| MIATA BUILD |
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 | |  | November 4, 2007 - The track day was with the Peak-to-Peak Miata club and took place at Pueblo Motorsports Park.
I was last there in March and it's a track that's fairly familiar to me. Not the greatest track in the world, but it does have a couple of interesting corners. More importantly, the club runs the track day as an open format. There are no run groups, so you can enter and exit the track whenever you want. This makes it excellent for both driver and car development and takes a lot of the tension out of a day. It wouldn't work with a group of unknown drivers, but these days tend to be invitation-only and everyone uses their heads.
For me, the goal was to sort the handling out and see how my new alignment worked as well as test the suspension at high speed. The first few laps felt good - the car was composed, but it was uninspired. There was a little bit of understeer. Very stable, but I didn't have the adjustability I wanted. So I installed a stock 11mm rear sway bar, as the car had been running without one. As you can see, the trailer makes an excellent sway bar adjustment rack.
That was better. The car was a bit more adjustable and turned in better, but it still wasn't quite there. I popped on a 14mm rear bar from a Mazdaspeed MX-5 and voila, we have a Miata. The car came alive with a great handling balance and excellent adjustability. It could dance.
Meanwhile, I also took a few sorties to work on the suspension tuning. A bit more rear compression damping, a touch more rebound and the car was able to handle just about anything on the track. I was driving over berms and trying to upset the car, but to no avail. One corner did give me the ability to bottom out the suspension, but I had to hit a berm at full cornering force to do it and it didn't upset the car at all. Once again, I found that I could move the rear end around if I wanted but it was still very easy to control. I believe this is due to the long travel available, keeping the wheels well planted on the ground. There are other suspensions out there with decent travel, but most will unweight the spring before reaching full extension. Not in this case!
There's one spot on the track where the exit berm on a corner has big bumps or teeth in it. On one lap, I brought the tail out on this one and went around with the rear wheels going over the teeth at full throttle. It was bumpy, but it didn't upset the car. That's the sort of composure I need.
The last turn on the track is a fast one that has widely varying surfaces as it travels across a drag strip. This means you go from patched asphalt to VHT-soaked asphalt to coarse concrete to VHT to asphalt again, with a couple of metal plates thrown in for good measure. Oh, and it's bumpy and you take it at wide open throttle in 4th gear. In a stiff car, it's painful and the car keeps skipping around. In the Targa car, I could feel the changes in lateral grip but the car didn't get upset at all. Very nice - I think we have a winner with this suspension setup. The Torsen differential was working as intended as well, putting down the power smoothly and cleanly.
So, all very promising then. I was able to run down and pass a Spec Miata which was gratifying, as he was running a much more track-biased suspension than I was. His front spring rates are more than double mine! There was a good battle with a Subaru STi that was promising as well, my handling and grip were able to make up for a 150 hp (or so) shortcoming.
Bill Cardell of Flyin' Miata tried the car and was impressed. The suspension he considered to be "suitable for a NYC taxi" because of the way it would absord anything. The engine feels good but it really needs more top end, that's something we'll work on. His only concern was the brake bias, as I have it a little strong in the tail for maximum braking. This means that the tail feels a bit loose in some situations. Not a problem on the track where you know exactly what the next corner looks like, but he pointed out that with the unexpected nature of the Targa course this could be a liability. Luckily, that's easy to adjust, even between corners.
So that's the good news.
entry 335 - tags: testing, suspension, brakes | | |  | November 4, 2007 - An unfortunate finish to the day.
Bill took the Targa car out to see how it was working, and I borrowed his Westfield. The little car was working beautifully and I was quicker in it than I had been in the Miata. With 700 lbs less weight and only a bit less power, that's not a big surprise. Bill wasn't lagging too much, though, and some slower traffic bunched us up. Shortly after getting free, we entered turn 5, the best turn on the track. It's like a baby version of Eau Rouge, as one driver pointed out - an uphill corner with a nice compression at the bottom and a blind exit. Very entertaining and nicely quick. I came out of the series of bends and noticed Bill was gone from my mirrors - and there was a big cloud of dust on the inside of 5 with a Miata shape inside. The car had stopped just short of a flag station and tire wall.
Back in the pits, we saw the typical damage for an off-track excursion around here - one tire pulled off the wheel and another with grass jammed in the bead. There were some scuff marks and scratches on the nose as well.
We pulled the wheels off and headed for the local Discount Tire. I was still wearing my driving suit, and when I got out of the truck a little kid asked "are you a racing car driver?". Not really, but I'm trying!
The staff at Discount were really helpful, getting right to work despite the fact that it was the middle of a busy Saturday. They pulled off the tires, vacuumed them out (to our great amusement) and reseated them in about 4 minutes. Then we were called in to have a look at the balancing machine. One wheel was wobbling badly. There are custom-made SSRs and can't be replaced, nuts. It's a good thing that I have access to a total of 8-12 of them.
Oh well, we figured we'd see how it felt. After all this, the tire shop didn't even charge us! Note to self, always wear Nomex to a tire store. Thank you Discount.
Back at the track, the tires went on and I headed to the track for some gentle exploratory laps. Heading down pit lane, I noticed that my steering wheel was off center. That was it, I headed for the trailer. Between a potentially shaky wheel with some damage and unknown suspension problems, it was not time to go push hard.
Nothing was obviously bent under the car although it appears one of the caster adjustment cams might have slipped. I didn't get the chance to mark the suspension settings before loading on to the trailer, unfortunately, and this simple change may account for the steering wheel offset. I'll check that out shortly. The paint damage is all on the lower half of the front bumper and should be easy to fix.
A sad finish to the day, but nothing that can't be repaired fairly easily and nobody was hurt. We never did figure out exactly what happened to cause the off, from looking at tire marks I think the car simply ran out of grip, possibly brought on by a slight crest in the track there. This is why we test on the track instead of the road, though!
entry 336 - tags: testing, other cars, tires, crash | | |  | November 6, 2007 - I pulled the differential out last night so I had the car up on the lift for a good check-over.
Underneath the nose, the plastic ducting for the radiator got smashed up in one corner. Easy to replace. The engine undertray got pulled loose from one bolt but a washer will solve that problem. I can fix up the paint damage easily enough of course.
There's no other sign of damage underneath although I'm still wondering why the steering wheel is offset. It has me worried as you might expect. I'm considering replacing the left front control arm regardless, that's the corner that hit hard enough to damage a strong SSR wheel.
About the wheels - I took a new wheel and the bent wheel/tire down to our local tire shop to have it mounted and balanced. I was waiting at the door when they opened up in the morning, as I needed to have the wheel and tire back on the car by the time Flyin' Miata opened for business so I didn't tie up a lift. First thing on a Tuesday morning, it should be quick. Not so much. It took over an hour for the single tire to be mounted and balanced and I had to be a bit of a pest to make that happen. A dramatic contrast from the friendly, speedy (and free!) service from Discount Tire in Pueblo. I wasn't wearing the race suit, that might have been the key.
entry 337 - tags: crash, suspension | | |  | November 12, 2007 - This engine bay used to look so nice.
It's amazing how much of a mess one little off-track excursion will create.
entry 338 - tags: crash | | |  | November 12, 2007 - This wheel used to have about 1.5 degrees of negative camber.
Now, it has none. A quick check with the toe plates indicates close to an inch of toe-out. Once I'd pulled the shocks out again (they're going in a street car for final evaluation as a Flyin' Miata product), I also pulled out the lower control arm on this wheel. Yup, looks like a crease in the top. That would explain the alignment problems.
Honestly, after bending a wheel like that, I'd be shocked if the control arm hadn't bent. They're intended to be the weak point in the suspension, absorbing the punishment to protect components like the subframe. I'll stick another control arm in, that's an easy fix.
entry 339 - tags: suspension, alignment, crash | | | November 19, 2007 - Comparing the new control arm to the one removed from the car, I can't measure any difference.
The crease I saw is normal. That's not completely reassuring, I'd like to know what's up with the alignment. I'll put things back together and see if I can get the car sorted. The subframe appears to be undamaged.
The suspension can't go together until the springs and shocks are back from street car testing. They're performing well though.
entry 340 - tags: suspension, crash | | | November 23, 2007 - Back on the wheels.
The AFCO shock setup is still under evaluation in another car, so I grabbed a set of springs and shocks from the pile at Flyin' Miata and put the car back together. I used a new front lower control arm for the time being because I have one, but measurements seem to indicate that there was no problem with the original. An initial check of the alignment would indicate that everything is straight, but I will have to drive the car to make sure everything's settled first.
So, the car's back on its wheels and drivable. The next step is some dyno work, to see if I can liberate a few more RPM out of the car. The engine is great down low, it just needs a bit more sparkle up top. I did come across a stillborn product at FM that might be handy, I'll have to keep scrounging for parts to make it work.
I need to get cracking on a lot of the detail work that needs to be done on the car. Items like the codriver footrest, the required gear and a way to stash it, and various electrical accessories that have been neglected. There's always something...
entry 341 - tags: suspension, crash | | | November 26, 2007 - Study material.
My coworker Jeremy dropped a binder on my desk this morning - the course material from the California Rally Series rally school. It's a pretty good collection of information, and it should be good prep for the school itself. I'm hoping to take it in early 2008.
A note about the car's alignment - I've had a couple of comments about my "alignment difficulties". I wouldn't characterize the results of the damage as particularly difficult. I've been writing about it a lot because I haven't been doing much else, but really all I've done is replaced one suspect part with a known good one. Once I get the chance to check the car, I think it will be all good. The fact that the suspension had to come out for evaluation in a different car is unrelated.
entry 342 - tags: skills, crash | | | December 4, 2007 - The car is all healthy.
I finally got around to taking it for a short test drive after catching up on some of the rest of my life. Using the scientific method of the steering wheel location when driving in a straight line, it appears that I have a healthy car. When it came off the track, the problems meant that the steering wheel was badly off center. Now it's almost right, which means I just need to align the car and I should be good. The car sure is dusty, and the temporary suspension that's installed sure isn't any good!
So, it's time to get down to work. I have a good list of jobs to do on the car, all in nice bite-size chunks. None of this "weld in roll cage, build an engine and paint a complex paint scheme" that I had before. I have some time between now and the new year so it's an excellent chance to get a lot of the required detail work done.
I also took the opportunity to take both my Mini and the Seven out for a spin yesterday. In all three cases, the last time the car was driven was either on the track or the autocross course. I think that's a promising sign.
entry 343 - tags: crash, suspension, other cars | | |  | December 5, 2007 - I fabricated a plate to cover the missing center console cutout and give me a place to mount some switches.
Of course, I counted the switches I needed, came up with four and then carefully drilled 5 holes. Nice work. That's okay, I'm sure something will come up that needs an extra switch. The one under the guard is for the wiring for auxiliary lights. I don't expect to have them installed very often and I'd prefer not to accidentally turn them on. Of course, that's just a justification for using the cool guard.
Finally, some work that isn't suspension!
entry 344 - tags: ergonomics, wiring | | |  | December 5, 2007 - Since the switch panel stood a bit proud of the dash surface, I wanted to try to make it integrate a bit.
So I curled the edges back. I'd love to take credit for mad metal shaping skills, but really I just bent the lip with a set of pliers and a vise, then did a little extra forming with a body hammer. A grinding wheel cleaned up the edges and a wire wheel gave it a nice sheen. I might paint it black, but it looks pretty good au naturel.
In other news, I ordered the bilge blower for the defrosting system today. First I visited a local boating store, where I had a hard time communicating that I needed a bilge blower and not a bilge pump. They were completely unhelpful, so Amazon came to the rescue. Maybe I'll set it up so it acts as an electric supercharger when I don't need the windshield defrosted!
entry 345 - tags: ergonomics, wiring | | |  | December 7, 2007 - Video time!
A friend of mine gave me a DVD of the car at the autocross back in October. Of the six runs I took, only a couple have any decent video. Still, quite instructive. Naturally, the car's development has progressed since that point but there is some behavior visible from outside that I'll take into consideration.
I've tried a different video setup than I've used on previous websites, using the DivX web player. I like the video quality and the ease in which you can pop it out to full screen. Comments are welcome.
Besides, if you've been watching the WRC footage as I have, you already have DivX on your system. Congratulations to Loeb for the world championship!
See the videos here.
entry 346 - tags: testing | | |  | December 10, 2007 - Ah, a 3-day weekend with no plans.
Time for a whole lot of work on the car, right?
Well, I did get the navigator's footrest installed. This is the one that was donated by Jason over on the Grassroots Motorsports forum. Thanks again, Jason! My original design for the bracket was made of steel tube. I took a second look before starting up the welder, and realized I could do better. The rear support is aluminum angle, putting the strength where I need it. The side brackets have a couple of holes so I can adjust the angle of the footrest, remove the whole thing or simply lower the main plate to get access to whatever's behind it. It's nice and solid and probably 1/4 the weight of the original plan. I'm pretty happy with this.
I also discovered that the switch for raising and lowering the headlights is double-throw, so I've ordered a few switches to allow me to wire the car properly and this has put off the installation of the switch panel. I've also been doing some research into header collectors, more on that later.
So, what else got done? Well, the master bedroom in the house has been repainted. Didn't see that coming, did you?
entry 347 - tags: ergonomics, wiring | | |  | December 15, 2007 - An electric supercharger has arrived for the car.
Well, it would be an electric supercharger if it were being sold on eBay, anyhow. For me, it's a bilge blower that moves about 240 cfm. Perfect for defogging a windshield. The SPDT switches I need to finish up the switch panel also arrived.
entry 348 - tags: ergonomics, wiring | | |  | December 15, 2007 - After a bit of crawling around, the switches are installed.
And labelled, of course. The "eject" switch is for Eric if he gets too nervous.
Almost out of sight is the bilge blower. It's been mounted in the footwell under the new Sparco footrest. The plumbing worked fairly well (you can see a bit of it in the picture) and there's a distinct breeze coming up the surface of the glass. This is the time of year to test it, too - next time it rains (instead of snow) I'm going to get all wet and try to fog up the car.
entry 349 - tags: ergonomics, wiring | | |  | December 19, 2007 - Time for a fun job.
The engine just isn't performing the way it should. At higher rpm, it's choking off. So it's time to replace the Racing Beat header (designed for a 110 hp car) with one a little more robust.
I had a very interesting conversation with an E Production racer, and he shared his header specifications with me. Yes, I know, they should be scientifically matched to my cams and port lengths and everything else. But an E Production Miata is the closest thing out there to my car, so I figured I'd take advantage of their knowledge base and see if uncorking the exhaust does anything at all. If so, I'll make another with a little more specificity.
31" primaries with a 1.75" tube size, right then. The first step is to get a collector. These are expensive - but a bit of searching turned up this beauty. Edelbrock makes merge collectors with 1.75" inlets for only $90 or so, street price. Sure, they're not as pretty as the $300+ units, but I can cope with that. Especially when it turns out the $90 price is for a pair!
Nice. Now all I need to do is figure out how to stuff all those big pipes underhood. The EP guys gave me some ideas there as well...
entry 350 - tags: header | | |  | December 19, 2007 - The last time I built a header was for my little Seven.
I used pool hose to work out the basic routing, then improved on that with some welding rod. It worked out well, but that car did have a lot of space available to work with. You can read the whole saga starting here, you'll have to skip over a few days worth of installing side panels and the like as I procrastinated.
This time, I have the advantage of a very cool tool. This "header Lego" from icengineworks is exactly what it sounds like - 1" pieces of tube that snap together into whatever shape I need. I have 2", 3" and 4" radius bends as well as short bits, and they're all beautifully marked up to make fabrication of the final product easy. Well, easier. This is going to be quite interesting to play with. I'm going to have some fun. Although I do think the pool hose might have to make a comeback to get me started on layout. Where did it go?
entry 351 - tags: header, other cars | | |  | December 20, 2007 - The starting point.
Except for a lapse in 1999-00, Mazda used a nice 4-1 header on the North American naturally aspirated cars. Overseas, some models got a long 4-2-1 design. It's actually a reasonable setup, much better than most stock exhaust manifolds.
I'll cut this up and use it for the flange, just as I did on the last header I made. The iceengineworks parts are designed to be fastened to a stub of round tube.
entry 352 - tags: header | | |  | December 22, 2007 - Step one complete!
A Sawzall made short work of the stock piece.
entry 353 - tags: header | | |  | December 22, 2007 - A couple of other Miata headers.
The complete one is the Racing Beat unit I pulled out of the car. It has 1.675" primaries - only 0.125" smaller than I'm planning to use - but they're much shorter. There's a bit of inconsistency in their length, but I'm coming up with about 15-16". Really, this header is tuned to work best at very high rpm according to the math.
The other pipe is from a Boig Motorsports header, one that had a great reputation in the Miata world for a while. It's for a 1.6. 1.75" primaries that are about 29" long. I'm going a little bit longer - about twice as long as the ones in that Racing Beat unit! Packaging is going to be a concern.
entry 354 - tags: header | | |
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