SCCA Solo C Street Discussion

[NJ10]

Originally Posted by slyphen

So my question is, for those who raced on stock tires and swapped to RE71Rs, how much time did you think you've shaved off on average? .

2-3 seconds improvement would be fair, I also have a problem with overdriving the fronts. I tend to make my car plough through corners. The stock tires are very talkative and you can learn a lot more about the balance. Like DocWalt said, I've switched to RE71s and my overdriving has caused me to wear out my fronts a little worse and a lot weirder than other local FR-Ss.

I'd suggest moving to the RE71s only if you feel you've reached your limit with the stock tires. I wish I spent more time fixing my driving style with the stocks.

[slyphen]

Originally Posted by DocWalt

Don't think about how much time gain there is going from stock tires to something sticky, you'll end up really frustrated if you throw the new tires on and don't go much faster and destroy the tires. Overdriving RE71Rs will wear them out VERY quickly (especially plowing into corners way too fast), so I'd suggest figuring out how to find the line between underdriving and overdriving now on the stock tires.

How are you comparing your times between autocross events?

My time has been fairly consistent placement wise, since every session has a different course. steady improvement at the beginning and the last few events has been plateauing. Annie Gill, Tasha Mikko has been giving me a lot of great tips and ride alongs, but my car right now is too tail happy. i'm waiting to try on the RE71s and see if it dial back the oversteer, if its still unbalanced, i will upgrade to 22mm front sway bar, which im sure will balance the car out. (currently have 7k front 8k rear springs on FA coils, once i get good enough, i will upgrade to KW or RCE)

http://www.conechaser.com/driver/qingrui.(jim).zhu

[Twinz]

My brother and I autocrossed my bone-stock FRS recently and, while we were way down on grip with the stock tires, we both thought the car's balance was great.

[NJ10]

@slyphen why not try the swaybar first, then the tires. Cheaper experiment too...

[Twinz]

Originally Posted by slyphen

Its getting frustrating that i can't get better time. i'm sure the driver(me) still have a lot of improvements to make, and i will keep doing so till my tires get here. areas i could work on at the moment is still looking ahead, braking early and finding the correct line.

Have you had instructors drive your car? How do your times compare to their times in your car?

[slyphen]

Originally Posted by Twinz

Have you had instructors drive your car? How do your times compare to their times in your car?

yes, the few times i did, i beat both of their times at the end of the day. (not annie gill, shes freaking crazy). the reason my balance is off is because of the spring rate i have. it used to understeer, perhaps more because of me than the car, so when i purchased the coils i over estimated the amount of oversteer i would get.

Dont get me wrong, im not saying its completely the tire's thats holding me back. I myself could probably get another 2-3 sec with some more seat time as i get better as a driver.

[Twinz]

As a natural overdriver myself, I know it's important to get that in check first. Good tires have a way of covering up mistakes. Crappy tires tend to highlight them.

[TrqlessWonder]

Originally Posted by NJ10

@slyphen why not try the swaybar first, then the tires. Cheaper experiment too...

even cheaper experiment: disconnect the rear for an event.

But yeah, I'd wear out whatever tires you have on there presently. Extra repetition/frsutration when fighting an uphill battle will help with technique a lot. Your hands will slow down and smooth out and it'll force you to be very deliberate with your inputs. Might even start changing your lines because you'll start to see how car position matters to eek out a respectable time out of the lesser equipment. IMO you'll be in a better spot to move on to the better tires once you stop gaining time (on index, imperfect as it is) on the event podium folk.

[slyphen]

Originally Posted by Twinz

As a natural overdriver myself, I know it's important to get that in check first. Good tires have a way of covering up mistakes. Crappy tires tend to highlight them.

No doubt! I spun in every event since Event 3 trying to find the limit. last event i crossed the finish line sideways praying not to hit the timing equipment. I've corrected a lot bad habits because of these shitty tires and i'm getting a really tired of them. last event going through wide sweepers, i couldn't apply 100% throttle cuz the back end keep swinging out. i kept it at the edge at about 80% throttle, losing a lot of time.

[Jawnathin]

I went ahead and calculated the thrust curves between the old car and new car.

I eyeballed the torque readings from the dyno chart and converted from nM into Lb Ft. Not 100% clean since the thrust chart spreadsheet I used goes in 250rpm increments while the dyno from Subaru is in 400rpm increments, but I think close enough. I included the datasheet for review.

On 225/45s the new car is about 3mph slower at the top of 2nd gear. I went ahead and added a plot for using 235/45/17s which gives it about another 1mph.

[Jawnathin]

Originally Posted by renfield90

Just look at nats results bro. The fastest BRZ was driven by a multi-time jacket winner, and was not well placed.

I am a little late to the party but a few observations on this. Brian in his BRZ was dirty on all runs for day two. He had the scratch time to get to 8th place which considering the level of competition at Nats is very respectable and shows it can compete. Also it is my understanding he was quite new to the car as in he just jumped in that summer. I think the BRZ is still very competitive.

Having owned both, the FRS is a little faster but not enough to separate classes with. The springs and swaybars help, but they're making the car better at what it already is good at instead of fixing some type of shortcoming of the car such as the torque dip, more mph in 2nd, more camber, wider wheels, etc. The advantage was smaller than I had expected once I drove the FRS.

Anyway, I don't care what they do with the classes, IMO they're close enough to be in the same class with or without the parts. But letting the BRZ run the TRD parts or splitting classes and letting non-TRD FRS/BRZs in a single DS class is fine too.

[DocWalt]

Originally Posted by slyphen

My time has been fairly consistent placement wise, since every session has a different course. steady improvement at the beginning and the last few events has been plateauing. Annie Gill, Tasha Mikko has been giving me a lot of great tips and ride alongs, but my car right now is too tail happy. i'm waiting to try on the RE71s and see if it dial back the oversteer, if its still unbalanced, i will upgrade to 22mm front sway bar, which im sure will balance the car out. (currently have 7k front 8k rear springs on FA coils, once i get good enough, i will upgrade to KW or RCE)

http://www.conechaser.com/driver/qingrui.(jim).zhu

The tires won't "cover up" bad balance, as I found out Do the bar first and figure out what happens on the different settings.

Oh, and say hello to Nathan with the white 3000GT and tell him I told you to get a ride along with him. He's quick, even in that big boat

[AlanLGuy]

Originally Posted by Jawnathin

I went ahead and calculated the thrust curves between the old car and new car.

I eyeballed the torque readings from the dyno chart and converted from nM into Lb Ft. Not 100% clean since the thrust chart spreadsheet I used goes in 250rpm increments while the dyno from Subaru is in 400rpm increments, but I think close enough. I included the datasheet for review.

On 225/45s the new car is about 3mph slower at the top of 2nd gear. I went ahead and added a plot for using 235/45/17s which gives it about another 1mph.

Ughhh Part of was hoping they'd fix the torque dip... The other part of me was hoping they wouldn't so I wouldn't have a big reason to trade in for 2017. Based on that data and the dyno... I don't think the 2017 is going to noticeably faster, the BRZ with the 7.5 wheels might be interesting.. But still would rather have the TRD Springs and sway.

[Jawnathin]

Yeah, no fix for the dip and the actual engine dyno numbers are very close. It'll be even closer to after drive train losses to the wheels.

Looking at the thrust curve I think the new car will feel a bit faster but mostly by virtue of the shorter gear. It'll come out of a tight corner better, it is out of the dip at 37mph while we need about 40mph.

However we get about 60mph out of 2nd on our cars now with 225/45s and the new car will top out around 57mph on the same tire. Seems like a disadvantage on paper but the ND is even shorter and seems to do quite well. Maybe the ND can get away with it since it is more likely a shift to third will be needed and it can actually stay there versus banging off the rev limiter in 2nd.

Add the 7.5" wheel on the BRZ PP and it'll be very interesting to see what happens in the real world. I suspect the new car will be incrementally better but they're still in the same ball park.