What is the best way to shift when racing?

[03cavyTT]

How are you supposed to shift when racing

[drew88]

fast

[GTR2b]

1st gear, then 2nd gear, then 3rd gear, then 4th gear....

[JekylandHyde]

Shift as fast and as accurately as possible.
Depending on your cars "personality" stay ON THROTTLE while shifting.

I stay abuot 1/2 - 3/4 throttle while shifting.
When I do this I increase my ETs by .2 - .3 compared to getting off-throttle to shift.

[mycivic]

Also, shift at peak hp or somewhere near there.

[JekylandHyde]

Originally Posted by mycivic

Also, shift at peak hp or somewhere near there.

That is not correct from what I understand.
It is certainly not correct for a turbo MR2.

Shifting has to do with Torque, not Horespower.

My understanding is that to find the optimal shift point (I posted this in another thread. copy/pasted here):

Please feel free to post anything that contradicts the following information. I am merely sharing what my research has found.
Nothing below is written in stone (As far as I know )

Shift point information:

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

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

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

Using the formula on the third link, my car should be optimally shifted well beyond redline ... and I do shift at redline.

Formula:
Lower gear ratio / higher gear ratio X RPM at peak Torque = Shift RPM

Using the same formula for a stock CT26 MR2, I get shift points:
1st --> 2nd = 6595 rpms
2nd --> 3rd = 5643 rpms
3rd --> 4th = 5595 rpms
4th --> 5th = 4915 rpms

Hope that helps.

Notice how the following both have the peak torque at the same RPM?

276 HP CT26
http://www.turboforum.net/dyno/imag...ins/dyno276.jpg

161 HP CT26:
http://www.turboforum.net/dyno/imag.../redmr2dyno.gif

Same turbo, same shift points :thumb:

[mycivic]

Originally Posted by JekylandHyde

That is not correct from what I understand.
It is certainly not correct for a turbo MR2.

Shifting has to do with Torque, not Horespower.

My understanding is that to find the optimal shift point (I posted this in another thread. copy/pasted here):

Please feel free to post anything that contradicts the following information. I am merely sharing what my research has found.
Nothing below is written in stone (As far as I know )

Shift point information:

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

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

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

Using the formula on the third link, my car should be optimally shifted well beyond redline ... and I do shift at redline.

Formula:
Lower gear ratio / higher gear ratio X RPM at peak Torque = Shift RPM

Using the same formula for a stock CT26 MR2, I get shift points:
1st --> 2nd = 6595 rpms
2nd --> 3rd = 5643 rpms
3rd --> 4th = 5595 rpms
4th --> 5th = 4915 rpms

Hope that helps.

Notice how the following both have the peak torque at the same RPM?

276 HP CT26
http://www.turboforum.net/dyno/imag...ins/dyno276.jpg

161 HP CT26:
http://www.turboforum.net/dyno/imag.../redmr2dyno.gif

Same turbo, same shift points :thumb:

I said somewhere close to that.

Peak torque maybe or peak horsepower. But my comment on that shift point beyond the redline...I also think is wrong. Shifting an engine higher than its redline will generally loose torque in its torque curve at a certain point, something like a saturation point. Thats why I said close to the peak.

[JekylandHyde]

mycivic look at this dyno:
http://www.turboforum.net/dyno/image...ns/dyno276.jpg

Torque Peak is at 4000 rpms and Peak HP (nothing to do with shifting) is around 4200 rpms. I gaurantee you the optimal shift point for THAT car is what I posted above:

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

That is no where close to 4000 - 4200 rpms.

It is quite possible that the "ideal" shift point is beyond redline.
That is the case with my turbo car.
I would love to increase my redline to reach it, but I would need to make sure the engine could stand more rpms.

[mycivic]

Originally Posted by JekylandHyde

mycivic look at this dyno:
http://www.turboforum.net/dyno/image...ns/dyno276.jpg

Torque Peak is at 4000 rpms and Peak HP (nothing to do with shifting) is around 4200 rpms. I gaurantee you the optimal shift point for THAT car is what I posted above:

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

That is no where close to 4000 - 4200 rpms.

It is quite possible that the "ideal" shift point is beyond redline.
That is the case with my turbo car.
I would love to increase my redline to reach it, but I would need to make sure the engine could stand more rpms.

I still cant see what your trying to point out. Lets use the last figure as an example. An ideal engine when revved higher will produce more hp or torque. But there is no "IDEAL ENGINE" that can just go on revving to say 15K rpm and not reach a saturation point. What I am trying to say is that (In my opinion) its best to shift "NEAR" peak power (hp or torque) because if you go past this, the "TORQUE CURVE" will start to go down. So generally, you make less power even when revving high. With your example that you gave, shifting at say way past 4000 rpm, you make less power beacuse of the saturation point. So you wont pull as hard.

[JekylandHyde]

I never refered to an "ideal" engine. I refered to the ideal "shift point".
I offered a fairly accurate formula for calculating that.

For my turbo MR2, with my T3T4 turbo, my ideal shift point is well beyond redline.
The MR2 turbo I used in the example has the OEM turbo and it's ideal shift points are much less than mine (as noted)

The problem with making a blanket statement like "shift at or near peak torque" is that does not take into account gearing.
The equation I offered does just that.

My dyno is here:
http://jekylandhyde.madpowaz.com/hydedyno.jpg
Notice my peak torque is around 5200 rpms.
I gaurantee you that is not my ideal shift point ... nowhere close.
My ideal shift point is well beyond 7200 rpms (my rev limit).

[JekylandHyde]

Max Toqrue is only one part of the equation.
To determine the ideal shift point, you would want to know:

Peak Torque
Max RPM
Tire Diameter (gearing)
Differential Ratio (gearing)
Gear RAtio (gearing)

[mycivic]

Originally Posted by JekylandHyde

I never refered to an "ideal" engine. I refered to the ideal "shift point".

I know you were reffering to the ideal shift point as you were saying. But lets also take into account that if you do shift at that "IDEAL SHIFT" point, there is no "IDEAL ENGINE" that can do that. You will loose power after peak power. Thats why I said in my first post that (In my opinion still) its best to shift somewhere near peak power.

[JekylandHyde]

Here are two interesting shift point calculators:

http://www.prestage.com/Tech+Info/Drag+Racing/1121.aspx

http://www.bgsoflex.com/shifter.html

I haven't played with them yet to see how accurate they are, but notice they both incorporate gearing.

[mycivic]

I know you incorporate gearing and all other factors but its still not wise to shift at the ideal shift point. You also have to take into cosideration the capabilities of the engine, like redline and the fuel cut-off point. If you do shift at that Ideal shift point...you "MAY" destroy the engine because the engine cant handle revving past the redline or fuel-cutoff point.

[JekylandHyde]

Originally Posted by mycivic

But lets also take into account that if you do shift at that "IDEAL SHIFT" point, there is no "IDEAL ENGINE" that can do that.

For a given engine with a given transmission with specific gears and specific tire diameter there is an ideal shift point. It is something that can be calculated.

Originally Posted by mycivic

Thats why I said in my first post that (In my opinion still) its best to shift somewhere near peak power.

Just because you see a dyno graph "fall off" doesn't mean that it is the ideal time to shift for maximum acceleration.
You have to take gearing into account.