I know that there have been numerous discussions about the high engine temperatures being reported by the rear cylinder head sensor, and justifiable concern about what levels of oil temperatures might be occurring. One of our forum sponsors, DK Custom, has in fact devoted a fair amount of video time to examining this issue and has developed a number of helpful solutions that lower the reported temperature a meaningful amount.

But a 60+ km test ride I did this morning, deliberately pushing my M114 engine notably harder than normal, seems to prove that the OIL temperature does NOT track nearly as high as the reported engine temperature - at least at moderate ambient outdoor temperatures.

HD does not make it easy to know the oil temperature, as its dash display systems, and its new Bluetooth tuner with gauge display capabilities, both do NOT include any oil temperature information.

But today I got lucky. My HD Bluetooth tuner, has on several attempts prevented me from doing its Smart Tune process (which customizes any eligible Stage 1 through Stage 4 tune to a user’s specific motorcycle). This is due to a known software fault which triggers a false “low battery voltage” message and stops the Smart Tune, even when the battery is fully charged AND when it is also connected to a 10 amp “smart” charger that is indicating it IS fully charged. Today, that message did NOT appear, and I was able to execute the entire Smart tune process and update my trike’s tune to reflect its advantageous results.

But here is the important part for this posting: The Smart Tune process requires as a first step that the rider ride the bike or trike using as many different combination of engine rpm and percent throttle as possible, in order to populate a data table which the Smart tune process builds for use in building the new customized tune. It takes a LONG time to fill in a truly meaningful percentage of the data fields possible in the table. I took about an hour to do so with my Breakout and got GREAT results (documented elsewhere on this forum), and so did a one hour data recording ride this morning with the RG3 chariot.

To do this, I had to run the engine under a wide range of loads and rpm, including full throttle accelerations in different gears and to different speeds, as high as 5500 rpm and 110 kph = 68 mph. (It is not necessary to achieve higher ROAD speeds. The table just needs high rpm and high throttle settings, so using different gears, it is possible to fill in all the table data points needed.

So, what I am saying is that this morning’s Smart tune recording ride certainly generated as much, or much more heat at times, than any normal ride done off of a race track could. If BOTH the engine temperature AND the OIL temperature were EVER going to get “hot”, this Smart Tune process would bring out the highest possible temperatures for each.

In fact, the engine temperature spiked a twice past 300F - once to 301 and once to 307 - DESPITE the moderate ambient temperature range for the ride. The ride started at low 50s F and finished at 61 degrees F ambient outdoor temperatures. Now this is NOT a completely satisfactory temperature test, since riders may find themselves riding in temperatures much higher - even past 100F for some masochistic riders. But, I view it as a good first test, which I wil follow up at ambient temperatures in the 81F range, which is the hottest temperature I personally care to ride at. You are free of course to do your own personal testing at 110F if so inclined!

I stopped 7 times during the hour to record the cumulative distance traveled, the oil temperature, and the engine temperature. I stopped that many times because I wanted to capture the “trend line” for the oil temperature, and stopping 7 times within an hour was about as much as I could do, as I was only willing to stop where a wider than normal highway shoulder was available, for safety reasons.

To measure the oil temperature, I used an HD LED combination oil temperature and oil level gauge dipstick. This sallowed me to get the oil temperature at the side of the road by merely reaching down and pressing an on/off button on the LED gauge. Fast, easy, and safe (I did not even need to dismount).

Here are the results, both numerically and graphically:






Note that while the ENGINE (top of rear cylinder head ) temperature hit 298F at the 4th stop, the OIL temperature never got above 216F. And, given the slorwrate of oil temperature change versus engine cylinder head, I can be confident that the oil temperature never got above that 216 mark even when the cylinder head got to over 300F.

216F is pretty safe for engine oil, especially for synthetic oil, which is what I will be changing over to at the RG3’s 1600 km = 1000 mile first service.

So, this is pretty good news.

Yes, I still need to do testing at higher ambient outdoor temperatures, but this is an encouraging start.

And, importantly, this test shows that OIL temperature does NOT rise and fall in sync with reported engine temperature, and that the oil temperature is FAR lower than the reported engine temperature.

That small oil cooler on our trikes is VERY effective. I can see now too why HD engineers built that oil cooling channel into the proximity of the cylinders’ exhaust valves. That WORKS.

Jim G

 

Jim,
Thanks for all the good info. If I remember correctly your bike was mostly stock less slip ons ?

Id like to see a 80 deg F and a 90 deg F report too.

Thanks, Mike

 

Mike, my RG3 has Rinehart slip-on mufflers, an HD Heavy Breather Extreme air cleaner, and a Stage 1 tune that I today customized to my specific trike by doing a very lengthy (1 hr) Smart Tune recording which was then used to modify my STage 1 tune. You will eventuallysee an 80 degree F report, but don't count on a 90 degree one. I hate being hot.

YOU'll have to do the 90 degree one!

Jim G

 

I am traveling right now, with limited time on the forum.

However, I will share a few salient pieces of information that you may already know, or may find useful.

-Oil temp always lags behind engine temp in heating up and cooling down.

-It generally takes 1 hour of constant riding, at a speed of 65 mph or more, for the engine to be fully heat soaked. Up until that point, the temperatures are still on the rise.

-Sustained highway speeds generate more heat than slower, in town, or country road riding.

-When an M8 is fully heat soaked, the oil will be about 30-40 F lower than the engine temp...if the engine temp is higher than 260F, or the oil is higher than 230F, that is not optimum for power, or engine longevity.

As you've noted, we have many videos documenting the above, with real world street testing AND dyno testing.

I should be able to be back at this thread by Friday or Saturday. In the meantime, at our Youtube channel, there are dozens of videos showing the testing, and showing what happens to engines that run hotter than the numbers I mentioned above.

Kevin


Kevin

 

Thanks, Kevin, for the additional useful information!

Jim G

 

Kevin: I sent a qustion to DK Custom customer service. My RG3 has a triangular shaped, 3D, plastic part that is secured by the RH tank mount bolt. That triangular part supports an electrical box of some sort so is not just "trim". I ordered your tank lift before I looked closely at my tank mounts, and am concerned now that the 3D nature of the triangular piece will either interfere with the tank mounting or could stress and crack the triangular piece. Will it in fact be a problem?

 

Note also the difference in the AVERAGE oil temperature versus engine temperature in my specific test above was ACTUALLY 79 degrees:



I don't know if this would continue to be the difference if I had run MORE than the one hour that I did, or at higher ambient temperatures. But, it is significant that in at least this one hour ride at moderate ambient temperature, the oil remained THAT much cooler than the temperature reported based on the rear engine cylinder head.

Jim G

 

Jim good morning ... just curious, did you have any other Harley Davidson Motorcycles before the "Breakout"

 

I thought HD said the nominal oil temperature is 235 degrees. On hot days my oil temp in my Trike and 2 M8s would run 250 to 260. Oil above 300 and the engine would start pinging under load. Measured by oil temp gauge that replaced the useless air temp, or by the digital temp dip stick.

So, IMHO…your temps look fine to me.

 

Yes:
1200 Sportster around 2010
The first Breakout in 2014
The 2nd Breakout this year
The RG3 this year

The other 54 motorcycles over 56 years were different brands. Why do you ask?

Jim G