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I've had a grand time doing an all-out turbo build in my other build thread HERE. Learned a lot about maintenance, fabrication, tuning and cars in general. Also fell in love with the track, and have gotten 30+ track days under my belt in the last 3 years.
Alas, I got a Cayman and no longer need a mixed-use street/track machine. I wanted to turn my attention to a 100% track Miata focused on safety and reliability, and maybe get into racing down the line. It would be fun to get into time trials or some of the endurance series like WRL, ChampCar or even vintage racing. It would have been more work/money than it's worth to put a cage into my current turbo Miata and put it back to something resembling race spec, so I'm going to sell it off.
In the meantime I found a good starting point for a new build locally. It's a 1993 NA6 with a clean title, no rust, never wrecked, really well done cage and brand new SM suspension. Has original motor with 220k miles, but compression is 170psi in all cylinders. It is 98% of the way to being a NASA Spec Miata, all it would need is wheels and tires, fire suppression and ballast. It wouldn't be competitive against a well-built NB SM, but it was priced right and seems like a good starting point for my needs. I also seem to have an affinity for underpowered, tired, old shitboxes so this should be right up my alley.
Initial plan is to keep it a Spec Miata and just get everything 100% right. If I decide my longer term classing aspirations do not include SM, I have all the bits for a really nice 1.8L NA build. No plans to turbo this one.
This weekend I changed the oil, brake fluid and coolant. Initial impressions are that the ghetto depowered steering rack sucks and needs a proper depower. The motor timing is nowhere close to where it needs to be, and there's no timing mark on the pulley so I'll have to find TDC and set that correctly. Otherwise, the car is pretty much right. It has the loathsome VLSD, but it had no problem locking up yesterday when I wanted to play in a parking lot and burn up the 9 year old tires.
Last edited by Schroedinger; 04-23-2020 at 11:48 AM.
Thanks Efini. I'm looking forward to doing a straight ahead track build- hopefully the tracks open up soon and I have a chance to run it this season.
Current priorities are baselining maintenance and addressing anything that's broken or not to spec. Most obvious issue is that there was a ton of thumping and popping noises coming from the rear end during driving. I tracked it down to two issues: one of the rear sway bar mounting studs was broken off, and the weird/loud custom exhaust was clanging into the rear subframe. I had to take off the rear exhaust anyway to get access to the sway bar stud. The culprit:
Ground it off, drilled it out and put a bolt in its place.
Finished product:
The exhaust hangers looked to be original to the car, and were, uh, flaccid. I replaced them all. The exhaust that I took out was really loud, and it still bumped into the rear subframe even with new rubber hangers. It just so happened that I had the original stock exhaust from my other NA6 outside in my shed. The only problem is that all the studs on the catalytic converter were broken off during removal. I started grinding and removing those studs to replace with bolts, but after an hour and four drill bits I gave up. It's damned near impossible to drill through that much metal with a hand drill. I checked out the local Miata FB site and found a guy selling an as-new 1.6 Magnaflow cat for small money. I picked it up, and put the whole stock exhaust back in. You just can't argue with OEM fit.
I finished the day by changing the differential fluid and setting engine timing. There was no timing mark on the main pulley so I pulled the #1 spark plug and used a stick on the cylinder to identify and mark TDC. I then found out that the base timing was actually retarded a few degrees from TDC, which is why the motor felt so gutless. I set it to 12 degrees advanced and took a drive.
In homage to the MT.net circle of life... the thing that struck me the most is how right Mazda got it with these cars in the first place. It had been a long time since I've driven a totally stock 1.6L, but it's a great little runner. Stripping the interior of these cars has the immediate benefit of dropping a bunch of weight, but also makes the whole car feel more rowdy- even the stock exhaust sounds kinda ballsy. I had a great time running the motor out to the rev limiter and doing parking lot donuts on the 8 year old tires.
Last edited by Schroedinger; 04-23-2020 at 11:51 AM.
Of all the car projects, dealing with safety equipment is my least favorite- especially for race cars that need to pass tech. Ideally this car could race in SCCA or NASA SM, SVRA, or ChampCar. Having built a Lemons car from scratch and installing safety in my last Miata, I at least feel like I have a bit of relevant experience. The right approach to building a race car is to pick your seat, figure out the best way to mount it for driver ergonomics, then build the cage around it. Unfortunately I'm doing this completely in reverse. I'm 6 feet tall, 210 lbs so I can fit in a Miata race car comfortably but it takes a lot of careful planning.
Here is the whole setup as it came to me:
The seat is a 15" Ultrashield on stock sliders and factory mounting humps. There are a number of issues with setup as it came to me:
- The sub straps for the harness were not properly installed, and were attached to the same points as the waist straps
- the seat did not have a back brace
- While I fit in the seat pretty well, I was sitting way too high.
- The seat wouldn't go back very far due to interference with the roll cage, and my legs were very cramped in the foot well.
The cage install was not going to make it easy to get the seat far back in the cockpit. I was worried that at a minimum I would have to cut out the additional up-high harness bar, and possibly re-do the main hoop diagonal brace as it extended so far behind the drivers seat headrest. First priority was to get the seat lower though. Before cutting out the seat humps I figured I would try a flat bracket mounted to the humps. I had one around that I made previously, but it took substantial modification to make it work for this purpose. Not pretty, but effective.
This actually worked very well and got me to an appropriate height in the car. Next challenge was getting farther back. Turns out that the interference with the seat was not from the harness bar or diagonal, but from where the door bar connected to the main hoop. I decided to notch out that part of the seat for clearance. Hole saw and cutoff wheel:
This allowed me to position the seat another 3" further back, which made it pretty much perfect from an ergonomic standpoint.
Turns out the harness bar is at exactly the right height, and the lower bar can be used for the back brace. I still need to install the sub straps.
Last job of the day was to replace the hardtop's window seals, which were missing. Pretty important because I store the car outside.
Last edited by Schroedinger; 04-23-2020 at 12:49 PM.
Shelter At Home is a great way to get car projects done. I'm bored out of my mind, so might as well get this thing ready for the track.
It looked to me like the clutch hydraulic components were all original to the car. As these are a known point of failure, I replaced the master cylinder, slave cylinder, and stupid coily line with a braided steel one from 5x Racing.
I forgot how much fun it is (not) to get this little bastard out of the back of the engine bay. Definitely a job made for people with little elf hands rather than my big meat fists.
Last edited by Schroedinger; 04-23-2020 at 12:48 PM.
I just signed up for a track day in June, so it's time to move this project along. I hate dealing with the safety equipment because it involves a million tiny, painstaking details, so last night I committed to knocking it out so I could move on to other things. I completed the following items:
- more fabrication to the seat bracket to make attachment points for harness sub straps
- planned and cut holes in the seat and seat cover for the six-point sub straps (seat previously had only the hole for a five point sub strap)
- installed I/O Port back brace on seat
- adjusted and re-installed harness straps
- installed SFI roll bar padding
- installed Longacre rear view mirror
All in I bet I have 20 hours of work committed to the safety equipment. It's nice to have it done, and I feel good about it. I'm very comfortable in the car, and the equipment is much better installed than what I had in the last Miata.
Last edited by Schroedinger; 04-23-2020 at 12:47 PM.
The biggest remaining job was fixing the ghetto looped-line steering depower. The car has 220k miles and the tie rod ends were also shot, so I just rebuilt the whole rack with new parts. After the proper depowering and before installation:
Installed with the steering rack spacers from 5x racing:
I also installed the Bauer extended lower ball joints while I was in there, and replaced the shot bearing/hub on the driver’s side. I picked up some Kosei K1 15x7 wheels from a drift kid locally, and got some 195 RS4’s to use for heavy lapping and rain. Took the whole mess down to the guys at Gran Turismo East to mount the tires and set the alignment.
The setup feels really good, and it’s almost track ready. First track day scheduled for 6/6 at Barber, I can’t wait.
Getting ready for track day ar Barber this weekend. The car didn’t have an undertray when I got it, so I found one locally. Before I put it on, I figured I would get rid of the coolant and go with 100% water and water wetter. While the coolant was drained, I figured I would do some more deferred maintenance- replace thermostat and gasket, cut radiator hose to correct length, and wrap crossover pipe with DEI foil tape. The thermostat housing was full of this nasty white crap...
... but I didn’t find it anywhere else. After doing my chores:
Sooner or later I’ll put a real radiator in there. For now, the cooling is dramatically improved. Maiden voyage on Saturday. Can’t wait.
Track day with JustTrackIt at Barber yesterday. 92 degrees and humid, meaning that it felt like about 150 on the tarmac.
I brought along a buddy with similar driving skills to co-drive. He was in Intermediate 1 and I was in Intermediate 2. This was the first track day at Barber since it was repaved. The new surface is great but there was no rubber on the asphalt yet. We ran our first sessions on RS4's and it felt a bit slick. Before our 2nd sessions we put the Hoosiers on; it is the first time that either of us had driven on them. What an amazing difference! The car went from feeling jumpy/jittery on the RS4's to feeling planted and confident on the Hoosiers. We were pulling 1.4 G's in the corners and there was more traction than we were using.
The track day was JAMMED, busiest one I've ever seen. My session was loaded with fast cars and drivers; other than a swapped NC, I'm pretty sure I was the only car in my session with less than 300hp. I wasn't quite the slowest guy in my session, but pretty close... it was hard to find clean laps with so many point-by's. I knew the track pretty well in my turbo Miata, but in a SM with no power and more grip I had to completely re-learn the track. As the day went on, my buddy and I started feeling the car and our lap times dropped dramatically. In each pair of sessions our lap times were within a second of each other.
Overall it was an amazing day. We flogged the car through ten 25-30 minute sessions and it performed flawlessly. It was great to co-drive with another guy of similar skills. Because we were in the exact same car, we were able to look at data and coach each other in areas where one of us was faster than the other. I probably learned more yesterday than I have in the previous five track days, which was the whole point of getting this car in the first place.
Last edited by Schroedinger; 06-07-2020 at 10:23 PM.
Regarding the cool shirt, I made a critical planning error. I have the system with the soft-sided nylon cooler bag, and I figured I would just strap it down in the passenger seat well with bungee cords. Unfortunately when I did that, it no longer sat upright and the pump went dry. Thus, no cool shirt for the sessions. Which sucked because that car gets SCREAMING hot inside. I have a stock exhaust with catalytic converter; the transmission tunnel was so hot I could probably fry an egg on it.
So, next steps- real SM exhaust and fabricate mount for Coolshirt cooler.
For me...a cool suit setup is a firm requirement for any track days or races in the South from about May to Mid October. I imagine Barber in early June was pretty brutal.
I'll be a Road Atlanta racing next weekend...cool suit is gonna get a workout!
The idea of this car is "reliable momentum car", but the fact is that it's really low powered and every little bit of power helps, within the SM rules. A few years ago the rules changed and permitted 1.6L cars to grind the big ugly welds out of the exhaust manifolds. This reportedly gains you ~2hp. It just so happened that I had an extra stock 1.6L exhaust manifold in my shed from my last car, so I got a die grinder and went to work. Here is the problem with the stock manifolds:
The new Makita 18v brushless die grinder I bought is AWESOME. Made this a very easy job. I ported the collector exit and welded back the heat shield bracket that had broken off:
Then I lapped the face with 220 grit wet/dry and ported the runners.
I also ordered the Kooks Ti-Speed SM exhaust. It doesn't add much HP but reportedly adds a lot of torque throughout the whole RPM range and should also drop a few pounds of weight. After building a turbo car it seems a bit ludicrous to be working this hard for 3-5 hp, but in a 100 hp car that's a 3-5% improvement so I guess it's not that ludicrous.
Last edited by Schroedinger; 06-18-2020 at 09:40 PM.
My biggest problem at the last track day was that I had nowhere to put my Coolshirt cooler. Today I fabricated a mount for it with some scrap steel I had lying around.
It bolts to the passenger rear seat humps.
The cooler is held in place with elastic cords. Overkill? Maybe, but I’m actually pretty proud of it. My fabrication skills continue to improve with each project like this.
I was getting pretty tired of my towing situation with the van and tow dolly. It towed fine, but loading/unloading the car four times every weekend was wearing thin. I got rid of the van and got this 2013 F-150 with the 3.5 Ecoboost and a trailer brake controller.
Then I found this trailer. It's a junker but the price was right and the bones are good. Fairly new tires and brakes on the rear axle.
It didn't come with ramps, so I found these ATV ramps on FB Marketplace super cheap. 7' long, rated to 3,000 pounds, very light weight.
It didn't have rear tie-down points, so I fixed that.
Also added a spare tire.
The Red Rocket loves its new home. It will be nice to just hitch up the trailer and take it to the track.
I’ve been giving more thought to my future plans for this car. I’d like to get my comp license with NASA this fall/winter spring, but I don’t yet have the skill to race SM, at least competitively. I’m still several seconds off of race pace at most tracks, and I know my tired NA6 wouldn’t really do well against well prepped NB’s. The hard reality is that I really don’t have the time to race either, and don’t foresee that changing in the near future. It seems like the next best step for me will be NASA Time Trials.
I’ve thought about pulling my motor this winter to deal with a bunch of maintenance stuff. In addition to the motor having 220k miles, it also has the original clutch and motor mounts, both of which are tired. I’m starting to research how to build the best TT6 car than I can. I have all the parts I need on hand to do a killer 1.8L build according to the “Emilio” recipe, although I will use a BP4W head instead of VVT. Anyone know if a 1.6L SM chassis with a built 1.8L motor would fall into TT6 or TT5?
03-23-2020, 04:34 PM
A not-really-competitive SM-ish NA6 track build
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