M8 Twin Cooling engine temp info - don't close those vents!!
#11
04-13-2017, 02:56 PM
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Infra red gun, 2" from the head, right behind the spark plug. We also use the ET readout on the Power Vision when monitoring temps.
#12
04-13-2017, 04:11 PM
Seasoned HDF Member
#13
04-13-2017, 04:13 PM
Great info! Thanks for posting it.
We've just barely begun doing our heat testing on the M8's, but have seen that while the M8 has a lot going for it, HD still did not solve the heat issue. We're seeing a lot of the same things on the M8 that we've seen on the Twin Cam. HERE is a report we did a while back.
Below is a copy and paste of a post on and oil cooled M8-
Heat & Performance on the Dyno-
Heat on the Road-
We've just barely begun doing our heat testing on the M8's, but have seen that while the M8 has a lot going for it, HD still did not solve the heat issue. We're seeing a lot of the same things on the M8 that we've seen on the Twin Cam. HERE is a report we did a while back.
Below is a copy and paste of a post on and oil cooled M8-
Heat & Performance on the Dyno-
The M8 reacted very similar to the Twin Cam on the dyno in regards to heat.
When doing comparative Dyno pulls it is important to have the engine temperature the same with every pull.
On both the Twin Cams and the M8, when the cylinder head temp crosses the 250* line power drops off, significantly.
We always get the engines heat soaked, then use the dyno fans to try and keep the temperature stable. However, just like on the Twin Cams, the M8 will go past the 250* mark very easily, even with the fans on. So there are times when we have to wait for the engine to cool down to get to our 240-245 range for accurate comparative pulls.
The upshot of all this is that the M8, while have less felt heat, still seems to have the same overheating challenges that the Twin Cam does.
When doing comparative Dyno pulls it is important to have the engine temperature the same with every pull.
On both the Twin Cams and the M8, when the cylinder head temp crosses the 250* line power drops off, significantly.
We always get the engines heat soaked, then use the dyno fans to try and keep the temperature stable. However, just like on the Twin Cams, the M8 will go past the 250* mark very easily, even with the fans on. So there are times when we have to wait for the engine to cool down to get to our 240-245 range for accurate comparative pulls.
The upshot of all this is that the M8, while have less felt heat, still seems to have the same overheating challenges that the Twin Cam does.
Heat on the Road-
We had the M8 for two days, and both days were cool, in the 50's. So all of our testing of temperatures were in relatively cool ambient temps.
We were disappointed to see that the M8, again, while have less felt heat, has some serious temperature challenges.
At 70 MPH cruising, in 54* ambient temps, we saw the Front Cylinder at 290* and the Rear Cylinder at 310*. This was after only 30 minutes in cool temp riding, One-up.
Another 45 minute test, again, one-up and easy riding at 56* ambient temps, showed a front cylinder temp of 288* and a rear cylinder temp of 317*.
Since we already know, from our time on the Dyno, that the ECM is pulling spark (retarding the timing) when it crosses the 250* mark, we know that in everyday riding, even when it is cool out, that the engine is not performing optimally, power-wise AND MPG-wise.
We were disappointed to see that the M8, again, while have less felt heat, has some serious temperature challenges.
At 70 MPH cruising, in 54* ambient temps, we saw the Front Cylinder at 290* and the Rear Cylinder at 310*. This was after only 30 minutes in cool temp riding, One-up.
Another 45 minute test, again, one-up and easy riding at 56* ambient temps, showed a front cylinder temp of 288* and a rear cylinder temp of 317*.
Since we already know, from our time on the Dyno, that the ECM is pulling spark (retarding the timing) when it crosses the 250* mark, we know that in everyday riding, even when it is cool out, that the engine is not performing optimally, power-wise AND MPG-wise.
Otherwise everything you experienced is exactly what I experienced. To optimize performance of a twin-cooled bike, its critical to keep the lower vents FULLY open and the coolant level full.
Last edited by Heatwave; 07-26-2017 at 04:15 PM.
#14
04-13-2017, 08:57 PM
Road Captain
#15
04-13-2017, 11:44 PM
#16
04-14-2017, 08:51 PM
Road Captain
#18
04-14-2017, 09:59 PM
Seasoned HDF Member
#19
04-15-2017, 04:57 AM
Thats why i asked what bike he has. The oil fan doesn't fit a twin-cooled bike but if he has a '17 M8 thats not water-cooled then the oil fan is an excellent idea. These M8s run hotter than my twin cam.
#20
04-15-2017, 08:21 AM
Road Master
Thanks for the info Heatwave..
I rode my bike yesterday(warmest day of the yr),,, Ambient Temp was 82*F,,, MoCo definitely has the EITMS "On" at a lower setting then my 2013 was( Or is this the difference between a Twin Cooled & Non Twin Cooled?)... Once my bike was at full operating temp, every time I stopped at a Red Light it kicked in. I did notice my idle went up from 950 to 1000... As soon as I get the 1000 mile check up & service the FP3 will go on it...
I've always done my own Services & work, but with this being a new engine design and a CVO it's dealer services till the Warranty is out.
I rode my bike yesterday(warmest day of the yr),,, Ambient Temp was 82*F,,, MoCo definitely has the EITMS "On" at a lower setting then my 2013 was( Or is this the difference between a Twin Cooled & Non Twin Cooled?)... Once my bike was at full operating temp, every time I stopped at a Red Light it kicked in. I did notice my idle went up from 950 to 1000... As soon as I get the 1000 mile check up & service the FP3 will go on it...
I've always done my own Services & work, but with this being a new engine design and a CVO it's dealer services till the Warranty is out.
Last edited by Sam D.; 04-15-2017 at 08:31 AM.