build diary
<< | show individual entries | >>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
September 6, 2005: 
One of the new front fender stays in place.
A 1/4" piece of steel plate is held in place by the upper bolt. I'll add a short brace to one of the other bolts to prevent the whole thing from rotating.
entry 978
The old vs new fender stay.
The old design had a slot that went over the upper bolt, it's been replaced by a hole in just the right place. Accuracy versus adjustability. The floppy straps have been replaced by 1/2" rod bent to the right shape and the ineffective brace to the upper brake mounting bolt is currently removed. This new design was also much easier to produce than the original one. I suspect the original design came from Champion's book and was never rethought.
entry 979
September 7, 2005:
I've been a bit tough on CMC for various things in the past, sometimes a little too much.
But this latest discovery? I'm not happy.
While working on the fender stays, I discovered the studded rod end used to join the steering knuckle to the upper control arm was worn. On one side, there was axial play. On the other, there was both radial and axial. In both cases the amount of play was significant. I know that rod ends are prone to wear but this sort of lifespan is ridiculous. It's not play in the pressed-in stud but in the ball of the joint itself. It squeaks too. Looking through my FK Bearing catalog - the supplier of rod ends to CMC I believe - I identified the part as a CM10Y. Low carbon steel, no teflon liner and no load rating. It's the cheapest studded rod end they sell based on their cheapest rod end. On a critical high-load suspension part! I know it was intended to be a budget kit but I made my intentions fairly clear when talking to CMC and it might have been smart to offer an upgrade. After some discussion with an FK supplier I've ordered a pair of HJMX10T rod ends to replace them. They're much better steel, high misalignment and teflon lined. They're rated at 28,109 lbs radial load versus the non-studded version of the supplied part which is rated for 9,813 lbs. Granted, they're $41 each instead of $7 or so but I'm willing to pay that for a critical part. There's no play in any of the other rod ends in the suspension and they are a better chosen M8SB with an oiled sintered bronze lining for lubrication. I'll have to use a bolt with the new rod end but that's not such a hardship.
I also checked the front camber. My driver's side wheel is running less than the passenger side. Why? I suspect it's because of a change I made at Thunderhill when a peanut gallery insisted things didn't match and so I altered one side to shut them up. It would explain the understeer on long right turns at the track though.
The fender stays are done and I'm quite happy with them. I'll have to take them for an extended test drive to make sure I haven't cut my clearances too tight, but they fit better than the originals ever did. It was embarassing to always have the fenders cockeyed before as it made the whole car look badly assembled.
And the engine? Well, it's getting happier. Bill Cardell helped me solve a stumble on part throttle by helping to synchronise the throttle plates. I had been making changes, then blipping the throttle. He told me to hold the throttle open at the problem spot and in 5 seconds he had it dialed in. Duh. Jeremy Ferber also spent some time setting up the fuel so the engine is running pretty nicely with the throttle bodies. It's still upset on a cold start but that will come.
entry 980
The new fender stay installed.
The big chunk of steel plate is aided by a piece of steel strap that hooks into one of the brake bolts. This prevents everything from rotating around the main mounting point. The U-shaped piece of round bar means that I can get a socket in to attach that bolt. I also have full access to the brake bleeder screw. Am I proud of this? Why, yes.
entry 981
The final fender stays with the new locating tab.
It's a good thing I didn't fabricate my own frame, I'd be up to photo 3000 by now.
entry 982
How to make a throttle cable do a 90 degree turn.
entry 983
The Seven looks pretty funny under a car cover.
entry 984
September 9, 2005:
I've just had a bit of a chat with Larry at Carbotech.
He had a lot of complimentary things to say about the Porterfield R4S pads I've been using and was surprised to hear that I had complaints about the braking. His theory? I've glazed the pads over in one of my early track days due to overheating. That could be related to the blued rotors in the rear. I'll try scuffing up the pads a bit based on his recommendations but I've also ordered a set of Carbotech XP8 pads. It's similar to what Formula Ford cars run and much better suited to track use. I'm a little heavier (200 lbs) but I have a bigger pad, so hopefully it'll work out.
There is a large group of Se7ens driving across the US from Houston to San Francisco. They'll be circling around my area for a few days. I'll buzz out to visit them in Durango in a couple of weeks, then run down to Moab a few days later. It's going to be very interesting to see my car surrounded by the "real thing". Of course I have a list of things I want to do to the car before then so it's in good shape. I'd like to have a lower windscreen done but that's a matter of will on my part. I also need to sort out my bouncy headlights and possibly put in a muffler that actually, you know, muffles. First job is to get the car on the dyno with the throttle bodies and see if these bloody things are worth sorting out. They look and sound very cool but they still require a bit of attention. I've also had the tires pulled off another set of 1990 Miata wheels so I'll refinish those in black and silver like the others. These will get the Azenis tires remounted although the Seven will likely stay on the RA1 tires. Janel wants the Azenis tires for track use. Hey, I'm not going to discourage this behaviour!
entry 985