Shift points

[Tearstone]

When you guys go to the track, what RPM levels are you shifting at? Last night when I was going, I was shifting at 6,000 most of the night, then when I started shifting later my trap speeds were getting higher.

[Tearstone]

So no one drag races on these forums?

As much as I hated to, I ventured over to the other MR2 board, and found they had a wealth of information about shift points. Based on when a CT26 hits max torque these are the optimal shift point numbers:

1st --> 2nd = 6595 rpms
2nd --> 3rd = 5643 rpms
3rd --> 4th = 5595 rpms
4th --> 5th = 4915 rpms

[v8killer]

So your assuming max torque is the ideal shift point? Not saying your wrong, but I wouldn't think so.

the 2nd to 3rd shift is at really low rpms..

I thought I read somewhere on an mr2 related website, the optimal shift points for all gears was close to 6800 rpm (give or take 100rpm or so depending on the gear).

Guess I'll go drag racing this year to find out!

Let me know if you come across anything.

[Sang]

"Ideal" shift point on a ct26 is at such a rpm that when you hit the next gear, it plants you in your powerband.

Really, there's nothing you can do about first gear, it goes by so quick i'd expect everyone to redline it. 2nd and on it's a bit less. I used to shift around 6000-6250rpms.

[Tearstone]

The shift points I grabbed off of OC from the Jekyl & Hyde guy's post calculating based on these articles:

http://www.lingenfelter.com/shiftpoint.asp

http://www.allpar.com/eek/hp-vs-torque.html

http://realbig.com/miata/miata/1995-12/910.html

http://www.datsuns.com/Tech/whentoshift.htm

I've always based my shifting on the dyno charts to basically get your shifts to land back on max torque.

Optimal Shift Points

By Dave Lum - 10/22/98
Looking to get maximum effect out of your car when accelerating? Try optimizing the RPM's you shift your car at. If you're shifting at redline, you're probably not getting the best acceleration out of your car - in fact, the optimum shift RPM will probably be different for each gear. You can calculate the optimum shift points, but it takes two pieces of information : Gear ratios of all your gears, and a chart of your torque curve.

If you don't understand torque curves, you may want to take a look at the horsepower article in my Technical Department before reading any farther.

The trick here is to keep your engine in the meaty part of the torque curve, as your acceleration curve will match your torque curve - meaning if your torque peak is at 3000rpm, that's the RPM your car accelerates the hardest. How do you keep the engine in the best part of the curve? Shift when you will be at an RPM where the car will make more torque AFTER you shift than in your current gear. This may sound confusing, but I will give some examples to help demonstrate this. Gear ratio is important because you need to know what your RPM's will drop to once you shift. EXAMPLE : If you're at 6500rpm in first, you need the gear ratio to know what RPM that will translates to once you shift to 2nd.

Well what do you know! You bracket the HP peak. HP after the shift is the same as HP before the shift. Now we know shifting at the torque peak isn't the answer, and neither is shifting at the HP peak.

The math required : next higher gear ratio / current gear ratio (i,e. second gear divided by first) = X

X * shiftrpm = nextrpm, where shiftrpm is the point your shifting AT, and nextrpm will be the RPM of the next gear at the same speed.

firstgeartorque = torque at shiftrpm times current gear ratio (example, at 6400rpm we have 95ft/lbs, multiply this by our gear ratio in 1st (3:1, or just 3) and you get about 245ft/lbs.

secondgeartorque = torque at nextrpm times next gear ratio (in out example, we have 120ft/lbs @ 4400rpm, times 2:1 (second gear ratio), and you get 240ft/lbs.

Change shiftrpm until firstgeartorque is equal (or close to) secondgeartorque.

[dufunk]

To me it has to be:

1st: 7250
2nd: 7000
3rd: 6500
ditto
ditto

For drag racing that is, funny how u have to be at 7250 everytime on the N/A to get neccessary power.

With Ct26 it also seems to have higher top end than ct20, turbo kicking more at 4k along with the acis 4250 so it seemed benifical to hold it above 7k