Grantsfo

I have a 991.2 Carrera T that I ordered from factory with all weight reduction options including pccbs , rear axle steer and manual with lsd. I have installed coilovers , gt3 front control arms, titanium headers, Tail intake runners and stage 1 APR tune for 91 octane. I run 315/30/19 and 265/35/19 Hoosier A7’s on 19 inch wheels. The car is very well suited to ax as small turbos spin up quickly and rear axle steer definitely helps the car get around slow turns well. Car only weighs 2980 lbs currently which helps as well.

‘’the car is quick but has some issues that seem to hold it back from being real contender in SSP. Occasionally if I activate abs stability control switches back on and pretty much ruins run. …..Is thEre a way to completely disable stability control without eliminating abs on 991.2 Carrera? I also seem to have issues with tune where car goes into semi limp mode that limits boost - haven’t figure out why yet but again when this happens car runs at about 75% of its potential - turns car from power car to momentum car instantly. I can’t figure out why tune is limiting boost . Finally has anyone heard of issues with rear axle steer - occasionally car will hang tail out as if RAS is confused. I can hold opposite lock and rear never recovers. Doesn’t
happen often but when issue happens pretty much ruins any run as I can’t push the car without losing rear traction.

so am I crazy for thinking this car might be competitive in SSP if I can figure out tune and stability control issues?

MikeKuhnRacing

Are you trying to be competitive locally or nationally?

Currently i'm the only one piloting a GT3 nationally that is competitive in SSP, and I run 295/345 A7's. Car weigh's around 3160lbs. With 265s up front I don't think you'll be as competitive as you'd like(I'm still trying to figure out how to fit 315s up front) The vette's we are up against are running 335s up front so we are already down to them on front end grip.

Grantsfo

I may have a little weight and low end torque advantage as well as fact car is narrower. Suspect if I roll fenders I could get 295 upfront. I have room currently with 265/315 setup. However currently it’s not lack of tire holding me back - it’s over intrusive traction control that can’t be turned off completely. I just wore out my rear pads on my pccbs after only 10 autocross events due to traction control dragging rear brakes so much! From my research apparently T has different traction control tuning than gt3 that is more aggressive with dragging brakes and trimming throttle - I’m looking into how I might get gt3 traction control logic flashed into my abs controller to at least eliminate over application of brakes to rear wheels.

As far as nation verses regional I don’t drive enough autocrosses personally to be nationally competitive. Takes me more than 3 runs to figure out what I’m doing! Only 4-5 events a year but I do like going to tour events when I can. I have built nationally prepared competitive cars that have podium placed in nationals in past however. I’m enjoying challenges of developing this car learning it’s quirks - car is getting faster

Grantsfo

Working with some well known tuners. Possibility of loading GT3 traction control map that allows full turn off of PSM in Carrera T. That would be game changer for this car. In my opinion overly aggressive traction control that can’t be turned off completely is one of biggest issues with this car. PSM still limiting throttle and aggressively applying brakes to rear wheels when trying to get on power. Carrera T has same ABS controller as GT3 and there is possibility of loading gt3 PSM with track mode on the Carrera. Should know in next couple weeks.

Grantsfo

Continuing to develop the car . I have pretty much got rid of intrusive traction control on engine side with APR tune. Still have overly aggressive torque vectoring that drags brakes on spinning wheel but overall power delivery is decent. I’m still on 265 front tire on 19x10 wheel but in looking at fender I’m pretty confident I will get 295 under a rolled front fender and I do have room to fit 325 rear. I’m just taking this slow for now.

Running my first SCCA event in 4 years at Crows Landing Tour . So suspect car won’t be the issue this round. 😂 ….My driving is ok at local level however I’m not to level of folks signed up for SSP. Multiple national champs driving SSP now. Fun thing is I’m only non GT car. My hope is just to not to get spanked too badly.

Joe250

Grant,

Please continue to update this thread. I always wanted to run an underdog 911 and develop it like you are doing.

Did you have to request anything special from APR or was the change to traction control something they commonly do? Is traction control under acceleration now permanently off or do you still need to activate that feature via a switch?

I'm also curious about your statement regarding the rear brake activating on a spinning wheel. As I understand it, the Vector Control is braking the rear inside wheel to induce/increase yaw on turn-in. If so, that shouldn't occur under acceleration but decel and/or steady-state when initiating the turn. If so, that is a very beneficial advantage. Maybe I misunderstood though.

Grantsfo

my tune from APR is off shelf stage one for pump gas. My initial tune was off shelf cobb. Lost of bugs with Cobb tune. With stability control fully off cobb still allowed throttle cut. APR tune doesn’t cut throttle at all. All I do is go to sport plus map and hold down stability control button until everything is turned off. Brake issue is definitely strange. It’s either torque vectoring or traction control. Brakes are definitely intervening. After 60 second autocross run my rear brakes are smoking hot. It’s not terrible but I like full control of throttle going to rear wheels.

My cars suspension is pretty much stock other than active coilovers and front lower control arms so lots more opportunity to make suspension even better for autocross.

‘Lots of opportunity with engine as well. I still have stock intercoolers, stock y pipe and plenum. I have stock cats as well. Then there is going to e85 tune for big boost in power . I’m waiting until suspension is dialed in before adding much more power as car already has hard time putting down power out of turns.

‘’With bigger tires and suspension complete I think this car is going to be wickedly fast.

Grantsfo

Just picked up a set of tarret gt3 hollow bars and end links . Now looking to get adjustable steering rod ends, adjustable toe arms. Etc.

…Man taking 4 years off from SCCA competition and then showing up for tour event was rude awaking to how slow iam in 3 runs. …and the SSP corvettes are monsters. Can see how much more mechanical grip they generate than Porsches with those huge A7s. Im rethinking tire widths now. Definitely going with 295 front and 325 rear as my next step up and now I see that’s still disadvantage to well setup corvettes.

MikeKuhnRacing

Yeah the vette's are fast.. Although I was faster than Jeff at all 3 events I ran against him last year. Would have taken the win at Nats by almost a second over him if I hadn't coned away my first run.

But yeah 345s squared on Jeff's car definitely gives him a ton more front end grip. We just have to make up for it in other areas.

Looked like a fun course this weekend though, wish we had fast concrete courses over here.

AdventureFlea

Cones Count (ha)... And Jeff has a bit more done to the car this year I think. Grant keep in mind you are dealing with a lot of National Champions in the class as well. But Doug and I have discussed that we both think my GT3 will be a lot faster than his Vette. So when he is not on the west coast we will be running in a Porsche

Grantsfo

….yeah on more technical course a GT3 would have some advantages over a vette. The course at crows had some fairly fast open sections that benefitted vette for sure. I was in 3rd gear in couple sections. But then got off line and was barely making it around some gates and even dnf’ing.

I have my new suspension ordered . Upgrading to tarret gt3 bars and end links, adjustable toe and caster arms etc. …..then drive drive drive. Lack of seat time for me is bigger issue than the car right now as I couldnt get my head around course in 3 runs. Knew I was in trouble when I was searching for next feature.

Grantsfo

Wow the big OEM GT3 front sway bar has transformed the car! I can now get on power earlier and rear end is far easier to control and car isn’t understeering. Next is bigger front tire going from 265 to 295. I may need to do fender roll but there looks like I have room as 265 has about an inch of clearance on both inside and outside. Now I understand how gt3s handle so much better than Carreras. Think I’m pretty close to gt3 levels of handling now.

im looking into going to e85 tune as well. I’m currently running APR stage 1 for 91 octane . Apr e85 tune picks up 90 ft lbs of torque and 50 more hp from my 91 pump gas tune. Should make this car a beast. I may need a stronger clutch with next level of power .

Joe250

Good stuff. Do you typically video your runs?

sgreer78

A front bar has given you GT3 levels of handling??

Grantsfo

lol! I’ve installed a few GT3 suspension pieces as well as aftermarket mods with coilovers a couple years ago. 😜 The car also was ordered with pccbs that are same as gt3 as well as RAS and I have put wider wheels and tires on the car. The big adjustable GT3 sway bars just went in. I had weeny non adjustable stock Swaybars with oem end links prior. Now the car is pretty dang close to GT3 in terms of handling. Something I observe over and over with good gt3 drivers is that they can come out of turn full power and hold rear end in a power slide . I could never do that in my Carrera prior to big front bar. It was like magic in autocross this weekend I came out of turn dropped hammer and I could feel both rear tires staying hooked up and rather than needing to let off I just stayed on go pedal with no drama . I know it’s the bar as that’s only change I made recently. I had just underestimated how critical bigger bar on the car would be.