The Build · NCM series, part 3 of 3 · By the numbers
Part one ended with the shakedown moved from Friday to Saturday, in public. This is the public part, on the stopwatch. The timing data is on SpeedHive for anyone who wants to check our math.
Bottom line, up front
Car #86 was classified 85th overall and 29th in Class C at The Colonel & The Sinkhole: 61 laps, all of them on Saturday, one driver, four stops, new pit-crew made up of only two people, and a Sunday spent in the paddock looking at oil the color of a grape soda float.
The report in three sentences: the driver, on a track he’d only run in a simulator, walked the pace from 3:28 to within two per cent of the sim’s race lap by his fourth stint, and did it in 95°F air. The car gained positions every stint it ran and lost them every time it stopped, and it stopped for three hours, almost all of it for the same oil line. The stopwatch says the seat is fine, the fuel model is on the money, the heat plan worked, and the whole weekend turned on an inaccessible hose.
Finish
P85 of 97
Class C
P29 of 30
Laps / miles
61 / 192 mi
Race time
6:24:00
Best lap
3:05.215
Best-lap avg
61.2 mph
The course, and the sky
NCM Motorsports Park sits across the interstate from the National Corvette Museum, which in 2014 had a sinkhole open under its display floor and swallow eight Corvettes. Lemons named the race for two of Kentucky’s most famous exports, the Colonel (of chicken fame) and the hole, and it’s hard to argue with either. The full course is 3.15 miles and twenty-three corners, run clockwise for this event, with two straights long enough to make 161 horsepower feel personal and corner names that read like a drink list: Corvette Curves, Deception, Thunder Valley, the Carousel, Table Top, Faux Rouge, Rockhouse, and the Sinkhole.
The sky did one thing all day, and it did it with conviction. Saturday was clear from the green: 86°F when the flag dropped, 91 by eleven, 93 at noon, and 97 by three in the afternoon, still 96 at five. The dew point fell from 72 to 61 through the day, which held the heat index to 97–99 rather than the 100-plus forecast, a mercy we sort of noticed but didn’t rely on. The wind was westerly and useless, and a Heat Advisory ran until seven that evening. Sunday was another day in the mid-90s. The car didn’t run it. We’ll get to why next.
01The shape of the day
Every flying lap, one driver, Saturday only. Pit, in, and out laps removed.
Read it left to right and the first thing you see is the test day we didn’t get, compressed into seventeen minutes. Lap one was a 3:27.7. Lap five was a 3:11.3, which is under the 3:12 the sim asked the driver to reach by the end of Friday. He got there on lap five of Saturday, with the KTuner still relearning under his right foot and ninety-six other cars for company. The tune was finished in that first stint, in traffic, which is not how anyone recommends finishing a tune but was exactly how ours got finished.
The second stint is the car settling in: a 3:15 median with the best laps in the 3:09s, and improving, right up to the four hollow points at the end. Those are laps 20 through 23, when the oil pressure started to fall and the driver started watching the gauge instead of his mirrors. He brought it in on lap 24.
Stint three opens quick, loses a minute to three slow laps in a row, the kind of block that is slowed by repeated yellows on the track, and then recovers. Stint four is the one to frame: laps 39 through 42 went 3:08.4, 3:08.6, 3:09.0, 3:05.2, the last of them the fastest lap of the weekend and within a fifth of a second of what the simulator predicted a healthy #86 would do. Then lap 43 goes hollow again, and the chart goes quiet for two hours and eight minutes, while the team chased a busted line and aggressive leak.
Stint five is the afternoon after the repair: fifteen laps, a flat 3:16 median at 96°F, and a deliberate one. By then the car had lost oil twice and the driver was running to the gauges rather than the sim, a decision we’ll defend below. The last two laps are hollow again. The oil was going for a third time, and at 4:24 the #86 crossed the line for the last time and parked with sixty-five minutes still on the clock.
02The one seat
We’ve withheld the driver’s name, which is harder when there’s only one of him.
| Stint | Laps | Air | Best | Median | vs sim 3:05.0 | Spread |
|---|---|---|---|---|---|---|
| 1 · the test day | 7 | 88°F | 3:11.3 | 3:26.6 | +11.7% | 4.1% |
| 2 | 14 | 91°F | 3:09.3 | 3:15.4 | +5.6% | 1.9% |
| 3 | 9 | 94°F | 3:06.8 | 3:14.8 | +5.3% | 3.9% |
| 4 | 7 | 95°F | 3:05.2 | 3:09.0 | +2.2% | 2.7% |
| 5 · nursing it | 15 | 96°F | 3:11.1 | 3:16.1 | +6.0% | 2.4% |
The comparison this time isn’t driver against driver; it’s driver against the model. The point-mass sim said a healthy #86 with a settled driver should turn a 3:05 race lap and live between 3:03 and 3:13, with a two-per-cent tolerance on the median. Stint four landed at 2.2 per cent, in 95-degree air, on a track the driver had never driven. The best lap matched the sim’s race lap to 0.2 seconds. That’s about as good as a spreadsheet gets.
The more interesting number is the slope. Stint two was 5.6 per cent off the model, stint three 5.3, stint four 2.2, while the thermometer went up ten degrees. Nothing changed on the car between those stints except the oil level, so that’s learning: a second and a half a lap found every time he got back in. The spread column agrees. Once the tune was in, the lap-to-lap spread sat between two and four per cent in every stint, including the one at 96°F, with no widening band anywhere in the day. That band is the signature we watch for when a solo driver in a heat advisory starts to run out of driver. The good news it never appeared, in part because of the hydration plan reinforced by the pit-crew.
Then there’s stint five, seven seconds a lap slower than stint four in the same air, and slower on purpose. Two oil-line failures in, with a two-hour repair behind him and the gauges telling a story, the driver ran the car home at a pace it could survive rather than one that would look good in this table. In this seat that isn’t a shortfall; it’s the job. The #86’s standing rule, learned expensively at Carolina, is that we drive to the limit of the car, not the driver, because the car is the one that has to make it to Summit Point. The whole stint of restraint cost less than one lap of track position. We’d make that trade every weekend, especially if it saves us from having to replace another engine; see the Team’s standing opinion on hero laps.
03The heat
The plan assumed 97°F and a heat index over 100. It got somewhere around 97 and 99.
Air, green to flag
86 → 97°F
Peak at 3 p.m.; still 96 at five.
Heat index
97–99°F
A falling dew point kept it under 100.
Seat time
3 h 12 m
One driver. Longest stint 49 minutes.
Paddock recovery
Ice + electrolytes
Never at a fuel stop, never on a schedule.
Fuel taken
11 gal
Two jugs, as planned.
We came to Bowling Green treating the forecast as the opponent to beat, and the forecast mostly showed up. What the data says about it is quieter than we expected: the heat didn’t take any lap time we can find. The stint medians got faster as the day got hotter, the spread never widened, and the one slow stint was slow for oil, not ambient temperature. The stop model earned its keep another way. With recovery confined to the paddock and the car never idling in the hot pit with a driver inside it, the seat never became the problem, and the longest run of the day, forty-nine minutes at 96 degrees, ended with the same lap times it started with.
The heat found the crew instead. Two people ran every stop, chased every leak, and did the two-hour repair in the sun, in a Heat Advisory, without once suggesting that a different hobby might involve air conditioning. That isn’t on the timing sheet. It gets its own section in the wrap-up.
04The climb
Overall running position after every lap, 97 cars.
This is the chart that says what the weekend was. From lap ten on, every time the #86 was circulating it was passing cars: twenty-five places in the second stint, eight in the third, three in the short fourth, four more in the cautious fifth. Every drop is a stop. The car ended Saturday 73rd of 97, seventy-two laps down, and sat there while the field ran Sunday, which is how a car that never took a black flag and never touched anyone finished 85th. Twelve cars finished behind us, and seventeen entries, ours included, never turned a lap on Sunday. Lemons is a hard place to break down, but a well-attended one.
05The ledger, and where the day went
Each stint’s pace, and the pace once the stop that followed it is folded in.
| Stint | Laps | Best | Avg lap | Avg incl. stop | What followed |
|---|---|---|---|---|---|
| 1 | 7 | 3:11.3 | 3:24.3 | 5:02.9 | planned · seals and fluids check, 12 min |
| 2 | 14 | 3:09.3 | 3:15.9 | 5:17.5 | unplanned · Accusump line split, 28 min |
| 3 | 9 | 3:06.8 | 3:19.8 | 4:42.3 | refuel and radio swap, 12 min |
| 4 | 7 | 3:05.2 | 3:11.3 | 21:30.3 | unplanned · line off, thermal event, 2 h 08 min |
| 5 | 15 | 3:11.1 | 3:17.1 | 7:38.3 | parked with 1 h 05 min left |
The “avg incl. stop” column is the honest one, and every row says the same thing: the stint’s pace didn’t decide the day, what came after it did. Stint four ran the best laps of the weekend and, with its two-hour stop spread across seven laps, cost 21 minutes a lap. The stops, by name:
- 12 minStop 1, lap 8: the seal-and-fluids check. Planned, because the test day never happened and nobody wanted to find a leak during a post mortem. Nothing found. See stop two for why it was worth it anyway.
- 28 minStop 2, lap 24: the Accusump line. The driver saw the oil pressure falling and temp starting to rise and came in, which was the right reflex and the reason there is still an engine. The line to the Accusump had split and the hose clamp holding it to the sandwich plate. Pit-crew reworked in the issue in the paddock; a loose electrical connection then kept the car from leaving for a few extra minutes, for variety.
- 12 minStop 3, lap 35: fuel and a radio. Eleven gallons, two jugs, exactly what the fuel model said the tank would want by then. The radio was swapped in the same stop. Bad comms issues persisted.
- 2 h 08Stop 4, lap 44: the line again, then the heat. This time the line came free rather than splitting; the pressure fell, the driver boxed. On the crawl from pit lane to the paddock the car had what the log calls a thermal event, the polite name for a temperature gauge doing something you’ll be discussing for weeks. The electric-fan switch had failed, so at walking pace there was no airflow at all. A leaking thermostat housing was found and fixed while the line went back on. The car went out again at 3:35.
- 1 h 05Lap 61, 4:24 p.m.: parked. Oil temperature high, oil pressure falling, for the third time. The driver brought it in and the day was over.
One good number hiding in that list: eleven gallons after thirty-four laps is a third of a gallon a lap, call it nine or ten miles per gallon on this track and this tune, against six and a half at Carolina on a richer map. The fuel model built from the CMP data predicted two jugs at that stop, and two jugs went in. Of all the documents we wrote in August, the fuel one came true.
06What the car was thinking
Day-one instrumentation: a pit-wall log, a driver’s eyes, and one very expensive Sunday morning.
The thing that worked. The crack in the transmission we filled with epoxy on Friday, under the car, did not weep a drop all weekend. The only component on the car with a flawless race is the one we repaired with a product that comes in a twin-tube syringe. We are reading exactly the right amount into that.
We don’t have a clean telemetry trace from Saturday; the ECU was busy relearning and the Pi logger’s first race is a story for another day. What we have is the gauge story, and it’s consistent: three oil-pressure drops, all caught from the seat, all traced to the supply line of the Accusump, a device installed after New Orleans specifically to keep oil in the engine. The Accusump did its job. Its plumbing took a more liberal view.
Sunday morning’s pre-race inspection supplied the last data point. The oil on the dipstick was frothy and the color of a milkshake, specifically a purple one, because Saturday night’s oil change went in with Royal Purple and the radiator was topped off before anyone knew the two systems were swapping fluids. When we tried to start the car, combustion pressure leaked into the cooling system; when the radiator cap was loosened it left, at speed, and hasn't been seen since. That's the textbook picture of a failed head gasket, and it’s our working diagnosis. The engine still turns over, which is the good news: it isn’t seized, and the K24 is at Haas Auto Service Center in Manassas for a likely head gasket rather than at the scrapyard for a wake. Whether the thermal event caused the gasket or the gasket caused the thermal event is a question for the teardown. Either way, the sequence starts at a hose.
07What we’re fixing before Summit Point
- The head gasket, professionally.It’s at Haas Auto Service Center. While the head is off we get a look at the bores and the bearings, and an answer to the only question that matters: did three oil-loss events leave anything behind?
- The Accusump plumbing, decisively.Multiple failures of one line in one day is not bad luck; it’s a routing, heat, or fitting problem, and it gets solved on the bench. If the fix can’t be made bulletproof, the baffled pan runs at the full mark and the Accusump comes off the car until it can. The safety device can’t be the failure point that kills us.
- Pressure-test the cooling system, and rewire the fans.The thermostat housing that leaked, the head gasket that failed, and the fan switch that died all live on the same circuit of consequences. The fans get a switch and wiring that survive a race weekend and don’t share a junction with the ignition; we learned that one Saturday night, in the dark, with a multimeter.
- The oil-alarm rule.The driver managed to get this right three times, but “right” took four laps the first time and one lap after that. New standing order: unexplained oil drop or oil temperature climb means box this lap, no judgment, no nursing. A warning light at that threshold would do more than any amount of coaching, so one is going to end up on the dash.
- Radios that work, or a plan that doesn’t need them.Three races, three radio problems. We ran most of Saturday on hand signals and a pit board, which worked because we’d rehearsed it, but it isn’t a communications strategy. Not having radios also meant we weren’t able to collect telemetry on the car. Antenna, headset, and mount get sorted on the bench before we race again in October.
- Keep the fuel model. Keep the heat plan.Two jugs when the model said two jugs, and a 96-degree stint as flat as the 91-degree one. The August paperwork that worked goes into the Summit Point binder without edits. The paperwork that was too cumbersome gets fixed.
- Find out what minute ninety looks like.No stint at NCM ran longer than 49 minutes. Summit Point’s plan assumes longer, so the first clean session there is a stint-length test, judged on the widening band, not the median lap times. We don’t have the cubic inches to make up lost time in the straights, we need to be able to make up for out lack of top speed by going the distance.
- Plan the cold start, again.This is the second report to end this way. Carolina said the first cold, damp hour costs a full pace tier; Bowling Green never got below 86°F, so the note is still untested. Summit Point in late October will test it.
All the Way.
