I need to make the time to take the car on track more.
It has been over a year since I last had the car on track, which is unfortunate. Thanks to Covid it has been an absolutely hectic year, but when I got a message saying a few mates were heading to Winton, even with a different crowd (Winton Drive School, rather than EXE Crew or Track For Days) I knew I had to make the time to get the car on track at least once in 2022. At this time of the year it was hard to get the time off to both prep the car and actually attend, but I am really glad I was able to make it.
Track Day Prep
Coolant tank relocation
My stock coolant overflow tank was a very tight fit against the front of the timing case thanks to the thick triple core 42mm radiator, to the point where there would be very limited airflow around the passenger side of the engine and causing a large reduction in total airflow through the radiator on that side. I had already tried to solve this problem by closing as many of the gaps around the radiator as possible with self-adhesive closed cell foam and aluminium plates, but previous track days have still seen the coolant hit 100c+ after only 2 or 3 hot laps.
To try and increase airflow through the radiator I decided to relocate my coolant overflow tank. The stock one is tall, thin and doesn’t have great mounting options, so I ended up purchasing a generic aluminium 1l tank to re-purpose into holding the extra coolant. This was mounted to the passenger side shock tower with an aluminium bracket, meaning the alarm siren had to be relocated to the firewall.
As this is just to catch the coolant overflow the vertical position of the tank isn’t critical. The tank came with some clear tubing to act as a sight glass, and I marked the ‘full’ position by filling it up from the old tank and marking the level with a piece of heat shrink. A new longer hose was run from the radiator fill neck to the new bottle, and the fitting was modified with a piece of soft tubing epoxied into it to ensure it can pick up coolant even if the level is low. The vent port was connected to a line and wrapped up and over the tank to help prevent coolant from sloshing out.
Thermostat replacement
I had noticed an interesting trend after installing the much thicker radiator, which at 42mm thick and three cores holds almost 4 times the amount of coolant as the stock radiator. For general driving, if I drop it down a gear or two and accelerate hard the coolant temp dropped by 8-12c, before relatively slowly coming back up to operating temperature.
My theory here was the stock thermostat wasn’t allowing for enough coolant flow through the radiator to make use of the vast increase in volume; this was backed up with thermal images showing the drivers side of the radiator (the opposite side to the coolant hoses) was a good 10-15c cooler than the passenger side. By suddenly increasing the engine rpm, and thus subsequently increasing the water pump rpm, there was a flow-rate spike in the coolant system which caused the colder coolant the get sucked into circulation, decreasing the overall system temperature.
I swapped over to to a Tridon ‘High Flow’ thermostat (TT294-190), which after testing in a pot of boiling water showed an increase in area when fully open by about 12% compared to the factory one. As an added bonus this thermostat opens at a warmer temperature (88c vs 82c for the stock one), which will help bump up both coolant and oil temps for day-to-day driving for increased efficiency, while still allowing for more coolant flow when the car gets hotter- in theory at least.
Titanium brake shims
Mindful of the (relatively) small front pads and rotor rings of the AP Racing calipers I made a set of titanium shims to try and help prevent the brake fluid from boiling. Titanium is quite a poor conductor of heat, so even this thin 1mm shim should help prevent a significant portion of brake heat from being transferred to the brake fluid.
This was surprisingly easy to cut; a good set of tin snips made short work of the thin stock. The calipers were bled with Motul RBF660 as well to help fight fluid fade.
5203-2RS bearing replacement
From experience the 5203-2RS double row ball bearings don’t seem to last quite as long as the stock single row bearings in the serpentine belt idlers, and I had noticed mine getting a bit noisier over the last few months. When I initially did the upgrade I got a good deal on 6; the replacements are my last 2 giving a lifespan of only 1.5 years or so. Admittedly they see high sustained rpm in this car, but these angular contact ball bearings will also have more friction than the stock single row bearings and I will be switching back to the stock idler pulley bearing configuration when this pair are inevitably worn out. Hopefully the single row bearings will hold up to the RPM's better.
The track day itself
Weather wise this was one of the most perfect track days I have ever been to; starting around 16c and hitting a maximum of 26c and no rain in the area for a few days I was quietly confident that the car would hold up well.
The event itself was a lot busier than I am used to, however, with close to 80 entrants spread across 5 sessions. To make it even harder the first session was dedicated to actual race cars, including open wheelers, which although really cool to watch meant the rest of the street cars were jammed into the remaining 4 sessions. This put me in the second fastest street car session which also made for an interesting challenge.
Given the very wet winter and the long time since the last track day I felt incredibly rusty, but this didn’t stop the car from performing! The traffic meant I was unfortunately not able to set a new personal best, but my optimum time on racechrono throughout the day is actual 0.13s faster than my current PB; given the traffic and my lack of confidence I was decently happy with this!
Learning experiences- the most interesting part!
The coolant tank relocation made an enormous difference to the maximum operating temperature reached by the car, as well as how quickly the temperatures recovered! By removing the restriction to airflow down the passenger side of the engine there was a significant increase in total airflow through the radiator, and the coolant never got above 97c (in 26c ambient, with the heater set to max and the blower motor on setting 3).
This is still very hot, but compared to previous track days this is awesome news, and the car could be pushed as hard as possible for an entire 15 minute session without even having to think about engine temperatures. The car also noticeably cooled down on the straights; previous days it barely managing to drop 1 or 2c coolant temp on the main straight, but this time dropping a good 4-5c on the straights. Oil temps were similarly perfect, hitting a maximum of 129c.
I was a bit concerned about the higher opening temperature of the thermostat. This has cause the car to run slightly warmer for day to day driving, averaging 88-90c on the highway compared to 84-86c with the stock thermostat. This hasn’t been an issue in traffic, there is just less of a gap between the thermostat opening and the fans coming on. It held up perfectly on the few occasions I’ve been able to drive through the hills, but as I have learnt in the past that is a poor comparison to how hot a car gets on track.
In theory the maximum temperature of an engine is limited by radiator surface area and how quickly it can dissipate the heat, rather than the thermostat opening temperature. I was hoping this would be the case, but as everyone normally suggests a colder temperature thermostat if a car is running hot I was curious to see if I was right.
I’m not quite sure why people recommend colder thermostats; on the surface I can see why it makes sense but looking into how an engine cooling loop works it is clear that the maximum temperature is limited by the thermal dissipation of the radiator, not the opening temperature of the thermostat. Once the thermostat is fully open there is no more restriction to coolant flow and engine cooling, regardless of what temperature this is happening at.
I have noticed a small increase in fuel economy as well; not sure if this is a placebo or not, and it’s only about 0.2-0.4l/100kms on longer highway trips, but a hotter engine is more efficient on paper so it does kind of make sense. The hotter operating temperature also helps keep the oil temperatures in check in the cooler months we’ve had here in Melbourne.
The downside to this increase in hot air flowing down the passenger side of the engine is now everything there gets way hotter! The battery, fusebox, wiring loom and even the clutch slave cylinder were significantly hotter than they normally get; I will have to keep an eye on them. It also managed to melt the fittings out of the ABS body of the alarm siren! Luckily nylon cable ties held up a lot better and will probably end up being the long term solution.
The most interesting modification since the last track day is definitely the AP Racing brakes. Paired with RBF660 and titanium shims the brake pedal felt amazing for the entire day, with zero sign of the pedal softening even when the brakes got really hot. The paint on the calipers held up amazingly well, with the two pack clear coat holding up great.
There was one absolutely massive oversight in the setup, however, and I can’t believe I didn’t think of it beforehand. I had Intima RS pads installed in the REAR brakes, as these are a carbon track pad with less cold friction, to try and help bring the brake bias to a reasonable level for the street. With Intima SR (fast street pads, better cold performance) at the front the bias for street driving was perfect, and they held up for about 4 hot laps without any problems. The car pulled up really well, with a very confidence inspiring pedal feel and they were actually able to lock up hot AR1’s, which is not something I have experienced before and made it fun to use the brakes to initiate a slide.
The problems started after the fourth hot lap. Even with such large rotors, the (relative) small pad size meant the not-track-optimised SR pads were starting to fade. This would have been fine, except for the fact that the RS pads at the rear where right at their optimum temperature. This meant the pedal was still firm, but all of a sudden the front brakes weren’t doing anything while the rear brakes were working better than they ever have before, causing sudden and unexpected oversteer while braking. The first time this happened was definitely a brown pants moment!
In hindsight this is really obvious, but it’s also not something I have experienced on the street which I guess lulled me into a false sense of security. Just goes to show how much more load track use puts on things compared to even fast street!
Thankfully I brought the AP Racing pads as spares with me as well; swapping these into the rear brakes would stop that problem from occurring, at the expense of fading out faster than better pads. I also turned down the activation pressure of the proportioning valves going to the rear calipers; at an educated guess it is now operating close to 70/30 F/R split.
This new setup worked really well, with a firm pedal and good stopping ability. This was let down by the lower performance AP Racing pads, which started to fade out after about 3 hot laps. Not the worst problem in the world to have, and given the traffic on the day a cooldown every couple of laps helped get out of the worst of the traffic.
After swapping pads (I didn’t bother swapping the titanium shims) there was a noticeable increase in caliper temperature- even though I swapped to a much less aggressive pad. Unfortunately I didn’t have my thermal camera with me, but the titanium shims were definitely preventing a significant amount of heat from transferring into the caliper. Whether this was at a detriment to pad temperature remains to be seen.
The Quiafe rear LSD held up phenomenally well, and the car has significantly more mechanical grip than stock these days. With the correct line the accelerator can be held flat throughout most corners, relying on DCCD and the limited slip differentials to hold the car on the line. I am really happy with the driveline setup of the car at this point in time!
Overall I am happy with how the car held up on the day, aside from a few minor niggles. The pad issues will definitely need to be solved before the next track day; thankfully that problem can be attributed to a (pretty massive) oversight, and pads are cheaper than many other problems that could have come up. My biggest learning experience, however, is that I need more seat time, and I really hope I can get on track again before another year passes.
