Bracket Talk
Dragster gear ratio

This topic can be found at:
https://drr.infopop.cc/eve/forums/a/tpc/f/80760912/m/9227039286

May 05, 2019, 03:50 PM
Bucky
Dragster gear ratio
The top dragster guys are either racing or don't want to mess with slow cars. LOL. So I will post in Tech.

This is unchartered territory for me. Was: Small block rear engine 4 link car. Ran 7.9's with 8000 trap speed.

Added boost, took some test squirts at 10 psi. With terrible tire shake it ran 1.15 60', 4.797 1/8 and 148 mph. Obviously once I knock out the tire shake, the time will improve. I ran out of gear in the 1/4 and was tickling the rev limiter way early so coasted.
Wallace racing predicts 183 mph from that 1/8 mph.(does that sound right?) I'm shooting for low 7's out of this combo bracket racing.

It has a 4.30 gear and 107 rollout tire. I don't mind 8000 mph trap speed. I was showing 10 percent converter slip where I was letting off just after the 1/8th.
Initially I was thinking 4.10 would be my switch to gear. I'm still there 80%. Am I going to regret it? I can't think that this small block will be happy with anything number under 4.0. But I would prefer to not do this twice.
I don't need to rotate the earth and this is not a max effort build.


Foxtrot Juliet Bravo
May 06, 2019, 02:16 AM
racerdude2054
what was your rev limiter set at when you let out, where were you on the track? 1,000 foot?

most likely a 4.10 will be plenty fine
May 06, 2019, 08:45 AM
Bill Koski
A 4.10 is less then a 5% change, doesn't sound as though that will get you to the stripe at the RPM you're shooting for?


TAKE IT TO THE BANK!!!!!
Later, Bill Koski
May 06, 2019, 08:49 AM
Bucky
quote:
Originally posted by racerdude2054:
what was your rev limiter set at when you let out, where were you on the track? 1,000 foot?

most likely a 4.10 will be plenty fine


It was at 8000, but I noticed the setting gives a buffer zone where it starts dripping of 200. So I have some room to adjust there. I'm going to say it started at 900 feet or so where I lifted.


Foxtrot Juliet Bravo
May 06, 2019, 08:50 AM
Bucky
quote:
Originally posted by Bill Koski:
A 4.10 is less then a 5% change, doesn't sound as though that will get you to the stripe at the RPM you're shooting for?


I was thinking that too, but I was probably only at 7800. A little converter work may help too.


Foxtrot Juliet Bravo
May 06, 2019, 08:57 AM
Lenny5160
183 is probably accurate.

In Super Comp, my MPH at each point is 146/182. I've never run the car wide open in the 1/4 but it goes 1.06 4.66 @ 148 in the 1/8. I would expect something in the 7.35 - 7.40 @ 183-84 range in the 1/4.

This is N/A so I don't know how boost changes the 1/8 to 1/4 correlations.


Tony Leonard
May 06, 2019, 10:34 AM
Bucky
Perfect. Thank you!


Foxtrot Juliet Bravo