Build Blog

Superlap Battle is two days away! Since MRLS, there have been many updates. Since I’m currently running around like crazy getting the finishing touches done on both my car and the shop’s ND before the event, I’ll have to keep the update brief for now.

CCP Fab composite doors with my special request for a kevlar inner layer to help with debris protection. Very light, 5.55 lbs per door without hardware/latches. The aluminum rod was added to help with flex:

Beginning to add more of the aero package I have planned for this car, new side skirts/barge boards and rear tire spats fabbed up to control the air down the side of the car:

The apparent simplicity of these when you look at them really belies the complexity of making them. There are several pieces that go into the full thing, not to mention a full array of brackets for mounting and completely re-engineering the way you put the car on a lift or jack stands. The jack stand points are now these little removable units that have threaded tops that screw up through the barge boards in to receivers welded to the car so that when you remove them there’s only a nice flat surface left:

Also needed a jack point to lift the car from when at the track. The barge boards are too low/stick out too far to put a jack under the car. Moti recently solved this same thing elegantly on Creampuff with a receiver welded to the cage and a removable lift arm and I mimicked that design, but with mine located on a more rearward cage point since my doors have to swing open:

The receiver sits flush with the outer door face when the door is closed. Don’t have a pic of the removable lift arm but it slides into the receiver:

Further cutting weight, Buttonwillow has no sound limits. No need for extra weight in the exhaust for this event. Going full race car, no cat and minimal muffler. Dropped 10.5 lbs in total from the car. I will be packing ear plugs for this one.

Small titanium heat shield on the barge board:

Side of the car in the new SLB config:

Finally, adding all the downforce possible was high on the must-do list for SLB. Two weeks ago Moti and I spent 60+ hours over a weekend working on our evil world domination plans to build new next-level splitters for both Creampuff and this car. Design and mold construction took a massive amount of time, and there was only enough time to (barely) finish one splitter before SLB so we made the call that Creampuff should get that splitter.

I CAN’T WAIT for you guys to see what we have been cooking up on the new splitters, that will debut on Creampuff in a couple days. BUT that also means I’m still on my old generation splitter for this event. In an effort to maximize downforce production with what I have, with the little time I had left I put together add-on splitter extensions. Nothing advanced but it will be effective. These increase splitter total width by 10″.

To help balance the front additions, the rear wing gets some “go big or go home” endplates.

Car is on deck at the alignment shop, sans splitter:

Superlap Battle prep is in full swing. Since MRLS I’ve been in the shop every evening and weekend (except when I went up to BFW last weekend to lend Moti a hand on Creampuff). Will update as I get things wrapped up more, but for now a teaser.. some material arrived today:

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.

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.

Lots of little bits here and there to get bodywork on and working. Then went on to hood venting:

Cut the hood, and once the louvers came back from powdercoating I mounted them up:

The hood louvers used here are one pair each:

Singular Motorsports Universal Louvers: Type 1 (outer vents)

Singular Motorsports Universal Louvers: Type 2 (inner vents)

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.