Monthly Archives: May 2008

Between Race Updates

Despite the lack of updates, it’s been a relatively busy few weeks in the interim since the last La Junta event. I decided to finally make good on my idea of building an improved splitter for the front of my car, and to attach the “diffuser extensions” to the rear diffuser in an effort to perhaps marginally increase the ground effect of the car.

Rear Diffuser Extensions

I’ve got a few pictures of the diffuser extensions. The essential idea was to try and keep the diffuser sides lower, longer, to try and do more to prevent the ingress of higher pressure
air into the underfloor, which in turn may help draw more air through the diffuser. *shrug*

New Front Splitter

Also was a project of replacing the standard Radical fiberglass splitter with a plywood test version. The splitter is made of 5/8″ ply, a few “jiggle strips” of aluminum, and a pair of Dzus fasteners. The idea here is to have something that is cheaper to replace than the crappy fiberglass splitters, and will probably make more downforce. Further, it gets rid of that monster 1″ step between the bottom of the crushbox and the floor of the tub, which may be beneficial as well.

The final product is strong enough to stand on, weighs about 14# with fasteners, and may even make loading/unloading the car just a hair easier as well since it is radiused on the bottom edges, and has some cutting-board “rub strips” to keep it from falling apart when
it does make contact with the racetrack. Their secondary function will be to make sure that the splitter never 100% contacts the ground, and will prevent any possible “porpoising” if airflow under the car is cut off, either due to flex, or downforce.

We’ll see – shakedown is this week. Soon, hopefully, this test model will be replaced with the real splitter from Paul Trayhurn over in the UK, but this will serve me, I think, until it needs to. If the silly thing works, I’ll post my dimensions/plans/etc on how to make it, as it cost very little to make, and at worst, will be cheaper to replace than fiberglass splitters.

Air Shifter Updates

Dave sent me a new regulator to replace the “sticky” one from the last event, and this one includes a small shutoff valve, so I don’t have to screw/unscrew the bottle all the time. It’s been holding for about a week now, so that is a welcome improvement to the system. Will use it more at IMI this coming test and see what we get.



The 2008 La Junta May Daze race is in the books. All of my friends got their licenses with their new sports racers, and some without. Congrats to Paul, Grant, Joe, Lawrence, Dan, and Clay for joining the ranks. The smiles were unbelievably big throughout the crowd…what great fun for all.

for my part, my race writeup is in the Racing log, complete with some cruddy video of the
first few laps of Saturday’s race. Enjoy!

Pre-Stohr-Racing Invitational – May Daze

Race 1 Start (30MB Video – sound is off)

Race Video


More Video…


Ah, the first race of the season after a looooonnnng winter of wind, snow, and engine changes.

Grant and I caravanned down to La Junta Friday evening, me with the Radical, and he with his new Stohr 04C in tow. We arrived just in time for the wind to pick up epic levels – 40-50mph gusts. Getting tech done was a pain, making sure nobody’s bodywork went flying. Fortunately, it calmed down overnight, and Saturday dawned clear, calm, but quite cold – about 40* at 8:00 when our group hit the track.

This weekend was the first weekend for the informal “Pre-Stohr Racing” group that we have been gathering here in Colorado – a few Radicals, a Cheetah, and ironically, a pair of (pre-tunnel and pre-front-diffuser) Stohr CSR’s. Some of these guys are friends moved up from autocrossing, one is an FM convert, and the other is a fellow that came by an SR4 a while back, I’m not really sure how or when.

At any rate, our plan is to run together as much as possible, and do what we can to achieve pretty good parity, and have fun racing together. Should be very enjoyable – if this weekend was any indication, it is going to be absolutely illegal amounts of fun.

Practice 1

Fortunately, I was driving a car I know quite well. Oh, except it had a brand new engine, different springs, fresh shocks, different ride heights, and completely fresh suspension pieces. Uh…yeah.

Due to the school, we were combined with the “small bore” formula cars – FV, FF, SRF, etc, so I spent a lot of time carefully passing those cars, getting a feel for how closing speeds would be during the race.

The first session, predictably enough, was slippery as heck. A dusty track at 40* does not make for a lot of grip! Still, I felt like I had a ridiculous amount of oversteer – I spun quite quickly twice in 4, essentially in the middle of the corner. Yike – my first two spins on the racetrack versus autocross.

Tire temps confirmed that the rears were just sliding as the fronts were in the ~120 range, and the rears at only 90*. To play it safe, I moved the rear bar to full soft (from full hard), lowered the rear 4 turns on the perches, and reduced the bump from “4” to “2” on the canister. Figured that would help for the oversteer which was present at all phases of the corner.

Even with the slidy temps, I still managed a 52.4, better than I had ever done the year before with the R1. Not bad so far, and the only mechanical issue was the IAT having popped off of the airbox from the epoxy apparently failing.

Qualy 1

Qualy 1 was a mess, with about half the session having the wrecker on track, and cars everywhere off the outside of T7. Grip was starting to go up with the temperatures, and I was happy to see my time progress down to a 52.130. Balance was better, but still not great. In addition, having lowered the car, the sidewalls of the rear tires were now rubbing on the bodywork. To fix this, I raised the car back up the 4 turns, and installed the 650# springs, down from 700#. Tire temps indicated that front pressures were a bit high, so we dropped those 2 pounds to 18 hot, to even out the temp spread.

Race 1
Frustrating, isn’t it? two full test/shakedown sessions at IMI, and two full sessions at race pace on the racetrack, and it’s only the 5th session, in the RACE, when a part fails. Typical! This time it was a fitting out of the water pump housing, which pulled loose and let loose all of the water.
This happened around lap 13 or so, and while I thought originally it must have been the tape on the radiator, temps kept climbing even after pitting to remove these. I did ultimately take the checker, driving part throttle and about 8K RPM to get the finish, hoping temps would start to come down.

I was on pole for the start. Since I figured it’d give me an advantage, I brought the field up pretty slowly, at about 7K in first gear. I stomped it when the green flew, and immediately got about 2 car lengths on the FA next to me (an old SuperVee, I think?), and ran away. The car was a bit slidy for the first few laps – from the video (link at right) it appears like I was having trouble feeling like I could get it down to the apex, since I seem to be a few feet off of
everything. Confirms the feeling from the driver’s seat!

On the up side, while the car was still whole, it was great! I set a race best of 51.130, just about .2 off of the CSR track record, which I was thrilled with. Better, there were many 51’s throughout the race, so I felt like I was at least driving fairly consistently. The car was perhaps a bit oversteer-y, but manageable. Quite a difference to the understeer that has been my constant companion since buying the car. I guess that’s the combination of the various setup differences I’ve been working towards…good news.

So, due to the pitstops with the overheating, an easy win turned into a 14th place finish, 2 laps down. Ah well.

Saturday night was the usual school graduation festitivites. Grant, Paul, and Joe all were given their waivers to race Sunday in their sports racers, as were Dan and Clay in their doorslammers. The autocrossers are making a good name for themselves as good racing candidates, it would seem!

The rest of Saturday night for me was exacting a repair on the water pump housing – threading a hose barb into the extant hole, and then applying JB Weld to ensure everything sealed 100% for the weekend. On top of that worry of “will it hold??” was “did I hurt the motor?”


Sunday became the kind of day that you remember forever. It was a nice morning, with just a light breeze. My fears from Saturday night (what sleep?) were allayed early, as I filled the motor, started it up, burped it, and everything seemed 100% normal. I did a few heat cycles to ensure it was burped and that the repair would hold, and moved to my usual morning checklist.

Practice 2

Now this is great! Practice was now with the graduating sports racers, and a few additional FE, ESR, and FC drivers. It was great fun to see other SR’s out on track to play with. I was in cruise mode for the first few laps to see what the engine was like, would the repair hold. No problems at all, so I stomped it, and turned another few 51.1’s, much to my delight.

Qualy 2
2nd qualifying straightforward, with everybody behaving themselves. I qualified on pole again with a 51.x, with everybody else in the 52’s. I was discouraged that I’d slowed down, but for sure the car felt like it was sliding around more. Everybody else went slower as well, so perhaps the hotter weather was contributing to slower times.

Race 2

What started with what could have been a relatively straightforward win also became more complex, although this time it was my fault, although I’m glad it happened, as it resulted in an incredibly fun run up through the field.

I started the race same as before, and quickly drew away from the FA SuperVee who was next to me. However, on about lap 5, I tried a new entry into the very bumpy 3, and it spun me around to the inside of 3. Damn! I was down to 7th by the time I could get back on track.

I came back in right behind Paul Leonard in his Radical DSR. I could almost see Paul make the decision “Hey man, we’re racing”, and we had a great couple of laps together before I got by. Next was Charlie Sander in the FE, who made a very generous gesture on the entrance to 4, and stayed very wide on corner entry to let me through, even though I was miles too far back to have been able to make a pass. Thanks, Charlie!

I spent most of the rest of the race behind Joe Weathers in his SR4, another newly licensed driver. Joe raced like he’s been doing it for years. We spent lap after lap locked together. I kept getting just a bit of a run off of 7, but the big 1400 would pull away on the straight. I kept trying to duck in a bit at the entrance of 3, but Joe defended the line quite well. I couldn’t quite make the over-under thing work out into 4 either, as he was coming off of 3 better than I was.

A few laps later, I was finally able to stick my nose down inside and passed Joe into 3, but a yellow had just appeared for Lawrence spinning off in his Cheetah (lost the brakes), so I checked up to let Joe back by, just in case. Another few laps went by, and somewhere in there Pat spun off in the FM, so Joe and I were now fighting for 2nd place – what a race this was, trying to get by!

Finally Joe had a bit sideways moment on the exit of 7, and we went side-by-side through, 1, 2, and 3, all at over 100mph – thrilling stuff! My heart was in my throat going inside of 1 and 2 together, not knowing if Joe was going to give me the room or not!

Finally I was able to make the pass stick, and I spent the next 3-4 laps trying to chase down the Anson, which was stuck behind a few of the backmarkers. The only exciting bit was being run off the inside of 4 by a backmarker FC who didn’t see me inside him. By the last lap, I was only about 50′ behind on the straight, but the checkers flew, and that was it – 2nd overall, but the win over Joe in CSR.

Did I breathe even once?

Car Summary

So, looks like the new engine is a success – the extra 30 or so HP is really nice, and so much more driveble than the carb’d R1 was. There are a few bits to sort out before the next race, like the water pump, but nothing too bad. Temperatures all fine (if anything all too low),
and initial testing of the Rilltech pan seems to indicate it will work properly, although we did see ~25psi drops in all right-hand corners, so perhaps there is an issue yet to be dealt with.

Setup-wise, the car was perhaps a bit too tailhappy for my liking. I didn’t feel like I could get down to the apex well enough without the rear sliding, and I definitely had to be careful applying power on corner exit – later than I would have liked. I will check the set-down and see if anything is out-of-whack. Tire wear seems to confirm the oversteer diagnosis – the fronts look pretty good, and the LR just about dead. For the first time since I’ve owned the car, the rears wore out first!

Tire temps appear to be close, but need to get some hot-pit-lane temps to confirm, looks like the car still has a touch too much camber everywhere, perhaps 1/4* less will do it. No meaningful splitter wear during the weekend, until the race, where I had to dive off inside 4, as mentioned previously. So, the ~2.25″ ride height and the 450’s seems to work well for now.

So, going to search for a tad more rear grip next time around, and onward we go from there!

Driver Summary

Data shows a theoretical best of a 50.6 had I gotten everything right on both of my quickest laps. Key seems to be getting a better exit out of 3, and later in the weekend, I was carrying more speed through six into 7. For next time, I definitely want to work on 3 more, I never did feel like I was getting it right this time, nor last time. Anything to add from watching the video, I’d be interested to hear, of course, but I think the car was just a biiiit to oversteery, which I felt was making getting to the apex difficult, and getting power down as early as I wanted to.

Until next time…