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I ran my two Boxsters at the 2017 25Hrs of Thunderhill. We finished 12th and 13th overall and 5th and 6th in the E0 class.
The dry sump system continues to perform well. Here is a comparison of wet sump vs dry sump at Thunderhill:
I just did not have any concerns despite the early engine failure in 2015. Neither car used any oil during race and neither car had anything but perfect oil pressure for the entire race distance.
481 (running as #81 for this race) ran Toyo RR's and our new aero setup which includes a large splitter and wing. The aero parts were worth about 2.5 seconds at Thunderhill and the Toyo RRs were a further 2.5 sec/lap faster than the Hankook RS4s on the other car. 481 ran a 3.4 (99 996 engine but with 3.2 intake and electronics) engine for this race making an estimated 255rwhp. We ran the first set of Toyo RRs for 6 hours, but their performance dropped off badly in the last hour. Changing them after 5 hours did not fit into our existing driver change and fueling strategy, so the remaining sets were changed after 4 hours. Despite the more powerful engine and aero changes, 481 retained its normal handling balance of mild understeer. We had to replace the RF wheel bearing about 17 hours into the race. That was the "youngest" wheel bearing failure we have had so far. It failed around 1100 miles and I have reliably been getting 3000 miles out of these bearings. Early in the race 481 developed a slow cranking problem, probably due to a bad starter. We simply let the engine idle during the pit stops to prevent further delays from this.
482 (running as #82 for this race) ran the typical Hankook RS4s and without the new aero setup. It also had a new engine, a stock 3.2 making an estimated 250rwhp. This car suffered what was later found to be a broken front sway bar link in hour 3, which caused severe oversteer for the remainder of the race. The handling problems cost about 2 sec/lap on average. The first set of tires was removed at 6 hours in an attempt to cure the oversteer. The second set lasted the remaining 19 hours, with severe wear on the rears and almost no wear on the fronts. There were no other mechanical problems. 482 completed the race distance on one set of brake pads.
This race is challenging for Boxsters because they are among the slowest cars in the race. The fastest prototypes lap about 25 sec/lap faster than we can. The winning Audi R8LMS was about 20 sec/lap faster. The drivers of those cars were generally very patient and smart about passing us without risk. Most of the other cars are modified BMWs, most of which were a few seconds/lap faster than 481.
This race is also unusual in that about 14 hours of it is in darkness. The track is not lit up at all so it is a driving challenge. The cold weather means that cooling problems are non existent though.
This was the toughest race we ran all year in terms of preparation and driving. It is also the most expensive by far. It does offer some fun challenges though and we'll likely be back next year shooting for top ten finishes.
I ran my two Boxsters at the 2017 25Hrs of Thunderhill. We finished 12th and 13th overall and 5th and 6th in the E0 class.
The dry sump system continues to perform well. Here is a comparison of wet sump vs dry sump at Thunderhill:
I just did not have any concerns despite the early engine failure in 2015. Neither car used any oil during race and neither car had anything but perfect oil pressure for the entire race distance.
481 (running as #81 for this race) ran Toyo RR's and our new aero setup which includes a large splitter and wing. The aero parts were worth about 2.5 seconds at Thunderhill and the Toyo RRs were a further 2.5 sec/lap faster than the Hankook RS4s on the other car. 481 ran a 3.4 (99 996 engine but with 3.2 intake and electronics) engine for this race making an estimated 255rwhp. We ran the first set of Toyo RRs for 6 hours, but their performance dropped off badly in the last hour. Changing them after 5 hours did not fit into our existing driver change and fueling strategy, so the remaining sets were changed after 4 hours. Despite the more powerful engine and aero changes, 481 retained its normal handling balance of mild understeer. We had to replace the RF wheel bearing about 17 hours into the race. That was the "youngest" wheel bearing failure we have had so far. It failed around 1100 miles and I have reliably been getting 3000 miles out of these bearings. Early in the race 481 developed a slow cranking problem, probably due to a bad starter. We simply let the engine idle during the pit stops to prevent further delays from this.
482 (running as #82 for this race) ran the typical Hankook RS4s and without the new aero setup. It also had a new engine, a stock 3.2 making an estimated 250rwhp. This car suffered what was later found to be a broken front sway bar link in hour 3, which caused severe oversteer for the remainder of the race. The handling problems cost about 2 sec/lap on average. The first set of tires was removed at 6 hours in an attempt to cure the oversteer. The second set lasted the remaining 19 hours, with severe wear on the rears and almost no wear on the fronts. There were no other mechanical problems. 482 completed the race distance on one set of brake pads.
This race is challenging for Boxsters because they are among the slowest cars in the race. The fastest prototypes lap about 25 sec/lap faster than we can. The winning Audi R8LMS was about 20 sec/lap faster. The drivers of those cars were generally very patient and smart about passing us without risk. Most of the other cars are modified BMWs, most of which were a few seconds/lap faster than 481.
This race is also unusual in that about 14 hours of it is in darkness. The track is not lit up at all so it is a driving challenge. The cold weather means that cooling problems are non existent though.
This was the toughest race we ran all year in terms of preparation and driving. It is also the most expensive by far. It does offer some fun challenges though and we'll likely be back next year shooting for top ten finishes.
Chris Cervelli
Cervelli Technical Service
interesting data. what is the reason that the stock oiling wet sump gets much higher oil pressure when not pulling lateral g's?
is this a normal issue with all boxters, or all of the porsche flat 6s? thats not good... 1 to2 bar around turn 2. what do they do around turn 8 at willows?
interesting data. what is the reason that the stock oiling wet sump gets much higher oil pressure when not pulling lateral g's?
is this a normal issue with all boxters, or all of the porsche flat 6s? thats not good... 1 to2 bar around turn 2. what do they do around turn 8 at willows?
Chris could certainly answer -- but it's probably just plumbing loses -- which shows how well the dry sump is helping during cornering to be so flat a response.
Great info Chris -- and great driving and execution by your team.
BTW, this is how we felt at HPR 24H with all the Boxster's flying around us like we were sitting still
It's a lot harder to drive when you have to be watching both windshield and mirrors :-)
Congrats on finishing! A good friend does 12-24 hr racing and I understand that even finishing is a testament to car, team prep, and driver. What you did in two Box frames is awesome!
I set the track record at BW 3 weeks ago on a motor that had well over 100 hours on it. The second fastest guy only 5/10s off had a motor with 150,000 miles on it, and I honestly didnt see our gaps move while racing heading down the front straight = - despite what he would say :-)
I think in NorCal we have seen 1 or 2 pop, some get tired and drop some HP over time. If you wanted to run at Fontana every weekend I might suggest something different, but sub 5 second sustained Gs I just dont see data that shows we have an issue
I will caveat I am no expert, I can drive - I dont wrench.
Chris could certainly answer -- but it's probably just plumbing loses -- which shows how well the dry sump is helping during cornering to be so flat a response.
Great info Chris -- and great driving and execution by your team.
BTW, this is how we felt at HPR 24H with all the Boxster's flying around us like we were sitting still
It's a lot harder to drive when you have to be watching both windshield and mirrors :-)
Mike
That makes a lot of sense. good analysis . you lose a little pressure with no cornering forces, and have plenty of pressure for other conditions.
2.5 seconds for different DOTs , 2.5 seconds for aero? and another 2 seconds for a broken swaybar? Seems very excessive, the data showing that would be interesting to see.
at least from what ive seen from those changes, on an even faster car.
Originally Posted by CTS
481 (running as #81 for this race) ran Toyo RR's and our new aero setup which includes a large splitter and wing. The aero parts were worth about 2.5 seconds at Thunderhill and the Toyo RRs were a further 2.5 sec/lap faster than the Hankook RS4s
Great work and result Chris -- congrats on finishing with both cars. Mid-pack pace definitely makes it a tougher race than when you're in the top 3 or 4 fastest cars. Our race pace in the Toyo Flying Lizard Cayman (street tires) was only around 1:55-56. We pretty much had to race everyone at all times, hopefully we were good neighbors with you guys on the track. :-)
Here is wing only (2:03.xx) vs wing + splitter (1:59.xx) (used Hankook RS4s)
Some of the difference is due to better driving I'm sure.
The car had very severe understeer with the wing only.
Here is Hankook RS4 (used) vs Toyo RR (couple HCs) (no changes in aero)
Again the driving is probably better since we'd had more practice.
Data for the broken sway bar is an average of the first 105 laps vs the remaining ~545 laps. 2 sec/lap is pretty close. The delta was smaller than that with new tires, then grew as the tires aged.
Great work and result Chris -- congrats on finishing with both cars. Mid-pack pace definitely makes it a tougher race than when you're in the top 3 or 4 fastest cars. Our race pace in the Toyo Flying Lizard Cayman (street tires) was only around 1:55-56. We pretty much had to race everyone at all times, hopefully we were good neighbors with you guys on the track. :-)
-mike
Mike thats still a pretty good clip for the cayman. was it a GT4? and street tires, i think you meant, DOTs,
Yeah, i would say that most all the differences were driver. you just dont see , lap to lap differences of that amount due to a wing or a splitter or even a broken sway bar. sure, it will make the car drive funny, but it just means the same lap times become a lot more work. again, ive had thse failures and differences before. lap times might change a second or two for all of problems listed[, but not 7.
from the data, that one lap had a 10mph difference going into turn 1 and a big drop off the pace for turn7 (odd) that's a couple of seconds right there, but no differences to that level anywhere else. he might have been spooked on the high speed turns or questioning the entrance speeds. the car could do it as it proved in other places. gear choices could be an additive role in the effect
just looking around at the data. interesting stuff thanks for posting
Mk
QUOTE=CTS;14662856]Here is wing only (2:03.xx) vs wing + splitter (1:59.xx) (used Hankook RS4s)
Some of the difference is due to better driving I'm sure.
The car had very severe understeer with the wing only.
Here is Hankook RS4 (used) vs Toyo RR (couple HCs) (no changes in aero)
Again the driving is probably better since we'd had more practice.
Data for the broken sway bar is an average of the first 105 laps vs the remaining ~545 laps. 2 sec/lap is pretty close. The delta was smaller than that with new tires, then grew as the tires aged.
12-10-2017, 08:00 PM
Boxsters at NASA 25 Hours of Thunderhill
