AZ1000 Day 4
May
2009
We rallied around some pretty tough roads today near Cottonwood. Finally, a breakthrough on the difficulty we’ve been having all week. We could never seem to dial in on zero. On the transit back to the hotel, Marinus set the cruise control on a level section of I-17 at 70. He noticed that the SPEED readout on the driver’s display swung wildly while maintaining a constant speed. Rather than go 70, 70.1, 70.2, 70.1, it went 70, 93, 54, 67, 88, 51, 64…. Something is STILL wrong with the sensor unit. I thought the problem was all due to wheel spin of the bald tires. (It is it to some extent). I was madly adjusting the ODO and the factor to no avail. But now it makes sense.
Today, we rallied up to Crown King, a small little town in a canyon that nearly burned to the ground last year by some lost hikers setting a signal fire which got out of control. One car had 3 flats when we arrived. Note to self: buy fix-a-flat before going to Crown King. They fetch any price they want for it at the General Store. The current price is $10 per can! One car didn’t finish due to mechanical problems.
Tomorrow we end up at the Grand Canyon and finish up the rally.
May 15th, 2009 at 6:54 am
Are you using VSS for the odo input or an external wheel spinner? I had similar fluctuations using VSS on the WRX with both the Alfa and the Timewise and was never able to get a consistent reading until I used the magnetic sensors. I had an email chat with Jack C. about it but we never got to the bottom of the problem.
May 16th, 2009 at 7:02 pm
Jeff, we were using a regular Timewise sensor (barrel style), bolted to a R. Jones custom-made hub mount. It’s very similar to an EZ-pulse, just smaller in diameter. Revere’s used this style successfully since the ’98 Alcan.
In our case, though, there was something awry. The first factor we saw on Monday morning was ~34000. That’s a factor more befitting a four-magnet system than a two-magnet system (but that didn’t occur to us ’til later in the week). After some time on gravel the apparent factor dropped to ~27000 — which corresponds to a 5-magnet system (!). 27000 was what we ran Monday p.m. — Thursday, though it was a lot of work to run with it.
On Thursday night, in a frustrated rage, I went back to basics. After a visit (or three) to Home Depot I mounted the sensor to the rear control arm and put two magnets on the wheel. Boom! The factor was now ~69000 (fitting well with the tire diameter) and the mileages were rock-steady on Friday.
I can only surmise that the Timewise sensor was giving double (triple?) readings from the magnets in the hub-mounted unit — Jack C. describes a “bounce” situation if you try to read a bar-shaped magnet, giving two pulses for one pass of the magnet. Why that situation would come and go I can not say…. heat of the day changing magnetic potential? It was, as you can imagine, HOT.
May 17th, 2009 at 12:02 am
Re: “one car didn’t finish due to mechanical problems” — read: new Jeep Patriot not all that happy about 1000 miles running in 4WD. The driver’s description sounded like front diff failure, and/or transfer case seizure. Joy.
The AZ1000 toll:
(2) cars broken down on the way to the rally
(8) flat tires
of those, (5) destroyed tires
(1) front diff
(1) minivan on two wheels
(1) Contour SVT exhaust system
(2) angry bicyclists
(0) traffic tickets (AFAIK)
May 17th, 2009 at 11:11 am
Also
(1) GPS fried in the heat
(1) Alfa Clock fried in the heat
(1) Angry local in a truck/trailer combo going with racer (his word) traffic
(1) car broken down on the way to the rally and DNS at all
(1) Plastic spare tire cover which came off and skittered across the pavement