| MIATA BUILD |
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 | |  | September 15, 2007 - Whoops!
The last time I was at the track, the car was pinging above 6500 rpm. We pulled out some timing, but it persisted. I think I might have found out why. Two of the bolts holding the cam gear in alignment slipped, and the intake was at full retard.
A walk down to the hardware store at the end of the street yielded some replacement bolts and the problem was fixed for just a few cents. The car should hit the dyno soon so I can get an idea of the correct timing (they were set at the equivalent of stock to start), and then I'll loctite them in place. These particular gears have spent a lot of time spinning fast on several cars and this is the first time we've lost a bolt, so hopefully it's an isolated incident. It's a good thing I have the cam cover cut, or this would have been hard to spot.
entry 313 - tags: engine | | |  | September 20, 2007 - Spring time!
The (chrome) 450/300 lb springs have come out and the (yellow) 300/225 springs have gone in. The new springs are an inch longer as well. This is the spring set I've been expecting will work out best for the Targa.
How does it feel? After a quick run around the block (the block in question is not your average city block, but includes some low speed turns with bumpy exits, some mild crests and is probably 6 miles around) it's pretty good. It's time for a sway bar of some sort though, and I need to do a back-to-back comparison with the control car. The most obvious thing is that I could probably use another inch of spring length on the front to get the nose up to my desired ride height, but it's very functional right now and I have piles of travel. So maybe I don't need to raise the nose after all.
entry 314 - tags: suspension | | | September 20, 2007 - Susquehanna MotorSports has joined the Targa Miata team!
They will be providing some of their signature rally products, such as a first aid kit, map light for Eric, mudflaps and other bits and pieces. On top of that, they'll be helping out with advice and information thanks to their long experience in the sport. They're best known for their lighting parts, and if we didn't already have a good stash of Hella lights we would have been in touch for those.
You can visit Susquehanna MotorSports at rallylights.com.
entry 315 - tags: announcements, sponsors | | | September 24, 2007 - The 2007 Targa ended a bit over a week ago.
It sounds like it was a good event, but there was one stage with a wet wooden bridge that brought tears to a lot of eyes. It's spooky, because it's the sort of conditions I can't really test or practice very well. Here's some good video of the spot.
entry 316 | | | September 25, 2007 - I drove the car in to work today with the new springs.
It's gained a fluidity that I really like. I haven't had the chance to stretch its legs yet but I'm hoping to do that tonight. I'll put on a front sway bar soon and see if I can arrange a bit of track time to test the setup.
entry 317 - tags: suspension | | |  | September 28, 2007 - Sway bar time!
I have a good selection on hand. For the front, a 23mm front bar from a Mazdaspeed MX-5, a 7/8" adjustable aftermarket bar and a 1" adjustable. The rear will be served with a 14mm Mazdaspeed bar or a 5/8" adjustable. I'm trying a different setup than I usually use to ensure the rear wheels stay hooked up on rough surfaces. We'll see how this works out. I might see if my local alignment shop is willing to work with me on this, I expect it'll be spending a lot of time on the rack.
entry 318 - tags: suspension, alignment | | |  | September 29, 2007 - I have quite a collection of end links for sway bars.
From the left, we have 1999-05 stock, a set of adjustable ones with rod ends, a pair of Racing Beat ones with bushings and stock 1990-97. I'm using the rod end style because I have a full set of four and they will allow me to adjust the length and avoid any preload. These particular ones were made with inexpensive rod ends, and thus make a slight rattling noise. It's not a problem, just a little disconcerting when driving through a parking lot.
entry 319 - tags: suspension | | | 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 | | |
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