Optimum shift points - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

///M3_SPb · 10-09-2003, 06:18 AM

I am getting a redtop sr soon, and i will drive it stock for a while, i would like to calculate the optimum shift points, but i am not exactly sure of all the factors of equaiton. I have also heard the opinion that for the best acceleration, you have to shift so that your next gear will be in your torque peak. Can anyone state the equation I would have to use. Thank you

nrcooled · 10-09-2003, 07:41 AM

The best way to find your shift points will be to dyno your setup. Find your peak numbers and optimum RPM points. On my setup I stop making power at 7000 RPM so I try to shift at that point and it drops me in the sweet spot for the next gear.

On a bone stock SR (which I had) I stoped making power at 6200 RPM so it was silly to take it higher then that. I less restictive exhaust and higher PSI will allow you to make a little more power higher up.

cliffs notes:
1. Dyno YOUR setup and get numbers
2. Shift where YOUR SR stops making power
-Every SR is different and each persons powerband is slightly diffent from mods

///M3_SPb · 10-09-2003, 01:34 PM

but i have heard that for example to get to 4200 in different gears you have to shift at diffent points in previous gears.

So for example to get to 4200 in 2nd you have to shift at 6500 at 1st, to get 4200 in 3rd you have to shift at 6000 at 2nd and so on and that depends on your gear ratios.

nrcooled · 10-09-2003, 08:14 PM

As for gear ratios I have no clue. I have never sat down to crunch the numbers. Sorry I can't be more help. I would just find your optimum shift points for your engine then get calculations to find them.

In my car, as long as I shift after 6500 it will drop me back into boost.

240Dave · 10-09-2003, 08:21 PM

Hrm, I really don't know whether this is true or not, but...

In turboed cars with a boost guage, use it to determine shift points rather than tach...unless ofcourse you redline and are still building boost, in which case you need to rev higher

Sound right?

nrcooled · 10-09-2003, 08:24 PM

With the t2small I make full boost (14lbs) at 5000RPM but my dyno had me making power all the way to 7 grand

Take it for what it is...but it still is possible to be at full boost and still be making power after you make your target PSI

Red · 10-09-2003, 10:39 PM

I always thought the rule was... Shift at redline... Use every gear all the way... Dont do un needed shifting becus it slows you down more then you know.

*ca18guy* · 10-09-2003, 11:23 PM

To find the optimum shift points you need a graph of your torque/HP curve and the gear ratio's of your tranny. You need the gear ratio's so you know which RPM the engine will drop to when you shift. Pretty much you need to shift when your at a point where the next gears RPM will have more torque/HP then the last gear. Best way would be find how many RPM's it will drop after each shift and graph that window over the most meaty part of your dyno (the part with the most HP/TQ in the 'window')in each gear (all this probably makes no sense so I'll try to google some links)

Anyway I think its all useless, I would prefer to shift by feel because lets face it we can't be staring at the tachometer the whole time. I'd goto a drag strip and finding which shift combo works best :P

Heres the best link I found--> http://www.datsuns.com/Tech/whentoshift.htm

*exitspeed* · 10-10-2003, 03:57 PM

Gracphing your car really helps to find the right shift points but...

For example on my 2000 eclipse GT I stopped making power at about 5500rpms. However when I ran my best times I always shifted at redline, 6200rpms. It made at least a .2 sec diffence in my 1/4 mile times. So I really think it depends on more things. Practice, trial and error, and track time is the best way to find out, IMHO.

10-09-2003, 06:18 AM	#1
///M3_SPb Join Date: Sep 2003 Location: richmond hill Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	Optimum shift points I am getting a redtop sr soon, and i will drive it stock for a while, i would like to calculate the optimum shift points, but i am not exactly sure of all the factors of equaiton. I have also heard the opinion that for the best acceleration, you have to shift so that your next gear will be in your torque peak. Can anyone state the equation I would have to use. Thank you

10-09-2003, 07:41 AM	#2
nrcooled Nissanaholic! Join Date: Mar 2002 Location: Turn 8 'bout to get rolled by a SC'd ITR Age: 45 Posts: 1,849 Trader Rating: (0) Feedback Score: 0 reviews	The best way to find your shift points will be to dyno your setup. Find your peak numbers and optimum RPM points. On my setup I stop making power at 7000 RPM so I try to shift at that point and it drops me in the sweet spot for the next gear. On a bone stock SR (which I had) I stoped making power at 6200 RPM so it was silly to take it higher then that. I less restictive exhaust and higher PSI will allow you to make a little more power higher up. cliffs notes: 1. Dyno YOUR setup and get numbers 2. Shift where YOUR SR stops making power -Every SR is different and each persons powerband is slightly diffent from mods __________________ '91 hatch w/ SR Sold; '03 Evo Sold 401 HP; '03 MS Protege sold; '00 Evo 6.5 TME Sold 300HP

10-09-2003, 08:14 PM	#4
nrcooled Nissanaholic! Join Date: Mar 2002 Location: Turn 8 'bout to get rolled by a SC'd ITR Age: 45 Posts: 1,849 Trader Rating: (0) Feedback Score: 0 reviews	As for gear ratios I have no clue. I have never sat down to crunch the numbers. Sorry I can't be more help. I would just find your optimum shift points for your engine then get calculations to find them. In my car, as long as I shift after 6500 it will drop me back into boost. __________________ '91 hatch w/ SR Sold; '03 Evo Sold 401 HP; '03 MS Protege sold; '00 Evo 6.5 TME Sold 300HP

10-09-2003, 08:24 PM	#6
nrcooled Nissanaholic! Join Date: Mar 2002 Location: Turn 8 'bout to get rolled by a SC'd ITR Age: 45 Posts: 1,849 Trader Rating: (0) Feedback Score: 0 reviews	With the t2small I make full boost (14lbs) at 5000RPM but my dyno had me making power all the way to 7 grand Take it for what it is...but it still is possible to be at full boost and still be making power after you make your target PSI __________________ '91 hatch w/ SR Sold; '03 Evo Sold 401 HP; '03 MS Protege sold; '00 Evo 6.5 TME Sold 300HP

10-09-2003, 10:39 PM	#7
Red Zilvia Addict Join Date: Feb 2002 Location: Vancouver, WA - Portland, OR Age: 43 Posts: 734 Trader Rating: (0) Feedback Score: 0 reviews	I always thought the rule was... Shift at redline... Use every gear all the way... Dont do un needed shifting becus it slows you down more then you know. __________________ http://www.cardomain.com/memberpage/509537 http://www.imagestation.com/album/?id=4287415487 http://www.zilvia.net/f/showthread.php?t=21036

10-09-2003, 01:34 PM	#3
///M3_SPb Join Date: Sep 2003 Location: richmond hill Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	but i have heard that for example to get to 4200 in different gears you have to shift at diffent points in previous gears. So for example to get to 4200 in 2nd you have to shift at 6500 at 1st, to get 4200 in 3rd you have to shift at 6000 at 2nd and so on and that depends on your gear ratios.

10-09-2003, 08:21 PM	#5
240Dave Zilvia Member Join Date: Aug 2003 Location: . Posts: 241 Trader Rating: (0) Feedback Score: 0 reviews	Hrm, I really don't know whether this is true or not, but... In turboed cars with a boost guage, use it to determine shift points rather than tach...unless ofcourse you redline and are still building boost, in which case you need to rev higher Sound right?

10-09-2003, 11:23 PM	#8
ca18guy Premium Member Join Date: Jul 2001 Location: Clearwater FL Age: 41 Posts: 3,226 Trader Rating: (0) Rides Gallery: ca18guy Feedback Score: 0 reviews	To find the optimum shift points you need a graph of your torque/HP curve and the gear ratio's of your tranny. You need the gear ratio's so you know which RPM the engine will drop to when you shift. Pretty much you need to shift when your at a point where the next gears RPM will have more torque/HP then the last gear. Best way would be find how many RPM's it will drop after each shift and graph that window over the most meaty part of your dyno (the part with the most HP/TQ in the 'window')in each gear (all this probably makes no sense so I'll try to google some links) Anyway I think its all useless, I would prefer to shift by feel because lets face it we can't be staring at the tachometer the whole time. I'd goto a drag strip and finding which shift combo works best :P Heres the best link I found--> http://www.datsuns.com/Tech/whentoshift.htm

10-10-2003, 03:57 PM	#9
exitspeed aWingThing.com Join Date: Mar 2003 Location: Milwaukee, WI Age: 44 Posts: 20,900 Trader Rating: (1) Feedback Score: 1 reviews	Gracphing your car really helps to find the right shift points but... For example on my 2000 eclipse GT I stopped making power at about 5500rpms. However when I ran my best times I always shifted at redline, 6200rpms. It made at least a .2 sec diffence in my 1/4 mile times. So I really think it depends on more things. Practice, trial and error, and track time is the best way to find out, IMHO.