Mar 5, 2006 update to the Mazda STS2 Miata project car

Crunch Time!

Its been awhile since the last installment for two reasons. First, we took a vacation/racing road trip to Florida to compete in the Ft Myers National Tour and also the two-day Florida Special Tour held the week prior. We also found time to visit Mickey, explore the Everglades, and visit relatives at the beach. The second reason is the subject of this installment, which I am writing from the road to California, with an STS2 Miata in tow! Yes, we have achieved our stretch goal of making it to the first Pro Solo of the year, and will debut the car at the San Diego National Tour. But, I am getting ahead of myself.

When we first started this project, it seemed very doable to get the car ready in time but everything hinged on the motor. Our partners at Applied Racing Technology have been very busy in this pre-season period building motors for Spec Miata racers and we were right in the middle of that bunch. These motors take many iterations of handwork, assembly, and measurement. As such, it can be difficult to predict finish times. Prior to leaving for Florida, we informed ART that if we were to take the car to CA, we’d need the motor in our hands by Monday, February 20. I checked back on the return trip a couple weeks later and sure enough, it would be done.

So here we were, less than one week from the time we’d be leaving for CA. Build up a race car in a week? Been there, done that. No problem! And thus starts another most excellent adventure…

A call goes out to the usual suspects, veterans of the “Scrappy-build” STS Civic adventure from last Fall. Several key players are available, albeit at disparate times since the importance of this build is not quite as high as last year’s pre-nats situation. Special thanks go out to Steve Hudson (of the infamous Hudson’s Storage, Chop Shop & Wedding Chapel), Zack Barnes and Drew Vanderploeg for their assistance and camraderie.

As Tuesday morning dawns, we are rolling back into Austin. Another call to ART reveals that the motor is close, but will be at least one more day. We take the opportunity to visit the shop and take some pics of the final assembly stages, but we leave the Civic on the trailer as a back-up plan. The rest of the day is spent working on the rear end assembly, swapping out the open differential for the viscous LSD unit. It’s a very straightforward procedure, with the exception of setting the pre-load. The latter requires a dial indicator, calipers, and a deft touch. We’ve done one of these before, but we will have ART check our work to be sure.

Drew comes by on Wednesday and work begins in earnest. The motor is due late today, so we begin to unearth the car. As the pictorial reveals, leaving a disassembled car in storage for several years can turn it into quite the mess. All manner of stuff finds its way inside of, underneath, and on top of the chassis instead of nicely organized in bins on shelves. Some of it is just plain comical, most notably a huge tow-tube for boating and a stuffed Sponge Bob! Oh my…

Much of the day is spent moving everything from the one side of the garage to the other in which my daily driver usually sits. After removing enough stuff to actually get to the car we remove the TEC3 engine management system we used in CSP and replace it with the stock ECU. Though it’s a bit of extra weight, we leave the TEC3 wiring harness in there since it goes through the firewall and cannot be removed easily. It is coiled up on both ends and stored out of harm’s way. Bad news then comes in the form of a call from ART. No motor today, but definitely tomorrow morning. Damn! So instead we spend some quality time in the engine bay cleaning and prepping for the new powerplant and then call it a day.

Thursday morning bright and early I am at ART and there it is! All together, sealed up, and ready to go. Woo-hoo! We load up quickly and I am on my way. And almost immediately, the issues start. Here’s the “clutch story”…

Back when I competed with this car in the Stock category six years ago I had to replace the clutch and found out that Mazda had superceded the part at some point and the new clutches were a pound lighter than the originals. I also noted that the clutch was made by Daiken (now owned by Exedy) and that it was the same as what could be purchased from various parts stores in town. Given that, I had the guys at ART source one locally for me. When I opened it up at the house, though, I weighed it and found that it was the heavier version. One pound may not seem like a lot but it is flywheel-speed rotational weight which magnifies its effect on acceleration. Trips to parts stores yielded nothing so I checked with the local Mazda dealers and found that they no longer carried the original Mazda parts in stock (no surprise there). But they instead kept Mazda’s line of “Value Parts”. Hmmm… Trips to two dealers with fish scale in hand verified that these parts were the desired lighter ones. And they matched the original Mazda part exactly! Bingo!

The crew starts to arrive and we get down to it. First the clutch and flywheel go on, then the tranny is joined up and miscellaneous engine parts go on. Of course, finding some of these parts is always exciting since they been stored in various boxes above the garage for several years, or shoved in a corner somewhere. And Lord knows where the attaching bolts are! Much time is lost on search missions.

Progress is steady now as we move through the install procedure as outlined in the service manual. The motor/tranny are hoisted up and carefully placed into the engine bay and attached. Various hoses and wires are then connected, radiator goes in, sway bar, shifter, clutch slave, etc. Four major snags show up. One is that we do not have the intake manifold bolts/nuts, so our hopes of firing up the motor that evening are dashed. We also don’t have an original O2 sensor (long since replaced by the four wire TEC3 unit). Another is that the clutch slave has frozen from the long time off. The latter problem is solved via careful application of a large c-clamp. The final issue is that I had modified the accelerator cable to work with the TWM throttle body setup I used in CSP trim and it would no longer work for a stock motor. We call it a night with the drivetrain now neatly in the car, but much still left to do.

Friday morning is spent running around town to collect missing parts. First a trip to ART yields some intake bolts and an O2 sensor, and then a trip out to a local wrecking yard nets a throttle cable and a set of driver’s seat rails. The ST seat rules are more restrictive than those in CSP and my super-light kart seats would have to go. For now the plan is to use a set of stock seats, and later get something lighter that has a full-sized back and weighs enough to meet the ST rules.

That afternoon, the intake manifold goes on and Steve and I tackle the Chinese puzzle of trying to figure out how the OE air intake system goes on the car. Without pictures/diagrams for reference, its quite frustrating! And the service manual is useless. The same can be said for replacement of the accelerator cable. Hey, now would be a good time to pull out that driver’s seat! Good thing no one had a camera to record the contorted position that must be assumed under the dash to get the magic clip off that retains the cable to the firewall! Drew then calls and is on his way over. We divert him to a parts run for fluids (oil, MTL and coolant).

After dinner (did I mention that Ann cooked us all dinner each night?), we finish the remaining items on the motor and then realize that the gasoline in the tank has been sitting for three years. Yuck. Not what you want going through your freshly cleaned and blueprinted injectors. Its Steve’s turn for a parts run, this one for a few gallons of fresh high-test. The powerplant frame is now connected to the rear end assembly and the stock exhaust downpipe and cat are installed. Well almost. No nuts. We have lots that have the correct size but wrong thread pitch. Looks like one more parts run and this time everyone looks at me! Off to Home Depot with cat in hand, arriving just as they are closing. I enter before they can close the front door and find what I need quickly. While I am gone the team replaces the passenger side kart seat with the OE seat. The attaching bolts are frozen, but a die grinder makes quick work of the offending party.

Back at the house, the moment of truth is fast approaching and the excitement level is rising. I install the cat and…hmmm…no muffler…what to do? This is a residential neighborhood, after all. And its now 9:30 pm. In a moment of inspiration I spy the old CSP glasspack “shortie” exhaust and figure out that it can be bolted on the back of the cat…sort of. The “angle of dangle” is not quite right, but it will suffice to at least fire up the motor.

Here we go…everyone stands back and I turn the key. After a few seconds of cranking to build fuel pressure it fires right up! ART’s recommended break-in is to run above 2000 RPM for 20 minutes. I attempt to do this and have a hard time keeping it running steady at anything less than 3000 RPM. We shut it off and check everything. Gosh, the cam sensor is loose. Guess maybe we should set the ignition timing? Duh! So we do that and the symptom is a bit better, but the problem persists. At this point everything points to a vacuum leak causing a lean miss. I spy the make-shift “PCV valve substitute” that a certain someone fabbed when no actual valve could be located, but was assured over and over that it would work fine. We try again and just keep it above 3000 to seat the rings. Its now late and we are reminded forcefully by the head of the household that we are disturbing the neighbors, so we call it a night. I have a hard time sleeping while I ponder the surging problem.

Saturday morning I make a parts run to get a real PCV valve, and also visit Steve’s extensive used Miata parts inventory to get some more missing odds and ends required to make the car ST legal. I also pull the original stock exhaust down from the attic and install it to reduce the “neighborhood nuisance” factor. The PCV valve cures the surging and the motor now is purring like a kitten. In fact, it is noticeably smoother than a “normal” Miata motor. That “parts-bin” balancing really works!

Steve comes over and helps me install the hood and put wheels/tires on it. The car now sits on its own weight for the first time in three years and we anxiously prepare for the maiden voyage. As I back out of the driveway I hear some nasty popping/clunking sounds from the rear of the car. Ooops! Pull back in and look around, but nothing seems to be loose or amiss so we try again. I go up to a cul-de-sac and do some slow turns and hear ridiculously loud noises coming from the diff. Ouch! Back to the garage. Its now mid-afternoon and we are really wanting to autocross the car the next day for a shakedown. Our plan had been to use the clutch-style LSD for the regional event and run in CSP, using Monday to build-up and install the ST-legal viscous unit. Now there was no choice, the VLSD install would need to move up two days.

A quick call to Ed at ART reveals that he has come in to work on Saturday so I take the diff down to him to verify my measurements. For setting diff backlash, Ed has some custom tools and a very specific procedure he has developed over the many years as a Mazda Service Tech and racer. He does a lot of it by feel. Ed verifies that I was close, makes a small adjustment, and reminds me to check the torque on the saddle bolts when I get home. Back home, I do so, but also succeed in pulling the diff right out of the vise dropping it three feet down to the concrete floor!!! Arggggghhhh!! Miraculously, there appears to be no damage, not that I could have done anything about it at this point anyway. So I install the differential into the rear end housing.

The next step is to replace the differential mount bushings with the harder rubber ones from Mazdaspeed. Following factory procedure, we drill holes through the old ones to remove pressure and try to hammer them out. No dice. Out comes the grinder again and we grind away some of the metal where the two halves come together and then can easily remove them. Next, we use a trick that the ART guys told us about, and that is to use a hose clamp on the new bushing to hold the two halves together while they are hammered into place. This works pretty well on the first one and we have it together in short order. But the second one seems slightly oblong and does not seem to want to go into the hole. Since the differential housing is aluminum, there is trepidation towards hammering too hard. An urgent call goes out to another racer friend (Denny Feigenspan) who owns a press, I plead my case, drive over and he helps me press the other one in. It is now 8 pm and I spend the next 2.5 hours removing the offending rear end and replacing it with the new viscous-equipped one. It is now 10:30 and I once again take the car out for its maiden voyage. This time there are no issues at all and I drive it around town for 30 minutes. Success! We shall race tomorrow!

Sunday morning I awake from a dead sleep dreading changing tires and loading up the car on the trailer. Instead I decide to just drive the car on the old skinny tires the 100 miles to the event, race and drive back. Just like the good old days. Of course, the car does not have a current inspection sticker or insurance yet so getting stopped by the gendarmes would be a bad thing.

The trip over is fun in its own way as I rediscover the fun of a Miata as a street car. At the event, it performs well (i.e. nothing falls off of it and it doesn’t blow up) and we put down some good times. Halfway home I suddenly remember that I failed to tighten the bolts that attach the rear upper control arms! Of course, this realization occurs along a two-lane country road that I am traveling at 70 MPH and there is no shoulder and no place to pull over. Finally, a gas station appears and I check out the bolts. Yes, they are loose, but have not backed off at all from the finger tight install I did. Since I have no tools with me anyway, I simply press on.

Most of Monday is spent fabbing up a muffler setup so that the car will pass sound control at the San Diego Tour. The Supertrapp on the Civic worked for it, so I start by stealing that piece. Next, I cut the flange off of an old failed Miata cat and proceed to enlarge and reshape the hole, and drill out the mounting studs. The exhaust has to make a bend right at this joint so several hours are spent grinding and test-fitting until I get it just right. A two-inch piece of leftover pipe from a previous project is just long enough to do the job so I weld it all up. This results in a sporty exhaust note that can be easily tuned to meet sound limits, or uncorked for times when there are none.

At this point, the car still has an entirely stock intake tract and exhaust, except for the muffler. Luckily, part of this project will involve doing some future dyno comparisons of popular intake/exhaust parts. A quick e-mail to Per Schroeder at GRM and he is on the task. Several hours later he has arranged to have a Racing Beat intake, header and plug wires shipped to meet me in CA. Looks like we’ll be doing some parking lot installs!

With the car now totally presentable, its time to make it totally legal. Much of Tuesday is allocated to reinstalling the original soft-top, seat belts, brake proportioning valve and bleeding out the brake system. Ann goes off to see Vitek Boruvka at Axware Systems to have some “2’s” made to match our “STS” letters and numbers. Right around dinner time we are done and packing begins. Wednesday morning, we are on the road with our newly built STS2 Miata in tow.

While crazy at times, this sort of adventure with racer friends is what draws me to this sport. Its amazing what can be accomplished when you combine the wide-ranging talents of a group of racers. Everyone has their area of expertise, and all are dedicated to the goal however ridiculous it may be. In this case, we got a motor on a Thursday, and put a race car around it in time to race it on a Sunday. Two more days, and it’s a nationally competitive, legal race car. Pretty freakin’ amazing.

Next installment will be the results from the debut in CA.

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