[gypsymoth]

While playing with my Excel spread sheet I calculated the ideal shift points for a stock 2001 Subaru Impreza 2.5 RS (GC6):

1/2 Shift - 6730 RPM -> 4000 RPM
2/3 Shift - 5821 RPM -> 4000 RPM
3/4 Shift - 5321 RPM -> 4000 RPM
4/5 Shift - 5590 RPM -> 4000 RPM

What do you guys think of these results? Is this close to what you have gotten?

Chieh

 

[Guest]

How do you figure?

Doesn't the fuel cut at 6250 anyway?

 

[Siper2]

Well according to the brochures for all cars coming with the EJ25...
max torque is [email protected], and max hp is [email protected]

So... I'd say that somewhere in the high 4k range is the key, and from driving my car for a while now, nearly two years, I think that's about right.

-S2-

 

[gypsymoth]

How do you figure?
Doesn't the fuel cut at 6250 anyway?

Yes. So the ideal shift point for the 1/2 shift is at redline.
I used the following formula:

Shift RPM = lower gear ratio / higher gear ratio * torque peak RPM

I got this formula at http://list.miata.net/miata/1995-12/910.html

However, Sport Compact Car seem to have a different formula which gave a slightly different result. I will try that tonight . . .

Chieh

 

[Guest]

Actually no, the 1/2 shift point you listed is 500rpm beyond the fuel cut-off.

That's what I mean.

 

[COwannago]

Actually no, the 1/2 shift point you listed is 500rpm beyond the fuel cut-off.

Heh, no go after 6250.

Nick C.

 

[gypsymoth]

Actually no, the 1/2 shift point you listed is 500rpm beyond the fuel cut-off. That's what I mean.

Yes. I know what you mean. What I was trying to say is that since you can't get pass the redline, but the real/theoretical 1/2 shift point is pass the redline, you will have to shift at the redline for the 1/2 shift.

. . . did that clear it up? Or did I just confused you some more with that run-on sentence??

Chieh

 

[gypsymoth]

Using the Sport Compact Car Magazine algorithm:

If you prefer to play with spreadsheets, and you can get the torque data every 100 rpm or so, you can simply plot torque at the outptut shaft vs. speed for all of the gears. Anywhere the line for one gear crosses the line for the next, that's your shift point. If the lines never cross, take it to the redline.

You can find the full article here:
http://www.sportcompactcarweb.com/archives/technobabble/techno_0901.shtml

I got the following results:

1/2 Shift - 5208.33 RPM -> 3095.66 RPM
2/3 Shift - 4656.86 RPM -> 3200.21 RPM
3/4 Shift - 4645.27 RPM -> 3491.96 RPM
4/5 Shift - 4545.45 RPM -> 3252.71 RPM

Chieh

 

[gypsymoth]

comparison

Web Algorithm Result
1/2 Shift - 6730 RPM -> 4000 RPM
2/3 Shift - 5821 RPM -> 4000 RPM
3/4 Shift - 5321 RPM -> 4000 RPM
4/5 Shift - 5590 RPM -> 4000 RPM

Sport Compact Car Algorithm Result
1/2 Shift - 5208.33 RPM -> 3095.66 RPM
2/3 Shift - 4656.86 RPM -> 3200.21 RPM
3/4 Shift - 4645.27 RPM -> 3491.96 RPM
4/5 Shift - 4545.45 RPM -> 3252.71 RPM

It's obvious those are two very different results.

In the first algorithm, it emphasizes on shifting to the torque peak RPM. Its philosophy is that the vehicle accelerates fastest at the peak.

In the second algorithm, it emphasizes on shifting to the beginning of the power band. Its philosophy is that the vehicle accelerates fastest by centering the torque peak on the power curve.

Which theory is correct?

Chieh

 

[Guest]

I dunno but it feels like granny shifting if you lift off at 4500 rpm to shift, ya know?

And yeah, I understand what you meant before.

 

[Storm]

Numbers aside, if you shift at 4500, you're going to end up well below that when you finish the shift, so you'll be well off the peak for torque. Better to run it up higher so you finish the shift at the peak of torque.

Torque will get you moving, HP will keep you moving. Using this, the HP still climbs well after the torque falls off so use the HP to prepare you for the next shift, where the torque will peak and move you to a higher speed, and HP will pull you higher, and so on...

 

[CriboRS]

i dont understand something....if you shift at those shift points re you saying youll land on 4000rpms? if so, your info doesnt make sense, or atleast im not understang it.....are you sying that if you hypothetcially shifted at 6730rpm in first gear that would land you at 4000rpm in second???