage 3 some delay later? Simple on/off or progressive control of the stages? Pulsed?

[T/S 3477]

The 5" bore motors make more bottom end torque, hence the need for a numerically lower 1st gear to control the power and tire speed. Most guys are using the "simple on/off" method for applying the nitrous--1st stage on when the clutch drops, 2nd around .6 and 3rd around 1.6.