This shroud took longer to make than it stayed on the cart. Sunday I went to the local elementary school with a laser temp gun and a 10mm socket & ratchet to test the effectiveness of the shroud I made.
The engine was somewhat warm from an earlier ride. I took the shroud off since it was cool and then drove about a mile to the school. Driving around the parking lot was 1.03 miles. For all testing, I tried to maintain 20 mph and 3k RPM.
I did 4 laps and pulled over and took a temp reading. I then did another 4 laps and did another reading. The results were pretty close to each other so I felt good about that. I simply laid the shroud on top of the engine and didn’t bolt it down. I didn’t want to impact the temp readings while I took the minute or two to remove the 3 bolts that held the shroud on. With the shroud on, I drove 4 more laps, removed the shroud and took a temp reading in the same spot as before. I put the shroud back on and did another 4 laps. I pulled the shroud and took the final reading.
The results were not what I expected and had hoped for. With the shroud on, the engine ran about 10 degrees hotter.
The laser temp guns read a little strange when you try to use them on shiny or semi-shiny surfaces. So this morning I thought I would try something different. I put one of the prob from my digital thermometers that I use for smoking in between 2 of the cylinder fins and then packed it in place with aluminum foil.
This time I drove around the neighborhood. It is a mile circle that is relatively flat, so I can maintain a constant speed fairly well. I thought I would go 15mph instead of the 20mph from yesterday. I thought this might even the odds between the shroud and no shroud. I had already been out for a 9 mile drive, so the engine was already warmed up.
With the temp probe in place and the shroud off, I drove around the neighborhood and took a picture of the temperature monitor as I pulled in front of the house. After a mile at 15 mph, this was the temperature:
Since I could see the temperature without lifting the seat, I bolted the shroud on this time and went around the neighborhood again. Another mile at 15 mph and this was the reading with the shroud on:
I don’t think my laser temp gun was very accurate and there are certainly some flaws with this digital thermometer test. But since both methods showed that the engine was hotter with the shroud than without, that is good enough for me. Clearly there is plenty of cooler air flowing up and around the engine compared to the confined warmer air that the fan is blowing around and down the cylinder head. I would guess that if you drove 5 mph the results might be different. But who only drives 5 mph?