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:. Racing .:. "HPR May Daze" R/R

Lost in the Woods

With the schizophrenic state we know as Colorado finally doing its best to shuck off the cold of winter, it was finally time to head down to High Plains Raceway to begin the 2010 season. Thus far, a spate of bad weather and bad scheduling had prevented us from getting out more than just once for a test day to try and shake down the car from winter updates. Chiefly, I was really interested to fiddle with my homebrew Dauntless rear wing configuration, and see if it was better/worse/same/who-knows as my previous setup using the same Dauntless wing, from Jaremko's 2008 Runoffs effort. So, the weekend would be primarily a long, protracted test session, to see what I could discover. With no other D's registered, it was going to be a fairly low-stress weekend. Rob Adams in CSR Radical (with a Dauntless Wing) went home Friday with a failed engine, and Paul Leonard (Radial Prosport CSR) ran only on Saturday. Wings-and-Things was lightly subscribed, with only about 10 cars in our group.

The new rear wing in question is an approximation of Dauntless' current low-mounted wing kit. I started with the main lower element from the bi-plane wing setup first tried on Mark Jaremko's car at the 2008 Runoffs. It is a straightforward wing element, with a little less chord than their current kit, and without the whizzy twisted ends that help sort out the airflow coming over the rear fenders. I used that exact setup on my car to good effect at the end of last season, just barely pipping the track record that Chris Farrell set in Tim Micklos' car. If we're honest, lots of things went right for me to be able to catch Chris's time, and he'll doubtless be significantly quicker in his own car, but, being close is still a good feeling.

Atop that main element is the standard flap from Dauntless' kit. This was an early pre-production/repaired/blem/something, that Serendipity helped find its way to me. We moved the wing forward from its previous location in the "1.0" Jaremko iteration, since that had been made for the longer WF-1 bodywork. Its new location is now approximately the same as the standard WF-1 Stohr kit, but as the 1g body is about 5" shorter than the "long tail" WF-1", the wing sits over open space. By contrast, the WF-1 bi-plane rear wing actually overlaps the rear deck by approximately 1/2". Both wings are installed at about the same height, coincidentally, which differs from the current production Dauntless wing.

So, mumbo-jumbo aside, it was time to see if I could get everything sorted out. Easier said than done, as it turns out, as I did an excellent job of showing my woeful inexperience in dealing with a car as complex as this!

Friday we showed up early, and things began well. For the March test day, before the rear diff sprung a leak, I had started with about 2* of angle on the mainplane of the car, and had set the flap at a minimum ~15* angle, relative to the mainplane. We'd dropped it to 0*, then -1.5*, then -2.5*, each time picking up a bit of straightaway speed in the process, about 1mph per drop. Adjusting for ambient temperature (which in CO swings from about 40* to 80* during an early spring day), those seemed to be about the same as before, with perhaps slightly more rear-end stick.

Lap times at that test had remained constant in the mid 1:18's, with the best coming with the mainplane at -2.0, and the flap at +15 relative. (-12.8, as it turns out). This was around two seconds better than my previous best than the run of the "West Loop" the previous September. Everybody was setting new bests though, as the asphalt seemed to have weathered in over the winter, after being brand new in 2009.

So, we began Friday with similar settings. The car was fast, immediately running under my old track record for the full course, with several laps in the low 1:41 range. Unfortunately, the biggest problem of the weekend, and what probably offset the rest of the weekend, raised its head: the front splitter was rubbing, a LOT. In addition to picking up some grip over the winter --some estimates as much as two seconds per lap -- HPR has also picked up some bumps. A lot of long right-hand corners meant the left side of hte splitter was happily leaning over and grinding away the left-side rub blocks. Wary about hurting the splitter itself, we began raising the front of the car in 1-pushrod-turn increments, hoping the problem would go away. No such luck. Over the course of the weekend, reducing the car's rake so much ultimately resulted in a killer push, which I didn't put together until midway through Sunday. Smart, eh?

As an aside, I also tried running the floating front rotors once again, and once again, they began to have a bad vibration after 4-5 laps. We pulled them off and ran the solids all weekend. I'm getting frustrated with the brakes on this car - see below.

Also in an effort to try and curb the, ahem, curbing of the splitter, we changed the car's springrates from 1200/1400 to 1300/1500. As with the change from 1100/1300 to 1200/1400, the car felt a little more "propped up", and turn-in remains excellent. No issues putting power down (i.e. wheelspin), though perhaps that'd be exacerbated without so much mid-corner understeer caused by the reduction in rake. Suffice to say, this seems to be well within the range of springrates that folks are running on their Stohrs, so it'll do for the time being.

We played quite a bit with various wing angles, dropping the mainplane as far as -4, and the flap as high as +21 relative to the mainplane. Each adjustment definitely provides some trim effect, and has some effect on top speed, but there was enough spread in ambient temperature (40* to 90*), tire condition, car setup, and driver consistency (lacking!), that it was hard to extract any real trends, other than that ambient temperature seems to be the single biggest factor in ultimate top-speed of the car. At the moment, all I can say is that it seems to be at least as good as the previous Dauntless/Jaremko bi-plane setup, and, I suspect, better. Seems to have less drag for the amount of downforce I'm now enjoying.

It's worth mentioning that the car in its original configuration - 1g Stohr splitter and single rear wing -- was consistently 2-3mph faster down the straightaway than now, but on the order of 3-4 seconds a lap slower than it is now, other development and driver improvement notwithstanding.

We also played with adding/removing dive planes, with half an eye towards Road America in June. For sure, there was a significant effect on the front end of the car with those. Still out for better analysis is trying to determine their effect on top speed.

As you may be concluding by now, there were a lot of changes and tweaks made in an effort to try and find a balance in the car, with very little success forthcoming. I think we identified a few trends about the wing angles, dive planes, rake, and such, but as the car sits right now, I'm a bit dubious about the current setup.

We stayed Friday night in the travel-trailer RV that the parents had brought, and as it turns out, staying at the race track overnight is awful nice. Getting up in the morning, stumbling around for a bit, and then wandering over to the race car with a hot drink in hand is a nice experience.

Saturday dawned - if such a term could be used - cold and windy. A slight shortage of workers meant that we'd be running the shorter "West Loop", that we had tested on back in March, with good results in the mid 1:18 range. First session of the morning, on the same practice tires as from that March day, I was quickly in the low 19's, despite the various mishmash of changes from Friday. A fresh set of tires from last year's national win (wow, stickers!) was good enough for a mid :18 in qualifying. The car really came alive on new rubber, and I thought that the car's setup was quite good, especially over that short run. Feeling like I had the rear mainplane angle about where it might want to be, we went ahead and added the forward "stay" extensions to the rear endplates, and connected them to the body, which you can see in the pictures.

The race on Saturday was a bit of a mess, unfortunately. Halfway through the race, the car began its old behavior of going off progressively towards understeer, to the point where I began having to lift in the ~110mph T7, where I've never had to lift before. Essentially, I had a hugely rear-biased downforce - either too much rear wing, not enough front, and probably both. Post-race inspection showed that I had absolutely SCORCHED the left front tire. Granted, the West Loop is very intensive on that poor LF, but a race worth of understeer and leaning on that tire pretty hard had just shredded it. Going back to some head-scratching, a lack of rake, lack of dive planes, a healthy dose of rear flap, and maybe extra endplate area from those forward stays, had conspired to create an imbalanced setup that the fresh tires had been able to get around for a few laps, but not for a race distance. Could those forward extensions really make that much a difference to the car's downforce? Despite consistently raising the front of the car, we just barely had some rub block left on the left side of the splitter.

Almost as an afterthought, in light of the car being two seconds off of my earlier pace, I re-set the DSR track record for the HPR West Loop at a 1:20.xx.

So, after a bit of head-scratching, tantrum-throwing, tea-leaf-reading, and crystal ball work, on Saturday evening, we raised the front splitter a hair by grinding the mounting holes, and hoped that would do the trick for rub. Further, we decided to put the dive planes back on to try and save the front, and pulled a bit of wing angle out to try and even up the aero. The flap went from +21 (i.e a lot) down to the ~17 range, relative to the mainplane.

Many kebobs and much beer was consumed to try and help sort out the confusion of the day. Barclay shouted and told stories deep into the night, and a good time was had by all.

Sunday finally felt like a race day. We rolled out of bed, and onto the track as first session, which was now the full course, a few extra knights-in-white having been found to man the corner stations. Inexplicably, the car - or me - was dog slow on the straight - 3-4mph down from Saturday's race, and I was only able to dip into the high :42's, versus the test day's low 41's. The same was true in Qualifying. Thinking that we'd really screwed something up, we rolled the car over to the Doyle's scales, re-set the cornerweights, and sat down to think a bit.

Fortunately, raising the splitter had reduced the rubbing enough, so we went back down a turn on the front pushrods, dialed a yet more wing out, and removed the dive planes (once again!) to see if the straightaway speed would come back. Sure enough, it did, and I definitely noticed the reduction in front grip in the high speeds T4 and T10. Since top-speeds had been high in the race with MORE rear wing than during Sunday's practice or qualifying, I can only chalk it up to a problem with the driver during those Sunday sessions. That said, with dead tires, a dubious setup, and a weekend of changes behind me, I was mostly curious to see if the small increase in rake would regain some of the car's low-speed balance (it did).

More worryingly, on a warmish day (85*), after about 7 laps, last year's problem of the brakes going soft started to reappear. Over the course of a lap, the pedal got progressively worse. I slowed my pace, and after about 3 laps, curiously, the pedal came back. I continued to push, and about 2 laps from the finish, the pedal went soft again. Once the car cooled, the pedal is once again firm. Troublesome.

For Next Time
So, what have we learned? First, for as much as we absolutely lost our way in the woods in terms of the car's setup, a lot went right. The new truck is working well. the 28' Pace is turning out to be a perfect size for our operation. The engine ran flawlessly all weekend. The only niggles were too much oil from the overflow breather, an intermittent radio mike on my side, and the aforementioned vibration from the floating front rotors.

A good friend told me that he's learned a lot more from his screwups than from his successes, so I'll try to take that as the message for the weekend. I'm going to restore the car's settings more or less back to where the weekend began, bar the spring change, which now that we've raised the splitter to its normal position, should be just fine.

For the PPIR N/N, we'll try:
  • the 20x9.5 FA-sized Goodyear. This should help those low-and-mid speed corners, and we'll adjust springs, rake, and shocks to match.
  • Reinstalling the dive planes, since they seem to help, and appear to have only a small effect on top speed for our lower-speed tracks.
  • Taking a page from the ALMS guys, I'll be installing the larger/more open louvers from my spare nose, in an effort to help front downforce even more.
  • We'll pay a lot more attention to rake, as that seems to be a big knob on the Stohr for those mid-low speed corners. Oddly, at approx 9/16" of rake, I seem to be running much more than the normally indicated 1/4 or so inch?
  • changing only a few things at a time so we can figure out what the hell we're doing!
So, lessons learned, if not a huge amount about the actual setup of the car, and particularly, setup and efficacy of the rear wing configuration. Times are getting better, and there is LOTS of downforce to be had -- more than I'll ever be able to balance the front end with -- the quesetion now is getting the car balanced, and figure out at what drag penalty - if any - that the downforce is bringing with it.
3-4 laps of Saturday Qualifying. How many tumbleweeds do you count?

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