Monthly Archives: May 2012

Third Time’s A Charm?

Nice easy night in the shop tonight. Installed a new Hella master switch from Pegasus. The switch seems to have more positive ‘clunk’ when it engages. The posts on the old switch seemed to be slightly loose, thought it may have just needed for me to snug down the lock nuts that I saw on them once it was removed. So, we’ll see if the switch was the problem or not…I sure hope so.

Corner Weights

I got my first set of corner weights with me sitting in the car:

230 229
278 279

for a total of 1016, and a 45/55 weight distribution. That’s with somewhere in the neighborhood of about 3 gallons of fuel in the car, meaning that the car, when empty, would be juuuuust about at the minimum, which is what we’ve seen so far.

So, that means that with perhaps a bit of weight reduction at the back, we might need to add in that 15# ballast plate that I made for the front tea tray to be safe, and also perhaps that would help us even out the weight distribution on the car.


Friday we headed back out to HPR to do some more testing on the car to see if it was all set for Seattle or not. As it turns out, not, but there are some good positives.

On the upside, the problematic brake line didn’t leak at all. We did see some wetness on the driver’s side of the car after the first session, and thought perhaps it was leaking again (cursing ensued), but it turned out to be some migratory oil from the oil temp sensor near the water pump.

The new wing support cables worked quite well, though I had to snug one back up after the first session. They actually look almost factory!

Big downer from the day was a high RPM misfire/hesitation that manifested as I started pushing the car harder, and steadily worsened throughout the day. I tried replacing the
throttle bodies, removing the FlatShifter, and even rewiring the ignition/fuel pump switch to a spare to see if that would solve the issue. On the last session, I noticed that the
dash also shut off when the engine stuttered. Unfortunately, I didn’t have any time left to try anything else, but that definitely points to something far upstream, like a bad
master switch or perhaps even a bad battery.

Among the frustration, there were lots of good points. First and foremost, the car doesn’t seem to have any big problems. It’s going where it’s pointed mostly, the balance seems OK. Nothing is coming loose, the chain is staying put, and the shifting is good. FlatShifter is working pretty well on downshifts and flawlessly on upshifts. All the leaks are fixed up and the radio seems to be at least OK to start with. Lots of good so far, just one more issue to sort out, and then it’s time to do some debugging.

Shocks and Motion Ratios

One of the noteable downers on the car is the shock damping – it is HUGELY stiff. It feels even more sensitive to bumps than the DSR did before sending the shocks off to Chris Billings for revalving. As such, I’ve gone and measured the motion ratios as well as I can on the car (which isn’t all that well). Both seem to have a decreasing curve – i.e. the further into bump you go, the lower the motion ratio gets. Near as I could measure, they were both around 0.94 at the ride heights I have. I think it starts closer to .98 or so in the rear, and the front might be a bit lower, perhaps .90-.92 or so. Note that I’m using the ratio as shock:wheel travel, so in my measurements, the shock is traveling .94 of an inch for every 1″ of spring travel.

My unsprung weight measurements were 39.0# front, and 49.4# rear, very similar to the DSR.

Post-Test Cleanup

After getting the car back home, I had just a bit of a cleanup day – reinstalling the switches in their normal spots after having stolen the rain light switch as an ignition switch briefly,
and drilling the spare throttle body set for the FlatShifter blipper.

One installation note: the fill tube on the side-fill cell on the F1000 can make R&R of the center body section extremely difficult. However, the metal fill neck is quite long, so one thing you can do is significantly shorten the plastic fill tube, to reduce how much this interferes with the body as you try to reinstall it, and get the metal fill neck back into the fill tube.

Post Test Cleanup

Tuesdays after a track day are always a bit of a relaxing checkup for the car, since it’s the first time to really look at it after a weekend, and none of the parts to fix the weekend’s problems have arrived yet. Some misc notes from the day:

  • FlatShifter Debugging: I spent some time debugging the lack of any blip on the FlatShifter downshift. Wiring was OK, as I could hear the valve in the box click
    when I actuated the downshift test switch. After playing around with a vacuum pump, I was able to determine the blipper wasn’t getting enough vacuum from the signal line I’d installed on the throttle bodies. This engine was from a Calfornia car, so I’d teed into one of those nipples. As it turns out, despite the nipple being quite large, the orifice from which it takes the signal is very very small. Drilling out the orifice to around 1/8″ or so solved the problem, and now I have all the blip I need.
  • Video: Video seems to be working OK on the car, and even the G-sensor. Kudos to ChaseCam for zeroing the PDR’s axis on startup: even though my PDR is mounted at an angle, the G readings appear to be zero when the car isn’t moving. Nice.
  • Ducting: Stohr included some lightweight duct hose to run from the over-rollbar intake down into the engine bay to cool the headers. I cut that hose in half and ran it down
    each side of the engine bay – easy.

Flaring Nostrils, Flaring Brakes

The biggest issue of the test was a leak from the left side of the car where the front hard brake line mates to the rear hard brake line. Despite my best efforts to seal this before leaving, it apparently was still leaking when real-life braking pressures were applied to it. After taking a good long look at the flares and the union fitting that joins the front and rear lines, I cut off the old flare, made my own new flare with a flare tool from Lowes, and then cranked the holy hoppin’ bejesus out of it with a couple flare wrenches. We’ll see if it holds now…

Cool Runnings

Finally, everything assembled and seemingly leak-free – I get to drive my new car!

Load up, head down, and enjoy a nice wonderful Colorado spring day, right?

Or, maybe, 35*, windy, and threatening snow? Welcome to the high plains everybody.

Still, figuring that we needed to do some laps and get things figured out a little bit, even if just for a few laps, out I went for the first laps. Woo!

I did just one very tentative initial outlap, and even then made some initial notes: First, seeing the wheels is pretty darn cool, though you stop noticing it quite as much after a little while. Still, it allows for very precise placement of the car indeed. The mirrors do seem to be in the way slightly – seems like I found them in the way of my apex sighting from time to time, so I may find myself moving those later on.

So far, the bead seat seems to be OK, and the upshift on the FlatShifter is nice and smooth – just like the old HoleShot on the DSR was. Effort on the paddles is a little bit high, so I’ll have
to see how that develops as I get used to the car. Brake pedal feel from the new PFC’s is tremendous!

After the initial run, I snugged up the new chain a touch, and pulled data to check the logs. Nothing untoward there. My trusty crew (AKA Mom and Dad) reported that the wing was vibrating quite a lot going down the straight. A post-test phone call to JRO confirmed that is a bit of an issue, so I’ll support those a bit with some cables before next time out.

Other upsides: brake pedal feel from the PFC calipers was AWESOME. Downside though – there was a leak on the left-hand side floor. After the second session out, the leak was even worse, the brake fluid eating away at the paint on the floor.

Unfortunately, that was about the same time that the sleet came, putting the end to our test day. But, a few things learned, and back to the shop we went.


This week was fairly frenetic, with a nice fellow from Santa Rosa coming to pick up the silver Radical, Lazaraus, and give it a new home.

Final preparations for the Stohr were mostly down to getting it aligned. The brakes bled OK, and the masters seem to have finally sealed, so we might be OK in that regard. I did replace
the front master cylinder with a new one, and used the proper NPT to AN tee, removing the problematic banjo fitting.

First challenge was to make some new toe bars. Since the F1000 is 8 or so inches wider than the DSR, my 72″ wide bars from the DSR weren’t wide enough. I went and bought some 1″x 1/8″ aluminum angle at Colorado Metal Distributors 76″ long, and drilled small holes to put fishing line through for toe bars. The next challenge was in mounting them to the car. The rear was not so bad, using small aluminum adapters that Chris Farrell gave me
that formerly went on the front tow bars on the WF-1’s diffuser.

To mount the fronts, I had to attach them to the front of the frame. To do this, I installed two small nutserts in the frame, and then used some small tubular 1.25″ aluminum spacers through which a 2″ long 10-32 bolt could go, and attach the angle aluminum to the chassis. The spacer is necessary to clear the transponder and the front of the brake master cylinders.

The setup itself didn’t take too long, since I’d spent just a bit of time trying to get the toe and camber closer after last week’s failed attempt with the camber adjuster. Heights set up nicely at 1.25″ and 1.5″, and the corner weights came out almost exactly perfect.