Autocrossing at San Marcos Airport with Spokes

March 13th, 2009

Autocross course laid out by Andy Hollis at San Marcos Airport for Spokes.

 

Spokes (www.spokes.org) is the local autocrossing club in Austin, they use all of the SCCA classifications and most of the rules but are a little more lax with some of the rules and therefore a little more fun.  I missed their first outing of 2009 and was wrenching on the Camaro in an attempt to get it together for their second outing, but alas it was not to be.  So I saddled up my daily driver, the 2001 Pontiac Trans Am WS-6, for a little auto-x!  In terms of prep, I pretty much just checked the fluids and tire pressure and emptied the car out before heading to San Marcos in the morning.  It’s about an hour drive from where Cris and I settled in Cedar Park, TX, so I left just a bit after 7 AM.  The drive was enjoyable (down US35 toward San Antonio) and uneventful.  I arrived at the San Marcos Airport a bit after 8 AM and was waitlisted to race since they had a full registration. 

 

As I was waiting I met Ann Hollis, she the wife of Andy Hollis, autocrosser extraordinaire and instructor at Evolution Performance Driving School (http://www.evoschool.com/).  Andy has his own Wiki (http://en.wikipedia.org/wiki/Andy_Hollis) which is pretty cool!  Andy is a six-time SCCA Solo National Champion and was the designer of the course at San Marcos!  Anyway, Ann was very sweet and welcomed me to the region and introduced me to a whole slew of people (sorry I don’t remember all of your names!).  Ann is an accomplished autocrosser in her own right and is I believe also an instructor at Evolution…but she is modest and doesn’t have her own wiki, so I am not sure about the details.

 

Well, I made the “cut” (in fact I think all of us on the waitlist did) and was allowed to race my first time out with Spokes.  Tech inspection was uneventful so I was off to walk the course and try to map it out.  Prior to leaving in the morning I had printed an aerial photo of the airport space where we were racing from Google Earth.  As you can see from the scan, the course started out with a three-cone slalom to set up a roundabout on the right.  After the roundabout, there was a short straight with a turn to the right through a tight gate, which was followed by a sweeper back to the left.  Another fast turn to the right with a few cones up top and then a tight right turn before entering the long slalom, which ended with another chicane and then an offset slalom to end the course.

 

I worked the first heat, and was keeping my eye on the blue Corvette of Lance Adams in SS who was the first to run the course in under 60 seconds.  He managed a 59.818 s; at that point I decided if I could run within 10 seconds of that time I’d be doing pretty well, given that the Trans Am was almost certainly one of the heaviest cars at the track that day and that I was rolling on some bald Sumitomo HTR-Z (UTQG 160 A A) that would be replaced next week.  So I set my goal to break into the 60s.

 

On my first run I ran 73.866 s, slower than I had hoped for, but I did a conservative run and hit no cones (no sense making a fool of myself drifting all around the course in my first outing with Spokes!).  Run number two was over two seconds faster at 71.838 s, faster through all three sectors of the course.  I was feeling that the 60s where in reach.  I had a passenger for run number three (chicks dig the Trans Am!), and cut another second and a half off at 70.372 s.  I had another passenger for run number four (actually the boyfriend of first passenger) and made a fairly major mistake coming out of the first sweeping left turn too hot and nearly taking out an entire row of cones.  This forced me to come nearly to a complete stop to avoid the cones and killed my time.  Although I was faster through sectors one and three of the course, I added over two seconds in sector two, netting me a 71.750 s, the only run of the day in which I didn’t improve. 

 

My last two runs were solo, and I put together a 69.559 s run on my fifth run; I also had my fastest times of the day for sectors one and two on this run.  For my last run, I was about 0.150 s slower through sectors one and two (combined) but I shaved an entire seven tenths off in sector three, so finished with my best time of the day, a very satisfying 69.020 s.  I had improved on all but one run, hadn’t hit any cones on the day, and ran within 10 s of a very well-driven SS Class Corvette.  As an added bonus, I also beat both of the Mustangs that showed up (sorry Paul M!).  Add to that I met some great folks, all of whom were very nice and inviting, and I had a great day of racing!


Cyberdyne Digital Fuel Pressure Gauge

July 18th, 2008

Cyberdyne fuel pressure sending unit
Since I had two weeks before my next SCCA Solo II Autocross event in the 68 Camaro after United Airlines left me in Austin, TX and I missed my July 13th event, I decided to put a digital fuel pressure gauge in the Camaro so I could keep an eye on the fuel pressure generated by the Walbro 255 inline pump and the Holley fuel pressure regulator.  I wanted a digital gauge in red to match the Dakota Digital dash and the Holley Wide Band Air/Fuel Gauge I had already installed.  The best bang for the buck seemed to be Cyberdyne; their digital fuel pressure gauge for EFI reads from 20 to 100 PSI, comes with the sending unit and wiring, and can be found for under $100.  I needed an adaptor in the fuel line somewhere to tap the sending unit into. 

Cyberdyne fuel pressure gauge sending unit

The sending unit has 1/8th NPT threads and you can buy a pressure gauge adapter with either barbs or AN -6 fittings on either end but I decided to machine my own from brass with barbs to go inline in the 3/8ths rubber fuel-injection rated hose (SAE J30).  I put a ½ diameter brass rod in the lathe and bored the center out to 0.330” before turning down the ends to 0.375” on either end.  I left the center at 0.500” and also left the barbs at 0.440” with sixty degrees backcut and forty five degrees on the end going into the hose.  I radiused all of the cuts and put the tube in the milling machine to drill and tap the hole for the 1/8th NPT threads.  I also picked up a couple of stainless steel worm clamps to put the adapter in-line in the fuel hose.  I installed the gauge on the passenger side firewall with a plumbing clamp I found at the local hardware store and re-bent to fit securely over the unit with a single screw.  This is essential for proper gauge performance because the sending unit needs to be grounded, which the rubber fuel hose obviously doesn’t accomplish.  For the gauge mounting I simply drilled an additional hole in the 20 gauge sheet metal panel I had made to mount my Holley Digital Wideband Air Fuel gauge in the dash.  I also made an equally-space dimple in the center of the panel so the addition of a third gauge in the future will be easy.

Holley Wideband Air Fuel and Cyberdyne Fuel Pressure Gauges

Wiring the gauge was straightforward: I tapped into the twelve volt supply for the Air/Fuel Gauge as well as the ground while routing the sending unit wire through the firewall grommet with the wiring harness from the Holley Commander 950.  The gauge worked well and confirmed fuel pressure at about 41-42 PSI upon putting the key in the ignition position.  The fuel pressure regulator is vacuum referenced and with the car running at idle fuel pressure was around 35 PSI.  The gauge fit well into my red LED scheme and allowed me to monitor the fuel delivery system for problems which is critical when retrofitting the 68 Camaro with EFI so I was happy.

Nearly Undrivable Camaro

July 16th, 2008

Holley Stealth Ram throttle linkage in 68 Camaro

Upon pulling out of the carport I realized the Camaro was not going to be as docile as I hoped when I spec’ed out that mild 112/118 duration cam!  It was very torquey and surged when attempting to accelerate and torque braked hard as soon as you let off the gas.  This was noticeable even in third and fourth gear.  This made it almost impossible to log useful data in traffic as the only way to drive it without the car violently bucking around was “flat out”.  My first test drive also involved topping off the gas tank and I found out that I had a leak somewhere high up on my tank (it was not leaking when not full but leaked when full).  This wouldn’t be that big of a deal except I still didn’t have a reliable reading from my 68 Camaro’s 40-year-old gas gauge sending unit so I was guessing about how much fuel it had at any moment—making it difficult to fill it up three quarters of the way.

 

I put the following on the www.pro-touring.com forum board hoping for some help:

When taking off in first, i find it very difficult to not spin the tires. If you are going balls out on a track it might be OK until you have to come off the gas–but in street traffic when taking off at a stop light and then trying to feather back off the gas so as not to rear end the vehicle in front of you, the car surges forward, then if you let off the gas it jerks or bucks very hard due to the torque braking. I have the Commander 950 software running and am looking at my throttle position sensor when i am doing this, and i have a relatively light foot (TPS is 1 closed and 172 for WOT, i am applying values of ~10 when this is happenning). I have found for the street the only way to drive it is to let traffic leave me to create a gap, then take off aggressively in first, then go to second almost immediately, then go to third and essentially allow the car to idle along in traffic (idle is 850 RPM). In third, the ammount of torque on tap is diminished enough relative to the load that i can come on and off the gas (again, i’m talking 3-5% of WOT) with controllable surges rather than violent bucking. Traffic around me still think i’m an idiot because the car bucks with even the slightest progressive addition of gas (i looked at my datalogs and i’m talking TPS values of around 5–roughly 2-3% of WOT).

 

There were a lot of thoughtful responses, and three things I could implement pretty quickly: double checking throttle linkage and spring tension, moving the idle up higher in the RPM band, and setting the shocks softer.  I disconnected the spring from the throttle linage but didn’t see any other way to make it more progressive in the short term.  I also set the DSE-sourced Koni adjustable shocks at one click out from full soft in the front (they had been set on one click from full hard) and to ½ turn from full soft in the rear.  Then I raised the idle RPM to 950 in the Holley Commander 950 software and adjusted the throttle return set screw to get the idle correct so the idle air control solenoid was in control of the idle.  I figured I would deal with the gas tank leak later since it only leaked with a full tank of gas.  Upon taking it for a test ride, it was still very rough but seemed somewhat improved mainly by the throttle spring and idle speed changes.  Unfortunately upon adjusting the front suspension I was now bottoming out on bumps at speed.  Although I had the 2001 Trans Am as a back-up, I decided to race the Camaro on Sunday and see from there what to do next.  Unfortunately I was travelling on the mainland for work and United Airlines stranded me there on July 12th, the night before the race I had been waiting 3 months for!  The only good news was that there was another SCCA Solo II race two weeks later, so I wouldn’t have to wait too long to test out my modifications.