:. Racing .:. 2005/04/21 - IMI Test Day
Results: *none*
Testing!
After a lot more changes from the last autocross, I felt I needed a bit of a test day to go into the next Solo2 2-day weekend with a bit more confidence.
The major issues at hand were the awful off-idle bog I've been getting trying to launch, and needing to scrub in the new R25A tires, and see if they were going to have any issues. If there was any extra time, we'd fiddle with setup a little bit and see if there was anything to learn running shagged R35 tires.
Rolando was my dutiful crew/helper again, and we headed down to IMI around 10:30, and arrived there about 11:00. Weather was perfect Colorado spring weather. 65* ambient, and mercifully, no wind. IMI is a smallish Kart track east of Erie, and as such, it makes a pretty darn good simulation of the kind and frequency of turns you experience solo'ing. Plus, at $25/day, it fits within my currently hurtin' budget.
As Carroll Smith teaches, I went out with a very solidly defined testing plan, and I was able to get all the issues I had set for myself sorted out - it was a nice feeling of accomplishment. We wrapped up around 3:00, so it was nearly 4 hours and about 50 laps worth of seat time, experience, and test-data. We beat the rain home even, so great stuff.
The first set of laps out, I did with the car in its "existing" configuration, after having not done much except to reduce the front toe-out from nearly 1/4" total (!!) to 1/16, and having lowered the front another 1/8" of a turn since the last solo, to get to around 3/8" of rake. No big surprises - maybe a bit less understeer, but that was about it. Brake bias was definitely "off". Water temps were in the 160's, oil in the 210's all day - perhaps a tad higher than I'd like, but given the high RPM running in mostly second gear at lower speeds, that's not too bad.
I feel like I may be chasing my tail with the bias, which is probably going need to change again when grippier/new tires go on the front. One nice part is that by moving the brake pedal out a bit more, and having moved the gas pedal down, I can now heel toe just how I want to - thanks NASA Racer!
After that, since it was an easy/known thing to do, we mounted up the R25A's on the converted 8" and 10" wheels. First impression? The wider wheels look MEAN on the car. Very cool! How did they feel? Well, I stayed fairly gentle on the new tires, but the car's balance was a fair bit different. Much more front grip relative to the rears, although I'm not sure how much of that is attributable to the fronts being brand new, and the rears being at least a month or so old. Hopefully the imbalance will not be too great for effective autocrossing, or it will at least moderate with time. The wider wheel felt like it helped turn-in quite a bit, so I am happy. Experience and advice both indicate this will be very good for solo. I think the wider wheels will make the car a good bit faster - I'm curious to see if they would pay off in a road racing venue too? Who knows. I'll wait to find that out until I'm a good bit better at road racing speeds.
After a couple easy laps, then a few at about 75%, and one at nearly 100%, we took the car in, and put the R35's back on, since the next item on the testing list was to play with the carburetors and see if we could solve the launch bog.
Over the last weekend, I took the idle screws and moved them *all* the way in to try and lean things out, and it seems to have worked - the car had no stumble/bog/etc all day - just a tiny bit of a hesitation when I tipped in the throttle too much at around 4-5K, but the car pulled right through it, instead of bogging down and sputtering continuously. May be I just tipped in too much throttle at low revs, which is a consequence of the flatslides, I understand.
The idle seems much "sharper" with the leaner mixture, so I think it may be in the "good enough for now" category. Ultimately, I'll probably put in a smaller pilot jet, so I can get to the proper "1-2 turns out" screw location, and then see about dropping down a bit on main jet sizes if I'm running much too rich currently. I'll try to enlist a carb-knowledgable friend for doing much in the way of jet/needle/main jet changes though. My kingdom for four fuel injectors!
So, having solved the gross issues, we turned next to the pyrometer to get some baseline setup numbers, and to play with my new pyrometer (Thanks Ma! <*grin*>). For both sets, I did about 8-10 laps, and we got some numbers. I'm not 100% confident in the rear numbers, since we had some consistency issues, but here's what we saw:
Session 1:
|
LF |
RF |
LR |
RR |
| Inner |
132 |
123 |
141 |
148 |
| Middle |
152 |
136 |
133 |
149 |
| Outer |
129 |
122 |
114 |
135 |
| Pressures |
18 |
18.5 |
19.0 |
19.5 |
Session 2:
|
LF |
RF |
LR |
RR |
| Inner |
122 |
128 |
143 |
148 |
| Middle |
143 |
145 |
130 |
149 |
| Outer |
127 |
116 |
116 |
132 |
| Pressures |
18 |
19 |
18.5 |
19.5 |
As I mentioned, IMI is a very tight Kart track that we ran counter clockwise. Lots of camber/bank to the turns, and a lot of elevation change. There are tight corners in both directions, in about equal numbers, so one would expect *fairly* equal temperatures, especially as there is a hard RH sweeper with a hard LH sweeper right before the pit exit. I attribute the overall higher rear temps to the fact that they have a lot more rubber left than the fronts.
So, my conclusion from this is that it looks like the fronts need just a bit more camber, the RR may be about right, and the LR may need a bit less, and I may also reduce its toe to 1/32 to match the RR, when I do go ahead and make those changes. I'm trying to decide if it seemed like the car had more understeer to the right than it did to the left - if so, that would corroborate the LR camber being too high, as well as the rear toe-in being excessive. Since I *think* the camber measurements were about -1.25* front, and about -0.75* rear, needing a bit more front and a bit less rear matches with the -1.5 and -0.5 settings I've been told are a pretty good balance. Again, I'll see how things feel with the R25A's, and act accordingly from there, and see if I can get a camber reading I'm a little more confident in as well.
For a baseline though, this doesn't seem to be too bad, although the occaisional very hot crown numbers seem odd, since the pressures are almost exactly where they should be, according to the wonderful guys at Hoosier. The slight inconsistencies in the readings are curious too. As a result, I don't think I'm putting 100% confidence in these numbers yet - perhaps some more numbers from this weekend's Solo'ing will help with that, and give a reasonable idea where to head in that regard.
Brake Bias: To help the front-heavy brake bias on the car, I moved the bar 1/2 turn towards the rear, and that seems to be the best balance I've felt yet. Braking was much less dramatic this way. I really wish I had a dash adjustable handle. I am getting better with the braking feel though.
Shocks: to get a feel for the shocks (currently set at full soft on all adjustments after the awful beating I took at outing #2), after we got our temps, I set the bump settings to 3/3, and took a few more laps. Turn-in was much sharper, with no perceptible reduction of corner-exit power down. The car definitely rode much stiffer, and I felt the bumps more, but did not feel as if the car was being upset over the bumps. I'll have to evaluate this more at the much-more bumpy DIA lot and see how that works for that venue. Maybe the front will want to stay high, and the rear will want to go back to 1? No idea - more testing is necessary here, on some good tires.
Ride Heights: I had no rubbing issues on bumps etc, so I may be able to go lower with the car, down to about another 1/4" or so, to get to the ~2.0"/2.5" working-low I've been told by the Radical guys. Again, this will depend on bumps/gaps/patches/etc at DIA, so I'll have to see how much lower I can go, and at what risk.
Engine Pressures + Gauges: I took a look at the oil pressure at the end of the big LH and RH sweepers - looked good - high 50's at around 8-9K (I think). Having trouble seeing it though, so the need to either move the dash or get a chop-top wheel may be in my future. Still need to build a foam insert for myself so I'm not using towels to stay properly "inclined".
Gizmos and Widgets: the no-lift shift box needs some fiddling, as the actual shift and the engine cut seem to have very little relation to eachother. I just turned it off and shifted with a bit of a lift and clutching some for the 1-2 shift for most of the day, and it worked fine. Not sure how much time I'll devote to getting it set up right - it just doesn't seem very necessary to me? The Digi-Gear gear indicator remains entirely schizophrenic too - it basically chooses a random number between 1 and 6 to display as the gear, although I doubt I was able to get it correctly programmed. Not really sure where I'm going to find a straight long enough to get it programmed, honestly. I'm learning to keep track of things in my head anyway, so I doubt this will be of much consequence either, as I get more accustomed to the car. I do wish it just had a nice gear readout like the Suzukis do. *shrug*
Just for grins, Ro timed me on the stopwatch on one run, and it was around a 59.1 or so. I've no idea how good or bad that is though. Only took me about 3 laps to catch one of the bikes out there, but I suspect a good driver in a kart would be much faster than me.
So, for next time: I'll watch the camber at the autocross, see how the new R25A's feel, and based on balance and temperatures, decide what to do with the alignment, ride-height, and suspension settings. Based on bumpiness, I'll see where the bump adjustments want to be, and if they want to be different F/R. I think that's about it for now...we'll see how things are come Monday after the next 2 races!
NEW CHANGES:
- carb tuning (leaner idle mixture)
- 1/8" lower in front
- Set front toe (roughly 1/16" out total)
- Measured Alignment (not changed from as received): -1.25?/-.75? Toe: 1/16"out F, 3/32 in rear (2/32 on LR??)
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