Destination SSM One Miata's Journey through Hell

8Jul/120

Packwood ProSolo

Posted by David de Regt

The ProSolo was an interesting weekend.  The course was the most annoyingly not-fun collection of ridiculously tight offsets and stupidly slow corners that I've ever driven.  I feel like, in 8 years of autocrossing, I have to have driven a less fun course than that, but none come to mind.  On the upsides, I managed to squeak out a win (barely -- 0.009 seconds) and it highlighted a lot of things to focus on for the next phase of development for the car.  Also, we had zero reliability issues with the car again, so I'm just waiting for something expensive to explode at this point...

One of the big obvious weaknesses this weekend was power application.  I think that part of the problem with my current build is the forward weight bias (we're at about 56% front right now), which isn't leaving any weight on the rears to put power down.  I've been working on a design to try out that will let me drop down to a 1.6 motor, non-intercooled, which would drop a ton of weight off the front end, and potentially give me room to ballast up the rear.  In the interim, I need to explore a fuel cell so we can run less fuel without starving, allowing me to ballast up the rear a bit.  I'm starting to wonder in general about just running more fuel after seeing Sam Strano, a man who is already heavily ballasted, running a full tank of fuel in his SS C6 Corvette, because the extra power application he gets out of the weight over the rear is worth the weight gain from the gas.

An unrelated huge problem this weekend was that my front splitter wasn't playing nice with the Pro light sensors. I could get the car to "stage" in a couple different places, and it was very hard to tell which one of the two places I was staged in.  As a result, when runs really mattered, I had to run extremely conservative lights (7xx-8xx) just to make sure I wouldn't redlight.  If I'd hit the deep stage hot spot, then I'd still redlight even waiting that long (see my first run of the challenge, for example -- 498 redlight, and I didn't even start to release the clutch until right before the GREEN light came on, so I must have been deep staged millimeters from the next sensor...)  I've emailed Howard Duncan to ask how high the lights are, so I can make some "endplates" for my splitter to make sure that I hit the sensors in a reliable place at the next event.  This problem made every run an unpredictable nightmare.

I also need to just learn how to launch.  I cut everything from a 1.935 to mid 2.2s 60-ft times all weekend, mostly doing around 2.10ish, which is pretty terrible.  On low grip asphalt, even after the course rubbers in, the car has enough torque to break the rears loose at basically any point in first gear, so it's extremely hard to find the balance between a little bit of wheelspin and way too much wheelspin.  I'll hopefully learn eventually, but until then I'll be running almost STS 60 foots while I burn up expensive rubber.

2Jul/120

Packwood National Tour

Posted by David de Regt

The whole month of June has been filled with rainy weekends that we didn't even bother bringing the car out to autocross in.  One of the downsides to running a high power car is that, in the wet, you just get hosed on PAX.  So, as little fun as I have autocrossing in the rain in general, it's also uncompetitive, so the idea of towing for 3 hours each way to get creamed in the rain is unappealing.  Seattle might not have been the greatest place to build this car...

Fortunately, it gave me some time to mess around a bit with the car.  I bought a 12+1 tooth crank trigger wheel from Trackspeed Engineering, and after ~20 hours of trying to make it run reliably, I gave up and switched back to the stock wheel.  I don't know if there's noise on the crank hall sensor from something or if the AEM just doesn't like getting that many tooth updates, but it's off the car until I have time to spend more time debugging.  I replaced both the cam and crank angle sensors with brand new ones from Mazda (they had absolutely no effect on the 12+1 wheel, incidentally,) and replaced the main relay (the relay that broke in Lincoln) while I was in there, which, interestingly, had been superceded by a much different part.  We also learned that we're not allowed to run shoulder harnesses in a non-rollbar-convertible, so we pulled the 4/5 point belts and put in simple lap belts, which removed a bunch of weight from the car and made it a lot easier to get in and out as well.

After having no problem with power application in Lincoln (and even limited problems with power in Packwood,) I upsized the crank pulley (that the SC feeds off) from 120mm to 125mm, and spent a bunch more time on the dyno.  We're up to 330rwhp and 258rwtq and spent a lot more time on the low RPM portion of the map.  The car is now faster and has much smoother power ramp-up, so it's more drivable too, and is better at putting its power down than it used to be.  I think this will be the end of my attempted power mods before 2012 Solo Nationals.  It's time to work on the suspension setup and on my driving.

The 2012 Packwood National Tour arrived in a real hurry.  I spent 2 weeks messing with the trigger wheel to no avail, and had to rapidly switch back to the stock wheel on the Monday night before the NT.  Wednesday the car went in to get a new muffler, since we were consistently blowing 102dB at Lincoln (over the limit.)  Thursday I spent 3 hours on the Dyno at Pina Motorsports, and then 6am Friday morning we pulled out from Redmond to head down to Packwood.

The practice course was the dirtiest (gravel/etc.) course I've ever driven on, but we did some rough shock tuning and the car was working really well.  Ironically, both of our paddock-mates' cars broke, so we spent some time helping fix them.  The rest of the weekend, the car performed perfectly (despite us driving it inadequately,) and I managed to put a 1.776 second victory on the class, running fairly consistent times.  At the end of the weekend, we rolled the car onto the trailer and drove home, ready for the Pro in a few short days.

We learned that the car's fuel starving at around a third of a tank, which will require some investigation after the ProSolo.  I am also sure at this point that the car will be faster with more confidence-inspiring brakes, so that will be another focus for after the ProSolo.  The traction control also needs some further tweaking, and the wing really needs some string+video attention and a Gurney Flap.  Time, time time...

Here's some videos of my fastest runs for the weekend (expand for 720p.)  As you can tell, I'm still driving the car incredibly abruptly.  It's still more than a bit of a shock, coming out of stock class.  At this point, I have at least as much speed to be gained in learning to drive than will be found with further car setup...