Just got back from a great Miatas @ MRLS event! I’m working on getting some pics/vid together from that. In the mean time, there were a couple things that sprang up at ACS that I needed to solve, and now after running MRLS I can confirm the fixes worked so I’ll cover those..
First up, the differential fluid was exiting the vent cap on the top of the diff, leaving a very traceable mess on the underside of the rear subframe and down the side of the diff. A quick check with V8R confirmed they’ve seen this happen and fixed it by replacing the vent cap with a hose barb fitting and running a vent line up higher.
Vent cap (right) is just removed with pliers. It’s being replaced with the 1/4″ NPT to 3/8″ barb fitting on the left:
Tapping the hole for the fitting is a treat when the diff is up in the car. I’d call changing the vent config on the getrag a must-do item so if you haven’t installed your diff yet, just do this now before installing everything:
Fitting and hose installed with a loop in the hose:
If the vent tube mod works, we can just run the hose to the open air. But since we didn’t know yet if it would work, I wanted to run the line to a reservoir to catch the fluid in the event that it was still losing any. I repurposed a Wilwood brake fluid remote reservoir for the task, with a barb fitting installed in the cap and a hole drilled in the top of the reservoir to vent pressure:
After 3 days at MRLS, the reservoir is still dry so that’s confirmed that the vent hose is working perfectly.
The second fluid that was trying to exit the vehicle was the power steering fluid. This one was a bit trickier to diagnose but I came to the conclusion that because the reservoir cap was a vented/non-sealed design, in high-G right hand turns the fluid was being pushed against the side of the tank and effectively submerging the side of the cap, and thus exiting via the cap’s vent.
The cap needed to be sealed. I didn’t take a pic of this but sealing the cap involved drilling out the spot welds that held the three pieces of the cap together, removing the vent ring, welding the two remaining pieces of the cap back together and then ordering a second cap to scavenge a second O-ring from and doubling up the O-rings under the cap to take up the height of the missing vent ring and seal to the reservoir neck.
With the cap sealed, the tank still needs a way to vent pressure. Drilled/tapped a small 1/16 MPT hole in the upper left hand corner of the tank and ran a vent line off that, with a loop to stop fluid from passing down the line:
Same as the diff vent line, to confirm the modifications were working as intended, I repurposed another brake fluid remote reservoir to serve as a catch can:
Same story, 3 days at MRLS and the reservoir remained dry. Fix worked.
Finally! Time to go stretch the car’s legs and see how it runs. This weekend was the first big shakedown. This is pretty much a completely fresh build at this point, and so you have to expect to discover issues and there’s a long teething process as issues are sorted out, items fixed and improved, etc. once it’s being used at the race track. This weekend was all about getting the car out there and running it as much as possible to discover those issues and to take home a long but focused to-do list for how to improve the setup.
Saturday was Mazfest at Auto Club Speedway and I had a great time showing the car when I wasn’t on track.
On-track was special, after this much time building the car it was great to just feel the thing doing what it is built to do. There is a lot of power on tap and the engine is super smooth and worlds better than the old turbo setup. Torque is just always there if you want it. I’m delighted to find the car is still very “Miata” with great balance and drives just like it should just with much more motor attached to the right pedal. That was the biggest goal with going with this engine package over alternatives that might weigh a bit more.
Here’s a run-down of notes on each system and any issues that did spring up.
– Engine (max temp 225 water / 265° oil): no issues to report. Ran like a dream, makes power everywhere. Currently running with no oil cooler, just the factory filter housing. Oil cooler will bring oil temp down a good chunk once I have that in and working.
– Transmission (max temp 200°): Grinding on upshifts. I believe it’s a pedal/rod length issue. Bled the system after 1st session with no effect. Drove around it the rest of the weekend by trying to be VERY patient on shifts to let the rpms drop to where they needed to be on the next gear… which was somewhat successful. Gearing is good. Used 3-4-5 at this track which has a really low speed ~50mph tight right at the end. 3rd pulled right out of it, I won’t ever be using 2nd on a road course.
– Differential (max temp 180°): puking fluid out of the vent on top. V8R says running a breather line will fix this. Otherwise, the limited slip characteristics feel great.
– Power steering (max temp 190°): leaking fluid from the cap. We’re suspecting it’s from high-G right-hand turns which effectively submerges the left/lower side of the non-sealed cap. I’m implement a fix in the next couple days. Steering feel with the NB power rack is good and I’m much less worn out at the end of a session than with a manual rack. I think I’ll be keeping the power steering for a while.
– Ergonomics: new seating position and controls are all perfect. I did accidentally hit the fuel pump switch to off when shifting once. Might need to move the switches or add a guard.
– Display dash: I’ve already forgotten how I lived without one of these. The dash is set up to monitor all the temperatures and pressures without me having to do anything. If something is amiss, it lights up a warning light and lets me know. Otherwise, I just drive.
– Suspension: the spherical bearings and Feal 442 shocks are butter. I haven’t even begun making adjustments here yet, just set compression and rebound to dead center of the available range and left them there while I focused on everything else.
– Brakes: The V8R/ST four wheel kit has some serious stopping power and is easy to modulate.
– Powdercoat: powdercoating has a “squish” in the coating that prevents proper torque on bolts. I lost a spindle to caliper bracket bolt on track which prompted checking every bolt on the car that was in a powdercoated surface. Several had loosened. The rest of the weekend I re-torqued bolts after every 2 sessions. Will be adding split lock washers to most of those bolts this week since the lock washer will cut through the coating.
A great thing about the temps listed above for steering, diff and transmission is this confirms what we suspected – these items are all way under-stressed in a small lightweight Miata. Zero need for diff or transmission coolers.
Joe working the pedal while I bleed brakes:
Chatting with Sean about something. Probably about how something tried to fall off the car:
It was great fun to see so many friends at Mazfest who were there for the track day portion or who just came up to check things out. Being back out on track in my own car with fellow Roadster Cup guys felt great:
Spent all of Saturday with a passenger riding along and sorting out issues, and got absolutely no clean laps without traffic but I still ended up setting the fastest time by a Mazda at Mazfest with a 1:11.x.
Quite honestly surprised by how much pace the car had out of the box with zero time spent on dialing things in. Since it was still running well I signed up for the Redline Time Attack competition coming up the next day and grabbed a hotel for the night.
Sunday: Redline Time Attack
Sunday morning first practice session in the cool air I went out with no passenger and did a 1:08.763. That is a new lap record for a Miata at this track (Auto Club Speedway Infield) by a gap of almost 3 seconds.
Time sheets after the practice session revealed that not only was it looking like I could take the win in my Limited Rear Wheel Drive class, I was actually within range of contention for the top overall time with the unlimited cars. There’s no way I could ignore that carrot dangling out in front of me so “I’m just testing things this weekend” went out the window at this point and it was game on. I did a little research around the paddock to scope out the cars that were at the top of the time sheets with me:
At the top of the sheets, this 500hp BMW M4 built for NASA ST1 competition running in Unlimited RWD:
Bulletproof Automotive’s 750hp GTR in Limited AWD:
Time Attack veteran Amir with a 660hp aluminum V8 swapped E36 M3 in Unlimited RWD:
In true Time Attack fashion, Redline has just two Time Attack sessions where it all counts. Only three laps in the session, do or die time. Cars are pre-gridded by lap time from practice so I was third in line behind just the GTR and M4.
That lap took 1st overall by a gap of just 0.08 seconds ahead of the M4.
By the second afternoon time attack session temperature had climbed a lot and some teams didn’t run because they knew they wouldn’t go faster. The GTR and M4 both went out to try to take the top spot. They both went slower. I did a 1:08.8 again, so that lap would have been even faster in the cool morning.
SO… first shakedown weekend with the car… fastest Mazda at Mazfest, 1st place Limited RWD and Top Time overall at Redline Time Attack, and a new Miata Lap Record.
We’re on the right track here. With some more track and tuning time this car is going to rip.
Had an awesome weekend at the track. If the shakedown was any indication, there are great things ahead. Jumped right back into another crazy work week here at GWR so I’m still working on getting a bit of a writeup together with pics/vid but will get things up as soon as I can!
Brett from TrackHQ posted this clip in my build thread over there. Sums things up.
More fab this weekend of various small bits, then drove the car around on the street to do some datalogs. Confirmed, car is loud and moves with urgency.
Back in the shop, mounted up a “small” wing I’ve had sitting on the shelf since it was built by Kognition two years back.
The louvers pull pressure out of the engine bay to optimize airflow through the coolers and reduce lift. It’s rather incredible how well they work – with the radiator just venting into the engine bay like normal the louvers will pull the majority of air that passes through the radiator up and out through the hood. Since this car is about getting that last little bit everywhere, I’m also ducting the radiator’s exit up towards the hood vents to maximize front downforce.
Work in progress:
Finished duct:
The ducting directs the radiator exhaust directly up to the larger middle two vents and isolates that flow from other pressure sources I’ll be playing with in the nose of the car.
New fence on the splitter to seal behind the lower edge of the bumper skin:
Plugged all the now-unused holes in the bumper skin that used to feed the oil cooler and front brake ducts. This pic reminds me, still need to relocate that “tow” decal to the hood:
Things are coming together:
Went to reinstall the fire extinguisher, discovered the new frame rails blocked the holes the extinguisher bracket had used. Made a new bracket with wider mounting points that tucks the extinguisher up as much as possible under the front edge of the seat:
Tires arrived and mounted on 15×10 Tungsten 6ULs. This is the 245 Rival S 1.5. Tire tech evolves crazy fast, even from just a couple years ago… back when I was running street tires to fit into a certain class for Miata Challenge I was on the original RS3… then the original Rival came out and it was better because you could actually use the brakes! Now for RLTA and GTA my class requires 100tw or greater, but these “Super200’s” are faster than the 100tw options. I’m betting this combo here is easily 2 seconds faster than the old worn out 225 NT01s on 15×9 that I ran at Superlap in 2014.
Tons of things going on, a lot of it is little details. Need a small bracket here or a tweak of something there and before you know it many hours have disappeared.
One big thing:
The Getrag diff was not operating like an limited slip unit. At first we chalked it up to the fluid and additive still needing to get cycled around better since it hadn’t driven around much, but after a lot of figure 8’s in the parking lot and still no improvement I started digging. GM superseded part numbers so when you call your GM contact to find out if the PN on your diff is for an LSD, they might know that number was superseded by a different number or they miiiiight tell you that’s not a number that comes up in their system and have no idea. Eventually we got it nailed down and it turns out the salvage yard that advertised this diff as an LSD unit got it wrong. That was over a year ago so nothing to do now but buy another one.
As for those part numbers…
3.42 NOT LSD: 15793753 – superseded now by 25873499 3.42 LSD: 15793754 – superseded now by 25873500
New diff arrived, correct original PN on it. That diff now lives in the car.
The final thing I needed to get to the Racepak: RPM. The ECM has no tach signal output. Autometer tach signal adapter part number 9117 was the solution.
Pic here shows how it’s wired in, this was just temporary crimps to verify it worked before wiring it in properly…
The signal adapter gets wired in-line with the two main +12v supply wires that go to the coils, one wire to each bank. Follow the instructions included for an LS engine but your wire color is different. Pink/black is what you’re looking for in the LFX harness. Start at the coils and follow the light gauge pink/black wires up-stream until you find where they split out from a thicker gauge pink/black. That’s the wire to intercept. There are two of these wires, one for each bank. The autometer box outputs a lovely +12v square wave standard tach signal. The Racepak instantly reads it. Change the Racepak to V6 Even Fire (default seems to be V8) and voila.
Engine is in and fires up. Tying up loose ends right now.
Top of that list is some frustration with the Racepak stuff. Bottom line is it simply cannot read any PIDs from the 2012 ECU I have. Not with the OBDII adapter cable or with the CAN hi and low hardwired directly to the dash, despite the fact we can view live data streaming via that same diagnostic connector with either a scan tool or HP Tuners. Racepak themselves have no idea why it can’t read this ECU, and I’ve verified this particular dash will pull PIDs via the adapter cable to diagnostic connector on other cars such as an ND that was here in the shop.
SO… I’m bypassing the ‘read the ECU’ plan. Wired in a temp sensor for coolant and adding the Racepak GPS module for speed. RPM is a bit of a puzzle because these ECUs have no tach signal output, but I have an MSD signal converter on the way that should take signal from the coil wire and output something the dash can understand.
Only thing I’m stuck on at this point is my oil pressure sensor… using a second factory GM OP sensor to feed signal to the Racepak. Problem is in configuring the dash to read it. Configured for a standard 0-150 psi sensor (0.5v=0psi, 4.5v=150psi) the scaling is funky. Sensor is outputting 0.43v with engine off (0-psi) which would be -2psi. I can’t find any info for this sensor online or in the GM database to use for a custom calibration.
I want to be able to have complete confidence in the OP reading so the best approach is to test it personally and then manually calibrate the Racepak based on those results. I built a bench tester today, will get to play with it tomorrow.
Figured I’d take a little extra time to make something that could be useful in the future. NPT ports for all the common sensor sizes, two air valves so I can fill/bleed and monitor pressure without switching back and forth, portable enough that it can be placed in the engine bay so the sensor is operating on the vehicle wiring. Can be used to bench test temp sensors as well by standing it vertically, removing the end cap, filling with water and then heating the water and validating the temp with a thermometer.
With this new bench test contraption, I was able to confirm it’s a 0-130 psi sensor. I was able to calibrate the Racepack very accurately to the specific scaling of this sensor. Dash reads OP perfectly now.
So the engine didn’t just come back out a second time just so I could add some heat shielding…
With the car running I drove across the street for an alignment (sitting in the pic here waiting to go on the rack)…
On the drive back across the street to the shop, the rear tires locked. Fun times sliding into our parking lot. Motor was seized. Oil pressure was strong and everything was running right so best guess right now is that it was the thing I had feared in the back of my head from the beginning – this engine had come from a donor car that we discovered had been flipped, so if the engine had been running while it was upside down, the bearings were doomed from the start.
Not going to allow this to stop me, I gave myself one day to come to terms with things and began the hunt for a motor the next day. Made some calls and found that Cord Bauer of Catfish fame had a unicorn of a motor sitting around that he was willing to part with – this one from a 2013 with only ~500 miles on it (!!) Thanks Cord!
That engine is here already, and I’m about half way through transferring everything from old engine to new:
LFX’s are growing on trees around here! That’s the new motor on the right, with nearly everything swapped over:
A peek inside the pan from the old motor confirms that yeah those bearings are done! Thoroughly cleaning everything in the oil system before swapping over to the new engine (pan, pickup, adapter plate, lines, cooler, etc.)
Interesting discovery while swapping parts over from the old motor to new…
2012 valve covers – plastic, 3.45 lbs each
2013+ valve covers – aluminum, 6.40 lbs each
So the newer engines have 6 more pounds up high. The plastic valve covers are now on the new engine.
The engine’s out again. I’ll get to that update when I have it concluded.
While it was out of the way, I added heat shielding on the firewall behind where the engine resides:
I also added a second shield to the transmission tunnel (it already has a layer of adhesive backed insulation from the turbo days). I’m leaving the first layer in place and adding to that a modern-style thin aluminum layer with an air gap between it and the tunnel – very much like Moti did on Morpheus.
I started with a tunnel shield from an ND Miata. With the insulation layer removed (black part in the photo) it is a featherweight. Essentially no weight penalty for adding it.
