Shifting for dummies

Rich Anderson · **Posted:** Tue Mar 21, 2006 8:48 am

Got a dyno plot and gear ratios? I would be interested to see where the optimum shift point is. It is rare that there is a car that doesn't require redline in third for best acceleration. I would like to know as an HPDE instructor the third to fourth shift is the most common upshift. I figure one day I will be in a STi and I would like to know rather than guess.

LDUCSP.

Richard Casto · **Posted:** Tue Mar 21, 2006 10:49 am

I love all of this talk of third gear and beyond. My car is geared so high.

I don't think I have EVER shifted into 3rd at an autocross. Going with about the smallest diameter tire that I can get and still get decent width, my gearing calculates out to about 63 at redline in 2nd. I was flat going into, through and after the sweeper. As I was approaching the slalom I just knew the rev limiter was going to kick in any second, but it didn't. It HAD to be very close however.

Rich Anderson · **Posted:** Tue Mar 21, 2006 11:15 am

So no dyno and gear ratios?

Brian Herring · **Posted:** Tue Mar 21, 2006 11:33 am

Rich Anderson wrote:

So no dyno and gear ratios?

Dyno? Depends on the AWD dyno you go to. I have seen from 235awhp to 250awhp. As far as graphs, they are out there as well with a double torque hump and boost bleeding from 14.7psi to 11(?) psi at redline.

Gear Ratios... I don't have time, but google them and they are out there.

To me, it doesn't matter. That is the way I am going to drive unless I just need more gearing.

Short Shifting FTW.

Quote:

No more and then.

aaaaaannnndddd then?

- dow

Rich Anderson · **Posted:** Tue Mar 21, 2006 11:53 am

Brian Herring wrote:

Rich Anderson wrote:

So no dyno and gear ratios?

Dyno? Depends on the AWD dyno you go to. I have seen from 235awhp to 250awhp. As far as graphs, they are out there as well with a double torque hump and boost bleeding from 14.7psi to 11(?) psi at redline.

Gear Ratios... I don't have time, but google them and they are out there.

- dow

Well if you shift at 6000RPM from thrid to fourth, you are putting yourself at ≈4600 RPM post shift. I have found no near stock dyno that indicates that the car makes more horsepower at that point that at 6100. Basically, you should shift from third at ≈6500 rpm for best acceleration on an STi according to what I have found. Of course, without a real dyno reading this all a guess.

Chris Landi · **Joined:** Mon Mar 08, 2004 6:31 pm **Posts:** 579

Rich,

Do you have a link for a site that calculates shift points based on a Dyno plot? I have a dyno plot to work with so I'd be interested in seeing what my optimum shift points should be.

Thanks, Chris

Jason Mauldin · **Posted:** Tue Mar 21, 2006 12:01 pm

Rich Anderson wrote:

Brian Herring wrote:

Rich Anderson wrote:

So no dyno and gear ratios?

Dyno? Depends on the AWD dyno you go to. I have seen from 235awhp to 250awhp. As far as graphs, they are out there as well with a double torque hump and boost bleeding from 14.7psi to 11(?) psi at redline.

Gear Ratios... I don't have time, but google them and they are out there.

- dow

Well if you shift at 6000RPM from thrid to fourth, you are putting yourself at ≈4600 RPM post shift. I have found no near stock dyno that indicates that the car makes more horsepower at that point that at 6100. Basically, you should shift from third at ≈6500 rpm for best acceleration on an STi according to what I have found. Of course, without a real dyno reading this all a guess.

Seriously, you do not have to help this guy go any faster.

Scott Johnson · **Posted:** Tue Mar 21, 2006 12:03 pm

Chris Landi wrote:

Rich,

Do you have a link for a site that calculates shift points based on a Dyno plot? I have a dyno plot to work with so I'd be interested in seeing what my optimum shift points should be.

Thanks, Chris

Hit #1 via a Google search www.google.com for "shift point calculator"

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

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

scottjohnson wrote:

Chris Landi wrote:

Rich,

Do you have a link for a site that calculates shift points based on a Dyno plot? I have a dyno plot to work with so I'd be interested in seeing what my optimum shift points should be.

Thanks, Chris

Hit #1 via a Google search www.google.com for "shift point calculator"

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

That's a good link. I always did it with a spreadsheet

The E30 was revlimiter in 1,2, and 3, and 400 RPM off revlimit for the 4-5 shift. The M3 is revlimiter for all 4 shifts.

Rich Anderson · **Posted:** Tue Mar 21, 2006 12:20 pm

Chris Landi wrote:

Rich,

Do you have a link for a site that calculates shift points based on a Dyno plot? I have a dyno plot to work with so I'd be interested in seeing what my optimum shift points should be.

Thanks, Chris

If you can do Excel you can make one easily. You just need an RPM based horsepower output in a column. Find out the percentage drop between gears based on the gear chart, then calculate the RPM after the shift for a given RPM. If HP is lower than pre shift, run it again at 100 rpm an see what that does. Once your pre and post shift HP are equal (or as close as possible, you are done. Repeat for each gear. There are probably much more sophisticated ways to do it, but my way makes sense to me.

I might make a universal one once I have my new engine so that I can see what changes would do to shift points.

Chris Landi · **Joined:** Mon Mar 08, 2004 6:31 pm **Posts:** 579

Interesting..For HP matching I do a 2-3 shift at 6339 rpms and a 3-4 shift at 6215(rpms lower to 4700 which is 400rpms below peak hp). To maximize the area under the curve the shifts are at 6500.

Where does torque come into play? I've got a LOT more tq at 3600 rpms than I do HP.

Rich Anderson · **Posted:** Tue Mar 21, 2006 12:28 pm

Chris Landi wrote:

Interesting..For HP matching I do a 2-3 shift at 6339 rpms and a 3-4 shift at 6215(rpms lower to 4700 which is 400rpms below peak hp). To maximize the area under the curve the shifts are at 6500.

Where does torque come into play?

When it is multiplied by your RPM and then divided by 5252 to determine your HP. Torque means nothing except as a part of horsepower.

From what you typed, it appears that you car has a lower HP peak than the one I found on google.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Rich Anderson wrote:

Chris Landi wrote:

Interesting..For HP matching I do a 2-3 shift at 6339 rpms and a 3-4 shift at 6215(rpms lower to 4700 which is 400rpms below peak hp). To maximize the area under the curve the shifts are at 6500.

Where does torque come into play?

When it is multiplied by your RPM and then divided by 5252 to determine your HP. Torque means nothing except as a part of horsepower.

From what you typed, it appears that you car has a lower HP peak than the one I found on google.

You sure about that? I don't want to get into the HP vs TQ argument here, but in my shift point calculations. I optimized Force At The Tire/Ground. Tires exerting force on pavement is what causes acceleration. Force at the ground is based solely on torque, gearing, and tire size. Just be careful in your assumptions....

Les Davis · **Joined:** Fri Aug 29, 2003 2:04 pm **Posts:** 2059

Jason Mauldin wrote:

Rich Anderson wrote:

Brian Herring wrote:

Rich Anderson wrote:

So no dyno and gear ratios?

Dyno? Depends on the AWD dyno you go to. I have seen from 235awhp to 250awhp. As far as graphs, they are out there as well with a double torque hump and boost bleeding from 14.7psi to 11(?) psi at redline.

Gear Ratios... I don't have time, but google them and they are out there.

- dow

Well if you shift at 6000RPM from thrid to fourth, you are putting yourself at ≈4600 RPM post shift. I have found no near stock dyno that indicates that the car makes more horsepower at that point that at 6100. Basically, you should shift from third at ≈6500 rpm for best acceleration on an STi according to what I have found. Of course, without a real dyno reading this all a guess.

Seriously, you do not have to help this guy go any faster.

Yeah Brian, I think your being way to hard on your car running it all the way up to 6000 rpm. I mean thats a nice car, and you want it to last awhile don't you? 6000 rpm is really hard on the engine rotating assembly. No way you'll get 200K miles out of an engine doing that all the time. I really think your best option is to limit your engine RPM to 4000, maybe even 3500 rpm. I'm just looking out for your car you know. :wink:

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Rich Anderson wrote:

Chris Landi wrote:

Rich,

Do you have a link for a site that calculates shift points based on a Dyno plot? I have a dyno plot to work with so I'd be interested in seeing what my optimum shift points should be.

Thanks, Chris

If you can do Excel you can make one easily. You just need an RPM based horsepower output in a column. Find out the percentage drop between gears based on the gear chart, then calculate the RPM after the shift for a given RPM. If HP is lower than pre shift, run it again at 100 rpm an see what that does. Once your pre and post shift RPM are equal (or as close as possible, you are done. Repeat for each gear. There are probably much more sophisticated ways to do it, but my way makes sense to me.

I might make a universal one once I have my new engine so that I can see what changes would do to shift points.

Again, I will disagree - just to point out that one person's opinion might not be gospel (sorry Rich). I think the Torque*gearing number is what needs to be optimized. I'll leave it to some higher authority or someone with some tech to be the tiebreaker.

Mike

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