Archive for the Suspension Category

Packwood National Tour

Posted in Handling, Reliability, Suspension, Traction Control on July 2, 2012 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and replaced the main relay (the relay that broke in Lincoln) while I was in there, which, interestingly, had been superceded by a much different part.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…

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Second Packwood weekend and Spring Nationals Leadups

Posted in Delays, Handling, Suspension, Traction Control, Wiring Harnesses on May 29, 2012 by David de Regt

It’s been an incredibly hectic two weeks.  I spent a couple days tearing into more of the electrics and found that the fuel pump wire down the driver’s side of the rear harness had rubbed through to the chassis, which is probably what started everything.  I ran a new thicker gauge wire and re-loomed/moved some of the harness, so it should hopefully never rub through again, and the thicker wire will be less prone to heating.  I also ordered a Deutchwerks 300LPH pump due to my decreased confidence in the Walbro, intending to use it as a spare if the Walbro died.  Finally, I moved the fusebox out from under the side of the engine bay into a spot near the intake with some airflow, in case it just needed some ventilation as well.

The subframe that we were told existed wasn’t actually the right subframe, which we didn’t discover until after close of business Thursday night.  We got to wake up early Friday morning and call every parts shop in the area to find a new subframe.  The only one we could get before Monday wouldn’t be pulled until 5pm that night, 2 hours from home.  So, we picked it up, got back home around 7:30pm, and spent the entire night swapping the subframe and front control arms.  Shaikh finished up the shocks Thursday night and overnighted them so those arrived Friday morning, and when we finished with the subframe, we got to also assemble/swap the new shocks (mounting canisters, etc.)  Around 11:30pm we finally finished with all the work, then spent until almost 2am doing a ride height set and string alignment.  We realized the alignment wasn’t going terribly well, and we couldn’t get enough camber out of the front anyway, so we called it good enough for a shakedown and went to bed.

We decided that waking up in 3 hours and driving to Packwood for the morning session was out of the question, so we went down for the afternoon, which was a nice dry day, and had no major issues at all with the car.  The car was pretty loose, but still drivable, and we settled into liking a RaceLogic setting of 20% slip and 5.0mph wheel differential.  Sunday morning we woke up to a wet ground and ongoing rain, and we ran a very wet morning session, where we got to throw on the Hoosier Wets (225/50/15 H2Os on 15×9 6ULs) and play with the RaceLogic to figure out a wet setup, which worked out quite well.  We tried 5%, which seemed pretty good, but 10% was really the sweet spot, if you had quick enough hands.  The car is remarkably drivable in the wet, which is good to know.  On a very representative course, I was only 0.4 behind the Hyman GT-R car in full wet trim, which is closer than I would have hoped to get.  We had no issues with the car in the wet either, called it a day, and drove home.

On the tow home, the alternator on the truck let go, though, adding some more insult to the existing injury.  Nothing is ever easy…

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Ups and Downs

Posted in Delays, Subframes, Suspension on May 15, 2012 by David de Regt

It’s been an interesting month.  Soon after the last post, I decided that nothing was coming in soon enough and that I should just bring the car in to get painted.  I had Showcase Auto do it, and it came out great (for a racecar — painting carbon fiber body parts is never fantastic unless you put 20 pounds of paint and bondo on it, hence removing the point.)

I got the car back a week and a half ago, just in time to try to put all the new parts that arrived on it.  The Ciro Designs wing came in, and we fabbed up a splitter (currently in revision 1, there’ll be canards and paint later).  The control arms and delrin finally came in, and we spent days assembling the car and finally, this past weekend, had a chance to bring the car down to Packwood for what was supposed to be a 2 day event, getting a ton of runs on the car in preparation for the Lincoln mini-nationals in 2 weekends.

Unfortunately, that was not to be the case.  We took a couple runs in the car, which were pretty good, but quickly started getting some nasty rubbing making the sharp turn to get to the start line from grid.  We ignored it, planning to look into it at lunch.  A couple runs later, we started getting something acting like the car being out of gas in the middle of my dad’s run, and then shortly thereafter it gave out entirely and refused to run any more.  Some quick diagnosing led me to find that the ignition lead was shorted to an always-on battery line somewhere, and it wasn’t obvious where.  In addition, when you shorted the fuel pump on with the diagnostic connector, the circuit main relay under the dash started buzzing heavily, and was rapidly heating up (to the point that the wire insulation was melting).  So, after spending a while with it, we decided to bail and head home to diagnose with more tools and time.

Monday, my dad and I converged on the car and pulled the front wheel off, only to discover something really unfortunate.  The rubbing apparently was caused by the new front control arms pretzeling themselves under the stress of the Packwood bumps, or somethingorother.  I’m working with the EPMiata folks to try to figure out if we have a good answer, or if their arms are just not strong enough for SSM autocross duty.  However, that give us a bit of a major problem.  There’s one more weekend of events (19/20th) and then we have to hit the road Tuesday to get to the Lincoln events in time, which means we only have one more shot to test this stuff out, and it needs to be ready for this weekend.

As a result, just to have a prayer of making it to Lincoln, I’m enacting a fallback plan of using stock front UCAs.  AWR is overnighting me some delrin bushings for them, which come in Wednesday, and I’m putting the V8Roadster ball joints into them.  We’re going to bend them in a press a little bit to get the camber level we need, and run it as is for now to hopefully get some events under it before going with another custom solution of some sort.

I also pulled apart most of the electrics in the car today (pulled the dash, fuseboxes, and relay blocks) to try to figure out the problem.  The only issue I can find so far is that two of the wires in the main fusebox had melted together, which shorted the ignition (white/red) line to another fused always-on line (white/green).  I re-insulated them and separated them, and I will be moving the fusebox to somewhere with more airflow to keep it cool (the event this weekend was quite warm, and I think the splitter was keeping underhood temps higher than usual).  In addition, I should probably add some vents to the hood to let some of the air out, which will likely assist with front downforce as well.  I’m replacing the main circuit opening relay with another I had kicking around from a lower mileage car, and hoping for the best this weekend.

With any luck, I’ll have better news to relay soon.  Tomorrow I get a different used front subframe to swap mine out with (we had to drill the front UCA sleeve out to 5/8″ to use the EPMiata control arms) so I need to get another stock one to put the stock arms back onto, and the delrin bushings come in to reassemble everything.  The real DA shocks come in from Shaikh either late Thursday or early Friday, leaving me a few hours to get the car aligned for the weekend.  From there, hopefully our last minute changes here will keep it running long enough to abuse it all weekend, then head east to Lincoln a few days after that…

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