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A PDK in 2nd with that 19" tire should run to about 72mph. Could be perfect for auto-x.
It's a little hard for me to wrap my head around cars that will theoretically peak accelerate at 0.85g or so in 2nd gear. A stock C6Z06 only pulls about 0.7g peak in 2nd with the 315/30-18 Yok that most use. I found it an easy car to autocross having had previous Corvette experience.
If the PDK 2nd only gives 69mph because the tire is smaller it might be bouncing off the rev limiter too often, assuming it hasn't been raised. Some are offering tunes that raise the limit, but AFAIK only for manual cars.
For my 987.1 Cayman base in CS I've focused on increasing the transient response to where the car can match the ND in a slalom even though it is 3" wider and 600lbs heavier. Data comparisons say I've done that. For a 718 vs. C6Z06 maximizing TR is probably not the proper goal since it will already dominate in that respect. That's why I've been paying a lot of attention to acceleration first and grip a close second in this what-if exercise.
At a place like Grissom, it is not uncommon for me to hit 3rd gear and at times, 1st gear up in the prison turn or the odd really tight spots. That is one reason I love the PDK - It is always keeping the little 2.0T on the boil. A neat data point from a couple of years ago - After the Champ tour at Grissom, the Tri state group ran an event that mimicked the champ tour course. There was a section that had you get pinched down pretty tight by the zombie house and then had you cut across the course adjacently (different than what we typically do at grissom) - a pretty fast section. Anyway, Simms was there that day in his C6Z (and I verified he was having a good day driving ha) and we were chatting about that section. My car was going from 1st to 3rd, whereas his was a little bogged coming out of the tight spot in 2nd (and shifting down to 1st would have been harder) and took a while to spool up. At the end of the day, we were P1 and 2 and I was ~0.2s behind him and definitely feel like that was a "green" sector for me.
At a place like Grissom, it is not uncommon for me to hit 3rd gear and at times, 1st gear up in the prison turn or the odd really tight spots. That is one reason I love the PDK - It is always keeping the little 2.0T on the boil. A neat data point from a couple of years ago - After the Champ tour at Grissom, the Tri state group ran an event that mimicked the champ tour course. There was a section that had you get pinched down pretty tight by the zombie house and then had you cut across the course adjacently (different than what we typically do at grissom) - a pretty fast section. Anyway, Simms was there that day in his C6Z (and I verified he was having a good day driving ha) and we were chatting about that section. My car was going from 1st to 3rd, whereas his was a little bogged coming out of the tight spot in 2nd (and shifting down to 1st would have been harder) and took a while to spool up. At the end of the day, we were P1 and 2 and I was ~0.2s behind him and definitely feel like that was a "green" sector for me.
Thanks for that. This alters my thinking. I keep forgetting that there's a 3rd gear in the PDK box!
So, 67mph in 2nd with a light wheel/tire package using the 295/30-18 Bridgestone (that I know so well) producing tuned Z06-matching 0.87g. Gets to 67 in hurry and a quick shift to 3rd if more speed is needed. The car gets lowered 1.2" from stock just from the tires which will have a very good effect on handling and grip by itself.
That would be fun!
Last edited by edfishjr; Jun 19, 2025 at 12:32 PM.
Thanks for that. This alters my thinking. I keep forgetting that there's a 3rd gear in the PDK box!
So, 67mph in 2nd with a light wheel/tire package using the 295/30-18 Bridgestone (that I know so well) producing tuned Z06-matching 0.87g. Gets to 67 in hurry and a quick shift to 3rd if more speed is needed. The car gets lowered 1.2" from stock just from the tires which will have a very good effect on handling and grip by itself.
That would be fun!
I really enjoy my car in Base-T form. An SST prep would be a hoot.
You guys know the 718 S/GTS is out for comment to be added to SST, right. If it goes, I was talking with Lugod who suggest JRZ RS Pro's with his custom valving. Not cheap but reasonable. A set of 18x9.5 or 10 fronts and 18x11 rears, tune, and a diet, and it be a great car. All these numbers can't fully assess how much you gain with proper camber and alignment as the C6Z already gets what we can't. I'd bet a GTS could get to 420 hp 380 ft. Lbs without going crazy.
You guys know the 718 S/GTS is out for comment to be added to SST, right. If it goes, I was talking with Lugod who suggest JRZ RS Pro's with his custom valving. Not cheap but reasonable. A set of 18x9.5 or 10 fronts and 18x11 rears, tune, and a diet, and it be a great car. All these numbers can't fully assess how much you gain with proper camber and alignment as the C6Z already gets what we can't. I'd bet a GTS could get to 420 up 380 ft. Lbs without going crazy.
I didn't actually know that, but I've convinced a local with a GTS to run in SST this year, with permission of the others in the class, in order to obtain data to use to make the case.
APR states 399 lb-ft wheel for 93oct tune of the 2.5
Last edited by edfishjr; Jun 19, 2025 at 07:53 PM.
I didn't actually know that, but I've convinced a local with a GTS to run in SST this year, with permission of the others in the class, in order to obtain data to use to make the case.
APR states 399 lb-ft wheel for 93oct tune of the 2.5
I'm reluctant to quote APR numbers which seem high but yes a tune would be worth the juice.
I'm reluctant to quote APR numbers which seem high but yes a tune would be worth the juice.
APR is usually pretty dead on with their claims.
SST in a GTS would be interesting for sure... But really bad for my wallet. I think it could definitely be competitive. Just a local this past weekend, but I out-PAXed Mark Ponusky (3rd place SST at nats last year), and I coned away all my good runs that were over a second below my best clean runs. Coulda-woulda out RAWed him if I drove better. Same run group so fair comparisons. 66 second course on asphalt at Devens, so relatively representative of a big fast nats course minus the surface.
(Can also add dual driven RE71RS in 94 degree heat with way too little time between runs to my "drivers excuses" list).
More camber, more power, better dampers, wider tires? Oh man. My car is currently just wheels and tires.
To explain my hesitancy about APR numbers and without getting too wonky, different dynos (Dynajet, Mustang, Dynapack which is very similar if not the same as Mainline) all read different outputs on the same car for different reasons. If you look at the APR numbers, Porsche shows stock output at the crank as 365HP/317# at the crank whereas APR project stock at the crank as 382/355 and at 442/412 after their stage 1 93 octane tune. I would suspect this is because they are using Mainline or Dyanpack dyno which connects to the hubs which reads higher rather than reading measurements on rollers where Dynajets read lower and Mustang dyno lower still (see link below). If you read their disclaimers, an interesting part says "...Dynos are for reference only. Results will vary. Contributing factors include the vehicle condition, vehicle setup, dyno type, dyno setup, environmental factors, fuel quality, and more...." This is not to knock APR. Disclaimer -- I have no tune and am not affiliated with any tuner. I do suspect this is why many feel that Porsche and BMW numbers may be understated which is likely a byproduct of which type of dyno's they use and the type of fuels they run in Europe. I don't think the 718 GTS has the numbers stock which APR reports. That said, the delta of increases of 60 hp and 47# torque are well worth the investment if you were to head the SST route.
To explain my hesitancy about APR numbers and without getting too wonky, different dynos (Dynajet, Mustang, Dynapack which is very similar if not the same as Mainline) all read different outputs on the same car for different reasons. If you look at the APR numbers, Porsche shows stock output at the crank as 365HP/317# at the crank whereas APR project stock at the crank as 382/355 and at 442/412 after their stage 1 93 octane tune. I would suspect this is because they are using Mainline or Dyanpack dyno which connects to the hubs which reads higher rather than reading measurements on rollers where Dynajets read lower and Mustang dyno lower still (see link below). If you read their disclaimers, an interesting part says "...Dynos are for reference only. Results will vary. Contributing factors include the vehicle condition, vehicle setup, dyno type, dyno setup, environmental factors, fuel quality, and more...." This is not to knock APR. Disclaimer -- I have no tune and am not affiliated with any tuner. I do suspect this is why many feel that Porsche and BMW numbers may be understated which is likely a byproduct of which type of dyno's they use and the type of fuels they run in Europe. I don't think the 718 GTS has the numbers stock which APR reports. That said, the delta of increases of 60 hp and 47# torque are well worth the investment if you were to head the SST route.
As usual, I am late to the party here.
I considered setting up my 718 Base for SST last year (I owned one already) but the car I just don't think can hang with the Supra or Corvette.
Mine is tuned and I have dyno'ed with and without a cat as we were working with another local shop to develop some lightweight exhaust options for the platform. After seeing the power numbers, I just don't think the car can hang in unless its an S/GTS so I hope that proposal goes through. Then the Cayman platform may then have a better chance.
As far as wheel fitment goes, 18x10.75 is all you are getting out back on a 981/718 body and it takes a custom wheel/offset to clear the stock rear toe links. You can fit a 19x11 as well. So 295 or 305 for tire fitment. I've tried both but my car is MT and I like the 18's better for gearing on track. I run a 265 up front currently on a 9.5" wheel, 285 is likely possible on a 10" wheel but then you're mixing wheel sizes and/or tire compounds in the setup at that point.
I am going to bring my 718 to Nationals now instead of my AS 981 - mostly just for fun though, it's prepped for Sport 2 TT...but essentially that means everything is done to it for ST* prep except for actual coilovers (seats, exhaust, tune, bars, camber, cooling).
Green OE Cat, Blue catless 18x10.5 295 Nankang CRS Stock strut
18x11s on the rear fit fine as long especially if you do offset strut mounts. But yeah you're not getting much more than 295s on it but with the exception of maybe a very tuned 718s the power level and chassis don't really want/need more tire than that anyway.
Edit: I should clarify that this applies to the 981, I think the 718 has some minor rear suspension differences.
As a comparison, I ran my 718 GTS in our regional "pro class". Last weekend.
Grant Reeve was a 58.28, Mark Ponusky (3rd SST nats last year, with a freshly rebuilt engine now) 58.99, and I kept barely clipping cones, but ended up with a 59.76 (intentionally backing it down a bit in my last run), and a 59.23+1. Fully stock 718 GTS except for wheels and tires.
Also noted that I'm WAY under driving in the slaloms - I lost a full half a second there to basically everybody else in class. That was just straight bad driving by me, so assume a better driver is half a second faster than my times.
So, with a tune, wider wheels and tires, and better suspension? I think the 718 GTS or S would rip in SST!
As usual, I am late to the party here.
I considered setting up my 718 Base for SST last year (I owned one already) but the car I just don't think can hang with the Supra or Corvette.
Mine is tuned and I have dyno'ed with and without a cat as we were working with another local shop to develop some lightweight exhaust options for the platform. After seeing the power numbers, I just don't think the car can hang in unless its an S/GTS so I hope that proposal goes through. Then the Cayman platform may then have a better chance.
As far as wheel fitment goes, 18x10.75 is all you are getting out back on a 981/718 body and it takes a custom wheel/offset to clear the stock rear toe links. You can fit a 19x11 as well. So 295 or 305 for tire fitment. I've tried both but my car is MT and I like the 18's better for gearing on track. I run a 265 up front currently on a 9.5" wheel, 285 is likely possible on a 10" wheel but then you're mixing wheel sizes and/or tire compounds in the setup at that point.
I am going to bring my 718 to Nationals now instead of my AS 981 - mostly just for fun though, it's prepped for Sport 2 TT...but essentially that means everything is done to it for ST* prep except for actual coilovers (seats, exhaust, tune, bars, camber, cooling).
Green OE Cat, Blue catless 18x10.5 295 Nankang CRS Stock strut
Thanks for posting.
I agree: that Dynojet hp & Tq won't get it done, with or without a cat.
As a comparison, I ran my 718 GTS in our regional "pro class". Last weekend.
Grant Reeve was a 58.28, Mark Ponusky (3rd SST nats last year, with a freshly rebuilt engine now) 58.99, and I kept barely clipping cones, but ended up with a 59.76 (intentionally backing it down a bit in my last run), and a 59.23+1. Fully stock 718 GTS except for wheels and tires.
Also noted that I'm WAY under driving in the slaloms - I lost a full half a second there to basically everybody else in class. That was just straight bad driving by me, so assume a better driver is half a second faster than my times.
So, with a tune, wider wheels and tires, and better suspension? I think the 718 GTS or S would rip in SST!
I was watching Reeve today, working course while he was running. Very impressive driving!
