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Discussion Starter · #81 ·
Eleven inch wheels in the rear is very interesting to me. I'll bet they look very nice. I am mulling tire size stagger front to rear and the effect on handling. That will be in the future when I rebuild my Sally account and after I get some experience with the current configuration.

Tire width and grip is an interesting subject that is very complex and I don't even want to get into the oversimplifications and assumptions that are so easy to find in the literature. What I will say is that IN GENERAL, a wider tire is slightly better at putting power to the pavement. It may not, however, be better at producing lateral traction because lateral traction is a function not only of the tire aspect ratio, but tire construction, suspension geometry and characteristics, tire pressure, temperature, loading and a host of other variables that are co-dependent. The closest thing to an independent variable is the compound of the tire. SO, if you want to insure more traction, get a stickier tire. "Sticky" - That's a technical term, right?? ;)

Suffice it to say, I have not found a tire generalization that does not have a bunch of caveats. And finding real data is nearly impossible because a tire's performance is so influenced by its application. The only rule that I do not believe has an exception is 'Never tune a motorcycle to have understeer."
 

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Discussion Starter · #82 · (Edited)
I just got back from a weekend of track work at Carolina Motorsports Park (CMP) at a PCA Carolinas Section sponsored DE. It is only my second event with the Carolinas group, but I must say that I have very much enjoyed meeting the members - who are representative of the region of the country that grows car lovers - and who are polite and really care about what they are doing. The event was run professionally with just the right amount safety reminders and cautions and friendly conversations. I was very comfortable with everyone I met and will gladly participate in more of their events.

Now for the track stuff. Recall that my car has undergone a major rework: 3.7 engine transformation, Methanol injection, Guard 60/40 LSD, GT3 brake master cylinder, Precision Friction 330 mm front brake rotors. There is one other mod that I have not mentioned before and that is the TPC Dynamic Suspension Control (DSC). I'll describe that later. I will also say that I have not been on a track since last October when I had the D-chunk failure in my engine, so there was a learning and re-familiarization factor involved in my evaluation as well as a lot of personal rust to scrub off. My consistency was not very good which gave me multiple opportunities to examine error correction.

Overall, I think I have achieved a very well balanced combination of power and handling. I think I finally have enough power to take advantage of the Cayman's natural balance and the suspension setup. I was on a set of Bridgestone RE-11s, very good tires but at the end of their useful life, so tire dynamics made fast lapping more of a challenge but enhanced the evaluation of handling corrections and enhancements. The dying tires meant that several people whom I paced to evaluate turning performance and acceleration performance could out turn me and separate slightly in a turn. All of the cars I used as pace had track tires and I really believe that my ability to stay as close as I did in turns is a tribute to the suspension design and setup. The suspension setup was perfect for morning periods but the increased temperatures in the afternoons (about 90 deg f) made the track a little greasy and resulted in noticeable understeer. (I'll fix that by softening the front sways)

The understeer correction was the most dramatic characteristic I discovered. In a stock Cayman, if you add power in an understeer situation, you simply make the understeer worse. Even with my 3.4 turbo, the car would mostly try to straighten out. With this engine torque (380 ft-lb in low boost, the only boost I used this weekend) in third gear, pushing on the throttle results in the back end very controllably rotating toward the outside of the turn, allowing you to center the wheel and "square" the turn. It is a dance step Sally didn't have before. And let me see if I can characterize the step. With the LSD, she no longer throws her rear end evocatively to one side, but gracefully sways toward the outside of the turn, allowing you to feel her change in direction and react with her instead of being surprised. It results in a very controllable and confident maneuver. And with the torque being so constant between 3500 and 7000 RPM, the foot and hand motions to step the back end out are remarkable consistent throughout the 3500 to 7000 RPM range - and I like simple. The ability to completely overpower understeer with the right foot was probably the most pleasant discovery of the weekend. It made me smile many times.

The linear performance of the car is remarkable. There was not a car there that I could not haul in on the straight. However, exiting a second gear turn will require more right foot education. I tended to overpower the rear wheel traction and, in more cases than not, ended up swaying Sally's backside out more than I desired. I left a lot of tire money on the exit of turn 14. But again, control was never an issue. It happens faster than in third, but I was able to react and get the front end back on the velocity vector with no more than about 15 deg of drift. By Sunday afternoon, I had educated my right foot to smoothly exit the drift so that anyone watching would assume I meant to do it. Looking good while screwing up is a very valuable talent.

Since I did not change anything in the suspension system that would affect directional power stability other than the LSD, I have to assume that the LSD is the major contributor to this major increase in behavior predictability.

Next is the brakes. The GT3 MC has erased every uneasy feeling I ever had about the brakes. The stock MC never generated confidence because it was just plain squishy (is that a technical term?). I ALWAYS worried if there was air in the line or is the MC failing. The GT3 MC is high and tight. Pedal stroke to engagement is not noticeable and the pedal is very firm. I was expecting more pedal pressure to be required because of the increased bore in the GT3 MC, but the 330 mm rotor made the pedal pressure feel not more than required before the build. The braking was very linear and controllable and brake steering in a turn was very predictable. The only distinctive characteristic was the RRRRrrrrr sound of the slots going by the pads. By Sunday, I was using the frequency of the sound to help me judge turn entry speed. Anything to help me be more precise.

Now the Dynamic Suspension Control (DSC). It was developed by TPC by analyzing a ton of race data to increase the dynamic control of the dampers. It uses the normal set of measures (lateral accel, longitudinal accel, wheel position, yaw rate, speed, etc., but adds lead terms like steering wheel rate and brake master cylinder pressure rate along with acceleration rates in both the longitudinal and lateral axes. The computer monitors the incoming data at 200 kbits/sec and the processor is a 32 bit machine instead of the OEM 8 bit. The increase in data precision and speed facilitates the computation of predictive algorithms about where the chassis is going. The DSC is a form, fit, and function replacement for the OEM box and installation requires no tools and takes 5 minutes max. The system has 3 modes (1, 2, and 3). Mode 1 is most applicable to street use and I qualitatively evaluate mode 1 as comparable to a non-PASM car on 19 inch wheels – a little harder than PASM in Normal mode, although Mike Levitas is sending an updated box with a more compliant Mode 1 plus some updates to modes 2 and 3, so I will update my impressions after I check out the new software. You can think of modes 2 and 3 as two levels of enhanced PASM. The selection of the levels is through the PASM button on the dash and the mode is indicated by a solid light for level 1, two blinks followed by a short dark interval for level 2 and 3 blinks followed by a short dark interval for level 3. I evaluated mostly level 2 on the track. Now for a little disclaimer: I am a gross amateur at evaluating the compression/rebound in all four corners based on turn entry, mid-turn, and turn exit handling characteristics. I have neither the experience nor the fine-tuned sensory perceptions to even comment on the exact algorithms, so my comments can go no deeper than my overall impressions. I meant to take my OEM PASM box with me this weekend to perform a session-by-session comparison, but my car prep time got crunched and I forgot it, so these broad-brush comments are based on what I remember from my first visit to CMP. Also, I need to say that I have no business interest in TPC Racing and I am in no way being compensated for this or any other evaluation. The money flow has been ENTIRELY from me to them.

For those of you with experience at CMP, you know the “kink”. For those who do not know, the kink is a turn between 2 straights and on the inside of the turn is a hump that is highest at the inner edge of the turn and decreases to nothing at about 25% of the track width. The hump is unsettling to most cars and, in my first time at CMP, going over the hump made me very nervous because the car would not track truly and if you lost it, you were in for a high speed off-track event. In my 2 weekends at CMP, I have seen two 911s go off track because of the kink, so the turn demands a lot of respect. By Sunday, I was going over the highest part at elevated speed with the car tracking beautifully and predictably. The same was true for running over the curbing on the inside of turns 2 and 3. No upset at all, no strange lead steering requirement. Also, looking at video, the car stays amazingly flat, even during a panic deceleration (because I braked late) and nearly jerking the wheel into the turn (because I was still 100% braking at the normal turn point). I have nothing else to attribute the improvement in handling to than the DSC.

A GT3 Cup racer rode with me to experience the car and commented that the car is amazingly stuck to the track. He also commented that his GT3 cannot handle the kink and curbs as well as my car. He also commented that the way I stepped the back end out to exit turn 7 (a decreasing radius turn) would scare him in his car. I have no idea how good a driver he is, but he gave me several tips that improved my line and performance, so he knows enough to be constructive and to consider the car’s characteristics in adjusting the line. His last comment was that the car is a real beast and he encouraged me to get “real track tires”.

The Methanol: I was particularly interested in how much methanol the car uses. I burned 18.8 gallons of gas and consumed about 7/8 gallon of methanol, so I figure a 20 to 1 gas to methanol ratio is good for track work. (For normal street driving you use essentially no methanol since it does not even start spraying until 2 psi boost and heavy throttle.) With 93 octane gas at $3.80/gal and racing methanol at $7.00/gal, my fuel bill (for about ¾ of the weekend) was $71.44 for gas and $6.13 for methanol for a total of $77.57. If I had purchased 100 octane fuel at $9.00/gal, my fuel bill would have been $169.20. So, by American merchandizing logic, I “saved” $91.63.

Another interesting aspect about the methanol is the exhaust tip deposit color. As anyone with a TPC turbo can tell you, the tips turn as black as sin with carbon. When I arrived at the track, my tips were totally black. After the first 4 sessions on track, this is what the tips looked like My apologies for holding the darn camera directly in the sun line).



Interestingly, after a 40 mile overnight round trip to my hotel and back to the track, the right pipe (exhaust) was already noticeably darker than the left pipe (waste gate) which was not used in my transit.

Several people were interested in the car and stopped by to ask questions. The most interesting conversation involved two guys and the conversation went like this:
First guy: "This is the car."
Second guy after looking at the tires: "No f$(&ing way. No f$(&ing way a Cayman could get around me on street tires. No fu(&ing way!"
I was sitting under a tree about 30 ft away and first guy asked if I was the owner. He then asked if I had passed a [color] [car] and I acknowledged that I had. We then discussed the car at length. After talking about the car, Second guy said, “Thank God. I thought there was something wrong with my car. Then when I pointed you by, you didn’t pass me, you BLASTED by me. Then when you got to the end of the straight and lifted and I saw flames coming out the back, I told myself, ‘This is not your standard Cayman.’” He then very gentlemanly offered an apology for holding me up which I dismissed by saying that I used the time to learn from his line (which I did). He was smooth and quick and it was everything I could do to keep up with him in the turns. And, truth be known, the first time I finally stayed close in a series of turns, he pointed me by, so I had no beef with him in any event. But his comment was right on: This is not your standard Cayman. It sets new standards on what a Cayman CAN be.
 

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I just got back from a weekend of track work at Carolina Motorsports Park (CMP) at a PCA Carolinas Section sponsored DE. It is only my second event with the Carolinas group, but I must say that I have very much enjoyed meeting the members - who are representative of the region of the country that grows car lovers - and who are polite and really care about what they are doing. The event was run professionally with just the right amount safety reminders and cautions and friendly conversations. I was very comfortable with everyone I met and will gladly participate in more of their events.

Now for the track stuff. Recall that my car has undergone a major rework: 3.7 engine transformation, Methanol injection, Guard 60/40 LSD, GT3 brake master cylinder, Precision Friction 330 mm front brake rotors. There is one other mod that I have not mentioned before and that is the TPC Dynamic Suspension Control (DSC). I'll describe that later. I will also say that I have not been on a track since last October when I had the D-chunk failure in my engine, so there was a learning and re-familiarization factor involved in my evaluation as well as a lot of personal rust to scrub off. My consistency was not very good which gave me multiple opportunities to examine error correction.

Overall, I think I have achieved a very well balanced combination of power and handling. I think I finally have enough power to take advantage of the Cayman's natural balance and the suspension setup. I was on a set of Bridgestone RE-11s, very good tires but at the end of their useful life, so tire dynamics made fast lapping more of a challenge but enhanced the evaluation of handling corrections and enhancements. The dying tires meant that several people whom I paced to evaluate turning performance and acceleration performance could out turn me and separate slightly in a turn. All of the cars I used as pace had track tires and I really believe that my ability to stay as close as I did in turns is a tribute to the suspension design and setup. The suspension setup was perfect for morning periods but the increased temperatures in the afternoons (about 90 deg f) made the track a little greasy and resulted in noticeable understeer. (I'll fix that by softening the front sways)

The understeer correction was the most dramatic characteristic I discovered. In a stock Cayman, if you add power in an understeer situation, you simply make the understeer worse. Even with my 3.4 turbo, the car would mostly try to straighten out. With this engine torque (380 ft-lb in low boost, the only boost I used this weekend) in third gear, pushing on the throttle results in the back end very controllably rotating toward the outside of the turn, allowing you to center the wheel and "square" the turn. It is a dance step Sally didn't have before. And let me see if I can characterize the step. With the LSD, she no longer throws her rear end evocatively to one side, but gracefully sways toward the outside of the turn, allowing you to feel her change in direction and react with her instead of being surprised. It results in a very controllable and confident maneuver. And with the torque being so constant between 3500 and 7000 RPM, the foot and hand motions to step the back end out are remarkable consistent throughout the 3500 to 7000 RPM range - and I like simple. The ability to completely overpower understeer with the right foot was probably the most pleasant discovery of the weekend. It made me smile many times.

The linear performance of the car is remarkable. There was not a car there that I could not haul in on the straight. However, exiting a second gear turn will require more right foot education. I tended to overpower the rear wheel traction and, in more cases than not, ended up swaying Sally's backside out more than I desired. I left a lot of tire money on the exit of turn 14. But again, control was never an issue. It happens faster than in third, but I was able to react and get the front end back on the velocity vector with no more than about 15 deg of drift. By Sunday afternoon, I had educated my right foot to smoothly exit the drift so that anyone watching would assume I meant to do it. Looking good while screwing up is a very valuable talent.

Since I did not change anything in the suspension system that would affect directional power stability other than the LSD, I have to assume that the LSD is the major contributor to this major increase in behavior predictability.

Next is the brakes. The GT3 MC has erased every uneasy feeling I ever had about the brakes. The stock MC never generated confidence because it was just plain squishy (is that a technical term?). I ALWAYS worried if there was air in the line or is the MC failing. The GT3 MC is high and tight. Pedal stroke to engagement is not noticeable and the pedal is very firm. I was expecting more pedal pressure to be required because of the increased bore in the GT3 MC, but the 330 mm rotor made the pedal pressure feel not more than required before the build. The braking was very linear and controllable and brake steering in a turn was very predictable. The only distinctive characteristic was the RRRRrrrrr sound of the slots going by the pads. By Sunday, I was using the frequency of the sound to help me judge turn entry speed. Anything to help me be more precise.

Now the Dynamic Suspension Control (DSC). It was developed by TPC by analyzing a ton of race data to increase the dynamic control of the dampers. It uses the normal set of measures (lateral accel, longitudinal accel, wheel position, yaw rate, speed, etc., but adds lead terms like steering wheel rate and brake master cylinder pressure rate along with acceleration rates in both the longitudinal and lateral axes. The computer monitors the incoming data at 200 kbits/sec and the processor is a 32 bit machine instead of the OEM 8 bit. The increase in data precision and speed facilitates the computation of predictive algorithms about where the chassis is going. The DSC is a form, fit, and function replacement for the OEM box and installation requires no tools and takes 5 minutes max. The system has 3 modes (1, 2, and 3). Mode 1 is most applicable to street use and I qualitatively evaluate mode 1 as comparable to a non-PASM car on 19 inch wheels – a little harder than PASM in Normal mode, although Mike Levitas is sending an updated box with a more compliant Mode 1 plus some updates to modes 2 and 3, so I will update my impressions after I check out the new software. You can think of modes 2 and 3 as two levels of enhanced PASM. The selection of the levels is through the PASM button on the dash and the mode is indicated by a solid light for level 1, two blinks followed by a short dark interval for level 2 and 3 blinks followed by a short dark interval for level 3. I evaluated mostly level 2 on the track. Now for a little disclaimer: I am a gross amateur at evaluating the compression/rebound in all four corners based on turn entry, mid-turn, and turn exit handling characteristics. I have neither the experience nor the fine-tuned sensory perceptions to even comment on the exact algorithms, so my comments can go no deeper than my overall impressions. I meant to take my OEM PASM box with me this weekend to perform a session-by-session comparison, but my car prep time got crunched and I forgot it, so these broad-brush comments are based on what I remember from my first visit to CMP. Also, I need to say that I have no business interest in TPC Racing and I am in no way being compensated for this or any other evaluation. The money flow has been ENTIRELY from me to them.

For those of you with experience at CMP, you know the “kink”. For those who do not know, the kink is a turn between 2 straights and on the inside of the turn is a hump that is highest at the inner edge of the turn and decreases to nothing at about 25% of the track width. The hump is unsettling to most cars and, in my first time at CMP, going over the hump made me very nervous because the car would not track truly and if you lost it, you were in for a high speed off-track event. In my 2 weekends at CMP, I have seen two 911s go off track because of the kink, so the turn demands a lot of respect. By Sunday, I was going over the highest part at elevated speed with the car tracking beautifully and predictably. The same was true for running over the curbing on the inside of turns 2 and 3. No upset at all, no strange lead steering requirement. Also, looking at video, the car stays amazingly flat, even during a panic deceleration (because I braked late) and nearly jerking the wheel into the turn (because I was still 100% braking at the normal turn point). I have nothing else to attribute the improvement in handling to than the DSC.

A GT3 Cup racer rode with me to experience the car and commented that the car is amazingly stuck to the track. He also commented that his GT3 cannot handle the kink and curbs as well as my car. He also commented that the way I stepped the back end out to exit turn 7 (a decreasing radius turn) would scare him in his car. I have no idea how good a driver he is, but he gave me several tips that improved my line and performance, so he knows enough to be constructive and to consider the car’s characteristics in adjusting the line. His last comment was that the car is a real beast and he encouraged me to get “real track tires”.

The Methanol: I was particularly interested in how much methanol the car uses. I burned 18.8 gallons of gas and consumed about 7/8 gallon of methanol, so I figure a 20 to 1 gas to methanol ratio is good for track work. (For normal street driving you use essentially no methanol since it does not even start spraying until 2 psi boost and heavy throttle.) With 93 octane gas at $3.80/gal and racing methanol at $7.00/gal, my fuel bill (for about ¾ of the weekend) was $71.44 for gas and $6.13 for methanol for a total of $77.57. If I had purchased 100 octane fuel at $9.00/gal, my fuel bill would have been $169.20. So, by American merchandizing logic, I “saved” $91.63.

Another interesting aspect about the methanol is the exhaust tip deposit color. As anyone with a TPC turbo can tell you, the tips turn as black as sin with carbon. When I arrived at the track, my tips were totally black. After the first 4 sessions on track, this is what the tips looked like My apologies for holding the darn camera directly in the sun line).



Interestingly, after a 40 mile overnight round trip to my hotel and back to the track, the right pipe (exhaust) was already noticeably darker than the left pipe (waste gate) which was not used in my transit.

Several people were interested in the car and stopped by to ask questions. The most interesting conversation involved two guys and the conversation went like this:
First guy: "This is the car."
Second guy after looking at the tires: "No f$(&ing way. No f$(&ing way a Cayman could get around me on street tires. No fu(&ing way!"
I was sitting under a tree about 30 ft away and first guy asked if I was the owner. He then asked if I had passed a [color] [car] and I acknowledged that I had. We then discussed the car at length. After talking about the car, Second guy said, “Thank God. I thought there was something wrong with my car. Then when I pointed you by, you didn’t pass me, you BLASTED by me. Then when you got to the end of the straight and lifted and I saw flames coming out the back, I told myself, ‘This is not your standard Cayman.’” He then very gentlemanly offered an apology for holding me up which I dismissed by saying that I used the time to learn from his line (which I did). He was smooth and quick and it was everything I could do to keep up with him in the turns. And, truth be known, the first time I finally stayed close in a series of turns, he pointed me by, so I had no beef with him in any event. But his comment was right on: This is not your standard Cayman. It sets new standards on what a Cayman CAN be.
Sounds like you had a lot of fun. As an FYI, even a non-turbo Cayman with the proper suspension setup and LSD can rotate the rear end of the car in a predictable fashion as opposed to plowing the nose in understeer. I highly recommend it for everyone!

Now go get you some real tires!!!
 

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Discussion Starter · #84 ·
Sounds like you had a lot of fun. As an FYI, even a non-turbo Cayman with the proper suspension setup and LSD can rotate the rear end of the car in a predictable fashion as opposed to plowing the nose in understeer. I highly recommend it for everyone!

Now go get you some real tires!!!
Does that mean you have replaced your TBD with a real LSD?

I wish I had done an LSD a long time ago, but I consciously delayed the LSD because I was scared that I would overpower the car and go Frisbee-ing across the countryside. I second your recommendation. In my experience, I could step the back end out only with dynamic clutch action or brakes. As it got hotter, I tried to constrain the understeer with tire pressure adjustments which was unsuccessful. I knew in my heart that I should soften the sways, but it was hot and I was lazy, so I hoped that the pressure adjustment would be enough. Shame on me. Hope is not a strategy for success.
 

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Kenny - If you were able to blast by cars in the straights in low boost, just think what you would have done in high boost! I have to admit that flames shooting out the tailpipe sounds pretty cool. :banana:

Mike
 

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Discussion Starter · #86 ·
I could hear the exhaust popping on several occasions during shifts and during lifts at the end of straights. A couple of people observed that the exhaust sound is awesome.

I forgot to mention that the flat torque curve gives no indication that redline RPM is approaching. In the stock car and in the 3.4 turbo, I could feel the torque drop and know that I was getting close. In this car, I need more RPM gauge scanning because I hit the RPM limiter more in the last 2 days than I have in the entire prior lifetime of the car.
 

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Nice review. I want to see and feel this car's performance! I'll gladly offer to coach you from the right seat. Any chance that you'll attend the Carolinas region DE at VIR in November?
 

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Does that mean you have replaced your TBD with a real LSD?

I wish I had done an LSD a long time ago, but I consciously delayed the LSD because I was scared that I would overpower the car and go Frisbee-ing across the countryside. I second your recommendation. In my experience, I could step the back end out only with dynamic clutch action or brakes. As it got hotter, I tried to constrain the understeer with tire pressure adjustments which was unsuccessful. I knew in my heart that I should soften the sways, but it was hot and I was lazy, so I hoped that the pressure adjustment would be enough. Shame on me. Hope is not a strategy for success.
I sent a message from my phone yesterday but it doesn't look like it went through. Nope I still have the TBD as opposed to LSD but the TBD provides plenty of lock up on acceleration to make the rear end dance out and let you control the car with the throttle. I can't imagine driving a Cayman with an open diff anymore, it would take a lot of the fun out of it! :)
 

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Cayman The Destroyer!
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Great review/ info. I talked to Tom Chan at TPC today and I'll have a DSC in time for my first track day Saturday. My car has the TPC PASM Damptronic setup.
 

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Discussion Starter · #90 · (Edited)
Okay, I finally got time to look at the track performance. I also went out and did a couple of performance runs.

I'll talk to the performance runs first. I suck. I followed a procedure that was guaranteed not to tax my clutch. Rev to 3500, floor the gas and quickly let the clutch out. Result: spinning end-of-life RE-11s. Data result: 60 ft times that suck dead goats. Totally embarrassing. I will say, however, in my defense (that means excuse) that I have not done a real hole shot in 42 years. I will also say that I did not tune the clamping force of the clutch for a hole shot and (if you care to look up the threads where I have repeatedly stated that this car is not geared for hole shots) the car is not geared for hole shots. My best 60 foot time was 1.9 sec and my best 60 ft speed was 20.8 mph. Respectable numbers, considering this car's geometry and tires would be about 1.4 sec and 31 mph. therefore, I humbly admit that my best time of 4.63 was due primarily to my incompetence and is not representative of the capabilities of my car. That was confirmed when I repositioned after the first run and saw 2 prominent very black stripes proceeding forward at least 40 ft. As my old drag buds would say, "You were trying to gas your way out of greased owl sh!t."

Now to the track data where (fortunately for me) first gear doesn't mean ****. Here is a very expanded data shot of the front straight of Carolina Motorsport Park.



The last turn, 14, (at the start of the graph) is a 2nd gear turn and I do not believe that this data is my best exit, but it shows what I want to show. Look at longitudinal accel starting with the dotted vertical line. From the lateral accel data, you can see that I am not yet quite straight and the wiggle indicates that I overpowered the exit but corrected gracefully (;) (just bragging a bit).

Look at the shape of the three acceleration ranges. They are all essentially flat, the result of a flat torque curve, or, more precisely, the torque no-curve. From that reference point to the shift from 2nd to 3rd, the car accelerates from 48.62 mph to 68.34 mph or 19.72 mph in 1.75 sec, or 11.3 mph/sec. For reference, a stock Gen 1 Cayman does 14.7 mph/sec peak (not average) in 1st gear. In 3rd, the car accelerated from 74.48 mph to 93.29 mph in 2.39 sec, or 7.87 mph/sec. In 4th, the car accelerated from 97.6 mph to 107.4 mph in 1.64 sec (time to brake!!!) or 5.94 mph/sec. The total time from 48.00 mph to 107.98 mph was 8.13 sec.

To put it in perspective, the next time you stomp on your Cayman, think about being able to maintain your peak acceleration until 12,000 RPM. That's what Sally feels like - in low boost - on an 89 deg day. :):):):):):)

I will say that there were a couple of things that surprised me. The longitudinal acceleration numbers tended to increase with RPM. That means that the torque absorbed by the increase in aerodynamic drag was less than the torque absorbed by the accelerating dynamometer (because the dyno showed a very flat torque curve but the track data shows a slight tendency toward an increasing torque with RPM. That all feeds into the assumptions made for the dyno run. From my track data, I can conclude that the dyno data is slightly conservative compared to real life, and that is exactly the way I like it.
 

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Discussion Starter · #91 ·
I drove the second version of the TPC Dynamic Stability Control (DSC), several times on the street and today on the track.

In Level 1, the street ride was noticeably improved, with a decrease in the sharpness to the response to sudden changes in road surface level like bridge expansion joints that are misaligned. The overall ride in more comfortable but gives a feeling that the car is very planted.

On the track, I used Level 2 except for a few laps at Level 3. I do not have the skill to recognize any difference between Level 2 and Level 3. I can only characterize Level 2 as amazing. In reviewing video, nose dive during hard braking and roll during rapid turn initiation are not detectable. A fellow driver, viewing the video, said, "Geez, Kenny, I've never seen a car stay that flat." I also had the opportunity to experience it during a couple of unintended maneuvers. Cutting the inside too close and going over the rumble strips didn't bother the car at all. Sliding too far to the outside and hitting the rumble strips did not upset the car at all. Either of those maneuvers when I had the PASM box would have destabilized the car enough to cause a momentary doubt of control. It definitely increases my confidence.

For driving Roebling Road, I loosened the front sway to the center hole and stiffened the rear to one hole from max stiff. The setup worked great and I ran equal pressures front and rear. Roebling is a track where nothing happens fast. All of the turns are rather sweepy and require patience. There were several turn exits where I was able to add power and unwind the wheel and end up in a zero-steering-angle drift. It made my heart smile.
 

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Cayman The Destroyer!
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Kenny, great data. thanks for sharing.
 

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Discussion Starter · #93 ·
It was a great day. In the first session, I ended up behind a Z06 that, I found out later had had "some work done". In low boost, I would stay with him on the straights and we were pretty equal in the turns even though I was on end-of-life RE-11s and he was on fresh Pilot Sport Cups. We talked after the session and arranged to cooperate in the second session. He led the first four laps and I led the second 4. Result was not enough difference to notice and we both noticed that my car would tend to get faster than his at about the 2/3 point in the front straight. After that session, I mentioned that I had not driven high boost and would like to just to get some data. We did the same setup: I followed him for 4 laps and had no trouble keeping up. Then I took the lead and on the first front straight, opened about a 3 car lead. I waited a bit after turn 2 and we went on around through turn 7 where I waited on him again (but just slightly). When he was behind me, he just waved me ahead, so I took off. By the end of the session, I was between 200 and 300 yards ahead. Afterward, he described how I moved steadily ahead in the straight, especially the second half. He also stated that I moved away significantly in the short straight path sections between turns.

The car is amazing to me. I never believed that I would own such a car.
 
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