Tricky corners, how to know when to stay in 3rd and when to go into 2nd
 

I posted this on rennlist, but there are not as many Boxster folks there...

In my 2000 S 6 speed, there are a few corners where I am not sure whether to stay in 3rd or go down to 2nd, like T7 at Road Atlanta or T12 at VIR.

In both of those corners, I seem to consistently have a vMin of 40 when I drop down to second, and vMin of 43-44 when I stay in 3rd. But my best lap time at each track was set when I dropped to 2nd, but because of traffic and other things, I don't feel it is as simple as that (aka I still don't know if 2nd is better). And I don't know enough about data to look at it and see. I do have an AIM Solo DL that I have been using and so the data is there once I can learn to use it. For now I mostly use it for lap times, predictive lap times, and data overlay for videos.

T7 at Sebring (vMin 36) is a no brainer to go to 2nd, but on some of the other corners it feels like it is right on the borderline between 2nd and 3rd, but by staying in 3rd and learning to roll more speed, I feel like staying in 3rd is the right choice.

T3 - vMin 53
T10 - vMin 49
T13 - vMin 55
T16 - vMin 55

Next time I go to Road Atlanta (T7) or VIR (T12), I wonder if I should focus on:

Roll more speed and leave in 3rd
Try and roll more speed, and don't overslow as I go to 2nd

What strategies do you like for knowing when to try and roll more speed in a higher gear, or to get the downshift so they can pull better after the corner? Do you have a target RPM that if the corner takes you below, you like to get the lower gear?****

Thanks!

​​​​​​​Steve

you're over-braking on the downshift into the corner, vs not having enough torque on the exit.

try downshifting in the middle of the corner instead. i know, hearsay! just be smoooooth.

I am trail braking pretty far into those corners, maybe I can do the shift closer to the apex right before I release the brakes.

The trick is not to overslow... it is probably all mental...

This.

Even if you can roll 3rd gear through a corner, you may not be carrying sufficient speed to accelerate out of the corner very quickly because of lower torque at lower RPM's.

Thus, going thru the corner in 2nd, even though the cornering speed might be slightly slower, can result in a faster overall lap time because you will be at very high rpm on corner exit and get a great jump out of the corner and carry that speed all of the way down the next straight.

I experience this issue at Buttonwillow raceway in the Star Mazda turn in the counter-clockwise direction. I have found that going to 2nd and then hammering out of the turn results in a better lap time than rolling through in 3rd and waiting for the torque to come on as I exit the turn.

Of course, the best answer is to get good enough to go through in 3rd fast enough that the rpm's are high on corner exit! :)

Does your data show your speed at the end of the straights? That is what you should look at, when comparing 2nd or 3rd gear in the same turn. You need to see which gear gives you the most speed at the end of the straight. As thstone says, it's about the acceleration coming out of the turn.

I recommend getting your downshifting done before the corner, so you can concentrate on getting through the corner as smoothly as possible. Downshifting in the middle of a corner is good way to unsettle the car, not to mention increase your chance of a mistake. Sorry RK, I think you are speaking hearsay!

VIR I find I get the best launch out of T12 in second gear. The true tell is your brake point speed at the end of the back straight. If I come out of T12 in 3rd I top at 128-130. If I come out in 2nd I can reach 132-136. Its all uphill any torque you get converts to speed at the end.

Diamond the entry to 12 this also give some extra entry speed. Cut so your headed at the back rumble strip brake quick while straight then turn toward the inside rumble strip and as soon as you can lay on the gas drift out to the outside strip then it all acceleration.

My warm lap time at VIR is 2:19 in traffic to 2:15.5 in clear track

if you're not damn near ****************ting your pants at turn in, you got on the brakes too much.

I'd stay in third.

Everything I know about this comes from Superbikes.... But the parts I'll tell you about most certainly apply to cars as well. :-):cheers:

There are two rules I always emphasize at the racetrack:

1) Three-Time World Champion Freddie Spencer always said "Go Fast in the Fast Stuff".
Everybody is slow in the slow stuff. If you want to beat somebody, it happens by learning how to go faster when and where it matters. Others have alluded to it here already: use the slow stuff to setup for the fast stuff.
Which brings you to rule number:
2) The quickest way to find the fastest way around a race-track is to learn it backwards.
Start at the fastest part of the racetrack, and ask "if I want to go fastest here, where do I have to be when I enter the straight? That means making that straight as LONG as possible (meaning you reach full-throttle earlier in the straight). So if I want to be able to be "here, this fast" at the beginning of the straight, then where and how fast do I need to enter the corner? .... etc ..... etc..... work your way backwards through the racetrack like that.

So the question is exactly as another commenter below has posed: which gear gets you the most speed at your braking point on the straight?

For me, in the car, I tend to think I can carry more speed through the corner and thus begin my straight from a faster start. But invariably the car understeers, scrubbing speed, and I can't get the car to turn so I end-up lifting the throttle and ruining my drive. Being a little more patient (going slower) earns me huge dividends on the drive out of the corner, and that equates to more speed all the way down the straight.

A Short-Shift (does this term work in the car-world?) can be very handy on occasion, when it lets you go WOT when you're tempted to get greedy, and it very slowly picks-up speed through the corner and is finally in the power by the time you're driving out. This is a very smooth way to exit a corner fast. But if you find you have to lift AT ALL, then you blew it and you should be in a shorter gear.
On the other hand, if you find you have lots of corner-exit left, then you aren't going fast enough and should probably be applying that throttle judiciously in a shorter gear.

Doe that all make sense?

These! On these corners, at turn in, I am going too fast for second, but by the time I get to the apex and get back on the gas, I am lugging in 3rd. So I end up overslowing and getting my shift done, but then I can really rocket out of the corner in 2nd :)

If I can keep that extra 3 mph and still get my shift, I think I could pick up some time... And to do that, I am going to have to move the shifting into the turning phase while I am still trail braking, which carries more risk than shifting in a straight line. I have chirped the back wheels a time or two on a flubbed throttle blip, and I have seen cars upside down on the wall at T7 at Road Atlanta, so that is something to keep in my mind...

Yes it is terrible to get a great run through a corner and then be lugging in 3rd :) I guess the question is, can I get fast enough through the corner for 3rd to be effective? In some turns, I have been able to get faster (like at T10 at Sebring which used to be right on the borderline between 2nd and 3rd for me, but now is a solid 3rd gear corner).

This is the tricky one - last time I was at Road Atlanta, and I was running T7 in 3rd and getting a good run through there (43-44 mph). For some reason, on one lap, I decided to go to 2nd, got a 40 mph vMin, and as I was headed down the back straight, the predicted lap time started dropping... that lap turned out to be my fastest lap of the weekend and new personal best at Road Atlanta (1:48.something). So it seems like that definitely does answer it :)

If I can just get to where I don't overslow for the shift...

That is smoking fast! I watched your videos (and a couple of others, truegearhead, etc) before going to VIR before Thanksgiving, that was a fun weekend.

I think I got up to 129 on the back straight, launching in 2nd at 40 mph from T12, although I think I also got to 129 when I laucnhed in 3rd at 44 mph. When I get up to that speed it increments very slowly. I got to 140 mph at Daytona right around the start finish line after a long run from the bus stop through Nascar 3 & 4. I think you have a little more power, I love watching (and listening) to your videos.

I got a high 2:21 that would have been a 2:20 but I had to lift and give a point by right before hog pen. My next fastest lap was a 2:23 so that one lap was my flyer. I can't wait to get back.

Great discussion! Thank you everybody.

That is the 2nd time I have heard the term "diamonding a corner", the first time was at Sebring a few months ago when I rode with John Gaydos from Soul Performance in his Cayman R (what a car!). He sailed into T5 way faster than I would have thought, then using the brakes he swung the back end around and then nailed the gas and rocketed out of the corner. He called that Diamonding the corner. He has tremendous car control, he was sliding through T1 and through Bishop very fast. it was crazy fun and was the last session of the day, I wish I could have jumped back in my car while it was still fresh in my mind.

Is that what you mean by Diamond the entry?

when determining best rpm, i think they call it 'staying on the cam' - keeping your rpm in a certain torque band - say 3.5 or 4k rpm to 6.5 or 7k rpm in our cars. hence the downshift; as your car slows in a turn you downshift to stay in that band.

so, if you are not downshifting and your rpms drop below a the magic number then either (a) downshift, or (b) be faster (hey; just the act of turning the steering wheel slows the car even without any brakes - i think quadcammer is on the money there).

or, if you are downshifting and seeing that your corner entry speed is lower than if you didn't, then your downshift is causing you to either (a) over-brake, (b) come off throttle too soon (c) not pay attention to the turn-in, or (d) not be in the right gear on entry (ie, the corner entry is too fast for second, but the exit is too slow for third).

fix (a)(b)(c) by getting better or getting a pdk. fix (d) by changing where you shift. think two situations:

late apex/reducing radius turn - second may be too slow at entry, but exit may may be too slow for third. if you are downshifting on entry then you are overslowing the car, but if you drive it in third then you lug on exit. you have to move your shift point deeper into the turn.

early apex quick little turn off a long straight - you are coming at it FAST and a lot is happening on the downshift/braking/turn in - try combining them - let the downshift help you rotate (similar changing brake bias or pads front to back) and let the throttle blip be your gas on out of the apex.

realise - if you are trail braking then you don't car what gear you are in or what your rpms are at - you only care about that when back on the gas at apex. people say don't shift in the turn as it will upset car balance, but note the transition from brake to gas also changes balance, so why not combine the two actions?

Allot of people I watch trun and hold the turn thru all of T12. Which mean you have to slow completely to your turn speed before you cut in. I try to slow enough to turn in and cut across the first rumble strip maintaining some speed. Now your headed diagonally across the track to the outside rumble strip, tap the brake set the nose and turn towards the inside exit. As soon as the the car grips hit the gas. This will shoot you out at better speed and push you too the outside exit rumble strip.

If you look at it from overhead it's squares off the turn. Light turn in, straight, finish the turn. Diamond shaped

Good conversation.

My basic rule is to always stay above 4k exiting a corner, nail all of the apex, and get on the gas as early as possible to lengthen the straight. I want to be at or near full throttle and unwinding at the apex so this dictates my corner technique. If on a right-hander my wheel marker is still at 3 o'clock and I am hesitating on throttle at the apex, I am doing it wrong.

Trust the data. Run one full session taking the difficult corner in 3rd, and one full session taking it in 2nd. Which method consistently rewarded higher speeds at the end of the next straight? Which method resulted in faster laps? It will almost always be the same session because higher speed at the end of the straight overcomes lower corner speeds.

Take the corner out of the corner. Cars run faster when pointed straight with tires unloaded so spend as little time as possible side loading the tires. "Squaring the corner" or "diamond the corner" mean the same thing and are a double apex method. Come in hot, turn in and brake across the corner, quickly rotate the car for a very straight apex and exit at full throttle. You give up corner speed, usually need to select 2nd, but gain by carrying more speed into and out of a corner. This does not work on most corners but a 180* like 4/5 at AAA Speedway, Star Mazda at Buttonwillow, or the bowl at Chuckwalla CW it might be your best move. Run it both ways and compare the data, then decide.

Makes good sense, I have heard Ross Bentley say something similar - often the big gains can be had in the fast corners. Another saying I have heard is that a common mistake is to go too slow int he fast stuff, and go too fast in the slow stuff.

Short shifting is a good technique - I have used it when building up to full throttle in fast sections like Bishop at Sebring - I am almost there, although it was pretty hot last time I was there so the car was down on power a little - I am going this weekend and it should be a lot cooler so we'll see if I can do it.

If you fall below 4,000 RPM then not much is going to happen for a while, that's for sure :)

For me 4,000 RPM in 3rd is about 52 mph and 2nd gear at about 6,400 is about 62 (I can dig out the gear chart and get better numbers, this is from looking at my AIM data which I think has some smoothing, and the RPM is only read 2-3 times a second), so if I were to try and use that as a guide, then unless I could roll a vMin through a corner of 50 or more, then 2nd gear might be a good option.

Things to think about :)