EOT meter for OEM oil cooler

[dsinned_imp]

This has been a learning experience for me, and kind of a FUN project. I learned there are some things you just can't do, but always another way. The main issue has been finding the "ideal" size "pusher" fan. A 4 inches fan is too small. 5.2 inches is too big. The sweet spot is somewhere in the middle, around 4.5 inches, but locating a powerful enough fan with the correct dimensions for a pusher application has been very difficult. The first fan I tried has the right dimensions, but isn't nearly powerful enough. I am currently trying another more powerful fan of 5.2 inches, but its actually a little too big to fit the EOC on the CB1100.

Another snag, this weekend I learned the hard way that I cannot use a Trail Tech to control a more powerful fan. TT must be using a low power MOSFET to supply current to the fan, but when I connected a Spal 5.2", Trail Tech's temp meter and with an integrated power switching control circuit immediately failed. This circuitry is sealed inside an encapsulate meter module, so I could only troubleshoot it externally to come to this conclusion. Fortunately, as a temperature/voltage display "meter" it is still functional, so I'm continuing to use it solely as a monitoring device.

Despite this limitation, I decided to use the more powerful fan made by Spal; a 5.2" pusher fan, but will now have to control it with a manual On/Off rocker switch mounted on my handlebar. This switch is located next to the TT meter on the center section of the handlebar for easy access and viewing. Luckily, Honda's handlebar has a diameter of 7/8", which is the most common size for this type of rocker switch.

I came to the conclusion that a more powerful fan is necessary to move sufficient air to be of any real benefit. I already had this fan, so might as well use it for this project. The added advantage of this fan is that it has a finger guard (most others do not). The disadvantage is that it draws a lot of current, approximate 4.5 amps, which may be too much extra load on the battery. To prevent overloading the battery, having a manual power switch for the fan and the means to monitor EOC temperature, I can just leave the fan off until it's actually needed.

Because of the high current, I wired it directly to my bike's 12V battery, and fused the fan at 7.5 amps with a single conductor power lead to the positive polarity of the battery. I connected the negative polarity of the fan motor via a short pigtail to frame ground. I'm using the upper attachment mounting bolt to the frame for the oil cooler to make this ground connection. This is a very convenient location since it is only a few inches from where the fan mounts to the front of the EOC. It also simplifies the fan and rocker switch overall wiring scheme.

Another advantage of this fan is that it can be heard running over the CB1100 engine idle, so no need for a fan running indicating light. No place to easily put a status light anyway.

I finished the installation late this afternoon and did a stationary op check in my garage. The fan, On/Off switch and TT monitor all work great! I didn't have time for an actual test ride to verify the fan's effectiveness on the road, so that will have to wait till next week. My expectation is with THIS fan, I will not have to worry about being stuck in stop and go traffic anymore.

Stay tuned for a follow up test report on this project . . .