Friday, March 22, 2013
I had a run in with the cops today. The weather reached a high almost 37F, the sun was out, and the roads were dry, so I decided to take my car for a little spin. This was the first time since early January. I leisurely drove out of my neighborhood and took a left onto a busier street. As I pushed on the gas, I notice the car did not shift from 2nd to 3rd gear -- its like it slipped completely out of gear and all I could do was coast to the shoulder.
I put the car in Park, turned on my flashers, and tried to shift from Park to Drive, Reverse, etc, but the transmission would not engage. I frantically kept trying to get into gear, any gear! Until I saw flashing lights.
The first car to drive past was a pair of undercover police officers in an unmarked car. They put on their flashers, pulled up behind me, and came over to chat. They asked if everything was OK and offered to use their car to push my car off the main road, or call a tow-truck. I explained that the car was in "experimental" stages and that I had converted from gas to electric and the transmission was not going into gear. That got them interested and they started asking questions and I showed them the ins and outs. Luckily my house was a couple hundred yards away and my brother was coming with a tow strap so they let me wait without calling a tow truck.
A squad car pulled up with a 3rd officer and he stayed to block traffic while the unmarked car left.
My brother towed me back home, and once safe again in the cul-de-sac in front of my house I experimented around a bit until I figured out what was going on. If I shut the car off, and turned it back on, the transmission would engage, but after the RPMs rev'ed up, the transmission would disengage. I noticed my RPMs were actually bouncing all over the place. This is a sign that the circuit I made that converts the actual motor RPM to the car's ECU input is not working properly. In fact, it looks like a ton of noise is being injected into the system and causing the micro controller to miscount the RPMs, thus the ECU is getting confused and ultimately telling the transmission to disengage.
A few things come to mind -- this was not a problem when I parked the car in January, the wiring near the motor has been changed and is not fixed in place, the car is now running at 350V, not 250V. So with these things in mind, the additional voltage definitely creates more powerful noise waves, and the location of the RPM sensor wiring may have changed and may need to be shielded better to prevent the unintentional pickup. Maybe I need a better low pass filter on the input.
So now I need to figure that out before I can take it on the road again, hopefully tomorrow!