build diary

August 16, 2005:
Thank you Supertrapp!
The sound testing was an interesting process. The way the muffler works is by simply diffusing the sound through a set of discs. The more discs you use, the less muffling goes on and the louder the car is. It seems a little counter-intuitive at first until you realise you're basically opening up more area for the exhaust to escape. Unfortunately as you remove discs to quiet the exhaust, you also increase the backpressure. According to Supertrapp, 24 discs is approximately equivalent to no muffler at all with regards to backpressure and I suspect also with regards to silencing.

The first time out, I set the Supertrapp up with 12 discs. It's the most I had. I wanted the worst-case scenario. After a couple of laps I came in and the track owner looked concerned. Obviously I was too loud.

For the second test, I used 6 discs. This made the car noticeably quieter. I came back in after one lap and the track owner told me he wanted a few more samples. I was to go out and lap the track until he waved me in. Sigh, the hard work I have to do for this car. After about 5 laps, he had all he needed. The 6-disc setup knocked about 7 dB off the peak. Excellent. Since the track owner is also a car nut (why else would you do it?) he wanted me to put some discs back in for maximum performance. Oh well, if I must.

The next test was with 9 discs. I let Bill Cardell take the car out so I could watch it. Well, that was the plan. We were also testing transponders so it was suggested I take out the supercharged Miata so we could check how they worked. The Miata had already come in with overheated brakes and was not set up well for the track at all, so I decided to simply play around. I'm sure the noise peaks from that car came from the tires instead of the engine as I practiced my sideways driving. Hee hee!

While I'd been hooning around in the Miata, the Seven had shown itself to be borderline for sound. So we took out one more disc (to 8) and I went out one last time. I also had three transponders stuck on the back of the car. The sound levels were perfect so I just stayed out to play. The car was right at home - the front end stuck well once I sorted out my entry speeds and the slow track (almost all second gear) allowed me to steer the rear of the car whenever, wherever I wanted. The soft springs meant I could still hammer the berms without upsetting the car but the sway bars kept it flat on corners. There are no high speed corners on the track so I couldn't check out the behaviour at the limit, but for a kart track it's a good little car. The transponders showed that I was lapping fairly consistently, ranging from 1:07.234 to 1:07.888 over four laps. Not too bad considering I'm still learning the track and trying different things. The LED tach worked perfectly, allowing me to judge engine speed easily and also acting as a speedo of sorts.

Do I have a great job or what? This sound testing was done in the middle of the day when I was supposed to be at work. Not only was I allowed to go, but my boss came along to play as well. We'll be going back tonight with the others from the office for more "sound testing". Whee!
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The datalog from the sound testing.
You can see all four of my test sessions with nice quiet periods in between. The limit at this track is 95 dB. The sound meter could also export a wave file of a peak, giving some nice recordings of the Seven on the track. Cool.
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August 17, 2005:
More "sound testing" at the track.
Last time was legit, this time was just a chance to play. A few Miatas came along, ranging from Janel's supercharged car to a couple of turbo monsters - and one frustrating little naturally aspirated car with a sick motor that beat a couple of the forced induction cars. It was good fun with a bunch of coworkers. Personally, I dropped down to a 1:06.818 - that's about 3/10ths slower than the fastest car at last year's Open House. That driver isn't coming this year so hopefully I'll be able to take the top spot. The Seven proved to be both solid and fun and I spent most of the lap in a slide and giggling. In the middle of one of my fastest laps, I decided that all the work had been worthwhile.

Interestingly, a coworker took the Seven out (after many subtle hints on his part). He found it a little abrubt in the transition to oversteer and had the front tires go off on him after about 5 laps or so. Neither Bill nor I had the same problem. He also complained about the same thing in his own car so perhaps it was driver-related.
entry 955

More "sound testing".
The Seven and a few Miatas dropped by the track for a little more fun.
entry 956

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.
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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.
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On the track, accelerating hard.
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An artsy shot of the car in the paddock.
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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.
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Video of the Open House trackday.
In this screenshot, I'm just about to lift a wheel.
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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
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