Mark Plaia
True Classic
During the trip to attend the Oregon 2010 meet last weekend, I had two systems failures on the car.
On the way down to the meet, a 225 mile trip, the wide band oxygen sensor system went on the blink. It was set up to provide closed loop feedback to the Megasquirt controller. Fortunately, my control map is very close to optimum, and running in open loop mode was not fundamentally different than having the closed loop control. However, light throttle running and descending hills on the overrun led to some exhaust popping and rough running. But not bad. The control unit for the sensor system is what went out, so it is now back in the hands of Innovate Motorsports for repair.
Then, as I fired the car up to leave at the end of the meet, the alternator decided that it did not want to work right. It was sick, but did not die. Symptoms were not enough charging at idle, and too much charging at speed - approximately 15.2-15.5 volt. I found that if I ran the heater fan (not a bad thing on a hot day) that the load pulled the charge rate down to the desired 13.8-14.2 volt. This is a Delco/GM conversion alternator. I took the alternator to a local shop and had it tested. The test machine showed exactly the conditions that I saw on the road. When they tore it down and checked, the cost of the parts to rebuild was higher than their cost for a fresh GM remanufacture alternator.
I had the shop check in to the possibility of fitting a larger pulley to the alternator. The pulley that was on it was sized for a GM V-8 application that turns considerably less RPM than my 1300. The ratio that was on it ran the alternator at approximately 2.25 times crank speed. So, when I shifted at 8000 RPM, the alternator was turning about 18000 RPM, right at the recommended upper limit. The alternator maximum output is about 6-7000 RPM. I obtained a pulley that is about 50% larger diameter than was on it and lowered the drive ratio to about 1.72 times crank speed. This lowered the maximum alternator speed by over 4000 RPM, and puts the alternator right at it's maximum charging RPM at highway speed. Additionally, my idle RPM went up 180 RPM. :sun: That means that there is less load on the motor, and I have to say that, so far, the car seems a bit zippier.
So, even though it cost me some money, I now have a rock solid alternator and a bit more performance to boot.
Ciao,
On the way down to the meet, a 225 mile trip, the wide band oxygen sensor system went on the blink. It was set up to provide closed loop feedback to the Megasquirt controller. Fortunately, my control map is very close to optimum, and running in open loop mode was not fundamentally different than having the closed loop control. However, light throttle running and descending hills on the overrun led to some exhaust popping and rough running. But not bad. The control unit for the sensor system is what went out, so it is now back in the hands of Innovate Motorsports for repair.
Then, as I fired the car up to leave at the end of the meet, the alternator decided that it did not want to work right. It was sick, but did not die. Symptoms were not enough charging at idle, and too much charging at speed - approximately 15.2-15.5 volt. I found that if I ran the heater fan (not a bad thing on a hot day) that the load pulled the charge rate down to the desired 13.8-14.2 volt. This is a Delco/GM conversion alternator. I took the alternator to a local shop and had it tested. The test machine showed exactly the conditions that I saw on the road. When they tore it down and checked, the cost of the parts to rebuild was higher than their cost for a fresh GM remanufacture alternator.
I had the shop check in to the possibility of fitting a larger pulley to the alternator. The pulley that was on it was sized for a GM V-8 application that turns considerably less RPM than my 1300. The ratio that was on it ran the alternator at approximately 2.25 times crank speed. So, when I shifted at 8000 RPM, the alternator was turning about 18000 RPM, right at the recommended upper limit. The alternator maximum output is about 6-7000 RPM. I obtained a pulley that is about 50% larger diameter than was on it and lowered the drive ratio to about 1.72 times crank speed. This lowered the maximum alternator speed by over 4000 RPM, and puts the alternator right at it's maximum charging RPM at highway speed. Additionally, my idle RPM went up 180 RPM. :sun: That means that there is less load on the motor, and I have to say that, so far, the car seems a bit zippier.
So, even though it cost me some money, I now have a rock solid alternator and a bit more performance to boot.
Ciao,
