Tom@TPC Racing

Thanks for sharing your experience. I have not seen that before. Good reference for the future.

In my case, the one axle nut that back off was a nut designed for the 993. That was the only nut I can get that day to finish the job. The thread pitch is the same but the design of the nut flange is different. Both the axle flange and wheel bearing are new when I installed this nut. I also taper cut the leading threads on the axle because they were stripped. I think all of these are contributing factors in my case. Never a dull moment.

Tom@TPC Racing

After the last round of prep I went back to Summit Point Raceway, this time the event was hosted by CHIN Track Days. Had great weather, great host, great group of cars, and great drivers. Had the time of my life being in the mix with a couple of 991 GT3 RS's equipped with DSC Sport controller and track alignment driven by experienced club racers in the advanced run group. Here are some pics.





















Icing on top is during a chase I set my personal best at this track from 1:19:78 to 1:19.34 in Lap # 4 in this video thanks to the awesome rabbit car and driver!

HarmonyJim

Tom, how did your car fare against the 991.2 RS on the straights? Did your engine build give you an equivalent level of straightline speed, and out-of-the-corner lunge? Do you think the R&P change was a big part of the performance difference? Always look forward to another new posting.

Tom@TPC Racing

On track, I'd say 80-130mph is about the same. After 130mph the 991.2 RS builds a gap. The newer cars are aerodynamically superior(less drag) and the gear shifting time and extra gear of the PDK is untouchable by old fashioned H-pattern manual gear shift G50. Every manual shift I make I lose more than a car length. The 997.2 Cup-replica rear wing on my car is set at 10.5 degrees, it feels like an anchor when I lift the throttle, even for a shift. Corner exit depends on layout of the corner and what gear I'm in; by selecting a lower gear I may have to be more patient with the throttle and have to make an extra shift during exit.

The 991GT3/RS PDK have pretty close to 4:1 R&P from the factory, so if anything the Cup 4:1 R&P in my G50 gearbox makes for a slightly more even comparison.

I want to clarify that I am trying to out do the evolutionary technology of the newer cars, I just want to make my old car the best I can make it and have fun with it.

Tom@TPC Racing

Got the engine oil sample analysis report back. Here it is. It is what I hoped to see. Engine is running strong. Doesn't like to idle for too long with the Cup S exhaust cams but I don't care. The 33ppm of Lead is from consuming 22 gallons of race fuel each track day.

Tom@TPC Racing

Here's my report from Sunday, August 11, 2019-


This was day two of CHIN Track Days at Summit Point partnered with DSC Sport for DSC track demos. On the day one I followed demo participants to get a gauge on how they're doing with/without DSC and get some footage. I put down some pretty good laps following a few different 991 GT3 RS's from a non-intruding distance and had a lot of fun doing it. In between the session I checked on customers and participants so the day went by quickly. The set of Pirelli DH tires I had on were used, with 3 heat cycles on them prior to me running them(that I know of, with 1 of the heat cycles being a 90-minute enduro race on a 997.2 Cup). By the end of day one with 4 additional heat cycles added, both the tires and the track surface grip had diminished some.

I had a goal to achieve for myself that weekend. I figured the only opportunity to attempt to achieve my goal was on day two in the first session before the tires run out of heat cycles. Running out of time and heat cycles to achieve my goal, I woke up at 4am, drove 90 minutes to track(I went home from the track because I wanted to spend time with my better half since we both had busy work weeks), loaded up on expresso, I was the first person to be at the track just before 6am. I swapped my wheels & tires from left to right, bled the brakes, and then hide from everyone to study video, data, and got myself in the mindset to achieve this goal.

Here it is. 3 warm up laps for the Pirelli DH's. 2 laps to work through traffic. And GAME ON!

I best my previous of 1:19.34 with a 1:19.13 in Lap #6. And then achieved my goal for this event of getting into 18's with a 1:18.72 in Lap #7. In the 18's is good enough to be right in the mix with "Prepared Street Class" race cars in PCA Club Racing at this track. Since I was on a high note I came in right after that lap because I was coming up to traffic and I know exactly how to do this lap again and even better next time via data and mental prep(I was a timid to throttle at apex of T3 which would have gotten deeper in the 18"s.). Rest of the day I made my rounds with customers, gave rides at a slower pace, and just ended the day on a high note. That's all for now.

voodoo

Nice job, Tom.

Tom@TPC Racing

A few people asked me which electronic settings I used for this run so I thought to share this info-
TC ON (Interesting fact is with the combination of suspension components, tire size and compound, and setup with factory Traction Control ON it is not intrusive at all. I found this out by accident when I forgot to turn TC OFF. I believe this is the result of the car having a lot of rear grip and the taller rear tire further improves the situation by raising the rear wheel spin detection threshold)
Engine Sport Mode OFF (Because I personally find that with Engine Sport Mode OFF the throttle modulation is better)
Suspension Mode I have been using DSC, the two modes are programmable by user. I use DSC Normal Mode for street and wet track. I use DSC Sport Mode for dry track.

Argon_

Interesting point with the taller rear tire. I've been thinking about that as a way to make BMW traction control less intrusive.

Tom@TPC Racing

I have also experimented with the opposite end of this by using a shorter rear tire and/or taller front tire, the TC let me know it wasn't happy in a very intrusive way!
Separately, taller front tires(taller than OEM height by more than half inch) understeers like a truck!

Tom@TPC Racing

My car has been running flawlessly, besides occasionally getting the "Low Windshield Washer Fluid" message and "Random Misfire" CEL. The Low Windshield Washer Fluid message is from a defective fluid level sensor. Over the Winter I will probably delete the entire system(washer bottle, pump, lines, nozzles, bypass sensor) since I don't even remember the last time I actually used it! The CEL for Random Misfire only comes on when I drive to work during morning rush hour traffic at under 10mph with zero load for an extended period of time. This is from the combination of using racing spark plugs that are couple heat ranges colder than the OEM plugs and valve overlap of the Cup S exhaust camshafts in rush hour traffic conditions(product misuse on my part). The engine doesn't sputter it just sets the CEL when OEM thresholds are met at low rpm and zero load. The CEL goes away with key OFF. But I use PIWIS or Durametric or COBB AP to read and then reset the ECU anyway. The cure for this is ether to stop driving in rush hour traffic with real race car engine parts or ask my boss(COBB Pro Tuner) to raise CEL trigger threshold for under 1500rpm. These two quirks don't bother me enough nor make my car any less fun to drive on street and track. In fact the more I drive it the more I love it.

Made couple changes since I just can't leave things well alone. LOL The first change is swapping the rear brake pads from Stoptech SR33 to the more aggressive SR34. Even though I had absolutely no braking bias issue with SR33 all around, the car consumed a set of front pads in 6 track day(~2 hours pers day), at the time of the front pad change the rear pads had ~70% thickness remaining(and after 8 track days the rear pads had ~60% thickness) This fact leads me to believe I can go with a more aggressive bite rear pad to brake slightly deeper with less effort without creating oversteer during braking. After switching the rear pads to SR34 I did a few hard stop on the street on Michelin Cup 2's in both straight line and bend, the braking stability was fine. Will see how it goes with Pirelli DH's on track.

This is a SR33 rear pad after 8 track days. Still has ~60% material remaining. The fronts were all used up in 6 track days.



The second change I made was the transmission gear oil. I switched from Mobil 1 Delvac 75w90 to Redline 75w90. I used a 50/50 mix of Redline 75w90 and 75w90"NS". This was the "cocktail" we used back when we raced 996 Cup cars in GrandAm and Daytona 24-hour. I actually used this mix before my transmission was rebuilt by Copans last Winter. Before the rebuild I found the Redline mix to make gear shifts "lighter effort" on track. While I found the Delvac to be better shifting on street especially when its cold. These are just my personal experiences, my customer and friends don't all concur with my experiences with the gear oils. But I suppose it has to do the internal operating tolerances and wear factor on each transmission. Anyway, on my transmission it was better with Delvac right after the rebuild, after 10+ track hours it seems to like our Redline mix better.



Another reason for switching the gear oil is that in my mind the Redline mix has less friction modifier for the differential clutches and may be they will shed less metallic material. I know this may look alarming to those who doesn't wrench, but those who do their own transmission gear oil changes know this is pretty normal looking for a decent clutch-type limited slip. This pic is with Delvac. Right after switching to Redline on a street drive I can feel the diff "unload" more distinctively during mid-corner throttle off(I did this on street, don't do this on track at or near limit of tire grip!). Since it disengages more aggressively I have to assume it also engages more aggressively.



The Delvac did come out super clean. Nothing to worry about with the gears and syncros.





That's all for now. Need to work in another track day or two before the season ends.

DJN

Thanks for posting Tom! Excellent as usual.....I may try your gear oil cocktail at some point....although I have quite a stockpile of Mobil 1 Delvac.

Quick question: Do you know the difference in the friction coeffient for the Stoptech SR33 to the more aggressive SR34 pads? I will be installing my StopTechs this month.

Cheers
Doug N

rbahr

Hi Tom,

I am curious what you were running for spark plugs?

I pulled a couple of plugs and they seemed to be running a bit hot, so wondering about alternatives. The 2005 GT3 cup is calling for FR 5DTC, the 2009 Cup S is calling for 5DDC EA=0,8. I am guessing that EA is the gap in mm

The motor is a 3.8l like yours, and spends most of it's waking hours >5K rpm wise :-)

Thanks

Ray

Tom@TPC Racing

Hi Doug. Thank you.
I don't have the coefficient chart. From my subjective feel, SR33 feels similarly linear in torque to RS29 but better in that the threshold modulation feel more precise, which is very confidence inspiring, and that the braking torque stays consistent all the way through the life of the pad with heat cycles in the two digits. My guess is SR34 would feel similar to RS14 in terms of initial bite.
Note: My subjective feel above is from using Pirelli DH slicks where I can stand on the brake pedal like doing squats at the gym. Can't do that on Cup 2's and less sticky tires without ABS kicking in immediately.

rbahr

WRT Redline,

Don't use their Shockproof product in the tranny. I say that because if you do a search on redline cocktail you will find 'Uncle Scotties' which calls for some of this. In a previous life, it messed up or covered up a multitude of sins that just got worse!

Ray