Monthly Archives: June 2008

Another race in the books

My latest race writeup is up and posted from this weekend’s event
at La Junta. Quite an eventful weekend, to be sure!

Car Updates

Lots of updates to report on for the car between this race and last, which I’ll get to as I have time, including:

  • A new front splitter setup
  • new tire sizes & compounds
  • rerouted brake bias cable line
  • new APR Performance rear wing elements

Technical Redux

Thought I would distill some of the measurements/knowledge gained from this weekend of racing, various changes, etc:

Experiment #1: Wooden front splitter

This was a huge success. No loss of straightaway speed relative to the Radical fiberglass splitter. Had several “offs” and it emerged 100% unscathed. I have some slight rubbing on the bottom, but even at 1 7/8″ front ride height (the Goodyears are shorter than the Hoosiers, no wear to speak of. I’m stoked. Length is 24″ from bulkhead to front of the car, with a small angle cut out for tire clearance, width is 60″. Three “jiggle strip” brackets of .090 aluminum to hold the nose down. Weight is about 13# per, and cost including brackets is about $50 apeice. This is good value.

Some details of the construction: I used 5/8″ plywood, and for the shape, traced the profile of the existing Radical splitter. The length from the front of the tub to the end of the splitter is 24″, which I chose because that means I can get 2 splitters per sheet of 4×8 plywood. The splitter is fastened to the bottom of the crushbox with countersunk socket-head bolts, with tinnerman washers (from Aircraft Spruce) to spread the load. The jiggle strips holding the nose down are .090 aluminum, bent in a “Z” with about 3/8″ rise, and 2″ in width. The center one is 10″ long, and the two sides are 5″ long. Two Dzus fasteners hold the corner of the nose in. A can of black spraypaint finished the job.

Experiment #2: Larger front tires

Also a big success, back-to-backing 20x7x13 Hoosier withthe 20×7.5×13 Hoosier. The car was immediately faster, by approx 1.0 sec with the larger front tires. Difference was in corner entry and mid-corner speeds, according to the data, I could really haul ass into the corner, crank it down to the apex, and then go nuts with the throttle on corner exit. Big difference.

Experiment #3: Goodyear vs Hoosier
At least between these sets of tires, the Goodyear R160’s were clearly faster than the R35 Hoosier was. Higher corner speeds everywhere, and they were wearing better for me as well. Tire temps were about ~20-30* warmer with the goodyears, but everything was still cool enough to indicate I might even be able to get away with R25’s, even though it was nearly 90* outside. Further testing to determine, but for now, the GY’s were definitely quicker.

Experiment #4: APR Performance wing elements

A qualified success. Significant additional drag, but significant additional grip. Net laptime gain of approx .5 to .75s on a pretty straight track. I continued to reduce wing angle throughout the weekend, and picked up a few of the lost MPH on the straight. Traces under the suction side of the wing (courtesy of somebody with an oil or water leak ahead of me) show airflow separating on the odd “flat” portion of the APR main element profile, so I may try one of their normal “non-cambered” wings that has a more traditional shape to it, and perhaps that will be more efficient, while still providing the additional grip. Corner speeds were way up from a month ago – 5-6mph in 80-100mph corners. The elements I’m using are their 7.5″ and 5.5″ elements, with a small bracket to mount to the existing Radical uprights.

Misc Other Tidbits

  • I ran the car low on fuel for the first time, and experienced fuel starvation with a significant amount of fuel left in the tank (i.e. at least 2 gallons). This is with a Fuel Safe collector in a ~8 gallon fuel cell. I’ll eventually move to the “fuel pot” method that others have used to correct this, but for now, will just continue running the car tipped up with fuel.
  • Put some hi-temp paint on the rotors. Burned the 800* paint, but not the 1200* paint. Anybody else ever tried this?
  • As mentioned above, I ran the car the last day at 1 7/8″ F, 2.3/8″ rear ride heights, with no ill effects, on 450/650# springs. Was surprised to find this when arriving home, but it worked quite well, so I’m leaving the car where it is for now. Mild rubbing on the bottom of the front ~1″ of the splitter underside, but that’s it.
  • I relocated the brake bias cable with the Tilton 90* fitting, to prevent the cable from binding on the clutch. This IMMEDIATELY improved brake feel, so that had to have been causing problems. I was able to brake later and deeper at IMI, and all weekend at La Junta. Once I had the bias set, the car feels great on the brakes.
  • The Digi-Gear is still unreliable, so I am going to go to absolute basics and power/ground it directly off the battery and see if it will work then.

Survival

Race 1 Highlights from Paul’s Radical – 24MB

Race 1 First laps – from Lawrence’s Cheetah – 23MB

Time for our second race of the year, back to La Junta for some more fun in the sun. We loaded up Thursday evening and began the shortish trek down to La Junta. I caravanned with Mark Baer from SCR this time, since he had gamely – or foolishly – agreed to help crew for me on the test day being offered. Also on board was my new girlfriend Angela, who had bravely – or foolishly – signed on for a weekend of racing. The tow was pretty much  uneventful.

Friday Testing

I had a pretty big test plan cobbled up for the weekend. I had my new front splitter setup to test, new tire sizes and compounds, and a new rear wing to try. Also in need of doing was getting the brake bias dialed in a bit, since it’s been troublesome since installing the bias cable – long story.

After a few baseline/installation laps, I began playing with braking and brake bias. It was clear right away that it was still far towards the rear. With Mark watching from T4, I kept dialing it towards the front. Highlight of the morning was a snap-spin at 130mph when I was hard on the brakes over the big bump at the entrace to 3. The car did two complete rotations, and before it came to a rest I had it back in 2nd gear and set off towards T4 again. Who says video games don’t help?

After getting the bias set up about right, and squaring off some old tires, I came in and we swapped to some newish Hoosiers in the same size I’ve been using, to establish somewhat of a baseline. The track had received some new asphalt, and was very dirty from disuse, so I figured that a basline from a known previous configuration was important.

I went out, and set some times, the best being a high 52 – about 1.5s off my best from last time, but at least a marker to use for comparison. The front of the car was feeling a bit darty, so we checked toe and found 3/8″ (!!) of toe-out. Reduced this to about 1/16″ of toe, and that problem was solved. That will teach me to “just figure it’s OK” and not check the toe before the weekend…

Due to the car still feeling quite nervous at the rear, and under the brakes, and because I was excited to try it, we installed the new rear wing with the SWAG angles I’d put on with the endplates – this turned out to be about a 2* AOA on the mainplane, and about 25* (!!) on the flap. The results were pretty cool – about 6mph loss on the straights, but a .5 to .75 improvement in laptime. Hot damn! Not bad for a first try, and I spent the rest of the weekend dialing the wing back to try and reduce the drag.

Next change was to stuff the 20×7.5 Hoosier “under” the front of the car. This change was also for the better, nearly 1.0s improvement. From the data, this appeared to be almost all in mid-corner speed, since the car had so much more front grip to really crank it down to the apex. Really cool to have two good, positive changes one right after the other.

So, front splitter was durable, larger front tires a clear success, and the rear wing a good success, and certainly a confidence builder. The car went from evil, twitchy, and slow, to absolutely planted, lots of grip, and much faster. Some of this perhaps the track cleaning up, but I was feeling very confident in the car now, and felt that a very drivable car was going to be necessary with the crowded track for the weekend.

As for the others, Grant Barclay was present in his newly reassembled Stohr CSR. He came back in after one session covered in dust and as wide-eyed as I’ve ever seen him. A snap-spin in Turn 1 (110mph) and subsequent trek through southern Colorado desert had him pretty excited. Perhaps PSR is for “Powdery Sand Racing”? Pat’s Stohr was also extremely nervous out on track, with him mentioning at one point “Oversteer? Yeah, I got oversteer. Hell, I’m getting loose coming out of the trailer.” Ultimately the problem was solved for both him and Pat by a toe adjustment, and they started to settle in a bit more with their new cars.

Saturday

Our field was pretty good for SR – 6 cars split between CSR and DSR, in our unoffical PSR (aka “Pre-Stohr Racer”) community. As expected during the practice session, clear track was hard to come by. I did manage a 51.080 in the cool of the morning, just about 0.1 off of the CSR record, so that was encouraging. My work from Friday paying off! The rest of the PSR gang had upped their game as well, with Paul and Lawrence dipping into the 51’s as well. The session was plagued with CF’s and FF’s rocketing off the track and miscellaneous contact. When two SRF’s got together, I came off to avoid the tow-truck circus. Paul had some minor contact with the Anson SuperVee, but no major damage to either car. Definitely a reminder for us that racing can sometimes involve some mistakes or miscommunications.

On the lighter side, John Deere stickers appeared on Lawrence’s Cheetah and Pat’s trailer in honor of their Agricultural exploits at the past race meeting. Current suspects are a certain Spec-7 driver, or perhaps Pat himself, running some misdirection. IH and Kubota stickers are expected at the next gathering….stay tuned.

Saturday Qualifying

Qualifying was much cleaner, and relatively uneventful. I was having fun chasing Paul and Lawrence, and flying around all the FF’s, getting a feel for who used their mirrors, and for whom the mirrors are purely decorative. As things warmed up, or perhaps driver was a bit off, I qualified with a 51.5, which was good enough for pole, about half a second clear of Paul with another 51.9. Lawrence qualified 3rd in the Cheetah.

Saturday Race

The Saturday race was reasonably clean. I brought the field up extremely slowly, knowing that I still had a drag issue with my new rear wing. I figured if I could get to Turn 3 at a much lower speed than normal, the others wouldn’t be able to drive by me on the straight. The strategy worked. Lawrence and I got an excellent jump on the start, and Lawrence slotted in behind me, 2nd, with Paul 3rd.

Joe mugged the Anson in with his big 1400 SR4, and the race was on. Lawrence stayed large in my mirrors for about 5 laps – neither of us gaining or losing any ground. Fantastic fun. Lawrence suddenly disappeared, replaced by Paul. As it turns out, Lawrence clouted the huge T6 curb, and bent his RF upper control arm. Paul stayed behind me for another lap or two, then spun in 3.

After that, messes started happening, with a few cars off here and there, bringing out the wrecker. Allan in the SuperVee had a huge wreck with a spinning FF at the exit of T7 – all I could see was a huge dust cloud, and a broken rear wing and rear corner off of his car. I carefully threaded my way through everything, keeping an eye for anybody in my mirrors. Two laps from the end, I saw Joe some distance back, but he wasn’t close enough to mount a challenge, and I took my 3rd overall race win. No lap record, but a slew of 51’s, with a best of 51.340.

Postmortem on the race was a bit grim. Lawrence had the aforementioned control arm issue. Paul’s starter was working only intermittently. Both Grant and Pat had discovered cracks in their lower rear control arms, and had not run the race as a result. Joe had some more damage to the “FrankenFront” on his SR4, but seemed pretty sanguine about it. No major issues for me, just swapped to the Goodyears to see how they’d be.

Sunday

Sunday practice was a bit cleaner than Saturday – everybody had shaken off the rust, I suppose. I felt immediately on the Goodyears that they car was much more stable, and felt like it had a LOT more grip than the R35 Hoosiers I had come off of. I clicked off a 51.1 and knew there was more time, so I did some analysis afterwards of my driving to find the time I had left out there. Ultimately I decided that I didn’t need to brake as much for 3, needed to carry more into the entrace of 4, really nail the apex at 5, and brake a bit early into six so I could be flat out *through* it into 7.

The analysis worked pretty well – I really tried to hit my marks in Qualifying, and turned a 50.520, about half a second under the track record, set by a tunnelled 1500cc Speads. Boy did that feel good, and man alive did the car feel fantastic. Maybe the tiniest bit of corner-exit understeer, but throttle balanced that nicely. Again, the car was very confidence inspiring to drive, no major quirks, just rotating and turning nicely.

I knew that time would be good enough for pole, but I did two more 50.x’s on the dash to make sure I could repeat it, and came in to save the tires.

Sunday Race

The Sunday race was chaos. Joe qualified second next to me, with Paul 3rd. Lawrence had broken his gearbox, and had packed up to head home. Grant and Pat were back it it, 6th and 8th, respectively, still getting used to their cars. Grid told us that the track was breaking up significantly between 4 and 5. I gave it a good looking over on the pace lap, and sure enough, the new asphalt was coming up and tearing apart quite badly. Yeuch!

I brought the field up very slowly again – 6K in 1st gear – knowing from last race how good Joe’s engine is on the straight. Paul and I both got an oustanding jump off the start, Joe accidentally in 2nd gear for the green. Paul barely got around Joe by T3, and proceeded to lock himself on my rear wing. Carnage started early, Joe and several others going off the outside of 5 due to the surface problems. I parked it in 4-5 to make sure I didn’t fly off, and still barely made the corner. The race became a series of sprints around to 4-5, followed by tip-toeing through the gravel – laptimes were 2-3 seconds off the rest of the weekend. So much for setting a new record!

Paul got by me about 5 laps in after I came into 4 a bit hot, and ran wide into the gravel. I took a slow exit, and he pulled right up, and drafted by me on the straight, taking advantage of a few FF’s to get a nice 50yd lead for a few laps. It took me a while to reel him back in. He made a brief mistake braking into 4, and I got by, but foolishly tried to go around the outside of him on 5, and nearly fell off the track in the marbles. I was at about 20mph and barely managing to keep the car pointed straight ahead. I chased Paul back down and got by again in 4 when he spun, I think, and marched off into the distance. My GOD is it fun racing with somebody like that – what a thrill!

Grant had pulled off very early with no drive, and by this time Pat was at pit-out, having pulled off smoking heavily. After getting by Paul, I came around next lap to Grant frantically waving his arms, and barely caught a double-yellow – Paul had been unable to restart his car, and was 90* to traffic in the middle of 4 (PSR = Paul’s Spun Radical?). I snuck by on the inside and resumed, and then drove relativley cautiously to the finish, since nobody else was left to chase me.

Thereafter, I had only a few close calls with inattentive backmarkers, including a narrow miss with the troublesome white FF on the outside of 6, and a newly graduated FC forcing me to put two off on the inside of 5. No biggies though, and good fun to get some more practice passing. Finally, the race was over, and I took my second win of the weekend, win #4 for me in racing. Woo hoo! Methinks I’d better enjoy them while they last, since the others are coming *strong*.

Summary

All in all, quite an eventful weekend. Unfortunately, not the best for the PSR group, but it is the 1st year for everybody else, and things will improve. We are getting glimmers of a close, competitive group, since almost everybody is showing signs of being very closely bunched. Should be tremendous fun when we all get our cars sorted out.

The only big thing on my list for now is to try and get more drag back out of the car while keeping the excellent grip. I am eager to try the new setup at Pueblo, since it should really be worth some laptime around the more numerous, higher speed corners. Perhaps 5 and 6 might be flat out with just the right lines? We’ll see.

Until next time!