Some of you may have read the thread in which I reported on how I used a combination of Stage 1 (intake and exhaust) + HD Bluetooth tuner + that tuner’s “Smart Tune” capability + homemade micro windshield to achieve some startlingly good engine power, smoothness, and fuel mileage gains on my 2023 Breakout 117 with its M8 engine.

In this follow-up thread, I will provide some hard data on how well the M8 engine does, and does not, control both engine temperature and timing, as I run the motorcycle through a tightly controlled test run at varying highway and city speeds that totaled about 60.6 km = 37.6 miles.


Speed & Conditions:

The test was run on a circular loop route that included mostly highway but also some small town and city riding, as described below.

The outdoor temperature was 16C = 61F when I started the test around 7:10am, and was 19C = 66F by the time I completed it around 8:15 (took that long because 2 gas stops were required as the first gas station’s pumps were down due to credit card system failure).

The wind velocity was VERY low for this region (which is why I acted today and this early in the a..m.!), blowing at only 3 to 4 kph = 2 to 2.5 mph.

Traffic at this hour on these routes was minimal, and did NOT require me to ever vary from my target speed on any of the test segments.

So, the test was about as clean as any road test on public roads can be.



The Concept of the Testing Protocol:

The concept of the testing protocol was to first examine the engine temperature and timing at different highway speeds in 6th gear , including 80, 90, 100, and 110 kph which = 50, 55, 60, and 68 mph. 110 kph was the maximum I tested at because that’s the highest speed limit on any highway segment in my region, and to ensure speed uniformity for each segment, I needed to stay at or below the local speed limit.

These highway test segments were run on a route that allowed me to run them in ascending order, so that the higher engine temperatures in higher speed segments could not pollute the results for lower speed segments via “residual” heat in the engine. I also ran long enough at each speed to ENSURE that I reached equilibrium temperature. That proved to never require more than just a few minutes at each speed.

After the highway segments, I deliberately ran through a suburban & city route of only 4.5 kilometers, which got to that total only because I had to go to first the gas station with the failed credit card system and then the gas station where I was able to refill the fuel tank. You will be AMAZED at how badly the M8 handled its engine temperature within that 4.5 km.

Note that the HD Bluetooth tuner enables a user to “see” a customizable “dashboard of guages” on your compatible iPhone or Android cellphone, and to take photo screen snapshots as your ride, without affecting the tuner’s ongoing functions. I used that capability to do this test.

Those of you who are particularly detail oriented might notice that on the screenshots, within the gauge that shows current vehicle speed,, there is a small notation under “KPH” that says “4750 RPM”. The tuner enables a user to set a custom “shift light”, that lights up this gauge with a bright green when the selected engine rpm has been reached.

I set this for 4750 rpm because at age 73 my reflexes are slower than they were, and the 117 M8 with a Stage 1 tune and Smart Tune accelerates VERY quickly - WAY quicker than my 2014 Breakout with 103 Twin Cam and Stage 4 + custom tune by Mike Lozano of Lozano Brothers could accelerate.



The Test Results:

This first photo shows equilibrium results at 80 kph = 50 mph:




Note that:

Engine rpm is 1801

Engine temperature is moderate at 248 F

Timing advance is 27 degrees, and is the same for both front and rear cylinders



Photo 2 shows equilibrium results at 90 kph = 55 mph:




Note that:

Engine rpm is 2009

Engine temperature is still moderate at 252 F

Timing advance is 30 degrees for the front cylinder, but 32 degrees for the rear cylinder. We know this is NOT the result of the sensor tolerances being different for the front and rear cylinders, since they were the same at 80 kph. So, the engine has backed off the front timing by 2 degrees to prevent detonation, presumably because the front cylinder is just a bit hotter than the rear cylinder. MAYBE because the oil cooler directly in front of the front cylinder is now adding some heat to the air that hits the frnt of the front cylinder?


Photo 3 shows the engine conditions as I passed through the small town of Raymond, Alberta, whose speed limit is 50 kph = 30 mph:




Note that:

Engine rpm is 1979

Vehicle speed is 52 kph = 31 mph

Engine temperature is moderately higher at 257 F

Timing advance is 36 degrees for the front cylinder, and is 34 for the rear cylinder. So, in this city riding, the front cylinder is doing slightly better than the rear, as evidenced by its slightly more advanced timing.


Photo 4 shows equilibrium results at 100 kph:




Note that:

Engine rpm is 2236

Vehicle speed is 100 kph = 62 mph

Engine temperature is moderately higher at 264 F

Timing advance is 36 for the front cylinder and 39 for the rear cylinder. Again, at highway speed, the front cylinder timing is 3 degrees retarded versus the rear cylinder.



Photo 5 shows equilibrium results at 110 kph = 68 mph:




Note that:

Engine rpm is 2478

Vehicle speed is 110 kph = 68 mph

Engine temperature is notably higher at 271 F

Timing advance is 34 for the front cylinder and 37 for the rear cylinder. Again, at highway speed, the front cylinder timing is 3 degrees retarded versus the rear cylinder. Maybe the theory that the oil cooler is heating the front cylinder a bit has merit? Other screenshot photos that I have not included, that showed the rise to the 271 F equilibrium, showed that this 3 degree difference in ignition advance was CONSISTENT during the rise to 271, at EVERY data point captured.



Photo 6 shows the engine readings right after I stopped at the first gas station pump:




Note that:

Engine rpm is 1004. The idle speed with Stage 1 tune is nominally 950, but varies from 900 to 1000 approximately

Vehicle speed is zero of course

Engine temperature is still notably high, at 264 F, after about 3 km of suburban & city riding

Timing advance is 13 degrees for the front cylinder and 17 degrees for rear cylinder, again continuing to show a 3 degree retard of the front cylinder versus the rear.



Photo 7 shows the engine readings after I restarted the engine, after realizing the gas station pumps were not working:




Note that:

Engine rpm is 973

Vehicle speed is zero of course

Engine temperature has INCREASED while shut down, from 264 to 293 F! And in fact, Harley’s EITMS system, which shuts off fuel to the rear cylinder and pumps through air only, to cool the engine, has kicked in (I could tell by the different exhaust sound). HD programs the M8 engine to do this whenever the engine temperature exceeds about 275F and the vehicle is not moving.

Timing advance is now 15 for the front cylinder and 19 for the rear cylinder. So both are improved from just before the shut-off, but the rear cylinder is now 4 degrees cooler than the front cylinder, due to the EITMS effect of cooling air.



Photo 8 shows the engine readings after riding about 1.5 km = 1 mile, in city riding, from the first gas station to the 2nd gas station, just before shutting the engine down again at a gas pump:




Note that:

Engine rpm is 951

Vehicle speed is zero of course

Engine temperature is down to 266 as a result of MOVING, even though at only slow city speeds

Timing advance is now 14 for the front cylinder and 18 for the rear, again showing the rear doing much better than the front cylinder, with EITMS NOT automatically engaged while the bike was moving on the 1.5 km ride to the 2nd station.



Photo 9 shows the engine readings after the gas tank was refilled, the bike restarted, and now enroute to home via city riding:




Note that:

Engine rpm is 1735

Vehicle speed is 45 kph = 28 mph

Engine temperature is 286 even though the bike is moving, because it’s just at city speed

Timing advance is 26 degrees for the front clyinder and 27 for the rear, so almost equal.



Photo 10 shows the engine readings back at home, in the garage, just before shutdown, after navigating through 3 km of city neighbourhood that includes traffic light stops and stop sign stops, 40 kph speed limits, a pause in my home’s street to find and hit the garage door opener in my pocket, and riding up the driveway into the garage:




Note that:

Engine rpm is 977

Vehicle speed is zero of course (in the garage)

Engine temperature is back up to 293 even though the bike WAS moving, because it was all just at very low city speeds and multiple stops including 2 traffic light waits

Timing advance is 15 degrees for the front cylinder and 19 for the rear, and EITMS has re-engaged now that the bike is stopped in the garage. Again, the rear cylinder is 4 degrees more advanced than the front due to the apparently very effective cooling provided by EITMS.



Lessons learned:

The BIG lessons learned from all of the above, and also drawing on what my prior thread on the tuner showed me:

• M8 engine temperatures are moderate (considering the M8 is a huge, V-twin, air & oil cooled engine) IF you can keep the bike moving at speeds higher than city speeds
• The M8’s programming maintains moderate to moderately higher engine temperatures when the bike is on the highway, although the equilibrium temperature DOES rise with increasing highway speed.
• Engine temperature starts to increase, and RAPIDLY, when the bike is NOT moving at good speeds or is stopped.
• Once the engine has begun to heat, it is not easy to recover. In fact, it is pretty hard, so sustained city riding and low speed parades are both best avoided.
• EITMS works about as well as anyone could hope for, BUT it obviously can work only on one of the two cylinders, and HD chose the rear one because they probably have hard data showing that the rear cylinder gets hotter than the front cylinder in city traffic conditions. But the front cylinder suffers from the oil cooler blocking its prime air entry channel, AND also preheating the air that does get through the oil cooler. HD placed the oil cooler there in an effort to hide it as much as possible, because the typical HD buyer hates the appearance of both oil coolers and coolant radiators, but the engine gets TOO hot without one of the two.
• With a Stage 1 tune, air intake, and exhaust, and a Smart Tune, and a micro-sized almost invisible but astonishingly effective windshield, an M8 bike CAN get fuel mileage as high as 63 miles / US gallon at 80 kph = 50 mph under ideal conditions. Fuel mileage gets worse as you up the speed, and this test today shows that while wind resistance is the primary reason of course, the fact that the engine temperature is NOT thermostatically controlled via water cooling contributes to that lower mileage.
• Oil life also falls as engine operating temperature increases, so higher speeds also shorten the safe mileage between oil changes.
• The testing in both the tuning thread and this thread have also shown me how pleasant slower riding can be in scenic countryside. Lots of time to view interesting things on both sides of the road, and more time to react to avoid unpleasant cager, pedestrian, and animal actions!

Jim G

 

I just noticed something else: There is apparently a "sweet spot" for the engine at 100 kph = 62 mph.

If you look closely at the timing advance numbers, you will see that GENERALLY, the the number of degrees of timing advance is directly proportional to engine rpm. This makes sense of course for an engine that is lightly loaded (i.e. not struggling under lots of throttle to get as much air as possible into itself). All the cruising speeds I tested at are light loading for this engine.

But, there is one exception. The timing advance at 100 kph is MORE than expected. Since 80 kph has 27 degrees of advance, 100 kph would be expected to have 100/80 x 27 = 33.75 degrees of advance. But, the actual advance was 36 front cylinder and 39 rear cylinder. The computer is programmed to provide as much ignition advance as possible without encountering detonation, as that results in maximized efficiency (the most power for the amount of fuel and air ingested). Since the computer gives more timing at 100 kph than expected, it has not yet encountered any sign of detonation, despite going beyond the number of proportional degrees that it can apparently provide at both lower and higher engine rpm points.

This SUGGESTS that for highway riding the "most efficient" speed, considering BOTH mpg and time consumed traveling, might be in the vicinity of 100 kph.

Jim G

 

You are missing a very important component on the timing tables, map. As rpm increases the timing generally increases. As map increases timing drops. I suspect the kpa @100 klms/hr is less than at 80 klms/hr.
Looking at a base map for your bike the rear cylinder has more timing up to approx 1500-2000, depending at what kpa your bike idles at. Where you would be riding it has less.

 

Here's another way to look at that map (manifold air pressure, for those not familiar with the acronym) effect:

If you examine the torque curve for the M8 117, you see that the torque is decent below 1800 rpm, but really starts to become, and stay, high by 2000 rpm and beyond. That suggests that air ingestion at 1800 and lower rpm is not that great, and finally becomes good after 1800 rpm and remains so until very high rpm (beyond 5000 rpm in the 117 engine). That means combustion efficiency is not great at 1800 and below, which would explain why the timing can be more aggressive at 2200 rpm than at 1800. Timing is higher but still proportionately inferior at rpm higher than 2200 maybe because while air ingestion is still very good at rpm higher than 2200, at 2200 the air ingestion and the swirl mixing of fuel and air happen to be optimal to support more advanced ignition without encountering detonation.

That does NOT produce "peak" torque and power at that rpm, because the peak torque produced by an engine occurs when the engine is doing its best air ingestion (more material to burn), and peak power occurs when the COMBINATION of torque times rpm happens to be the highest numerical value. (Power is simply torque multipled by rpm and divided by a constant). Most engines built today (but not industrial engines), are made to run at high peak rpm in order to get the most POWER (not torque alone), so we see both peak torque and peak power occurring at notably high rpm, with the torque peak being earlier than the power peak, and torque and power peaks getting closer and closer together in rpm as the engine powerband is narrowed to make a higher peak power. But peak power does NOT coincide with peak FUEL EFFICIENCY nor peak ignition timing efficiency. In many hotrodded engines, detonation is suppressed by rich fueling.

Jim G

 

Lonewolf176: Sorry, I should have proactively said that my entire focus on this test series was on engine temperature and timing. I wanted to find out how well this 117 cubic inch, air and oil cooled, odd firing interval, pushrod v-twin that HD's customers have forced it to keep despite its thermal limitations, can actually cope with heat at different highway speeds AND in the city. Engine temperature was an obvious parameter to monitor. Ignition timing is also an obvious parameter because the first thing a properly computer controlled engine does when it gets "too" hot is retard its timing to avoid damaging detonation.

I got my answers.

Jim G

 

Can you go over that again?

 

Sure!

Highway speeds: The M8 gets warmer with speed but no problem. Enjoy.
City: The M8 gets REALLY hot REALLY fast, even at just 19C = 66F ambient temps, and triggers EITMS. Avoid.


Jim G

 

I say: Just go out and enjoy your ride. Too much detail and thinking will limit your enjoyment.

 

I routinely ride in 100 + degree temp in the Mojave Desert. I turned off EITMS the day I bought my bike (new in 2019). Never had a problem with heat. Much ado about nothing, but it seems that you're having fun with your hobby so keep on it.

 

I'd say you too are having fun! I love your personal icon! 702's Avatar


Jim G