| MIATA BUILD |
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 | | September 29, 2007 - The sways are installed.
There's a 7/8" bar on the softest setting up front and a 5/8" bar on the softest setting in the rear. I considered using the 14mm Mazdaspeed bar in the rear, but the aftermarket version has longer arms so I suspect they're about the same in the current setting - and this gives me more options. This current setup is slightly more biased towards front stiffness than I usually run. Typically I'd have that rear bar on the middle setting. I also have a factory 12mm rear that I can throw on if required. One nice thing about the Targa Miata is that I can install the rear sway bar without even jacking up the car, thanks to the cutaway rear bumper!
I headed out for a run to test the bars. To make things more exciting, the wind was howling and rain was splattering down. It's the best imitation I've seen of Newfoundland weather here in the Colorado desert. I'm assuming I won't have to dodge tumbleweeds in the rain in Newfoundland, though.
The car feels great. It's got a very nimble feel and it just glides over imperfections in the road over 20 mph. Below that speed there's more impact felt through the body but the car just deals with it. One 2nd gear corner with a very corrugated exit caused the rear end to lose traction, but it had more to do with the cool tires, wet road and too much power than with the damaged pavement. The Torsen diff let the loose wheel just spin up, an indication of how little traction there was. It was a smooth breakaway and I just rode it out. The car is very eager to turn in and feels a bit darty, but that could also be the strong cross winds. I'll see how it feels over the next few days. The next track session is scheduled for November 3rd, but I might be autocrossing the car next week. We'll see.
entry 320 - tags: suspension, drivetrain, testing | | |  | October 1, 2007 - Hard Dog Fabrication sent along this trick dual-durometer rollbar padding.
The problem is that rollbars are hard. The SFI-compliant padding at right is hard enough to protect a helmeted head from the bar, but it's not soft enough to protect an unhelmeted head very well. Since I want to be able to drive the Targa Miata without a helmet, this isn't ideal. The solution is a softer outer shell, with a firmer SFI padding inside. It's obviously quite a bit thicker overall than just an SFI pad so I can't use it in a couple of locations, but it'll fit nicely around my head.
entry 321 - tags: sponsors, safety | | |  | October 7, 2007 - Miscellaneous work this weekend.
I installed the Revlight tachometer to the top of the instrument cluster. I really like these little guys, it's a shame they're out of production. A bright LED was added to the front of the cluster cover as well for a low oil indication. Yes, I have a proper gauge, but in the heat of competition a bright red TURN THE ENGINE OFF NOW! light is good. I have video of a driver on the track with all the unwatched gauges screaming danger as the engine destroyed itself. A big red light would have saved us a lot of work in the pits the next day as we had to install the new engine...
Anyhow, in the process of installing the oil light, I managed to crack the 16-year-old plastic of the instrument cover. This was after gluing the mounting brackets back on. Maybe it's time for a new one.
Meanwhile, Brandon did a bit of work on the driver's footrest. I also managed to get most of the parts for the VICS (a variable intake setup) fixed up and ready to install. This will add a bit of top-end power.
entry 322 - tags: ergonomics, engine, wiring | | |  | October 12, 2007 - Dyno time!
Now this was a frustrating day. Driving the car in to Flyin' Miata, I found I had a big vacuum leak. I'd folded the steel gasket between the two halves of the intake manifold while installing the VICS actuator. Thanks, Mazda, for making that one bolt so hard to access that I had to disassemble the intake! It's a good thing that FM keeps them in stock.
Once that was done, Jeremy at FM did a couple of pulls. He reported some pinging as the dyno was holding the car at 2000 rpm - a load situation that will never be seen in the real world, but still - and sorted that out, then blew coolant all over the shop. Turns out one of the fans had decided to stop working so the car got a bit hot and the radiator cap opened up. So, I spent some time fixing a remarkably recalcitrant wiring problem and also tracking down why the O2 sensor wasn't heating up properly.
It doesn't sound like much, but every time we had to stop it meant a couple of hours of delay before Jeremy was able to get back at the car. On top of that, it was obvious that the car needed a lot of dyno tuning, as the output was unspectacular. There's a big dip in the torque curve between 3000 and 4000 rpm, and the power tapers off dramatically just about 6000. Looking at a dyno chart of a similar engine, the bottom end is pretty good if you ignore a dip - but the top end prevents the big headline number from being very interesting. Because I needed the car to drive home, all the goofing around with other miscellaneous problems meant that we ran out of time. We established a baseline, that's all.
So what's wrong? Most likely the cam timing. This is an untested set of cams, and I'm not sure where they should be yet. The car will go back on the dyno shortly, and I'll do a lot of experimenting. I expect to pick up a fair bit of top end, hopefully without losing that nice spread of torque. I might also try another set of cams, the Webcam 505s that I'm running in my little 1.6 are quite impressive. Then it'll be time for a new, bigger header.
So, not the best day. But it's a start. I took the car for a spirited drive home last night, and it sure is fun to drive and seems awfully quick without any other cars around. Is it effective enough to keep up with some of the other cars at at the Targa? I don't know, that's why I need more from the engine, to give me a better tool to use!
entry 323 - tags: tuning, engine | | |  | October 14, 2007 - Autocross baptism.
I've heard the Targa described as a combination of an autocross and Solo I racing. So I'm using both types of venue to test. This autocross was put on by the local Corvette club. They allow a small number of "metal" cars to participate by invitation, and I'm usually welcome. So I brought out both the Miata and the Seven.
So how did the car do? Quite well, really. I learned that it's quite easy to drive on the autocross course, with great braking ability and a nimble feel - just what you'd hope for out of a light Miata. The car's easy to drive although I'd like a little more feedback on a locked wheel.
What I didn't expect was the inability to put down any power. Again. It's not a wheel lifting this time, but it sure does act like it. I'm wondering if the Torsen LSD is actually a Torsen. Maybe I got my hands on an open diff instead. I never actually checked inside the casing. I have a good differential in the Seven that would work well in this application, but I hate to take it out.
On my third run, I almost entered a trance and just drove around the course. No real effort was involved, the car just did what it was supposed to. The end result? A time that was 0.3 seconds slower than a rotary-powered Fiat X1-9 autocross special and a C5 Z06 Corvette - good enough for fourth fastest of the day out of a field of about 24 cars. First place was, of course, the Seven.
So, in all a very good day. The car performed well despite a real weak point and showed no evil handling characteristics. That's about all I could ask at this point!
Video now available!
entry 324 - tags: testing, other cars, drivetrain | | |  | October 14, 2007 - A study in whites.
Both of these cars are dirty, and photographed under a cold and cloudy sky. The Targa Miata is 1990-93 Miata white and the other Miata is a 1994-97. Okay, it's not that exciting. But it does show the result of the attention to colors - the Targa car pops, while the street car hides.
entry 325 - tags: paint | | |  | October 17, 2007 - So, what's the first thing you do after a successful race?
You take the car apart, of course. The shocks are going back to the manufacturer to be modified. Different bodies, different shaft lengths - this will give me the travel range I've requested. They're also going to come back with a bit more granularity in the adjustments, I believe, and I'll gain the ability to run the front a bit higher. Good, I need the ground clearance.
The next track test - a big track this time - is on Nov 3rd. They say they can turn the parts around fast enough. We'll see.
entry 326 - tags: suspension | | | October 17, 2007 - Bad news.
I'm not sure how this happened, but it's my fault. Way back when I obtained the differential out of a wrecked 2003, I assumed it was a Torsen limited slip. I'm not sure why exactly, but I jumped on this particular unit because it had the 4.3 rear end ratio I wanted. Well, now I know why I've been having so much trouble with wheelspin.
It's not a Torsen.
The car was a base model. I might have been fooled by the big brakes on it, something that was exclusive to the Torsen-equipped suspension upgrade until 2003 when it became standard. But I've been trying to maximize rear traction with an open diff! Argh. Of course, Flyin' Miata doesn't have any Torsens of any sort in hand right now, so if I want an LSD for the Nov 3rd track day I'm going to have to pull the Guru diff out of my Seven. This is a great diff and one I'd love to run, but I hate to handicap the little car to get it. I could run the track day with the open diff and wait for a Torsen to become available, or I could source a diff elsewhere. Decisions, decisions...
entry 327 - tags: drivetrain | | |  | October 23, 2007 - The Targa Miata gets mod.
MOD.07, to be exact. I fell under the spell of this gorgeous MOMO wheel a while back and finally decided to move my old crusty Champion to a different car, and treat the racer. There's a method to my madness, though. The suede grip will make the wheel easier to hold in my sweaty hands during the race, and the deeper dish puts the wheel usefully closer to my chest.
I ordered one with a silver center, and got sent a black one. I didn't realize until the wheel was already installed, and I doubt the supplier has both. Oh well, it looks good in the businesslike interior.
entry 328 - tags: ergonomics | | |  | October 23, 2007 - The newest sponsor of the team is Susquehanna Motorsports.
They're perhaps better known as "rallylights.com", as they're the best place to lay your hands upon, well, rally lights. They've provided some of their signature items, a well-stocked first aid kit, a spill clean-up kit, a light for Eric to read by, some country flags for the car and a set of mud flaps so the pretty white paint stays (more or less) clean.
They're also a supplier for Terratrip rally computers.
entry 329 - tags: sponsors | | |  | October 30, 2007 - Time to get ready for a big test.
There's a track day in Pueblo on Friday. This will be the first time I've taken the car on a "big" track, instead of the tight kart track I've been using. It's going to be interesting to see how it does.
One of the jobs to be done before heading to the track 200 miles away is to swap out of the differential. Howard Booster is building a Westfield, and graciously allowed me to borrow his differential for the weekend so I could test with a Torsen and not have to disassemble the Seven. Thanks Howard!
While pulling the diff, I discovered the source of a banging noise under hard cornering. I'd figured it was the exhaust hitting the differential. Close,but not quite. It was the exhaust hitting the flange on the two-piece halfshafts! You can see the evidence in the picture. The two piece halfshaft was never used from the factory with the 1999-05 exhaust system I'm running. I'd used two piece units because it makes it a bit easier to pull the differential, but after dropping the open diff out of the car today I've realized that it doesn't really make all that much difference! Substituting one-piece halfshafts gave me the clearance I need.
So, almost ready to go. I'm going to tow the car over so Janel can come with me. I'll pile a bunch of swaybars in the back of the tow vehicle so I can play with handling, and I'm going to try a couple of different alignment setups. Oh yes, and I have to receive and install the new suspension! Little stuff, you know.
entry 330 - tags: exhaust, drivetrain, interchange | | |  | November 1, 2007 - The reworked shocks are here.
These shocks are the ones I expect to use for the Targa. They're made by AFCO, a US company that has experience in both road and dirt track racing. They're pretty exotic and have a number of features designed for maximum durability and traction. I've been hugely impressed in dealing with AFCO so far, having a number of long discussions with the engineers about the damping, stroke and bumpstop design. These shocks will become part of the Flyin' Miata lineup, and they are definitely a custom item built to the Miata's needs.
The new shocks are quite a bit different than in their original configuration. For example, the fronts have a 2" longer body. After installing the original set, I made a number of measurements and sent them off to AFCO. From this, just about every component of the shocks was changed - the upper hats were shortened, the bodies changed in length and the shafts altered. Now I have the exact travel range I requested. I can also run the car a bit higher than I did before - not something that other Miatas will necessarily want, but it'll give me the ability to absorb all sorts of rough surfaces. Eric wants me to jack the car up to Paris-Dakar levels, but that might be a bit extreme.
One nice side effect is that they're also easier to install. Not that this is a critical aspect of shock design, but I sure appreciated it when it came time to put them in.
Today I'll cornerweight the car, then get it aligned. I'm experimenting with alignment settings that are closer to those used in Spec Miata, unlike the street-biased ones I've used in the past. The testing on Saturday will be used to determine how it works.
entry 331 - tags: suspension, alignment | | |  | November 1, 2007 - Cornerweight time.
This wasn't a very serious cornerweight session, as I'll be taking the suspension apart before too long. I mostly wanted to make sure there weren't any really major problems, and to set the ride height.
The car's fairly tall, as fast Miatas go. It's about 13.5" front and rear, although I need to recheck that after driving it home tonight.
The real question is - what does it weigh? A quick disclaimer first, I always weigh cars with a full tank of gas. Not in this case, because I forgot to fill up on the way in to the shop this morning. The car is showing 3/4" on the gauge. I'll fill it up on the way home and then add the weight of the fuel so I can get a good, comparable number.
Anyhow, with the 3/4 tank, the car came in at 2080 lbs. Not bad! It's nose-heavy, with 53.1% of the weight on the front wheels. That's okay, I'll have more weight in the trunk during the race and the occupant weight lands more on the rear than the front. I'm pretty happy with that. My target weight was 2070 lbs wet, and I'm pretty darn close.
update: it took almost exactly 4 gallons to fill the tank. At 6 lbs/gallon, that means the car is just a hair over 2100 lbs with a full tank. The final choice of sway bars will affect this, as will the installation of the rally computer - but it's a good start.
entry 332 - tags: alignment, weight loss | | | November 2, 2007 - Alignment time.
I'm trying a new alignment on this car (because I'm not trying enough other new things!) that has a fair bit of negative camber up front. I was aiming for about 2 degrees. Unfortunately, the right front wheel refused to cooperate, and the alignment tech was only able to get 1.2 degrees. Not what I was looking for! Part of this is due to my relatively high ride height, but the left front didn't have any trouble. So I'll be inspecting that area of the suspension later for problems. It didn't show up the last time the car was on the rack because I was aiming for far less negative camber and I had a lower ride height. It is odd, though, when I had the car on the lift yesterday I checked all the cams and they all appeared to have a lot of adjustment left.
The resulting setup has about the same camber front and rear while I had been planning on a slight front bias. I hope my collection of sway bars will allow me to make the car handle reasonably well. It doesn't really matter much, though, as I'm going to have to test all over again once I find my missing camber. Sigh. At least I'll be able to spend some more time on shock settings, the rest of the testing won't tell me much. Instead of a test session, it's going to be more of a play session. It's a shame, I don't have another opportunity at this track until May and it's a fairly major expedition to get there.
entry 333 - tags: alignment | | |  | November 4, 2007 - Off to the track.
It's a five-hour drive over multiple high passes, and we're leaving at about 6 pm. Makes for a long day. I've decided to tow the car for two reasons - one, we're expecting temperatures well below freezing and the car has no heater, and two, it means that my wife Janel will travel with me. It's much more pleasant.
The trailer may not look like much, but it's easy to load and tows very nicely. As it turns out, it was really good I had it.
entry 334 - tags: testing | | |  | 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 | | |
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