How to sort a rebuilt race car | Project Endurance Race Miata

Update by Tom Suddard to the Mazda Miata project car
Aug 11, 2022 | Mazda, Miata, lfx, Engine swap, Flyin' Miata, Good-Win Racing, Caliper Garage, Very Cool Parts

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We’d upgraded the safety gear in our LFX-swapped Miata, which meant it was finally time for the fun part: track testing.

We’ve written at length about how important test days are for building a competitive endurance racing effort, and we plan on spending plenty of time at our official test track–the Florida International Rally & Motorsports Park–sorting our Miata before its V6-powered endurance racing debut.

[10 lessons to keep your race effort disciplined]

But before we loaded up for the track, we needed an experiment: There’s no sense going without a goal, so before every test day, you need to design an experiment, run it, and measure the results.

So, what was our goal? Well, we’d completely replaced our car’s suspension, brakes, drivetrain, electronics, safety gear, and major body work since we were last on track. So we needed to test, uh, everything.

That wasn’t going to happen in one day.

[How to Execute DIY Track Testing Like a Pro]

Instead, we decided to focus on the biggest unknown: our drivetrain. We felt that our V6 swap had the most failure points and the longest timeline for repairs after all our changes, so it was important to test it first.

So our goal was to test our drivetrain, which made our experiment pretty simple: Do laps in progressively longer stints until the car can stay out for a full tank of fuel. Measure temperatures, lap times and driver feedback, and see what happens.

And before you email us: Yes, we’re still going to test those Flyin’ Miata brakes, Fox suspension and other changes. We’re just going to test them separately from our drivetrain shakedown. This way, we can isolate variables and focus all of our attention on what we’re trying to learn.

Since we’re not trying to test our suspension or brakes, we decided to shelve our race tires and wheels. Instead of those giant 15x10s from Good-Win Racing, we’d swap to a set of 15x7.5-inch wheels fitted with fairly tough Yokohama Advan Neova AD08R street tires.

This change should provide two benefits: First, it will keep our stack of sticky Nankang CR-1s safely in the garage. There’s no sense burning up our pricey tires for a drivetrain test.

[200-treadwear tire test | Falken RT660 vs. Yokohama A052 vs. Nankang CR-1]

Second, this tire swap will lower the amount of energy put into the rest of the car. Again, our goal with this first test is to run the engine for a few hours, not to dial in our suspension or set the fastest lap time.

We’re not savages, though, so we did align the car before the test. There’s no sense taking something that handles terribly out on track, or chewing up tires just because we were too lazy to set toe.

[How to prepare a race car for a test day | Project LS-Swapped 350Z]

Photography Credit: Tom Suddard

We installed a set of Racing Beat adjustable anti-roll bar end links to zero pre-load, then used our Caliper Garage string alignment kit to give the car a conservative track alignment.

Photography Credit: Tom Suddard

Again, the goal is easy: predictable handling. We set zero toe in the front, slight toe in in the rear and plenty of camber to prevent killing the outer sidewalls of our street tires.

Plan and preparations made, we headed to the FIRM and met our test driver, Wayne Presley of Very Cool Parts. Since the car was mostly built in his shop, we figured he should get first dibs at breaking it. So Wayne jumped in, headed out on track, and started clicking off laps.

Photography Credit: Colin Wood

First lap done. The car should be warm now.

Second lap… and he’s staying out. Apparently it doesn’t overheat!

Photography Credit: Colin Wood

Wayne ran a few more laps, then came in so we could look the car over. Fluids looked good, everything was still attached, and he reported that it drove like a dream.

So we refueled the car and sent Wayne back out on track. We were theoretically in for a fairly boring hour: sit by the track, watch for bad signs, and chat with Wayne in an hour once he was done or out of gas.

The car was back in five laps.

It wasn’t a complete failure as Wayne managed to turn a 1:23.22 lap time, which puts this car within a few hundredths of a second of a new BRZ, our Porsche 911, and a new Volkswagen Golf GTI.

But that’s where the good news ended. Wayne reported that the brakes had turned off like a light switch, and we couldn’t even use them to drive back from the pit road to our trailer. There wasn’t a fluid leak, but something had clearly failed. Now we had to find it.

So, was this test day a failure? Well, kind of. But any test day that discovers a problem is a success in our books. And we ran a surprisingly quick time considering our Miata’s neutered state. But we hadn’t accomplished our goal (test the drivetrain).

Time to take the car home, fix its brakes and go back to our test.

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