The evolution of shift points
05-16-2004, 03:39 AM
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The evolution of shift points
Hey Everyone,
There is no better teacher than evolution.
I'm surprised I didn't think to write this Easter weekend when it happened, but I had a pretty cool experience that taught me everything there is to know about optimizing shift points. Specifically finding the right gear for various cruise->accelerate transitions. This post was inspired by Sous 04 S4's thread below.
I will tell you how to figure out the optimum gear to shift to coming from any speed. For a given speed range, put yourself in a 2-lane 2-way passing zone, the kind with the yellow dashed line (passing lane = oncoming traffic lane), and moderate traffic. You will find out very quickly which gear is your money gear when making a bad choice puts your life at stake.
I had to drive from RI to VT right at rush hour that Friday. The interstates didn't go the direction I needed, and I didn't want to sit in traffic on them. So I found this great rural highway from Worcester towards North Adams/ I-91 (Rt 122). The kind with mostly 45 mph speed limits, but a few 35's, and goes through 5 or 6 towns over the 30 miles that it covers. Curvy, with an even mix of moderate traffic, and open road. The kind of situation where it's common that if it weren't for the one dope 2, 3 or 6 cars ahead of you going 45, you'd be cruising at 65+, really enjoying your car.
The next leg of the trip was even harier, on Rt 2. This is a 55 mph 2 lane *undivided* highway. That' s right - 1 lane each direction, with passing zones w/ oncoming traffic, full 55 mph limit (with actual crusing speads of 65-70).
The kind of situations where max passing ability have max payoff - getting you back to enjoying your drive on an open road. The trouble is, when you have to pass 3 cars, even with a helluvan engine, you still need a good size passing zone, excellent judgement, and a pretty hefty sack of ***** too.
Well, I found myself in this situation ~15 times that afternoon. In maybe 10 of those cases, the best opportunity to pass still involved an oncoming car, and the other 5 there was a curve at the end of the passing zone. So it was either play chicken for real, or play "maybe chicken."
I learned a *LOT* about passing in the B6 S4 that day. 1st lesson: It's not just about how much grunt you can get immediately after shifting gears. It's also about what speed you're going to need to get to, whether you'll have to shift again before you get there, and if so, whether the "big whump" of the lower gear will last long enough to pay for the cost of the extra gear change. And vice versa - whether the gear change savings of the higher gear will pay for the decrease in the whump if you go the other way with it.
So, what I learned is this:
1) If you're going to have to shift gears, then you don't want to get started at above 5000 rpm. 5500+, you'll have spent as much time in the lower gear as you spend shifting after it.
2) If your life is at stake, you don't want to be getting into this situation at below 3000 RPMs either. Not that the engine isn't powerful enough there, just that you coulda been in a gear lower at 4k, w/ more leverage.
So to summarize leg 1, IIRC, at 45-60 mph, 3rd gear is your best friend. Don't fool yourself w/ 2nd gear above 40. (btw 40 & 45, think twice). If you are going 60, there's another iffy spot from 60-65 where 4th feels a little week, but you'd run out of 3rd faster than you want to.
It's funny, you do enough situations like this, and you realize that some of the times where you had scared the snot out of yourself, you actually had a lot more room to breathe than you originally though, once you got the gearing right. Still more interesting though is that you don't think in terms of MPH and RPM. It is all feel/gut/impression/instinct. I'm translating the actual numbers, I may be off by a few MPH/RPMs. Really you just learn what the engine "feels" like when it's going to run out of breath too soon, and when it's just not going to give you the snap you need - and it's dynamic, the answer is different at ~50 mph than it is at ~30 or ~70, and you learn that too - your sensations factor in the sense of vehicle speed, and even the sense of the passing opportunity itself.
Leg 2 was insane. More spread out. Bigger passing zones. But bigger stakes and bigger challenges - lines of 6 cars more common, and a base speed of 65 more common too. At 60+, there's no question, 4th gear is the only one you want to be messing with. I did some 60-90's, and a couple 60-100's, passing as many as 6 cars, while there was an oncoming car less than a mile away. It generally took less than 1/4 mile to execute the pass I'd guess, so plenty of room for error.
Based on this, I'd have to extrapolate that in order for 5th gear to be your money gear, you'd have to be starting from a base speed of above 80, though I'm not sure how much above, and with a target speed of 110 or more.
I stand by my claim though, you will never learn anything in a car faster than you do when there's a car coming at you at a closing speed of 120-160 mph, and when your decisions alone are responsible for the conclusion of whether the situation works out ok or not.
(caveat: My definition of "works out ok" is not "didn't die." Rather it's "got out of the way before oncoming car had to consider you in his plans, and left enough room that pass-ee's also got to go about their daily routine w/out any adjustments." I also have an added goal of making the whole situation appear uneventful, keeping transitions smooth, mimimizing body roll. Tends to be less alarming to others).
There is no better teacher than evolution.
I'm surprised I didn't think to write this Easter weekend when it happened, but I had a pretty cool experience that taught me everything there is to know about optimizing shift points. Specifically finding the right gear for various cruise->accelerate transitions. This post was inspired by Sous 04 S4's thread below.
I will tell you how to figure out the optimum gear to shift to coming from any speed. For a given speed range, put yourself in a 2-lane 2-way passing zone, the kind with the yellow dashed line (passing lane = oncoming traffic lane), and moderate traffic. You will find out very quickly which gear is your money gear when making a bad choice puts your life at stake.
I had to drive from RI to VT right at rush hour that Friday. The interstates didn't go the direction I needed, and I didn't want to sit in traffic on them. So I found this great rural highway from Worcester towards North Adams/ I-91 (Rt 122). The kind with mostly 45 mph speed limits, but a few 35's, and goes through 5 or 6 towns over the 30 miles that it covers. Curvy, with an even mix of moderate traffic, and open road. The kind of situation where it's common that if it weren't for the one dope 2, 3 or 6 cars ahead of you going 45, you'd be cruising at 65+, really enjoying your car.
The next leg of the trip was even harier, on Rt 2. This is a 55 mph 2 lane *undivided* highway. That' s right - 1 lane each direction, with passing zones w/ oncoming traffic, full 55 mph limit (with actual crusing speads of 65-70).
The kind of situations where max passing ability have max payoff - getting you back to enjoying your drive on an open road. The trouble is, when you have to pass 3 cars, even with a helluvan engine, you still need a good size passing zone, excellent judgement, and a pretty hefty sack of ***** too.
Well, I found myself in this situation ~15 times that afternoon. In maybe 10 of those cases, the best opportunity to pass still involved an oncoming car, and the other 5 there was a curve at the end of the passing zone. So it was either play chicken for real, or play "maybe chicken."
I learned a *LOT* about passing in the B6 S4 that day. 1st lesson: It's not just about how much grunt you can get immediately after shifting gears. It's also about what speed you're going to need to get to, whether you'll have to shift again before you get there, and if so, whether the "big whump" of the lower gear will last long enough to pay for the cost of the extra gear change. And vice versa - whether the gear change savings of the higher gear will pay for the decrease in the whump if you go the other way with it.
So, what I learned is this:
1) If you're going to have to shift gears, then you don't want to get started at above 5000 rpm. 5500+, you'll have spent as much time in the lower gear as you spend shifting after it.
2) If your life is at stake, you don't want to be getting into this situation at below 3000 RPMs either. Not that the engine isn't powerful enough there, just that you coulda been in a gear lower at 4k, w/ more leverage.
So to summarize leg 1, IIRC, at 45-60 mph, 3rd gear is your best friend. Don't fool yourself w/ 2nd gear above 40. (btw 40 & 45, think twice). If you are going 60, there's another iffy spot from 60-65 where 4th feels a little week, but you'd run out of 3rd faster than you want to.
It's funny, you do enough situations like this, and you realize that some of the times where you had scared the snot out of yourself, you actually had a lot more room to breathe than you originally though, once you got the gearing right. Still more interesting though is that you don't think in terms of MPH and RPM. It is all feel/gut/impression/instinct. I'm translating the actual numbers, I may be off by a few MPH/RPMs. Really you just learn what the engine "feels" like when it's going to run out of breath too soon, and when it's just not going to give you the snap you need - and it's dynamic, the answer is different at ~50 mph than it is at ~30 or ~70, and you learn that too - your sensations factor in the sense of vehicle speed, and even the sense of the passing opportunity itself.
Leg 2 was insane. More spread out. Bigger passing zones. But bigger stakes and bigger challenges - lines of 6 cars more common, and a base speed of 65 more common too. At 60+, there's no question, 4th gear is the only one you want to be messing with. I did some 60-90's, and a couple 60-100's, passing as many as 6 cars, while there was an oncoming car less than a mile away. It generally took less than 1/4 mile to execute the pass I'd guess, so plenty of room for error.
Based on this, I'd have to extrapolate that in order for 5th gear to be your money gear, you'd have to be starting from a base speed of above 80, though I'm not sure how much above, and with a target speed of 110 or more.
I stand by my claim though, you will never learn anything in a car faster than you do when there's a car coming at you at a closing speed of 120-160 mph, and when your decisions alone are responsible for the conclusion of whether the situation works out ok or not.
(caveat: My definition of "works out ok" is not "didn't die." Rather it's "got out of the way before oncoming car had to consider you in his plans, and left enough room that pass-ee's also got to go about their daily routine w/out any adjustments." I also have an added goal of making the whole situation appear uneventful, keeping transitions smooth, mimimizing body roll. Tends to be less alarming to others).
05-16-2004, 05:35 AM
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Pretty good, but out of curiosity, what were your high end RPMs when you shifted?
Below 60 I totally agree, but at 60, you can still get 30mph out of 3rd gear before heading for 4th if you take it to redline. I use 3rd all the way to 85-90 out on the track regularly because of the extra oomph you get in the high RPM range. I typically run 4th up to around 115-120 and 5th is only occasionally used in long straights.
I also agree with you to never bog this engine down in low end RPMs (below 3K) and expect raw torque to help you out like the B5 S4's can do. That was one aspect of my driving/shifting habits I had to change after moving to this platform.
I also agree with you to never bog this engine down in low end RPMs (below 3K) and expect raw torque to help you out like the B5 S4's can do. That was one aspect of my driving/shifting habits I had to change after moving to this platform.
05-16-2004, 08:19 AM
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For obvious reasons I wasn't looking at the tach, but...
I carried it pretty close to 7k.
I may be off by 5mph, it may be 65 at which 3rd is no longer a good call. It matters less what speed you can get to in the gear than it does how long you spend in the gear, and whether the speed you need to get to is just outside that gear.
Passing is timeline driven. You need to get to a speed that is identified by feel, not by a needle. I may be 90, but it may be 95, and you don't know until you're at it. You need room for error too - like technically you might only need 85, but you can't necessarily predict how much you'll need that accurately. If it turns out you need 95, and you hit the wall at 90, you'd have been better off starting in the higher gear.
It's weird. The ability to get an extra 10 mph w/out shifting if it turns out you need it is worth more than getting to the right speed 1/2 sec earlier in a lower gear, coupled with the risk that that "right speed" might not be in that gear.
Another factor is that the last 700 rpms don't accelerate you faster in the lower gear. It's fine to use them if you're already in it. But before hand when you are choosing a gear, you learn to factor them out of the decison. E.g. if you're at 5k, you don't ask how much speed can I pick up until 7k, you ask how much until 6.3k - and then you ask how different that is vs. the higher gear. And then you ask if that difference is worth the shift.
Except it's not a 3-step decision process; it's 1 step - the real decision is "Did this work out well last time I did it this way?"
I may be off by 5mph, it may be 65 at which 3rd is no longer a good call. It matters less what speed you can get to in the gear than it does how long you spend in the gear, and whether the speed you need to get to is just outside that gear.
Passing is timeline driven. You need to get to a speed that is identified by feel, not by a needle. I may be 90, but it may be 95, and you don't know until you're at it. You need room for error too - like technically you might only need 85, but you can't necessarily predict how much you'll need that accurately. If it turns out you need 95, and you hit the wall at 90, you'd have been better off starting in the higher gear.
It's weird. The ability to get an extra 10 mph w/out shifting if it turns out you need it is worth more than getting to the right speed 1/2 sec earlier in a lower gear, coupled with the risk that that "right speed" might not be in that gear.
Another factor is that the last 700 rpms don't accelerate you faster in the lower gear. It's fine to use them if you're already in it. But before hand when you are choosing a gear, you learn to factor them out of the decison. E.g. if you're at 5k, you don't ask how much speed can I pick up until 7k, you ask how much until 6.3k - and then you ask how different that is vs. the higher gear. And then you ask if that difference is worth the shift.
Except it's not a 3-step decision process; it's 1 step - the real decision is "Did this work out well last time I did it this way?"
05-16-2004, 08:28 AM
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but again, it's the whole situation, not just the gear.
If you're going 75, and you've got 10 mph on the guy you're passing, 3rd is great. If he's going 75 too, and there's somebody in front of him, 3rd is not going to cut it for you. 90 ain't good enough to pass somebody going 70, and 70-100 is faster done all in 4th than it is w/ a 3rd/4th transition.
And yet *another* factor I just realized is that *when* the shift needs to occur also matters. There are certain points in an on-coming pass situation where you have too much on your mind to execute a clean shift. So if the shift needs to happen in one of those places, you'll pass quicker if you had started in the higher gear, and avoided the need to shift.
There were more than a couple times that day when I started in too low a gear, and found myself up against the rev limiter for about a second while I was getting around to shifting. Or maybe it was that I had counted on not needing to shift, and the change of plan took time to recognize & execute.
Life gets interesting when a 3-second event is experience-rich enough to take 3 paragraphs to describe ;-)
And yet *another* factor I just realized is that *when* the shift needs to occur also matters. There are certain points in an on-coming pass situation where you have too much on your mind to execute a clean shift. So if the shift needs to happen in one of those places, you'll pass quicker if you had started in the higher gear, and avoided the need to shift.
There were more than a couple times that day when I started in too low a gear, and found myself up against the rev limiter for about a second while I was getting around to shifting. Or maybe it was that I had counted on not needing to shift, and the change of plan took time to recognize & execute.
Life gets interesting when a 3-second event is experience-rich enough to take 3 paragraphs to describe ;-)
05-16-2004, 08:31 AM
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I probably spend a little more time staring at the tach out on the track
because I am doing the same turns again and again without trying to worry about oncoming traffic. I have the opportunity to explore that same chunk of road repeatedly with different tactics to see what works.
I have generally found that the low end for shifts is somewhere in the 3500-4500 range and I try to always stay above 3500 when I am doing laps. I agree that you don't want to downshift at 5K because a) there isn't enough left in that lower gear to make it worthwhile and b) that's a pretty good place to be for torque in the gear you are already in.
The 4500-5000 is the question mark range and a lot depends on what you are about to ask your car to do. In traffic like you are describing on the flats I would tend to leave it in the gear I am in and punch it. If I was looking for a lot of rapid gain in RPMs with a passing lane on a hill, I might be inclined to downshift even though it will be a short time in that gear.
I have generally found that the low end for shifts is somewhere in the 3500-4500 range and I try to always stay above 3500 when I am doing laps. I agree that you don't want to downshift at 5K because a) there isn't enough left in that lower gear to make it worthwhile and b) that's a pretty good place to be for torque in the gear you are already in.
The 4500-5000 is the question mark range and a lot depends on what you are about to ask your car to do. In traffic like you are describing on the flats I would tend to leave it in the gear I am in and punch it. If I was looking for a lot of rapid gain in RPMs with a passing lane on a hill, I might be inclined to downshift even though it will be a short time in that gear.
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05-16-2004, 09:07 AM
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Also remember, on a hill, you'll spend more time in the gear
making a higher RPM downshift more worthwhile.
I think on a 30% grade, I'd gladly elect to start a passing manuver at 6k rpms. Wait, that's not quite right. Let me try that again...
Were I to <i>choose</i> to start a passing manuver on a 30% grade, I'd gladly elect 6k rpms to be the <i>engine speed</i> at which I'd start.
I think on a 30% grade, I'd gladly elect to start a passing manuver at 6k rpms. Wait, that's not quite right. Let me try that again...
Were I to <i>choose</i> to start a passing manuver on a 30% grade, I'd gladly elect 6k rpms to be the <i>engine speed</i> at which I'd start.
05-16-2004, 01:57 PM
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Lol - I know exactly what you're talking about.
I often play scalps, to see how many ppl I can pass on my way to work.
You've tried to put into words, what I call driver feel to a situation. It's tough to describe and easier to demonstrate.
You've tried to put into words, what I call driver feel to a situation. It's tough to describe and easier to demonstrate.