ProCoach

Brake light switch would be fine, if only to compare brake points, but I can show you how to do that using only the long G.

luffe

A street tire pressure question: on the track, when the tires heat up, should I let out air until the pressure reaches the factory recommendation? Thanks

Matt Romanowski

I've found on many of the newer Porsche's the factory recommended pressures are pretty good for street tires. They give you a great place to start and experiment.

hf1

Car-makers usually recommend lower pressure in front and higher at the back in order to make the car understeer (less likely to oversteer) for safety reasons. You probably want that difference to be smaller for the track to make the car more neutral.

Also, car-makers may recommend higher pressures for improved fuel economy. You would be optimizing for grip and longevity at the track instead so the optimal pressures for those goals may be different (slightly lower) than the recommended.

Given all this above, you could use the recommended (cold) pressures as a ball park reference then experiment with higher/lower pressures depending on the grip and the wear patterns.

Veloce Raptor

Agreed.

bobt993

Looking at your Vmins/lat Gs since Peter suggested applying the speed trace:

T1 lat Gs shows a good amount of understeer ( LAT G stairstep ) on exit. Both laps show the same condition so this is part driver inputs and setup. T1 is down hill and allows gentle trailing to rolling transition on turn entry. You can populate lat G early with slight oversteer here and maintain a much higher Vmin (on your tires up to 70mph). This moves throttle slightly forward, but your way ahead of your current Vmin so your speed to T2 will still be higher. You can see you did this better in T6 (laces), but still have the stairstep. ( are you settling into your turn in wheel position or are sawing a bit ?). WG has some very sustained lat G corners. I would work on populating the midcorner speed (lat G) as Adam points out (missing in the Gplot). A good instructor /coach can help you explore this by riding with you and working on a bit more entry speed. You should notice the valleys on your speed trace to start going away. Just getting the mid corner improved is worth a bunch of time. When I was there in May the racer picked up over 3 secs over two days focusing on mid corner and small bit of car setup.

GuyIncognito

cold or hot?

Matt Romanowski

I've found what is printed in the door to be a good hot temp.

GuyIncognito

ah OK, that makes more sense

Matt Romanowski

I've never heard of looking for understeer by looking for a "stair step" lat g graph. Wouldn't an understeering car produce a flat topped curve, not a stepped? In my experience the lat G trace goes flat topped (or bottomed) when the car really pushes.

Also, do you really think his car can do a Vmin of 70 mph in turn 1? That seems way higher than I would expect based on the data I have from the Glen. From what I have, a 70 mph Vmin would be around a 2:10 lap and in something like a 996 Koni car.

ProCoach

Ha! For instance, the data I have for my 1:59 in a 145 bhp car at Turn 1 shows a minimum of 73mph, with a maximum of 126 mph before the bus stop.

A REALLY well driven RSR replica (with a bigger motor) on slicks doing low 2:01's does 71 mph and a Brabham BT-29 Formula B car (210 bhp on treaded tires) does 73 mph.

I've never seen a vMin at Turn 1 of more than low to mid 60's on a modern GT car on Continental slicks... Less on almost ALL DE cars...

Matt Romanowski

Ok, more to my point. I'm not sure a fairly stock 944 on Toyos will have a Vmin that high.

Veloce Raptor

Agreed. Less than likely...

pontifex4

It's a fairly stock 968, Matt. Clearly, that changes everything. Also, you guys are missing the bigger point that I'm way too big a coward.

Bob, this is the second time I've heard this more early LatG loading idea in T1. I'm just now working out when I'll be able to get down there again to work on what everyone has mentioned so far.

Also, for a total newcomer to data: can you show me the stairstep LatG formation that you're referring to on the exit of T1? Could this contribute to the feeling I have that I'm still adding or holding steering after the apex? You mention the laces, and I also get that feeling there. In answer to your question:

I don't think I'm sawing. Indeed, as a few have stated, I'm not really testing the limits. Representative laps start at 2:20 below:

Matt Romanowski

Sorry, I knew it was a 968. With that, it should do about 90 Vmin!

Come out to the NER event in August. I'll go for a ride with you and Peter Argetsinger will be there again for classrooms and coaching.

Overall, I think the big thing is you need to just carry a little more speed into the corners. When you get to the point in your braking where you think "just a little more," that is the time to take your foot off the brake. The first time feels like an "O-S#@$" moment, but then it works and becomes the new normal.