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Tracking / Autocross / HPDE / Drifting What these cars were built for!


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Old 10-16-2021, 09:05 AM   #1
ZDan
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When "better" gearing is slower

I've repeated this 1,000 times, but changing gearing is one of the least effective mods. It doesn't magic you any better power/weight, it only moves shift points around, which may help you but just as likely can HURT lap times, depending on the track.

I had two sets of Yok A052s at New Hampshire Motor Speedway (South Oval config) last weekend, 245/40-17 (stock tire diameter at 24.7") and 235/45-17 (25.5"). Running the taller 235s should be roughly equivalent to changing diff gearing from 4.3 to 4.16. Thing is, at this track, with the taller tires I could keep it in 4th gear at the end of the front straight entering the oval turn, same going into T3, and I could keep it in 3rd between T10 and T11. Best laps with the 235/45s were 0.4 seconds (or more) quicker vs with the 245/40s.

Here are my best laps from Sunday, green on 235/45-17s, purple on 245/40-17:
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Old 10-16-2021, 09:59 AM   #2
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Yep, gearing can only be optimized to a specific situation, not improved for every situation.
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Old 10-16-2021, 11:17 AM   #3
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For track purposes, yes. But for street fun and pure acceleration, shorter gearing is funner/faster.
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Old 10-16-2021, 11:56 AM   #4
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Originally Posted by Petah78 View Post
For track purposes, yes. But for street fun and pure acceleration, shorter gearing is funner/faster.
Until you have to upshift earlier and are in the next taller tansmission gear, where you are slower...
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Old 10-16-2021, 12:31 PM   #5
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Post the lat and long g plots too
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Old 10-16-2021, 12:53 PM   #6
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It depends where you are driving. When I was in Germany, there wasn't much need to switch to a shorter final drive ratio. In fact my factory 3.727 FD was much better, because I could achieve top speed in 5th gear (the 6th gear is very tall and it is just for fuel efficiency). When I moved to another country and I started driving mostly on the mountains and not caring about top speed, the 2nd gear didn't have enough torque and the 1st gear was too short to use it. So, I switched to a 4.3 FD to have a better 2nd gear with more torque on corner exiting.
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Old 10-16-2021, 01:09 PM   #7
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Until you have to upshift earlier and are in the next taller tansmission gear, where you are slower...
Even for track use, different tracks will dictate the optimal gearing. The data that you posted shows that longer gearing worked better on that particular track. But I bet you will be able to find other tracks that are opposite where shorter gearing is faster.

Fact is, shorter gearing will put down more wheel torque, gear for gear. More torque = faster acceleration = more fun. On the street, I will only hoon up to the end of 2nd and shut it down. I dun care if end of 2nd is 55mph or 65mph. The fact that I can feel more torque and accelerate faster to the end 2nd = more fun. But that is me and I can't say it applies to everyone.
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Old 10-16-2021, 01:35 PM   #8
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Originally Posted by Petah78 View Post
Even for track use, different tracks will dictate the optimal gearing. The data that you posted shows that longer gearing worked better on that particular track. But I bet you will be able to find other tracks that are opposite where shorter gearing is faster.
Which is what I said in post #1: "...may help you but just as likely can HURT lap times, depending on the track."

Quote:
Fact is, shorter gearing will put down more wheel torque, gear for gear. More torque = faster acceleration = more fun.
But for a given power/weight, "fun" is *conserved*. I.e. for all the time you'll enjoy a small acceleration advantage from a given speed in the same gear, there are going to be speeds from which you'll be at a significant disadvantage due to having to be in the next higher transmission gear.

Quote:
On the street, I will only hoon up to the end of 2nd and shut it down. I dun care if end of 2nd is 55mph or 65mph. The fact that I can feel more torque and accelerate faster to the end 2nd = more fun. But that is me and I can't say it applies to everyone.
It doesn't apply to me, I still don't get the idea that it's somehow more fun to accelerate slightly harder to a slightly lower max speed in a given gear. Fun for me has been more related to having the right ratios for a given track at 10/10ths, or for a given set of backroads curves at 6/10ths but in that case I'm not generally revving it to redline every time anyway so gearing not really critical...
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Old 10-16-2021, 02:15 PM   #9
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Quote:
Originally Posted by ZDan View Post
Which is what I said in post #1: "...may help you but just as likely can HURT lap times, depending on the track."

But for a given power/weight, "fun" is *conserved*. I.e. for all the time you'll enjoy a small acceleration advantage from a given speed in the same gear, there are going to be speeds from which you'll be at a significant disadvantage due to having to be in the next higher transmission gear.


It doesn't apply to me, I still don't get the idea that it's somehow more fun to accelerate slightly harder to a slightly lower max speed in a given gear. Fun for me has been more related to having the right ratios for a given track at 10/10ths, or for a given set of backroads curves at 6/10ths but in that case I'm not generally revving it to redline every time anyway so gearing not really critical...
Reading comprehension owns me!

Just different priorities/preferences. I see track 5-6 times a season and they are only casual lapping rather than time trails. A quicker 0.3 sec per lap is irrelevant to me. Fun for me is taking a turn or hwy ramp at 6-7/10 and then running out 2nd or 3rd. The faster that section is, the funner. And with shorter gears, the car is more responsive in any given gear. One of my close friend recently upgraded to a 991 CS and is sort of regretting it. He was referencing "gear frustrations" where he can't even goose 2nd without worrying about going to jail.
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Old 10-16-2021, 02:31 PM   #10
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For a street only car, I'd pick the FD so that both 2nd and 3rd gear can be used effectively without breaking the speed limit. I like 4.3 for revving the 2nd all the way to the limiter, and shifting 2-3-2-3 as I drive in the mountains. Quite unlike what Porsche did with recent Caymans.

For track, depends on the track. In my experience, Thunderhill is better with 4.1, Laguna Seca is better with 4.3.
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Old 10-16-2021, 02:47 PM   #11
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Quote:
Originally Posted by RedReplicant View Post
Post the lat and long g plots too
Here dey are. However "inline accel" makes no sense at all! IN the words of Bubbles: "Somethings f**ky..."
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Old 10-16-2021, 03:06 PM   #12
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For a street only car, I'd pick the FD so that both 2nd and 3rd gear can be used effectively without breaking the speed limit. I like 4.3 for revving the 2nd all the way to the limiter, and shifting 2-3-2-3 as I drive in the mountains. Quite unlike what Porsche did with recent Caymans.

For track, depends on the track. In my experience, Thunderhill is better with 4.1, Laguna Seca is better with 4.3.
Yup I love my 4.3 for laguna. Only issue I run into is going over turn 1 im at 4th gear redline (104mph) and I could shift into 5th to gain speed but it feels safer to focus on the upcoming braking.
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Old 10-16-2021, 03:56 PM   #13
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Here dey are. However "inline accel" makes no sense at all! IN the words of Bubbles: "Somethings f**ky..."
Yeah, something weird is going on there with both. The GPS (AIM) accel probably makes more sense to look at in this case, unless it isn't tightly mounted to the car.
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Old 10-16-2021, 04:15 PM   #14
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Wait hold up, we have to mention that this change isn't JUST gearing and must be taken with a massive grain of salt. More things change when moving tire sizes. Mainly, the shape of the tire changes as well as weight. Thus, pressures will have to be optimized for both.

Claiming that this data is due to gearing only is not true.
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