Grassroots Motorsports: The Hardcore Sports Car Magazine

Part 2 -

After the lightweight racing seat install, our second quickie performance improvement was to install a lightweight underdrive pulley. This helps out in three ways. First, it reduces the power loss through rotational inertia the same way a lightweight flywheel does. Second, the smaller diameter spins the accessories (water pump and alternator) slower, reducing the parasitic power loss. And finally, it takes weight off the nose of the car. The results of our install were dramatic. So much so, that we’d recommend this enhancement early on in the development of any STS2 car. It’s cheap and it works.

But first, a note of warning. Much has been said in various Internet forums about the possible downsides of these pulleys. Most of this centers on the loss of the original pulley’s damping function on crankshaft vibrations. As a dual-mass unit, the OE pulley helps to reduce the effect of these vibrations on the main bearings and the oil pump, which is driven directly off the crank. There is anecdotal evidence that suggests a link between aftermarket pulley installation and oil pump failure on the Miata, especially in forced induction motors. The “tribal wisdom” in the Miata community looks more favorably on such installations on normally aspirated engines. If considering such a modification, do some research.

Unorthodox Racing underdrive pulley

UR Pulley with outer groove removed

Installation is aided by raising the radiator

With radiator raised, access to crank bolt is simple

All ready to crank it up!

The pulley we chose was from Unorthodox Racing . Note that there are two versions depending on whether you have one of the dreaded early “short-nosed” crankshafts from model years 90-91, or the updated version found starting mid-year 1991 through 1993. 94-97 cars have only a single part listing. These pulleys come with both the alternator groove and the one for power steering and a/c. Since our car is the more “manly” base model with no PS or a/c, the unnecessary second groove was just added weight. Ah, but that’s what machine shops are for!

With pulley in hand, a quick visit to our good friend, and perennial F-Prepared Z-car fast guy, Tom Holt was made at Dell Speed and Machine. Tom chucked it up in a lathe and easily removed the offending excess aluminum. 20 minutes later, our pulley was much more svelte. A stop off at the post office on the way home gave us the confirmation. The OE pulley was 4.6 lbs and the UR pulley was 1.2 lbs, as manufactured. Our single-groove version netted out at 0.9 lbs. That’s a total of 3.7 lbs of rotational weight we removed.

Installation was relatively painless since the motor had been apart recently. Stubborn crank bolts can be a real pain, but ours came right off with an impact gun running on a small home compressor. To make the job easier, we raised the radiator up out of the way to gain a straight shot at the pulley. Removal of the plastic undertray, the sway bar, the fan and one piece of the plastic intake tract allowed the radiator to be moved up and back about six inches.

When installing a new pulley, its critical to get the woodruff key back in correctly, especially if you have one of the short-nosed cranks. There are articles on Miata.Net in the Garage section that detail crank failures as a result of incorrect reassembly. Read them and heed them.

With the car back together a quick run up/down the street was in order. Wow! A big difference in the way the car revved was immediately noticed. And the butt-dyno was applauding as well. For point of reference, before-and-after dyno tests on small Honda motors have shown a consistent 2-3 lb/ft increase across the entire torque curve. We believe it.

If considering a crank pulley for your Miata, you might look to the OBX parts sold on EBay. We went with the UR pulley since we have had good experience with them in the past, and also because we needed very quick delivery to meet our travel schedule. Others in the Miata community have had good luck with the OBX parts, which are only half the price of the UR version.

–Andy

With the Super Challenge win in Atwater, our Pro Solo plans changed. Its not often that you win one of these things and it usually puts you in contention for the Overall title for the year. Not that we have any grand delusions of actually winning that ultimate championship, but it just makes sense to put yourself in the position to be there if the stars all line up for you. That’s why we took the Miata to Mineral Wells and Peru, instead of the STS Civic as originally planned. Sure enough, the Challenge points garnered at the former have placed us in the early lead for the Overall. Hopefully Peru will also be kind to us.

This also kick-started a couple of other development projects on the Miata to pluck some more low-hanging performance enhancement fruit. Losing the class by .006 seconds (Atwater Pro) will also do that to you. We had originally put off our final big diet items until later in the year, but decided instead to thrash a bit and move the timeline up. These included lightweight racing seats and an aluminum underdrive crank pulley.

Kirkey racing seat on stock Miata rails

Close up of the front mounting bracket

Bottom view

Mounted in the car

Passenger side bolted straight through

The final product

Since we were pressed on time, the racing seats were stolen from our STS Civic and mounted in much the same way. These are a pair of Kirkey Economy Layback (10-degree) seats that are cheap ($100-$140 online), fit like a glove and weigh in right around the 15-lb minimum with the seat cover installed. Since they are hand made and come in a variety of sizes, there is some variance in weight, so each seat should be weighed to ensure legality. One of ours was a little light, so we shimmed the seating position up by laying a piece of flooring tile in between the seat cover and the aluminum shell. Doing so, it becomes part of the seat and is therefore legal. Mounting brackets and other bolt-ons don’t count towards that weight (watch for this rule to change for next year).

The passenger seat went in first and was the easiest. Four holes were drilled through the floorboards and the seat was bolted in place using fender washers to spread the load underneath. Carriage bolts (5/16”) were used at the top so as not to interfere with the passenger’s seating quality.

For the driver’s side, we chose to mount the seat on the original Miata seat rails to provide adjustability and make them easier to swap out (this is a street car after all). The biggest issue is that the base of the seat is narrower than the distance between the rails. This is overcome by fabricating a pair of L-brackets out of 1/16” steel sourced from the local Home Depot. A hack saw, vise, and angle grinder were used to make the necessary modifications. See the pictures for details.

We had to fab up some standoffs for the front of the seat to raise the base above the adjuster mechanism. This can also be used to fine tune the layback position of the seat to suit the driver. We used ½” square steel tube which nicely accepts the carriage bolt top. These took about four tries with the grinder to get the angles right on each end. Two original holes in the seat rails were used and two new ones were added, and the mounting bolts were cut to the proper length to keep from protruding inside the rail. Best of all, this whole project gave us the rationale for a new power tool acquisition as we finally replaced our antique single-speed drill with a modern variable-speed unit (also sourced from Home Depot)!

The results were great for two reasons. Since the original Miata seats weighed 25 lbs each, plus 5 lbs each for the rails, we saved 10 lbs on the driver’s side and 15 on the passenger side. For small, low-power cars our rule of thumb is that a 150 lb passenger slows us down by about .5 second. So each 30 lbs is about a tenth pickup.

Even better, though, was the newly lowered seating position. This helps gets the driver’s weight lower in the car, but in our case it also allows us to see the course without looking through the windshield header! The whole job took about half a day, including a trip to the hardware store, and the car is now faster and easier to drive. The cheap seats do take a toll on the streetability, though.

For Part 2 we lose weight and add power at the same time via the crank pulley.

Note: While typical of homebrew seat installs for autocross, this example is by no means recommended for track use or even safe street use.

It’s been a little over a week since I wrote that cloying “ode to a dictionary” entry in my blog, and I’m definitely rethinking that whole word romance shite. We’ve got a deadline that passed a few days ago, a load of stuff I still have to edit, a pile of proofreading I’ll probably never get to finish before the issue ships… in other words, it’s slash and burn time. We’re movin’ units, banging the stuff out, slinging the hash, in total System D mode, to borrow a professional cook’s term. This puppy’s leaving, and at this point I frankly don’t care how.

Don’t be alarmed, though; they all end this way. Welcome to the world of publishing and deadlines. On the plus side, once we ship an issue, we’re all made whole, shiny and new again. Or at least we lose that immediate urge to strangle each other.

I’ve been busy all day today playing what I’ve come to know as “PODTetris.” I’ve got a 16′ POD sitting outside my house I’m slowly filling it with all of our crap. I’m having fun trying to be as space/weight/time efficient as possible and I’ve got quite a bit of the house emptied and over half the POD remaining. It’s amazing how much stuff just fits together. I’ve got TVs cradled by chairs and held in place with stools…all padded, of course. We’ll see how it fares come next Friday!

Our illustrious Bill wrote this, “Of course basic cable doesn’t show you “everything.” You’ve got to go to their Web site for that. But who would want to go to www.fuse.tv/pantsoff to see a naked 80 year-old man or a average looking female who dances like a total spazoid? I’m guessing that if someone were to to get off thier couch to go online to look at naked people, www.fuse.tv/pantsoff is not where they’d go.”

Um, yea, Bill, I went to that site and suffered through the awful dancing. For what? they pixelated out the naughty bits. I’m disappointed. Seriously.

Today I brought my teeth in for service. Time for the semiannual cleaning. So, what’s the first thing the dental hygienist said when I walked into the room? Have you been flossing? Avoiding sweets? Those wisdom teeth bothering you yet?

Nope. She asked why I wasn’t wearing my Dogtown sweatshirt. I never thought I’d have a dental hygienist who was a skater. She’s cool.

I just snapped back to awareness after taking one of those Web-surfing side trips that can kidnap you unexpectedly in the middle of a work day.

No, I wasn’t looking at porn. It’s even worse: I was browsing the University of Chicago’s site on word usages.

As long as I can remember, I’ve had this fascination with language that bordered on perversion. Many are the papers that I’ve finished at the last minute because I kept opening the dictionary to look something up, and not resurfacing until a half-hour or hour later, once I’d had my fill of new and weird words and definitions.

The online dictionaries have been a real blessing to me in my working life, since my searches only return the word I am looking for, not all the wonderful and intriguing choices that share the pages adjoining, say, venturi. But the Internet has also provided a new temptation, in the form of many excellent online forums devoted to grammar and usage. These are the places where dweebs like me can debate the correctness of “importantly” vs. “important” (I prefer the latter, if you’re keeping count), or learn whether there’s a standard for replacing expletives with %@# or dashes. (There isn’t, and anyway I like to leave the expletives in when they’re used sparingly for emphasis, though there are some authors who start to sound like the only word they know is “shit” if you don’t do anything about it.)

I guess this makes me sound pretty weird and boring—which I am—but also oddly suited to my job as the principal copy editor for the magazines. What it may not reveal is how close to music I find language to be, and how similar its effects on those of us who love to put on the headphones and wander away on the sound.

Now, if you’ll excuse me, I have to get back to a story written by a freelancer who thinks “it’s” is the possessive form of “it.” Talk about nails on a chalkboard.

Here’s my daily double for this fine Wednesday…

I rode my Honda Hawk GT to work today. This is the same Honda Hawk GT that used to belong to Gabe. I traded him some artwork I had lying around—phots of former presidents mostly—and now it’s mine, which brings my total number of two-wheeled conveyanced to an even baker’s double (2). Sharing the bike cubby with the Hawk is a Suzuki Burgman 400 mega scooter. It’s big, it’s comfortable, it’s fast, it has a huge trunk and it gets spectacular mileage. The Hawk, on the other hand, is not quite as comfortable, it’s loud, a little buzzy on the hands, and when you get off you smell just a little like gas.

I think both these bikes are perfect. The Suzuki is perfect in that it’s the ultimate transportation tool. It can get you from point A to point B, as long as the span between is paved, quickly, comfortably and efficiently. You could easily live with one as your sole means of transportation, should you be forced to.

The Hawk, on the other hand, is just really good at being a motorcycle, and loves what it is. Some people have dogs who think they’re people. They’re wonderful creatures and excellent companions, but can sometimes seem more like roommates than ani-pals. Ever meet a dog who was just really, really into being a dog? That’s the Hawk.

Now, if the rain will just hold of long enough for me to get home…

Look, if you read the Davinci Code—even if you liked it—that’s fine. If, however, you think it’s an important tome pointing the way to the truth of greater enlightenemtn for mankind, you’re an idiot. It’s historical fiction, the key word being fiction. Just like Raiders of the Lost Ark wasn’t a deep, historically accurate examination of Nazis, or Lord of the Rings was not a true depiction of orcs, DVC is fiction, based on historical events. Nothing more, nothing less.

Now, for all of you who are beginning to fold your arms and nod your heads because you just KNOW that this book and movie is blasphemy and must be stricken from the land. Well, you’re idiots, too. If your faith can’t withstand a challenge from something bought in an airport bookstore, you might want to look into a tougher God.

Now, as for the X-Men, well, of course we all know that stuff’s real…

Kim and Per scrubbed in some new tires this weekend in DeLand. Kim got to scrub in new Kumho V710s while Per scrubbed in some Hoosier A6s. They were rewarded with a first and third place finish on PAX index. That’s Per’s sixth of the year…here’s the yearly scores thus far:
Yearly PAX scores

The tires were getting scrubbed in for a tire test that we ran yesterday. Look for the results in the August issue of GRM!