Using PDR to predict maximum corner speeds
Thread Starter
Cruising
Joined: Feb 2017
Posts: 14
Likes: 1
From: Freeland WA
Using PDR to predict maximum corner speeds
Using the PDR, one can get the speed and lateral g forcevalues for a curve. By using Google maps or a track blue print, corner radiuscan be estimated. Using the equation for lateral acceleration, it seemspossible to calculate the max speed for a corner assuming a maximal lateral gvalue. Does this make sense? I realize there are a lot of assumptions here suchas surface, tire temps, banking of corner etc, but I am trying to get an ideahow fast I can go in different sections of the track without having to push tothe point of understeer.
Le Mans Master
Joined: Oct 2011
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From: DFW, Tejas!
Sounds like a good way to wreck.
You mention yourself there are many variables and you event forgot some, like your vehicle speed (aero). Beyond that, most turns aren't perfect circles. Late apex, early apex etc, are you on the gas hard, brakes hard, etc.
It's not just lateral acceleration either. You should follow the edge of the circle on the accelerometer. The goal is to get on the gas the earliest, not pull the most G's.
Further, lateral acceleration is a static measure. It doesn't take into consideration things like weight transfer when you're talking about the max.
These things aren't insignificant, nor do you take turn in a uniform circle, under constant load. There are turns my car registers at 1.4 Gs. There are turns where 1.4 G's would have me upside down in a ditch. There are days I can take a turn at 1.4 Gs. There are other days that same turn at 1.4 would have me spinning. Heck, it changes lap to lap depending on tire temp- which again is a big deal.
Just keep working on a few turns every session, gradually building up. While G is a fun stat, it's not very informative for how well you're taking a turn.
You mention yourself there are many variables and you event forgot some, like your vehicle speed (aero). Beyond that, most turns aren't perfect circles. Late apex, early apex etc, are you on the gas hard, brakes hard, etc.
It's not just lateral acceleration either. You should follow the edge of the circle on the accelerometer. The goal is to get on the gas the earliest, not pull the most G's.
Further, lateral acceleration is a static measure. It doesn't take into consideration things like weight transfer when you're talking about the max.
These things aren't insignificant, nor do you take turn in a uniform circle, under constant load. There are turns my car registers at 1.4 Gs. There are turns where 1.4 G's would have me upside down in a ditch. There are days I can take a turn at 1.4 Gs. There are other days that same turn at 1.4 would have me spinning. Heck, it changes lap to lap depending on tire temp- which again is a big deal.
Just keep working on a few turns every session, gradually building up. While G is a fun stat, it's not very informative for how well you're taking a turn.
Last edited by village idiot; Oct 8, 2017 at 02:20 AM.
Tech Contributor
Joined: Oct 1999
Posts: 41,058
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From: Charlotte, NC (formerly Endicott, NY)
It is a little more complicated than that. Here is a YouTube discussion of M Schumacher's driving style compared to one of his competitor's.
It is an enlightening to see how he controlled throttle and steering to get through a corner faster by keeping the car on the limit.
Bill
It is an enlightening to see how he controlled throttle and steering to get through a corner faster by keeping the car on the limit.
Bill
Le Mans Master
Joined: Oct 2011
Posts: 7,079
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From: DFW, Tejas!
You can look at your accelerometer too I guess- that can help to a degree. At the end of the day, driving isn't formulaic.
Last edited by village idiot; Oct 8, 2017 at 10:32 PM.
Pro
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From: Houston TX
Pro
Joined: May 2012
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From: Milwaukee WI
There is a really neat paper someone did like this from a bmw club on road america. It says you can take the kink at like 140 at 1.1 g's or something street tireish. Which if i survived would make me rich. Extrapilating the pucker factor at 105 to 140 would definately cause diamonds to be created in my butt. 
Other then the kink and bill mitchel its actually pretty realistic though.
Other then the kink and bill mitchel its actually pretty realistic though.
Pro
Joined: May 2012
Posts: 666
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From: Milwaukee WI
http://badgerbimmers.org/cms/wp-cont.../Lap-of-RA.pdf
That isn't the actual one but I believe its possibly a variant of it. The sheet i am thinking of is more or less this same sheet but it has 1.0 1.1 1.2 1.3 1.4 g's corner speed using the donohue formula labeled at each corner in the printout.
That isn't the actual one but I believe its possibly a variant of it. The sheet i am thinking of is more or less this same sheet but it has 1.0 1.1 1.2 1.3 1.4 g's corner speed using the donohue formula labeled at each corner in the printout.
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https://www.corvetteforum.com/forums...i-toolbox.html
As far as lateral G's are concerned, I've not found that terribly useful but I've seen some pro coaches using G Sum to help a driver know whether they could go faster through a given corner. As others have noted though you can't expect to get to the same limit in each corner but it gives you an approximation. G Sum is just the total of lateral and longitudinal G's added as the absolute value of each.