I guess we’ll start an official project car page for this one after everyone’s back from the holidays, but here’s the latest car in the driveway: Subaru Impreza WRX. We have some neat editorial plans for this one, but right now we’re following the manual regarding the break-in procedure. (It’s that new.) Initial impressions: What a cool car. Practical, too.
In anticipation of a new season of autocrossing in a new car, we got a new bright orange XL G Force Racing Gear helmet. This helmet is under a hundred bucks with it’s M2000 rating, but does the job for us at an autocross. And no one mistakes it for theirs!
We drove the Saab up to Cleveland for the Christmas holiday. The new Continentals never saw real snow, but did slog through hour upon hour of wet and rainy conditions on both legs of the journey. They performed great and we’re happy with this tire choice.
A typical New Year’s resolution is to “lose weight” and in this installment we do just that! One of the weight-saving items which we never got around to last year was to replace the battery with a smaller, lightweight version. This is not as critical in the Miata as it is in other cars, since Mazda very wisely chose to locate the stock battery in the right rear corner of the car, effectively balancing out the weight of the driver. If you have to have weight, though, that’s a great place for it to be. Still, weight hurts our overall performance and we want to remove as much as possible without otherwise hurting the car.
Yuasa makes a great line of motorcycle batteries called the “YTZ” line, which are of the sealed, lead-acid variety, with the fluid absorbed in glass matting (AGM). This allows the battery to be mounted in any orientation, not just terminals up. Also, this particular line has an extremely high charge and discharge rate, which allows it to provide “cranking amps” many times higher than batteries of similar overall amperage. The battery we’ve chosen is the YTZ7S, which is rated at only 7 amp hours. Still, it puts out 130 cold cranking amps which is plenty to start our Miata in summer weather. We’ve been running one for two years in our STS Civic and it has performed well, finally giving up the ghost only recently. A note of warning, though…don’t ever leave your lights on or even leave the car in the “Accessory” position for very long. If you do, you’ll find the battery drained in no time flat! This is a battery for racing use, and should not be be expected to perform like a normal sized OE battery. It has very little reserve power. Also, don’t expect it to start your car when it’s freezing outside. It won’t.
When installing a battery it is important to properly secure it or Bad Things can happen very quickly, especially when you are subjecting it to high-g transitional movements. In addition, we also want to be able to swap the standard battery back in easily for longer-term street use. We work through a number of possible mounting scenarios on paper before finally settling on one that is very similar to the OE mounting. It requires some bracket fabrication and a couple dabs of welding, but is fairly straightforward.
First we chuck up some 1/4″ steel rod that we have laying around from an exhaust hanger project, and use a length of 1/2″ square box tubing around it as a “persuader”. We bend it into a “Z” shaped bracket that will mount like the stock one, only lower and shorter. Three bends later, we have the basic piece which is then test-fitted and “adjusted” with vise grips. We then bend a small fender washer to a 90-degree angle and tack-weld it to the Z-bracket to keep the bracket oriented corrrectly over the top of the battery. Finally, we mark and drill a 1/4″ hole in the trunk floor to allow for our tie-down bolt to pass through. This is a little tricky since there is not enough space to get a standard drill to line up straight either over or under the trunk floor. As such, we use a shorter, smaller bits to drill a pilot hole which then enable us to drill the final hole at an angle without walking the drill. For our tie-down bolt, we reuse the stock piece flipping it upside down with the nut at the bottom. It works like a charm. With everything now test fitted we disassemble it all, clean the bracket and paint it.
The next step is to attach the battery cables. Motorcycle batteries do not typically come with post connectors like a normal car battery. For some, you can install adapters which will provide a post. Our battery is so small, that this is not an option. Instead, we must effectively change our cable ends to a ring type which can be bolted to the battery post. Taking the easy path of chopping off the existing ends and replacing them with rings would make it very difficult to swap the standard battery back in for longer-term street usage. Instead, we flip the terminal on its side, remove the tightening bolt/nut, and bolt that down into the battery post. To use the special nut that comes with the battery, a 5mm x .8 threaded bolt is required. The ones provided with the battery are too short, so a quick trip to the hardware store yields a new pair that are 16mm in length. Together with a pair of 3/8″ nuts used as spacers to keep it all oriented correctly, the assembly goes together securely.
Now, for a couple of tricks that we learned the hard way. As displayed in the picture, it helps to use a small screwdriver inserted into the post underneath the special nut to lift it up to meet the inserted bolt which is hand threaded. Be careful as this is easily cross-threaded! Also, it is best to attach the negative cable first since it is so far back in the wheel well. Attach the positive next, and then install the mounting bracket by tilting the battery and inserting the bracket into the body hole. The tie-down hook is the last to be put into place and securely tightening the nut locks it all down.
A quick turn of the ignition verifies our work is good! Of course, now our corner-balance needs to be re-adjusted….
How much weight did we save? The original vented Miata batteries weigh 20 lbs. The maintance-free Mazda replacements like ours are 21 lbs., while our tiny Yuasa battery weighs in at only 4.5 lbs! And we saved another half a pound in mounting hardware. So our net loss was 17 lbs. What a great way to start a new year! Now, if we can only keep the weight off through a program of regular diet and exercise…
I’m heading north for the hale and hearty land of my youth, Northern Virginia, to spend the holidays with family, wonderful girl and long-time friends. It should be tons of fun, hopefully homeland security won’t have too much beef with my wrapped presents as checked baggage. I bring cheer, dammit!
In the interest of reflection and record-keeping, here’s what I learned in 2006:
Our trip up to Kirk Racing went very well. Mark Stewart, the owner, is a true craftsmen. The entire cage installation took about 20 hours of work, over two days. We had very few setbacks, as Mark had already figured out how he wanted to build the cage, as he’s also building a Spec E30. The final bill on the cage is somewhere in the 1600-1800 range, but this represents an incredible value. Mark wastes no time and builds some of the nicest cages we’ve ever seen.
My wife and I celebrated our anniversary earlier this week, and there was a good sign that we made a wise choice: We both gave each other the same Snoopy anniversary card. (Mine had glitter on it, however.)
I fully admit that I am nearly 100 percent out of touch when it comes to today’s pop culture. If they’re not a regular on Law & Order, I’m not going to recognize them. However, I found a good place for my celebrity news: I Don’t Like You In That Way (Note: This is not a G-rated site; it is funny, however.)
One of the nice things about living in central Texas is that you can run year ’round. Also, we have a bunch of available asphalt lots that provide similar levels of grip (low-to-medium) to Heartland Park Topeka, though most are much bumpier. This gives us a chance to do some valuable off-season testing in a low-key environment and this past weekend we did just that . Running with the San Antonio Sports Car Club we took the opportunity to try out a tire combination that we saw fast guy Jason Frank run so successfully on his STS Civic at Nats this year. That would be the 205/50-15 Falken RT-215 on the front of the car with the 205/40-16 Falken RT-615 on the rear. If you go back to the tire testing write-up we did early last season on our Civic, you’ll see that we were more consistently fast with the 16″ 615’s tire all around, yet were able to occassionally crank out a spectacular run on the 15″ 215’s. The 215’s had lightning quick responses in the transitions, but were like an on-off switch at the back of the car. So we opted for the 16’s all last season. After watching Jason, we came to the realization that we could potentially have the best of both worlds with a staggered setup. We could have the responsiveness of the RT215 on the front with the RT615’s progressive breakaway at the rear. What’s more, on the RWD Miata we could still have the gearing advantage of the 16’s as well.
We’ve still got several sets of RT215’s in the garage that we’ve been carting around as rain tires all season. We also have a pair of the tires we ran on our Civic at Nats in 2005 which were shaved and had only a few runs on them. Since the 16’s we currently have mounted have a bunch of runs on them, we figured this would be a reasonably fair comparison. Not exactly a scientific test, but enough to get a feel for the situation.
The other big variable would be the course. Good testing requires a consistent surface and a course that is easy to drive consistently. Again, we’d have to compromise here. At SASCA’s site, the lot is sealed and the grip level gets significantly better over the first couple of heats as the sealer is worn off. Also, a competition course is usually designed to be challenging and may or may not contain a good mix of elements. As such, we arrive at the event early to help setup and were able to give some input on the course design to improve flow and mix. In the end, the course is a good mix of challenging elements, but very hard to drive consistently quick.
By double-entering the event, we are able to run in each of the four heats (normally, you run two and work two, but we did our work assignments during setup/teardown). That gives us three runs in each of the morning heats and four in each of the afternoon sessions. We also run our MaxQData plug & play GPS data logger to gather info on the runs. We are big fans of this unit, as it is versatile and the software can provide helpful information even between runs. Look for a print write-up on this in a future GRM. Now, on to the testing …
We start with our normal 16″ setup as a baseline. First run out on a dirty course is a 56.2. It’s pretty much a throwaway as the tires are cold, and grip is down due to the sealer. By the time our second pass comes around, another 30 cars have run and times are beginning to fall. We run 54.8 with a minor bobble near the beginning of the course. Thenm on the third run we drop to a 54.4 by fixing the bobble and running everthing else the same (verified on the MaxQData).
Swapping fronts to the old 15″ tires, we notice that the surface of them is a bit “crusty” from oxidation. Heat-cycling a tire and then letting it sit a long time will do this. We should have scuffed them at home but there was no time now. Sure enough, our first run out on these tires the car is skatey for the first couple of maneuvers. But then the grip comes in bigtime halfway through the run and we start to feel that old “do no wrong” RT-215 responsiveness. The time is a 55.4 because of the bad first half. Next run we go right down to a 54.4 matching our best first-heat time for the 16’s. More importantly, the RT-215 is a dream through the tight transitional sections (tight Chicago box, double lane change, bent 6-cone 63′ slalom). With our confidence bolstered we go out on the final morning run and just hammer the car through the transitions dropping a full second to 53.3!
During the lunch break we have a look at the data logs and see that the car really isn’t going that much faster in the slaloms, but is instead carving better in the sweepers. Some of this is attributed to being able to more accurately place the car near the inside cones and reduce distance. It is also unclear just how much of the improvement is due to surface grip improvement on the sealed lot. The plan for the afternoon is to leave the 15’s on the car for the 3rd heat, and then swap back to the 16’s for the final heat. This way, the 16’s will have the best opportunity for “last say” and it will validate our initial conclusions. Also, our past experience has been that most of the surface grip improvement comes in the morning.
With cool tires on our first run in the third heat, we fall back to a 54.0. Then with everything now warm, the next run is a 53.7 with a bobble. After that a 53.5 and 53.4. The datalogger shows these runs all to be similar to the 53.3 we did in the morning, so we are confident that the lot has not changed subtantially since then. That said, if we were to combine the best parts of each run’s log, we could imagine a high 52.x run.
For the fourth heat, we bracket the test by putting the 16’s back on the car. Our secret hope is to go slower, but we give it our best shot anyway. Right out of the box we can feel that the car is tending a bit more towards oversteer. That would indicate that the 16″ front tires were gripping a bit more than the 15’s. Sure enough, we put down a 53.3. The feel is certainly worse, though, as the car has to be turned a bit earlier and is not crisp in transitions. Still, the clock doesn’t lie! Second run is slower at 53.5 as we get late with too much speed into the Chicago box. For the third run we focus on slowing down our entry speed in certain key sections and finally snag a 52.8. We back it up, though not perfectly, with a 53.0 on our final attempt.
Conclusions? Well, the test was not even close to scientific and we are not sure how much to attribute to overall grip changes, as well as driver improvement over the day. But it was pretty clear that there is some potential here. We were basically able to drive about the same times with both setups, with the edge to the 16″ RT615’s. We’ll have to repeat this test with fresh-shaved tires on a more straightforward test course and controlled environment sometime early next year.
Happy Holidays!
–Andy
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