build diary

August 22, 2005:
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

September 11, 2005:
Horsepower!
Finally, I put the Seven on the dyno. The car was not happy about the idea and did its best to convince me to rip the throttle bodies off the car and throw them away. But I'm either stubborn or a slow learned, so I did it anyway. My first run was underwhelming - 109 hp with lots of black smoke. About this time, Bill dropped by the shop to help out. So the car decided not to restart.

We eventually figured out a couple of things. One, something had been scrambled in the ECU during one of my program saves. And two, we eventually realised that in order to start, the car wanted a throttle position sensor plugged in and set so that it was off idle - but only if it wasn't hot. I can't explain that one but it got us to the point where we could consistently test the car. Bill sat down with the laptop at the dyno and started plugging away. The new injectors have a different response time than the stock ones, so while he was able to quickly able to dial in the lower load ranges by leaning out the overall fuel settings. It took a while to stuff in enough fuel to make the high power ranges work. Eventually he managed to get it rich enough (the injector response was radically different, not just a little) and the car made 146 hp at the wheels. See the dyno chart. That's the most this engine has ever produced by a fair margin, and I suspect I'll be very happy when I get the car back on its wheels. As an added bonus, the throttle bodies will (once the hood is cut for clearance) give a colder intake charge instead of the hot underhood air it's been breathing. It's quite possible that I'll find I have 20% more power on the track. Well, I'd like to think so anyhow. I'm still planning on testing the car with the long trumpets to see what difference that makes.

So what was I doing while Bill worked on my car? Helping of course. But I was distracted. Janel was also at the shop and we were stripping down two sets of wheels to be repainted. Apparently you lead an exciting life if you're a friend of mine.

Oh, and one more cool thing. Because the ECU doesn't cut fuel on closed-throttle deceleration (no throttle position sensor, it doesn't know what's going on), the Seven now shoots flame out the exhaust. Hee hee!
entry 986

September 12, 2005:
More horsepower.
Well, just a little bit. It's hard to say what the peak power is because it jitters around at the top end (mostly due to the way the dyno works) but it's definitely in the high 140's. Not bad for a 1.6! This evening I spent a bit of time comparing the short vs long runners once the fuel was dialed in a bit more. How did it do? Well, you can see the chart here. Red is the long runners, blue is the short. The long runners idle better and make a definite difference in the midrange. Right at 5000 rpm it sucked up a bunch of fuel and had to be fattened up. Above 7000 it got rich with the long pipes and was probably not flowing as much air, but it's a bit tough to tell from the charts how much less. I'll take 4 lb/ft in the midrange over a couple of hp above 7000 rpm though. This means I need to hunt down a new air filter. ITG makes one, hopefully I can find one somewhere.

So, almost time to put the beast together and drive it! Well, I'd like a hood before it goes too far. I'll build some solid motor mounts for the car tomorrow before cutting any sheetmetal. This will keep the intake from moving around as well as the exhaust. The car already has everything else bolted up solidly including the transmission so it's not a big deal.
entry 987

It seems that one of my tires has been chewing on the emergency brake cable.
Maybe I should tie that back.
entry 988
The Seven strapped to the dyno to see how the throttle bodies.
How did it do? See the dyno chart.
entry 989
A new music video starring the Seven.
Hey, I needed to spend some time exploring Premiere. It's a big file.
entry 990
Still on the dyno, testing different length runners for the intake.
entry 991
Short vs long runners.
entry 992
<< | show individual entries | >>