Shifting question... - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Drift Style S14 · 03-18-2002, 12:51 AM

How would you go about finding the ideal shift points for a 91 240? is there a formula or something? Oh and by the way does anyone play urban terror for quake 3? if you do want to start a 240/zilvia clan?

DuffMan · 03-18-2002, 01:26 AM

The mathematically ideal shift point is where the ratio of the current gear to the next gear is equal to the ratio of the torque after you shift to the current torque.

03-18-2002, 03:24 AM

well thats just dandy but i can't do squat with out a formula an idea of where to start.

240 2NR · 03-18-2002, 10:42 AM

I can't give you a precise formula, but the basic variables you will need are a dyno curve, gear ratios, final drive ratio and the diameter of your tires (i think you need this last one).

http://www.vettenet.org/torquehp.html

this article should give you a good idea of whats going on and why gears and torque are good.

*AceInHole* · 03-18-2002, 10:56 AM

what you want to do is shift so that your next gear lands in your optimal rev range, that's all.
basically, as you rev beyond your peak HP, the HP drops, so revving too far will eventually drop more HP than earlier in the curve, where an upshift might get you.  This means you'll want to know where each gear lands, meaning a shift from 2nd gear at 6500 RPM might mean 4500RPM in 3rd gear.  Once you know these points (you don't REALLY need to know all your gear ratios... all you have to do is drive your car and remember what happens) you can find a general shift point.  A dyno chart would help since it tells you exactly how much power you have at each point, but really you can assume your dyno chart will look like most other 240's...

In the end, I'd say shift between 6 - 6.5k.

03-18-2002, 10:42 AM	#4
240 2NR Zilvia FREAK! Join Date: Dec 2001 Location: Denver Posts: 1,131 Trader Rating: (0) Feedback Score: 0 reviews	I can't give you a precise formula, but the basic variables you will need are a dyno curve, gear ratios, final drive ratio and the diameter of your tires (i think you need this last one). http://www.vettenet.org/torquehp.html this article should give you a good idea of whats going on and why gears and torque are good. __________________ Steve 93 240sx FB currently very clean and for sale

03-18-2002, 10:56 AM	#5
AceInHole Autox Technician Join Date: Dec 2001 Location: New Haven, CT Age: 44 Posts: 3,961 Trader Rating: (0) Rides Gallery: AceInHole Feedback Score: 0 reviews	what you want to do is shift so that your next gear lands in your optimal rev range, that's all. basically, as you rev beyond your peak HP, the HP drops, so revving too far will eventually drop more HP than earlier in the curve, where an upshift might get you.  This means you'll want to know where each gear lands, meaning a shift from 2nd gear at 6500 RPM might mean 4500RPM in 3rd gear.  Once you know these points (you don't REALLY need to know all your gear ratios... all you have to do is drive your car and remember what happens) you can find a general shift point.  A dyno chart would help since it tells you exactly how much power you have at each point, but really you can assume your dyno chart will look like most other 240's... In the end, I'd say shift between 6 - 6.5k. __________________

03-18-2002, 12:51 AM	#1
Drift Style S14 Zilvia Addict Join Date: Sep 2001 Location: ............ Age: 42 Posts: 602 Trader Rating: (0) Feedback Score: 0 reviews	How would you go about finding the ideal shift points for a 91 240? is there a formula or something? Oh and by the way does anyone play urban terror for quake 3? if you do want to start a 240/zilvia clan?

03-18-2002, 01:26 AM	#2
DuffMan Post Whore! Join Date: Oct 2001 Location: in a cardboard box Posts: 2,517 Trader Rating: (0) Feedback Score: 0 reviews	The mathematically ideal shift point is where the ratio of the current gear to the next gear is equal to the ratio of the torque after you shift to the current torque.

03-18-2002, 03:24 AM	#3
Guest Posts: n/a	well thats just dandy but i can't do squat with out a formula an idea of where to start.