Last night was a quick, dirty, and temporary mod night.
I've been focusing on learning to drive the Metro since I did the
P&G vs just driving calculation. It showed me that optimal MAP is 4 psi (10.5 MAP on the SG). So, I've been trying to drive quite close to that. However, I was disappointed in the SG when trying to achieve this. It updated too slowly, and it also jumped around a lot (likely due to the 3 cylinders). I couldn't seem to just stick it at 10.5 very well. It would jump up to 11.3, then 9.8, then 10.7, and so on. So, I figured an analog vacuum gauge would be the way to go. I was SO right. I've only driven with the gauge once, but I LOVE it so far. I'll be looking for something a bit more permanent.
I started out with what I had kicking around. Its just a cheapo vacuum gauge for diagnosing engine issues. I must say it is nice to have a big gauge. It makes for better accuracy.
Next, I found the MAP sensor and used the included tee and some extra rubber hose to tap into the manifold pressure.
For now, I just ran the rubber line over the engine bay, under the front fender, and through the door.
To mount the gauge, I used some wire and hooked it into one of the vents. Its ugly, but it works, and its only temporary.
Using this gauge, I was able to get
71.9 mpg on the SG in to work this morning! It was 40F out. I did ecodrive pretty aggressively though.
I noticed that once I added the gauge, the SG readings seemed to smooth out a little. I'm not sure if this is due to the extra length of tubing acting as a filter/buffer/accumulator, or if I was just able to keep the pedal that much closer to optimal vacuum with the more instant feedback.
As mentioned, I REALLY like this gauge. With the smaller engined Metro, its very easy to find yourself cruising above optimal engine load. This gauge gives me instant and smooth feedback, and allows me to avoid P&Ging when unnecessary.
In other news, I also installed a quick and dirty voltmeter. I found my SG voltage reading is up to .5V off (reads low)! I've seen it off a little, but this is very far off. I'm wondering if I have a grounding problem? The battery still isn't being charged as much as it should though with the P&G I do. I'll eventually have to swap in a deep cycle.