Clubsport with the Z

I want to be at least somewhat data driven on this project, which means if I’m building a clubsport car I need to do clubsport things. Over the span of the year I’ve done small things here and there to resolve some quirks of the car while attending club events, but now I need to go participate in some trackday events to get an idea of how I can start shaping the car to live up to my vision in that aspect as well.

What do people actually do with clubsport cars?

Probably the most common entry point into clubsport activities is High Performance Driving Education (HPDE). A HPDE program is essentially that: a school designed to turn normal, everyday people into really competent drivers (and do so in a safe, consistent manner). Just like a kid doesn’t need to be a math genius to graduate public school with an understanding of algebra, someone doesn’t need to be a natural born racecar driver to learn to drive in a HPDE program. These programs allow anyone to develop their skills at their own pace, as their growth and / or budget allows.

But what does that have to do with engineering and nerd stuff? Well, I can’t very well know what I should change on the car, if anything, if I can’t drive it hard enough to see where its weakpoints are.

Fortunately, HPDE events are provided by many well regarded organizations, such as Sports Car Club of America (SCCA), National Auto Sport Association, Chin Track Days, and more. When I was researching these organizations and their schedules, I found NASA’s schedule and event layout to be the most appealing to me, at least for the time being, So I signed up for their November 2025 event at Eagle’s Canyon Raceway (ECR).

The state of the car going into the HPDE

The intention going into the HPDE weekend was to develop my driving skills and get a baseline understanding of the car’s capabilities and limits. With that in mind, it makes sense to document the state of the car going into the HPDE:

Drivetrain (Engine, Transmission, Differential)

Overall the car is probably still making close to stock horsepower. The most significant change to the drivetrain is probably the NISMO RZ34 differential (aka “diff”) assembly that I found on Ebay earlier this year (it was salvaged from a wrecked vehicle). At the time of writing this, all NISMO RZ34s have 9 speed automatic transmissions. A consequence of that design is that the final drive ratio in the differential is taller than the ratio in the unit that originally came with my car. I feel like the benefits of the 1.5 way mechanical LSD outweigh the potential drawback of the taller gearing, but I do think I’ll want to adjust the gearing in the future after I collect more data.

Aside from that, the car is equipped with an aftermarket exhaust (mostly for a better sound and look), an intake plenum spacer (installed by the previous owner, a common inexpensive modification that many owners report modestly increasing the engine’s power without any real drawbacks), and a new intake air filter (the car still has the OEM airbox).

The lack of engine modifications is intentional. The goal for this car is to be easy and comfortable to drive on the street, which implies that the vehicle must remain street legal and pass emissions testing for registration. Also, not heavily modifying the engine will (hopefully) make it easier to keep things reliable under hard driving.

Suspension

The car came with Tokico D Spec dampers (shock absorbers), also installed by the previous owner. I found them to be a bit harsh, they would unsettle the car over small bumps or seams in long high speed turns (like the many ramps and junctions we have on our highways in Texas). It also seemed like the left front damper was beginning to leak. I needed a quick solution to both of these problems for a road trip that was planned for the beginning of November, so I opted to install a set of Ohlins DFV Road and Track coilovers. I primarily chose these because I am familiar with their ride characteristics (I’ve installed them on a previous car I owned), and they lowered the vehicle the least out of all of the off-the-shelf suspension options I could find. They are also not as expensive as many would think (at the time of writing you can find them for $2500 - 2800, which is comparable to similar offerings from KW and Fortune Auto). Beyond my personal experience with them, they are widely reported to be good enough for early HPDE pace. Although I have long term plans for the suspension that will likely involve changing to dampers that I can service and valve myself, I’m very interested to see how far I am able to go with the Ohlins.

Wheels and Tires

• 18x10 +20 Enkei RP03
• 275/35/18 Continental Extreme Contact Force

My general approach in this area, at least to begin with, is to fit as much tire as possible under the fenders (as long as the engine has enough power to turn them). Really lightweight, low power cars might need to be less aggressive with their tire selection, but medium weight and heavier cars seem to benefit from as much tire as they can get.

I managed to get a good deal on the wheels from a fellow ZCCA member (which really made me happy I joined the club!), then I later sourced the tires from Trackday Tire, which is the official tire retailer of NASA. They provide discounts and benefits to active NASA members, so it was an obvious choice. The tires are generally regarded to have good grip and high endurance, which is exactly what I was wanting from my first set of HPDE tires.

Even though this wheel and tire combination is a bit wider than stock, it reliably fits under the front fenders without any bodywork or fender rolling. Since it’s a “square setup” (the tires are the same size in the front and rear, or “all four corners”), I am still able to rotate the tires to get more life from them. There really isn’t a concern with the setup causing too much oversteer¹, as these cars seem to be inherently stable (or biased towards understeer) in steady state conditions.

Brakes

The braking system is also not heavily modified, as I wanted to get a feel for what the factory braking system is capable of with good pads. The previous owner installed stainless steel braided brake lines, which are often reported to give better brake pedal feel (some people report that it makes the pedal less mushy).

I installed some Carbotech 1521 brake pads at the beginning of the year and flushed the brake fluid with Castrol SRF. Track usage is known for boiling brake fluid. When the brake fluid boils, the brake pedal becomes very soft and the brakes feel like they are no longer working (which is something I would like to avoid experiencing). Several companies produce high quality racing brake fluids, I chose Castrol SRF because it has a reputation for not needing to be replaced as often, and I’m kinda lazy so that appealed to me.

Other

Aside from an aluminum undertray, everything else was pretty much stock. Besides having nice looking wheels, you would probably walk by this car in the parking lot and not think much of it in terms of modifications or performance.

How was the HPDE experience?

NASA is more or less another club to join, so I think it’s worth talking about the experience. For registration and event information, everything was pretty easy to find on the Nasa TX website. I received a “HPDE Welcome Letter” the week of the event that provided more details on the exact schedule for all of my sessions, a map of the facilities, a track map, and other useful logistical details. I was also notified of any changes to the schedule via text message. Getting a Trackday Insurance Policy was also straightforward: when creating the policy I was able to select the track and organizer from their respective dropdown menus. The entire process only took a few minutes.

A weekend at a NASA event is very busy. They concurrently run their driver education program with their race events, so you will see touring cars and time trial racers getting ready to head onto the track as you leaving the track from your HPDE session. Because of this, punctuality is key. Missing a classroom session or being late to grid (the area where you show up before you enter the track) means you might miss out on track time. Despite the packed schedule, things ran smoothly almost the entire time. It’s an impressive operation. Overall, the HPDE students were allotted 3x 25 minute sessions of track time on Saturday, and 2x 35 minute sessions on Sunday, with a final “all swim” session (racers and faster drivers join the student drivers on track) of 40 - 50 minutes. Even if you skipped the mixed session at the end of Sunday, you were probably going to get at least 2 hours of time on track, barring a mechanical failure or some incident that throws off the schedule. Most people were tapping out before the final Sunday session.

The classroom sessions cover a lot of the information students need to know to safely drive their vehicle on track and begin increasing the pace of their driving. All new students start in HPDE1, which means we are guaranteed a personal instructor for the entire weekend. I was often provided with a microphone and earpiece to put into my helmet so I could ask them questions and get feedback from them as I drove around the track. Even though I memorized the track layout before showing up to the event, there were still some details that were hard to capture just from reading the track notes or watching videos of people driving the track. The instructor was able to help me fill in the remaining gaps pretty quickly in the first two sessions, and by the end of the day he informed me that he felt I was ready to move up to HPDE2, which means I could drive around the track without an instructor in the car with me. I passed the “check ride” during the first session the next day, and spent the rest of the weekend refining and consolidating the skills I developed in the earlier sessions.

The track was very fun to drive. There is a lot of speed variation and elevation change throughout the track, along with increasing and decreasing radius compound turns. You really get to feel the car move around in a lot of different scenarios. It seems like it’s probably a great track for learning, as even the blind corners had plenty of safe space for your car to go in the event that you did something wrong. It’s also smooth and has clear markings. New and experienced drivers alike all commented on how much they enjoyed driving this track. The track also had showers, a restaurant, a cafe, a gas station, and multiple good locations for spectators to watch from. My wife really appreciated the facilities, and having the restaurant and gas station on site also made it easier to find time to work on the car (foreshadowing) or socialize with some of the fellow participants.

Socially, the event started off with most of the new student drivers keeping to themselves, but everyone eventually relaxed and started chatting with each other a lot more as the weekend progressed. Overall, everyone seemed to have a great time and were chatting excitedly about figuring out which event they could attend next and continue their learning journey. I really got lucky because my instructor happened to be a Time Trial competitor driving a 370Z (the successor to my car, which has similar overall characteristics), so he was able to share a lot of useful information about his experiences so far with his car as well coach me on line selection and techniques that allowed me to drive my car around the track with more confidence. There was a banquet / social on Saturday night where my wife and I got to chat with some of the other attendees. Although it was an additional $10 per person to attend, I think it was worth it.

What did the HPDE reveal about the car?

The Good

It was an eventful weekend with a lot of great moments. Overall the car is fun to drive and I think it has more potential for me to unlock.

The car is actually fairly quick and a lot of fun to drive

During the first session I was surprised at how much grip it had, and how forgiving it was even when I was a little uncertain with the inputs. This was my first time “driving it in anger” so I wasn’t sure if it would respond in a predictable manner when pushed hard, but it seems like you have to be pretty heavy handed to really upset it. My instructor also mentioned that he thought my car had pretty good mechanical grip. The suspension was also very compliant over the curbs, so I could take more aggressive lines through the corners without upsetting the vehicle. The car has enough power to get out of its own way. Nothing to write home about, but enough power to actually enjoy driving the corner exit correctly, which is good enough for me right now.

Steering responsiveness was good. Brake responsiveness was also good. For the most part there wasn’t anything that significantly distracted me from driving the car and learning.

The Bad

There were a few nuisances, but that’s why I’m are doing this: to find areas for improvement. Things are things I more or less predicted would need improvement, but driving at the track gave me first hand experience as to how much of an improvement these changes will make.

I think the instrumentation needs improvement

I don’t find the gauges and instrumentation to be that helpful on track. The car has a built in programmable shift light, which is pretty nice since you can see it blinking even when you’re looking far down the track and not at the cluster. The car also has an oil pressure gauge, which seems nice in theory, but I’m not good at looking at it when it really counts (in the corners), and looking at it on the straight will only confirm that I’ve harmed the engine (if I’m going down the straight with low oil pressure, I’ve probably also done damage during the preceding corners). The coolant temp gauge is also somewhat suspicious, as it’s hard to know if the engine is “hot, but technically not overheating.”

Ideally I would have some form of alerting system that would notify me in a very noticeable, unambiguous way that my oil pressure is too low, that my oil / coolant / differential / power steering temperature is too high, etc. Many of these sensors do not exist on the car as it sits today and will need to be added.

Some of the existing data acquisition solutions can provide this, and since data acquisition is something I wanted to add anyway to help find areas for improvement in driver performance, it makes a lot of sense to prioritize this upgrade.

The seats aren’t the best for track use

This was something I noticed during the aforementioned road trip, but was very apparent when turning laps. I don’t really sit “in” the factory seats. The shoulder bolsters are more like shoulder blade bolsters. My hips are a bit wide for the factory thigh bolsters. Needless to say, I was moving around quite a lot whenever I was experiencing any g forces. I tried some of the classic seat belt tricks to help hold me in place better, but the driver’s door panel ended up being more supportive than the seat in the long run. I got used to it by the end of Sunday, but I want to improve the situation sooner rather than later.

The good news is I have some new seats sitting in my foyer as I type this, and I am just waiting on the mounting brackets to arrive!

The car needs better brakes, especially up front

My experience with the brakes this weekend reminded me of why I am often skeptical of even what the most well-meaning people tell me when it comes to critical systems. Prior to attending the HPDE, I inquired with multiple people both inside and outside of my personal network whether or not the Carbotech 1521 pads would hold up under HPDE1/2 conditions. Everyone said “they should be fine,” (although Carbotech themselves state that the 1521s are not intended for track use). I brought a set of XP10 front and XP8 rear pads with me, just in case.

I’m very glad I did, as it changed the entire outcome of the weekend.

In my first HPDE session my instructor was guiding me through the track and helping me develop my reference points and consequently bringing up my pace. Towards the end of the session we were carrying quite a bit more speed than and people were starting to point us by. I had a feeling that the pads weren’t biting as hard as they were in the beginning, but there was a lot going on during that session so it was hard for me to be sure that I was feeling what I thought I felt. Aside from autocross, most of my experience has been in a simulator or riding shotgun in another person’s racecar, so I didn’t have a sharp sense for some of these sensations and I was just doing my best to be vigilant. I made my instructor aware of my concerns just in case we needed to end our next session early and change the pads.

During the second session we were quickly back up to the pace we ended the first session on, possibly going even faster, and I decided that before I would push the pace any harder I would give the brakes a test by braking a bit early and pressing the pedal as hard as I physically could. It was then we discovered that the brakes couldn’t generate enough force to lock the wheels / engage the ABS. I notified my instructor immediately and we decided to reduce our speed and coast a bit before the braking zones to let the brakes cool off. Initially it was seeming like this would work out, as we were able to settle into a consistent pace for the rest of the session, but on the final lap during the downhill braking zone into turn 13A the brakes did not slow the car as much as I was predicting they would.

Noticing this, I stayed on the brakes longer than usual while turning towards the apex. This ultimately was a mistake, as it resulted in keeping too much weight on the front tires / too little weight on the rear, causing the car to enter a spin. In hindsight, I should have kept braking in a straight line and accepted that I would miss the apex, or released the brakes for the turn in and let the front tires scrub off the speed. Fortunately by that point we weren’t going that fast, so we were able to stop the car while it was still on the track. We let a few other students drive by, restarted the car (I guess I was a little too late putting “both feet in”)², and continued the short journey to finish the lap and exit the track. Coincidentally, the next classroom session was about what to do if you experience brake pad or fluid fade.

During the lunch break I managed to get the brake pads swapped to the XP10s and XP8s, eat lunch (thanks to my wife for grabbing some food for me), go for a quick drive to bed the pads in³, and still be back in time for the next session. The XP10 / XP8 combo seemed to work really well for the rest of the weekend. These pads will probably stay on the car until they’re worn out, as in hindsight I’m not actually sure the 1521s can reliably engage ABS from highway speeds with the current wheel and tire combination.

Ultimately I think the “buy once, cry once” solution for the front brakes is to upgrade them to something more robust. After examining the brakes after the event, I can see myself easily going through multiple sets of pads and rotors in a year if I attend a few events and turn laps in all of the sessions. A braking system with bigger pads and rotors should theoretically have less wear and transfer less heat to the fluid. At the current rate, I’m probably going to melt the caliper piston dust boots in the OEM brake calipers, which is another headache I’d like to avoid.

The rear suspension needs some work

Now that I’m more comfortable with the car, I need to do some basic tuning with the suspension, especially on the rear. The rear suspension is currently set to the factory recommended damper settings and maximum recommended height settings. With these settings, the rear suspension is very forgiving which makes it easy to put power down, but the suspension travel still seems to be fairly short. At ECR, the car would bottom out on turn 12 and kinda bounce off of the rear bumpstops⁴ twice before settling in. I’ve also experienced similar suspension travel issues during normal driving on public roads. This might be fixable with just damper adjustments, but I want to be careful not to over damp the suspension, as otherwise the car was well mannered and easy to push hard.

The Ugly

There are some things I did not predict (or at least hoped wouldn’t be a problem). But alas, they must be addressed.

Air conditioner

My air conditioning stopped working earlier this year. When I connected it to a set of gauges it appeared that it was a bad compressor. I resigned myself to the expensive task ahead and reached out to Francisco over at Galgo Performance to see if he had an AC machine we could use to evacuate my system (I could do the rest of the work in my home garage). As luck would have it, he had a brand new machine. However, when we went to evacuate the system we found that the car barely had any refrigerant in it. This was a bit concerning, and now I was wondering if I misread the gauge during my original diagnosis (which is totally possible). We performed a vacuum test on the system for over 20 minutes. No leaks. Weird. We recharged the system, disconnected the machine, started the car, and checked the temperatures at the vents. The AC wasn’t working. At this point, I was fairly certain of my original diagnosis, and I wondered if my compressor was also leaking, causing the low refrigerant situation. We evacuate the system again (not even 30 minutes after we’ve charged it) and the machine reported that the vehicle was once again low on refrigerant. We added some UV dye during the charging process, so we checked for leaks with a UV light. No dye present on the compressor… no dye found anywhere else either.

Now we’re very puzzled. How did it lose so much refrigerant in less than 30 minutes? How did we not hear it? Maybe we heard it and didn’t realize it? “Hey, Francisco… did you hear a hiss when you took the cap off of the refrigerant fitting earlier?” At this point I figured if we didn’t detect a leak during the vacuum test, it must be because the leak was in a place where the vacuum test wasn’t checking: the Schrader valves.

He took a moment then replied “… I think I may have. Let’s swap the Schrader valve.” We swapped one of the Schrader valves and charged the system, and the AC system started working.

I thought this was the end of the saga, but the issue reared its head again on the way up to Decatur, TX for the HPDE. I had to drive back in the rain on Monday without a functioning windshield defogger (well, the only way to make it function was to blast the heat instead of drying out the air with the AC, so it wasn’t a very comfortable experience). I checked the caps that cover the Schrader valves and both of them momentarily hissed when I unscrewed them, so I plan to swing by Francisco’s again and if the system truly has leaked down again and see if it passes a vacuum test. If that’s the case, I’ll probably just replace both AC lines and see if that sorts it out.

The car might be losing horsepower

During the Sunday session the car seemed to lose a bit of power, but was otherwise driving fine. Oil pressure was good (if the factory gauge can be trusted). Oil levels were good. Coolant temp seemed good (again, if the gauge can be trusted).

My instructor’s hunch was that the car was pulling timing due to running a bit hot. It seems to be a common issue with VQ powered Zs. However, due to lacking aforementioned detailed instrumentation we couldn’t know for sure. We decided to play it safe and return to the paddock early since I needed the car to be able to make the 5 hour drive to get back home the next day.

This isn’t an acceptable problem to have on a clubsport car, so we’ll need data to design a good solution to stop it from happening again. I think this will involve a bit more than just bolting on some parts, primarily because I’m not confident that the existing aftermarket oil cooler kits will be sufficient for the Texas summers. My instructor was driving a naturally aspirated⁵ 370Z and he still sees high temps with a 34 row oil cooler (the largest version commonly sold in the aforementioned kits), even with hood vents helping with heat extraction. I was able to sit in the passenger seat on Sunday and witness this myself, despite his AC condenser being removed and the temperatures being fairly mild (for Texas). On paper, the 34 row engine oil cooler should be able to handle the heat generated by the engine in that car⁶, so I’m excited that there might be an opportunity to design a more effective solution for both of our cars.

In addition, I should probably go ahead and put the car on a dynamometer to see what power it’s making today, as well as perform a compression and leakdown test so I can start tracking the wear on the engine.

I’m ditching the spare tire (at least for now)

Most clubsport cars don’t come with spare tires, and are instead provided with an emergency tire repair kit. Once I upgrade the front brakes, the temporary spare probably won’t fit anymore, so unless I go with a rally style setup and figure out how to securely mount a full size spare in the back of the car I’ll probably choose to carry an emergency tire repair kit instead.

Also, I basically broke the emergency jack that came with the car while swapping the brake pads. Thanks to that experience, I have zero desire to get another one and rely on it during an actual emergency.

On the plus side, I now have more space for activities in the trunk. Relocating the battery to the trunk would open up some potentially useful real estate under the hood while also shifting a bit more weight to the rear of the car.

The pedals might need some work

With the current braking setup, heel and toe downshifting is kinda challenging when braking at full force. There are a few ways I could address this. I could modify the pedals / add pedal covers to change the height of the brake pedal relative to the throttle pedal, as well as extend the throttle pedal surface to make it closer to the brake pedal. I could also resize the brake master cylinder to decrease the pedal travel (this will also increase pedal effort, but I’m okay with that). The end all be all solution is to install a racing pedal box and dual master cylinder setup, which I’m open to but I think we might be a bit too early for that at this moment.

Bonus

Since I’m pulling the seats out, I figured I may as well throw some better speakers in. The previous owner installed a decent aftermarket head unit, but the OEM speakers are holding it back and the driver’s rear speaker isn’t working at all, so it’s time to fix that.

Gear

Communications

My helmet comes with an integrated headset and microphone, but the communications system the instructors were using did not use the same connector as my helmet. Because of that, I had to use their earpiece and it was kinda annoying to try to shove an additional earpiece and mic into the helmet (there isn’t a lot of space). It would be nice if I can find an adapter cable that lets me plug my helmet into whatever that communication device is that the instructors are using.

Jacks

Since I broke the jack that came with the car (and it was pretty sketchy to use anyway), I either need to get a race jack or figure out how to power my quickjacks in the paddock. My truck has an integrated 120v inverter, but I’m not sure if it can reliably power the quickjacks. I also need a more stable base for the quickjacks so the pump doesn’t fall over and spill hydraulic fluid everywhere.

Scales

I’m also probably going to get a set of corner weight scales so I can finish my suspension setup worksheet and balance the car. The car drives well enough today, so this isn’t an urgent priority like the cooling and data acquisition / monitoring systems.

A Trailer

I have a truck. I rented one of the U-Haul car hauler trailers. It was not a fun time trying to get the car loaded, and once loaded there was no easy way to exit the vehicle (I couldn’t open the doors). We returned the trailer and opted to drive both vehicles up to Eagle’s Canyon. I would rather not do that again.

I have some people in my network with trailers, but I’d like a backup solution for when they are not available / they are using their trailer. U-Haul has a “toy hauler” trailer that I might try next. Maybe I’ll rent one for a day just to see what the experience is like. Ultimately I’d like to buy my own, but the more urgent priorities might prevent that from becoming a reality before the next HPDE.

Driving both vehicles to the event puts double the fatigue on the drivers and puts wear on both vehicles. It also makes breakdowns at the track more of a concern, since you need to be able to drive the vehicle back home (for me, the closest track on the NASA calendar for 2026 is 3.5 hours away).

I’m predicting that I will rent and borrow for the next year while I stalk the classifieds for a nice trailer.

Next Steps

So… in one weekend I had a lot of fun, developed my real world driving skills, and learned a lot about the car! Each of these issues will (hopefully) be addressed in depth in the mini-projects and subsequent blog posts to come.