build diary
<< | show individual entries | >>August 19, 2005:
This weekend is the Flyin' Miata Open House.
Last year, it was the Seven's first real test on a track. I was running on cast-off Toyo tires, there had been no tuning work on the suspension and the fuel pump was clogging up with bits of foam from the tank so there was a bad starvation problem. You can read about it here. This year, I'm a little more prepared and planning on going much faster.
The new Toyo RA-1 race rubber is mounted on the car. They're a 205/55-14 size. Since they fill out the front fenders so much, they really show off the poor fit of the fenders. I'll have to fix that soon. The car's run a wide variety of tires over the past year (mismatched all-seasons, worn-out Toyo T1-S, worn-out BFG R1s, Falken Azenis RT215s and now these) but I'm thinking this should do it. They're street-legal race tires and should let the car reach its full potential. I'll find out in a few hours when I head back to the track. It'll be interesting to see how it handles with the new rubber.
Some disappointing news. The Datatool Revlight that I'm using for a sequential tach is out of production. I have mine so that's good, but it's a pity for anyone else who wants one. It's a good product. The manufacturer says there was no demand.
entry 957
The Seven now has the tires it deserves.
A set of Toyo RA-1 tires in a 205/55-14 size.
entry 958
The Seven has always looked a little under-tired from the back.
Not so much now.
entry 959
August 21, 2005: 
Turn two at the track.
It looks as if the rear is going in to positive camber a little, but the car is well balanced at these speeds.
entry 960
I had the chance to watch the car on the track.
It looks very wide from behind and very stubby from the side. The black wheels really set the car off well.
entry 961
Whee! The Seven likes to dance.
entry 962
One of my fastest laps.
I was hammering this berm pretty hard but I didn't realise that I was lifting a front wheel up!
entry 963
This kind of says it all.
It's not the fastest way around the corner, but I'm sure having fun. Sevens love this sort of driving.
entry 964
August 22, 2005:
Another track day has come and gone.
How did the Seven do? Very well.
The track day was part of our Open House at Flyin' Miata, so I wasn't able to play all day. By the time I made it out to the track at noon, my fast time from a few days earlier had fallen. I did have the advantage of my new tires, though. Unfortunately, the first laps didn't show any improvement. Sure, I was under 1:07 consistently wheras I'd only dropped below that point on two laps before, but I'd been hoping for a big drop. The car was oversteering and a quick check of the tread showed that I wasn't using the edges of the rear tires. I dropped my rear pressures by a couple of pounds and the fronts by one. The pressures I were running were an educated guess based on what I'd run on the Azenis.
The second time out, times came down a bit. I knocked a half second off my time and was starting to explore the limits of the braking. The brakes don't bite very hard and take a firm push to get maximum retardation. I might experiment with pads a bit to get an intial bite back again. I might even try a set of Wilwood calipers on a custom bracket if I get really creative. But for the track day, I was stuck with what I had.
I took a couple of passengers out in the slower groups. This was partly to give them some thrills and also to keep the tires hot. I quickly remembered that the car had been set up for one person and not two - the Supertrapp tip scraped on all right turns and the car felt very different in balance. Still, I was able to have some fun.
By the time my third and final timed session rolled around, I'd learned that I had to be fairly aggressive to get the tires and brakes hot in the short warmup. We were being sent out on a 0.9 mile track, given one warmup lap, three timed laps and then a cooldown. Not a lot of time for a 1300 lb car to get a set of 205-series race tires up to temperature! My last session was a little ragged with one mistake that cost me a good lap. Still, I hit the rev limiter at one spot in the track on two laps where I'd never hit it before. I was obviously getting faster corner exit speeds. To go much faster on this track, I really need a slightly taller rear end as the straights are too short to bother shifting. Either that or I'll raise the rev limiter past the current 7500. I should have put in good springs when I had the head off! Anyhow, despite my fairly aggressive and choppy driving on my "fast laps" I managed to pull off a 1:05.585 with a 1:05.763 to back it up. That was the fastest of the day by 0.674 seconds. There's a video of what I think is the fastest lap.
One of my competitors - the coworker who drove the Seven earlier in the week - had a fairly big off in his turbo Miata and wasn't able to put down any fast times. He did the same thing he'd done in the Seven and went straight on turn one (now renamed the "Ferber straight" in his honor). At least he'd been able to gather up the Seven, the Miata ended up in the dirt faaaar away from the track. Everything was unharmed, it just took a lot of time to yank it out. Another coworker took the Seven out in a slow group and had a hard time with traffic, but he certainly enjoyed the oversteer abilities of the car. I was worried about him - he had the potential to go faster than I had!
The car behaved almost perfectly over the course of the day. On the first session, one of my front fender stays broke and let the front fender flop around. A bit of duct tape solved that problem. The suspension proved well up to dealing with some hard berm hits without upsetting the car too much but still cornered pretty flat. Looking at the photos, I suspect a bit more negative rear camber may come in handy. I'll have to do some temperature testing. From behind the wheel I was just having a ball - and that's the whole point, isn't it?
The best part of the weekend? Janel dropped 4 seconds off her time and is now asking for 1) her own helmet and 2) if we can go to a track day at Pueblo in October. We've created a monster.
entry 965
A late arrival, this is a shot of the Seven at the autocross.
entry 966
On the track, accelerating hard.
entry 967
An artsy shot of the car in the paddock.
entry 968
This is like one of those kid's games where you have to spot the differences between the pictures.
These three photos were taken on three consecutive laps. I guess I'm fairly consistent.
entry 969
Video of the Open House trackday.
In this screenshot, I'm just about to lift a wheel.
entry 970
August 25, 2005:
I've been given a few photos of the track day from various sources.
It looks as if the car is not aligned properly in the front, going to some serious positive camber on right turns. When I think about it, this is quite possible as I did have some understeer problems in a couple of those. It could also be the characteristics of the turns, but on that final right on to the front straight I never could get the car to rotate well enough. When I was at Thunderhill, a peanut gallery was telling me my front end camber was mismatched so I changed one wheel to make them feel better. I probably should undo that now. I don't want to run too much negative camber in the front as I want to retain as much braking capability as possible - maybe a larger front sway to keep the car flatter would be the best choice.
entry 971
A shot of the Seven on the track, taken by Richard Milewski.
I'm not 100% sure the horizon is straight, but look at the angle of that front wheel! I'm thinking a larger front sway bar and some more time with a pyrometer might help the Seven pick up some speed. This is the last corner before the front straight and I did feel that the car was understeering.
entry 972
Another cornering shot by a professional photographer.
Interesting, the positive camber problem seems to be less pronounced on this left turn. The car felt better as well. Is this due to the driver's position or a problem in my setup? Good question. Wear patterns and photos make it look as if the car is less bothered in left turns and it felt better planted.
entry 973
August 31, 2005:
Ahh, a life that isn't constantly working on cars.
Janel and I spent the weekend exploring the backwoods of Colorado. It's nice to get away sometimes. Of course, I had to put new tires and brake rotors on her Jeep first, and I was up late the night before realigning the front of the GTX. But still...
There is a large group of Sevens undergoing quite a trip. A couple of dozen cars were loaded into containers in the UK and are currently on the way to Houston. From there, the drivers will travel to Los Angeles via a circuitous route. They'll be spending about 5 days near here so obviously I'll be there to join them. It should be huge fun. I have a bit of work to do to get ready, though.
The first thing to do is to fix the fender stays. I've spent some time looking at my spare spindles and I have a few ideas. I don't know what will work best yet but I'm getting closer. It sure would be nice to have a car with fenders that fit consistently. I might also raise the headlights up a couple of inches to clear the fenders, as this is part of what pushes them off their alignment.
I'm also eyeing the individual throttle bodies that I tried in the past. At that time, I had some weird driveability problems due to unsynchronised butterflies and a very strange electrical problem. The former is fixed so I'm willing to give them another shot. This would also allow me to put a bit more bracing in the engine bay. First I'll find out if it's worthwhile from a power standpoint.
One thing I forgot to mention about our track days recently. At the kart track, many of the turbo Miatas were having trouble with cooling. The Seven? Steady as a rock at 94C, right where the thermostat opens. It looks as if the smaller rad with some good ducting might have worked just as well and prevented a lot of hassles.
entry 974
September 1, 2005:
I wandered back into the garage with the intention on jumping on a bike and heading out to the movie store.
Instead, an hour later, I was finishing the installation of the throttle bodies on the Seven. How does this happen? No matter, it was more fun than any movie would have been. The car fired up and there were no leaks. It's running rich - that's what happens when you put in 240cc injectors to replace 210cc ones and don't change your tuning - but it idles properly and sounds great when I blip the throttle. I'll drive it around a bit without a hood to see how it's behaving before I commit to having a hole in the hood.
I also spent some time looking at my fender stays. I can see about four ways to attach the new ones. All I need to do is decide what the best one is! I'll probably mock something up with welding rod, but one I start bending parts it should go quickly. I should also be able to move the fenders outboard a bit, giving me a better fit over the tires and cutting down on the headlight/fender interference.
entry 975
September 2, 2005: 
The throttle bodies are back on the car.
Will they stay this time? Hard to tell at this point, first I need to see how well they work out.
entry 976
September 5, 2005:
During the long weekend, I spent a few minutes here and there working on the Seven.
First, the throttle bodies. The first drive, the throttles started sticking open as things got warm. I thought I had enough slack in the cable but apparently not. The next sticking problem was solved by giving part of the linkage a little tweak. Now it idles happily at 850 rpm just like a "real" Miata engine. Well, almost. When it's cold, it's not terribly happy to idle. Part of this is due to the lack of any idle speed control valve and part of it is due to some fairly rough tuning at the moment. On the road, though, it runs reasonably well. Doesn't want much fuel, though. Hmm. Am I that far off on the correction for the new injectors or is the car not making much power? The dyno will tell. I know right now that the car is making some very cool induction noises.
I did discover one problem that had been driving me nuts the last time the throttle bodies were on. Every time I saved any changes to the ECU, the car wouldn't start up. This time I decided to hunt down the problem. Finally, I plugged the old throttle position sensor and idle speed control valves back in. Problem solved. The ISC makes some clicking noises so maybe that's what the problem was. Very odd.
Tonight, I decided it was time to do something about the foolish fender stays. The only time they've ever fit properly was on the first drive out of the garage. The front fenders hit the headlights at lock, they would move around on every drive, various parts of the stays would break and it was a pain to both install them and bleed the brakes. Those who have been reading for a while will know how much reshaping I had to do in order to make them fit in the first place. So, after they broke again at the most recent track day, I decided it was time to stop screwing around with the poor design and build something better from scratch.
I took inspiration from this Stalker build and picked up some 1/2" rod. It was easy enough to bend in a vice with a bit of leverage and after a bit of thinking, I figured out a simple way to make it all work. I still need to put a short stop on them to keep them from rotating around their mounting bolt but I'm very happy. The design is cleaner, much easier to install, leaves lots of room for bleeding the brakes and looks good. They're also much more solid and the fenders now clear the headlights and provide a little more stone protection. The downside? The new ones are 2.50 lbs instead of 2.30. That's a sacrifice I'm willing to make.
One last thing - while playing around with these, I found the rod ends used on the upper control arms were wearing. One side had axial play while the other had both axial and radial. Now, this car has seen a fair bit of racetrack use. But these must have been some pretty junky rod ends to start. I'll order some decent ones tomorrow and also replace the studs with bolts.
entry 977