What is the best way to shift when racing?

[JekylandHyde]

Originally Posted by mycivic

I know you incorporate gearing and all other factors but its still not wise to shift at the ideal shift point.

If your goal is maximizing acceleration, then it is wise to shift at the ideal shift point if it falls below the redline of your engine.
See the graphic I posted? ... it asks for the redline point ofr a reason.

On the stock-turboed MR2 graph I posted, the ideal shift point is around 5500 rpms. With my T3T4 turbo on the same engine my mathematical ideal shift point is beyond redline ... obviously I can't shift there. So my ideal shift point IS redline (7200 rpms).

Originally Posted by mycivic

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.

Then I wouldn't describe tht point as ideal!

[mycivic]

I see your point. I understand what you are trying to say. But it still doesent take into account the engine...where it cuts-off. Even though you shift at redline, you still may not be getting the most out of acceleration. You may actually be accelerating slower if you shift past peak power.

Hey, does anybody else have another opinion? This is kinda getting interesting.

[JekylandHyde]

The formula I posted using the stock-turboed MR2 I got shift points:
1st --> 2nd = 6595 rpms
2nd --> 3rd = 5643 rpms
3rd --> 4th = 5595 rpms

The calculator I posted from:
http://www.bgsoflex.com/shifter.html
Gave me:
1st --> 2nd = 6130 rpms
2nd --> 3rd = 5553 rpms
3rd --> 4th = 5524 rpms

[JekylandHyde]

Just becuase "torque" falls off on a dyno sheet does not mean that is time to shift.

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.

From this site:
http://www.datsuns.com/Tech/whentoshift.htm

[mycivic]

Using the calculator, and if it says that shift way past redline, is not ideal. I still believe that its near peak power.

Each of us obviously have our own opinion on what the ideal shift point is. And it seems that none will give in to another. So lets leave it at that and see what other people think is the ideal shift point.

[JekylandHyde]

mycivic, see my last post. We posted about the same time and I think you may have missed it.

Originally Posted by mycivic

Using the calculator, and if it says that shift way past redline, is not ideal.

If the math states that your target shift point is beyond redline, then redline is your ideal shift point.

Originally Posted by mycivic

I still believe that its near peak power.
Each of us obviously have our own opinion on what the ideal shift point is.

This has nothing to do with "believing" or "opinions".
I am offering you facts - from physics.
It is your choice what to do with them.

There are hundreds of sites out there that will back my statements.
I have offered no opinions.

[mycivic]

I dont know what else to say...

I still cant see past why it has to be way past peak power when it starts to drop in the torque curve.

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.

This, however makes more sense to me.

[JekylandHyde]

Hey mycivic, think of it this way:

Think of maximum turque over and range of rpms ... not just the peak point.

EXAMPLE:
Let's say your engine+tranny make it's most power from 4000-5500 rpms.
Let's say your peak TQ is at 4800 rpms.
What if you shift at 4800 and your rpms drop to 2000 rpms?!
UG....
You are not "in the power" for THAT gear. You want to shift when you drop down into the "meat" of the next gear.

You want to keep your car in the max power range.

[mycivic]

Originally Posted by JekylandHyde

Hey mycivic, think of it this way:

Think of maximum turque over and range of rpms ... not just the peak point.

EXAMPLE:
Let's say your engine+tranny make it's most power from 4000-5500 rpms.
Let's say your peak TQ is at 4800 rpms.
What if you shift at 4800 and your rpms drop to 2000 rpms?!
UG....
You are not "in the power" for THAT gear. You want to shift when you drop down into the "meat" of the next gear.

You want to keep your car in the max power range.

Ok, I get it now. I may have been wrong with what I said. I stand corrected with what ever wrong that I mentioned earlier.

[JekylandHyde]

No worries man... we are all here to learn and your questions pushed me to learn more today.

Thank you for that.

[mycivic]

Same here.

[GTR2b]

Slight "Disclaimer" to the individual that referred to the Lingenfelter site.

I just thought I should add this guys.

(Quote from LPE)
"When determining proper shift points it is also important to consider the safe operating speeds for your engine. Consult your owners manual or your engine builder when selecting shift points. Shifting after the redline or past the safe operating speed of the engine can result in premature engine wear or damage."

I just thought I should get that out of the way. In the quest for that last .05 at the traps people tend to overlook this little gem of wisdom.

[mycivic]

Originally Posted by GTR2b

Slight "Disclaimer" to the individual that referred to the Lingenfelter site.

I just thought I should add this guys.

(Quote from LPE)
"When determining proper shift points it is also important to consider the safe operating speeds for your engine. Consult your owners manual or your engine builder when selecting shift points. Shifting after the redline or past the safe operating speed of the engine can result in premature engine wear or damage."

I just thought I should get that out of the way. In the quest for that last .05 at the traps people tend to overlook this little gem of wisdom.

He mentioned that too when we were having the argument. It is not advisable to shift past redline because there is no ideal engine that can be capable of that. That is why there is a redline. If the "Ideal Shift Point" is way past redline...then the next best thing to do is sihft near redline and not past redline.

[jdrumstik]

THe way I understand it is you wait until the point when you shift you will be back in a higher toque/hp range. for instance, if you are at 5600 rpm and you upshift and now you are making less power that is bad, but then you hit the 6100 mark and your upshift will make you more power.

[drag1320neon]

fast