My fourth year of NB Miata ownership
I’ve now owned my NB Miata for four years. I have been writing post where I cover each year of ownership. This year I continue that format where I cover the year with a single photo and short description for each month of ownership. This particular post goes from March 2024 (where I left of last year’s post) through February 2025.
March 2024: Swapping in a rebuilt VVT motor with a 6 speed
Over the winter I prepped a BP6D VVT motor and got around to installing it into my car to replace the original BP4W in March.
I fell down the slippery slope of an engine swap. I was just going to drop in the motor as-is, but found the valves weren’t sealing very great. So I rebuilt the head. While the head was off I ended up doing a DIY hone with new OEM rings and Chinese pistons, along with a long list of goodies:
- Eagle forged rods
- ACL race bearings
- ARP head studs
- ARP main studs
- Boundary oil pump
With the new motor I put in a 6 speed transmission to replace my 5 speed. Everything went well at first, but less than a month in the head gasket started to fail. I blew out a freeze plug during an autocross run, the continuous near redline RPM caused the pressure in the cooling system to build up and one of the freeze plugs was the path of least resistance.
It was a very minor head gasket leak, but it meant I had to put in the old motor for the season. I did choose to keep the 6 speed installed, so at least I got that upgrade.
April 2024: Brake cooling ducts
In April I installed the brake cooling ducts that are available for the Supermiata BX11 brake kit I have on my car. I used two section of hose with a coupler in the middle so that if I damage just one part of the hose I don’t need to replace everything.
While the BX11 brake kit has plenty of braking capacity, I have found that the pad life isn’t the greatest since the brake pads are pretty thin. I was considering going with a bigger kit for bigger pads, but the cost and wheel fitment issues lead me down the path of trying out brake ducts.
Overall I have been very happy with the ducts. In my experience they have approximately doubled my pad life. The only drawback is really that the duct hoses are kind of a pain to deal with.
May 2024: Racing Beat Race muffler
In May I replaced my Racing Beat Power Pulse muffler with a Racing Beat Race Muffler.
My goal was to drop a little bit of weight, and make my car a little bit louder. The upgrade did exactly that. I was expecting a little bit more noise, but it was still enough of an increase to make me happy.
It’s louder, but not so loud that you’d immediately get pulled over for accelerating from a stop light, or run into noise level issues at the tracks that have noise limits.
My full exhaust setup is a Raceland header, Racing Beat Race resonated midpipe, and Racing Beat Race muffler.
June 2024: Ozarks International Raceway
If you haven’t driven, or even seen Ozarks International Raceway in person you might have a hard time fully understanding how much elevation change this track has. The picture above gives a little bit of perspective.
I was much faster here this year compared to last year, but there is still so much more time to be had as I get more comfortable. This track is truly something special in terms of how technical and crazy it is.
Probably my favorite track I’ve been to, either here or Hallett if I’m in the mood for something a little shorter and more forgiving.
July 2024: Trailering my car to High Plains Raceway
I got my dad’s old truck in June and used it to tow my Miata for the first time to I29 Speedway in June. My intention was to see how the truck handled towing my car so that I could be prepared for my trip to High Plains Raceway in July.
The truck was mostly trouble free in the 900+ mile round trip towing my Miata on a rental U-Haul trailer. I encountered some misfiring due to some oil-fouled spark plugs, and a spark plug wire that was a little too close to the exhaust.
Overall driving a more comfortable truck is definitely worth the tradeoff of spending more than double the cost of fuel when compared to driving my Miata with a tire trailer, at least for these long drives.
August 2024: Motorsports Park Hastings
Hastings is one of the tracks I do pretty well at since it’s the track I have the second most amount of time on (first place would be I29 Speedway). So coming back here for SCCA Time Trials again I was looking forward to seeing how fast I could go.
I managed to lead every session against everyone in my class, and even most of the driver’s in the class above me. My fastest time of the day was a 1:39.19 (3.59s faster than last year), I was in the 1:39’s for most of the day.
That’s faster than the NASA Spec Miata track record (1:40.415), and also faster than the NASA TT6 track record (1:39.625), but not quite as fast as the NASA TT5 track record (1:34.110). My car falls somewhere in between TT6 and TT5 classing wise so my time is in a pretty good place.
I also had pretty good success at I29 Speedway and Hallett Motor Racing Circuit this year.
September 2024: Building out a truck bed camping setup
For all of the multi-day events I have previously gone to I have been camping in a tent at the track. It’s cheap, pretty easy, and with a big tent there is a surprising amount of room inside.
The drawbacks to sleeping in a tent is that it takes a decent amount of time to setup, then haul all my things inside, and then tear it all down a couple of days later. This is especially challenging when it might be raining when setting up or tearing down.
I was able to purchase a cheap color matched topper / camper shell for the bed of my truck in July so I figured I might as well try to build out a sleeping setup in the bed for track days.
The idea is that there won’t need to be any setup or tear down, and it allows me to potentially have an A/C setup in the future to cool things off to sleep.
I was able to build out platform that sits above the wheel well on one side that can support a trifold cot sized (75 x 31) memory foam mattress to sleep on. The platform has a foot piece that can be removed so I can have room to sit or store things while in transit. The remaining 2/3 of the platform folds up for storage underneath.
On the roof I installed a MaxxFan Deluxe RV roof vent that can be used as an intake or exhaust vent. There are also solar panels up there to keep a battery charged to power the vent, lights, and other things.
I was able to use the setup in November at Hallett and it worked very well. I’ll be continuing to make improvements over time.
October 2024: Finishing touches on my own open car trailer
I purchased a cheap 18 ft open car hauler (16 ft deck + 2 ft dovetail) in July shortly after returning from High Plains Raceway and was able to finish building out the trailer exactly how I wanted by October.
Modifications include:
- Gray anti-slip patio / deck paint on the wood deck
- Badlands Apex 5500 lb winch
- Battery box with my old Miata lead acid battery, charged with a 50W solar panel.
- 12V battery tender is attached to the trailer battery and can be used to keep the Miata battery topped off if needed
- Wheel chocks and tie down straps to tie down 4x spare Miata tires at the front
- Mounts for 4x 5 gallon fuel jugs on each side of the front
- Plastic tongue box. Solar panel mounted to the top, and trailer related supplies inside
- Threaded nut plates screwed into the underside of the deck to allow me to bolt a canopy to the deck when the car isn’t on the trailer
- Replaced the jack with one further forward so that I could install the tongue box
I plan to continue to add on to the trailer going forward (things like a safety brake cable, and some fender lights), but it’s super usable as it is now.
My biggest complaint would be that the angle of the dovetail doesn’t work well with my low car. There is no hope of it working with the splitter, and even with the splitter removed it scrapes on my frame rails.
I was able to work around the angle by putting some short 2×6 pieces under my wheels when going onto and off of the trailer, and removing my splitter. Unfortunately no extended ramps can solve this issue because the dovetail is a fixed angle.
November 2024: Hallett Motor Racing Circuit
I made it to Hallett again this year, this time as part of the SCCA Time Trails series.
We ran both directions in the same day. It was nice to be able to drive both ways, but switching mid-day was pretty quick. As soon as I was getting the hang of one direction again it flipped around.
I went quite a bit faster in both directions compared to last year, and even was first in my class for a few of the sessions.
This is a really fun track with just enough elevation change to be interesting, but not so much that it’s overwhelming like at Ozarks International Raceway.
Since this was my last event of the year my tires were pretty worn out, and at some point I started locking up my rear wheels, which resulted in some flat spots that got worse throughout the day.
December 2024: What went wrong with my VVT motor?
In December I finally got around to looking more into the VVT motor with a leaky head gasket that I removed from the car in March.
Unfortunately nothing was majorly wrong. There were some minor scratches on the head, but none going between the coolant and combustion chamber. The head gasket and block surface also looked good.
It’s possible I could just slap a new head gasket on and be fine, but I’m still considering getting the head skimmed again just to make sure it’s all good. I’m also considering using something like hylomar which could help seal any imperfections.
On the block side I noticed that the thrust side of the cylinder walls had wear going through the hone towards the center of the bore. This could be the cylinder walls being out of round, or the piston to wall clearance not being quite right. The wear was like that before doing the DIY hone (maybe not quite as bad though).
I’m going to hold off on putting a new motor in the car for the time being since the original BP4W has been good for me. I also have another bare block that was honed and decked at a machine shop.
January 2025: Skunk2 intake manifold
Since it didn’t seem like I was going to be able to swap the VVT motor back into the car for 2025 I decided to try something else that could get me a little bit more power.
I previously had a Squaretop intake manifold in the car, which has worked really well. I have had my eyes on the Skunk2 intake manifold for some time and finally decided to buy one and install it for the 2025 season.
It’s not super clear if it will gain me much power, the consensus seems to be maybe 1-4 wheel hp at the top end of the power curve. For a track car I’m mostly in the high RPM range and not having the power fall off as much past 7000 rpm could be handy.
We’ll see what kind of power it actually makes when I dyno the car later in the year, if things are worse I can always swap back to the Squaretop.
February 2025: GMRS racing radio
With my time trials races one common occurrence would be me coming off of track and not really knowing how far ahead or behind I was compared to the fastest time in my class.
My family attended a lot of my events in 2024, and they have access to the live timing. I figured it would probably be worth installing a racing radio into my car so that I can communicate with family in the pits in 2025.
I went the super cheap route with GMRS radios. They should have good enough range, and the $30 for 10 years FCC license that includes you and your family is perfect for my situation.
In the car I installed a Baofeng UV-5R. It’s hard wired to constant 12V, but is switched so I can turn it on or off if needed. I used the Nerdy Racing NASCAR system for the harness, but ended up rewiring the helmet portion to use a IMSA connector instead of the NASCAR connector so that I can use a driver/passenger intercom radio in the future.
For the antenna I mounted an NMO antenna connector into the factory antenna hole (I had to add a small backing plate since the factory hole is slightly too big).
For the pits I have another Baofeng UV-5R, and a Baofeng UV-9G (a waterproof model could come in handy on a rainy day).
Conclusion
Just like most of the third year I spent most of the fourth year driving my NB Miata on track. In 2024 I completed 392 laps, totaling 12.1 hours of track time. That is made up of 16 days on track.
My Garmin Catalyst says I’ve done 1023 laps, or 34.6 hours of track driving with my car. I’ve driven slightly more since I did my first couple of days without a Catalyst, and there has been at least one time where the Catalyst didn’t work.
This year I also did 3 autocross events, all early on in the season. I decided to stop doing autocross since it was a lot of time for very little driving. My car is also more setup for track use at this point.
I was able to get faster at every track just with more seat time. I’m very happy with how my car is setup at this point.