Month: April 2016

I’ve been watching my digital temperature gauge (attached to the rear sparkplug) as I’ve been riding around. In my observation, there are a few (obvious) things that impact engine heat.
<ol>
<li>ambient temperature – the bike runs hotter on hot days. Of course, but the effect is less than I first thought</li>
<li>engine revs – the faster the engine is running, the hotter it gets</li>
<li>engine load – going up a hill or accelerating generate heat, going downhill or decelerating tend to cool the engine</li>
<li>air flow – the less the airflow, the hotter the engine, all other things being equal.</li>
</ol>
Now, when I ride around town at an average of 50km/h I’m usually in 3rd gear, so the engine is revving at 2017rpm. At 100km/h on the highway it revs at 2349rpm in 6th gear. So the revs aren’t too different, but the airflow in the city is half that on the highway. Add to that frequent high load as I accelerate between traffic lights.

No wonder it runs hot in town!

Thursday last week was extremely hot in Sydney, over 42°C in the suburbs. I got caught in traffic on the M4 going towards Parramatta after a truck breakdown. Traffic was crawling.

Unfortunately I’d removed my cooling fans for some adjustments, so I was just relying on the cooling fins and my oil cooler, but neither work well without air movement.

I still had my temperature gauge fitted. The cylinder head climber to over 220°C in the slow moving traffic, and stayed there. It even hit 230°C, that’s 446°F, at one stage. I reckon that is way too hot, and the engine was pinging and struggling big time. Even when the traffic started moving again it stayed well over 200°C until I got home.

So I’m convinced. I’ll make sure I have these fans fitted until the end of summer. Who knows when I’ll get another day like that.

I used the cooling fans differently today. I let the engine warm up a little and when the head temperature was 100°C I switched the fans on. I rode around town for a little over an hour (light traffic) keeping an eye on the temperature. Mostly it was about 130°C – 140°C but did peak at 154°C going up a hill.

It was a pretty warm day, about 34°C. Normally the engine would get very hot with this sort of riding – around 190°C.

Using the fans in this way is probably the best way to run them – it’s much easier to keep something from getting hot than to try to cool it down once it is.

10 minutes from home I switched the fans off. Engine temperature rose quickly and peaked at 203°C, settling around 190°C.

Yes, these fans work, and work well.

°

I rode the thirty or so kilometres from the Sydney CBD to my home this morning. It was a fairly mild day for this time of year – about 26°-28°C. The traffic wasn’t too bad coming out of the city so I maintained the signposted limit for most of the journey, about 60-70 km/h. But of course, there were multiple traffic lights.

Cylinder head temperature with the fans off: 185°-195°C
Cylinder head temperature with the fans on: 145°-155°C

I’m waiting for a stinking hot day to see what these fans can really do.

I’ve fitted my bike with a sensor that allows me to monitor head temperature while I’m riding; much more convenient than the hand held infrared device I’ve been using.

I know these fans work well at low speed and in traffic, but surprisingly, they also work well on the highway. They drop the head temperature by 10-15°C.
I wasn’t expecting that because at 100-110 km/h there is already good airflow over the heads – I didn’t think the fans would improve that much. But clearly they do. A 10°C drop is not huge, but every bit helps I think.
(tested at 27°C ambient temperature at constant speed on the M4 in western Sydney. Waiting for a very hot day to repeat the test)

More good results this morning. Not a particularly hot day – around 20°C so pleasant riding (apart from the traffic). Even so, head temperature reached 177°C without the fans. Turned the fans on and temp dropped to 130°C in just a few minutes.

Tested these fans in torrential rain last week (22 Nov). They ran fine.
You don’t really need them when it’s raining – water is an excellent coolant. But I wanted to check the fans were sealed up ok and water resistant. No problem.

Victoria Rd was very congested this morning (16 Nov); accident on iron cove bridge.
Head temperature reached 205°C even though ambient temp was only about 26°C. Switched on the fans and temp had dropped to 147°C in two sets of traffic lights. Down to 130°C by end of journey.
Very happy with the way these fans are working.