Sydney 300 - 2019

[david_syd_au]

The Sydney 300 enduro was held at SMSP GP Circuit last weekend, and as a participant in the event, as a pit crew member on Saturday, and then a suprise driver on Sunday, I though it might be worth recounting the experience for the couple of people on this fourm who might be interested :-)

My wife and I had arranged to act as pit crew for the weekend, along with 4 others, for David Johnston and Wayne Cooper, driving David's NB race car. We were all relative newbies, anf rolled up at the track early on Saturday. Most of the day was taken up with support events, with a few Sydney 300 practise sessions scattered amoungst them.Late in the day David brought the car into the pits for a driver change during a practise session and Marty noted there were oil smears on the front right wheel. Further inspection show the right side of the engine covered in oil, and after a lot of work disassembling the intake manifold (twice) it became apparent there had been a structural failure in the head, and the car would not be ready for Sunday. Our event was done.

I have an NC race car which I have been slowly developing for such enduro events, but it had suffered a major hub failure at the MX-5 Cup event last month, which while it had been repaired had not left me confident enough to have entered the Sydney 300 as a driver originally. However, I offered to substitute my car, and the team accepted, knowing that it was untested, and after I had told them we wouldn't be pushing 100% and that I wanted to treat the event as a test session. Wayne graciously agreed to step aside, leaving DavidJ and myself to drive.

There were a few hurdles to running the car:
- We had no idea of the fuel consumption and hence the required pit stop strategy
- The wheels I had been running on the car were unavailable as one had a destroyed tyre after the suspension failre, although I had bought another set of wheels and actually had the tyres fitted at SMSP on the Saturday planning to take them home. These wheels had never been on the car and I had concerns over clearance.
- The front brake pads were new and unused
- We had no radio in the car
- DavidJ and I have different dimensions, and we weren't sure we could make the necessary adjustments so we could both fit.

We ran the car in the 15 minute morning practise session. I got 2 laps, DavidJ unfortunately onlgoy t 1. We made an extimate of the fuel consumption from what it used during the practise session, and reckoned it was using around 2.2 litres a lap, and that with a 75 litre capacity we weren't able to do a one stop race. So we decided on 2 stops, with me driving the first stint of 17ish laps, handling the chaos of the start as I was more familiar with the car, then handing over to DavidJ with the tanks filled for a 32ish lap middle stint, then I would take over again to the finish. The fuel usage during the first stint would give us better data to decide how many laps DavidJ could actually do in the middle stint so we could adjust when to show him the in board.

Oh, btw, it was lonely for our crew on the pit wall, as everyone else had radios and so didn't need a pit board!

I did the rolling start, unsure on exactly what the rules were on no overlapping, overlapping or ovetaking, before passing the start line, as that hadn't been covered in my brief one-on-one driver briefing on SUnday morning! So I settled on the happy medium of an overlap of the car in front, but not an overtake. The first few laps were busy, but I didn't take any chances and gradually moved us up from our starting position 36th on the grid to 20th. The tyres started to get too hot after about 10 laps and I decided to back off a bit rather than stuff my new tyres. The brakes were also dodgy for most of the stint with the new pads bedding in.

The first pit stip went well, with the crew doing a great job, and as well as fuel and a driver change, we also checked and adjusted the tyre pressures and given the new wheels, also checked the wheel nuts. The tyres had started at 23 psi cold, and at the first stop the left side tyres were both around 28, which is waht we wanted, while the right tyres came in at around 32. Way too much.

DavidJ had a fairly uneventful sting, taking a few laps to get familiar with the car and to learn what gears to use where. Poor bugger had come from a 1.8 litre NB with no power steering to an NC 2.5 litre with power steering and different gearing. Both MX-5s, but very different.

We worked out the fuel consumption during the first stiong had been 2.33 litres a lap, and decided to bring DavidJ in after 29 laps. By then he had got back the positions lost in the first stop and we eer about 20th again. At the 2nd stop, the car was refueled, tyres pressures and wheel nuts checked again, and out I went. On the first flying lap between turns 1 and 2 I noticed some smoke behind the car. Thinking it might be from a slight tyre rub through turn 1, I decided to keep going and take it a bit easier around turn 1. However, after a few more corners the smoke also came into the car, and I could tell by the smell it wasn't from the tyres. I completed a slow lap and returned to the pits, where Stephen diagnosed that the pinion oil seal on the diiff had failed. I didn't have a spare, and so that was our day done.

We made 50 laps, of the 77 possible. A good effort by our team given the journey we took to get there.

Thanks to the crew (in no particular order)
Gaynor, Karina, Marty, James and DavidD.
A special thanks to Stephen Brennan (of SB Auto) who has been working on the car and offered to come along after I told him Saturday evening about the car substitution.
Thanks also to DavidJ for taking care of the car and rigorously following my reduced redline instructions, unlike me :-)
Thanks to Wayne for offering to step aside so I could drive on Sunday.

With the Wakefield 301 later this year as a target, and then the Sydney 300 next year for sure, I must remember to read this story again before those events to remind myself of what hjard work, and sheer fun they can be.

I have put a couple of videos on youtube.
DavidJs last few laps of the middle stint
https://youtu.be/MyG1oJavXt0

My first few laps of the race from the start
https://youtu.be/8ibZ2PtQsPA

If you read this far, well done. Your comments are welcome.

DavidL
Car #87, Sydney 300 - 2019

[SKYHI]

Well done David. It's not easy keeping composed during these sort of weekends at the best of times, let alone with that sort of extra drama thrown in. Good memories of weekends away with fellow racers doing the 1HR Prodsports races back in the day.

[Blesif]

I particularly enjoyed the videos especially the mechanical noises combined with the various corners and straights. Entertaining write-up as well and also my congrats on entering the car at the last minute and getting so far into the race. Good crew, good attitude. Best wishes, David. Neil

[Roadrunner]

Enjoyed the video and the write up. Is that a brake prop valve you're fiddling with on the right side of the steering wheel?
Was there to see the first dozen or so laps. Very entertaining.

[david_syd_au]

Josh, better to reply late than never.
The car has unboosted dual master cylinders with a balance bar to adjust front/rear balance.
That setup should be useful with a potential 75ish kg difference in fuel tank weight over the rear wheels in endurance events. Also, with an ITB engine there is no easy vacuum supply for a convential brake booster. Stephen Brennan at SB Auto helped get the brakes sorted and over the months before the Sydney 300 we did some mucking about with master cylinder sizes to find a good compromise between brake feel and pedal travel.
The brake balance is yet another variable to learn to run this car!

[david_syd_au]

As a bookend to my Sydney 300 report, the cause of our diff failure was improper clearances of ring and pinion in the diff that came with the car. This caused it to overheat and the pinion seal failed as a result. On inspection the gear set was found to be stuffed, so I have had the diff rebuilt using a spare gear set. Unfortunately the ratio is not as ..... exciting :-) ...... as the original.
The car acquired itself well at the last MX-5 Cup (15 Sep), although I have been away from regular competition for too long and it showed with many driving mistakes.