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Milwaukee-Eight - Dyno Charts & other Interesting Info



Twin-Cooled & Air Cooled M8's




Report of our Testing of Twin Cooled & Air Cooled Milwaukee-Eight's on the Dyno, and some extended street riding.



Unlike the Twin Cams, this M8 was NOT running overly lean from factory. When we swapped out the stock faux "stage I" air cleaner with one of our true Stage I Air Cleaner Systems, it did amazingly well with NO change to the tune.



 This next chart shows the improvement in the stock AFR on the M8's. You can see, except for the shift points (which are the peaks) that the blue line is staying between 14.5:1 and 15:1 AFR while cruising thru the gears.

On stock Twin Cams it was normal to see it up in the 16.5:1 to 17:1 range.

The red line in the chart is showing a base "Stock Improved" tune from the Power Vision. It is a tad richer, but not much, since it was already pretty good from the factory as far as AFR.


This next chart shows the difference between the stock tune and the Power Vision "Stock Improved" tune. Nothing was changed other than the tune. The air cleaner and exhaust are stock. The improvement from the tune is modest but very definite.


The next chart shows the stock tune, stock air cleaner, stock exhaust, vs. a Power Vision base tune with a M8 Outlaw 587 Air Cleaner System. The exhaust was Not changed, Nor was any dyno tuning done Nor any auto-tuning.

It is a very nice jump in Horsepower & Torque with just the PV base tune and a True Stage I A/C System. This is the same A/C system in the chart shown in the original post in this thread. The small improvement is from the addition of the PV base tune.



This chart show that at WOT (Wide Open Throttle) the factory AFR is good.  Unlike the Twin Cam, it is Not running too lean from the factory.



This chart shows that at WOT with the M8 Outlaw 587 A/C System, the factory AFR is Still good!



This first chart shows a comparison between completely stock and with the M8 Outlaw 606 Air Cleaner System with a base Power Vision tune. The exhaust was Not changed, nor was any dyno or "auto" tuning done.

The 606 gives a slightly better jump in horsepower and Torque over the 587. 



This chart shows a comparison between completely stock and the M8 Outlaw 636v Air Cleaner System with a base Power Vision tune. The exhaust was Not changed, nor was any dyno or "auto" tuning done.

This 636v was with the standard oval filter element. 

The jump in torque was fantastic. While most folks seem to be pre-occupied with peak Horsepower #'s, our focus is on the peak Torque. This is for a few reasons:

1. Peak horsepower occurs at an RPM that is rarely ridden in daily riding.

2. Peak Torque occurs at RPM's that are in the everyday riding range.

3. Torque is the feeling of "grunt" that most folks really enjoy about their Harley

You can see from the nice bump in Torque, and how long it lasts- breaking 90 ft. lbs. at below 2000 RPM and staying above it til almost 4500 RPM- that this kind of power is a lot of fun to ride with, and is one of the reasons why we are impressed with the M8 and its' potential.




This chart is a comparison of Completely Stock A/C & tune with the M8 Outlaw 636v Air Cleaner System using the Shorty Oval Filter Element & base Power Vision Tune. 

It has just a tad less increase than with the standard oval or Monster Round Elements. But it still kicks the stock A/C's butt, AND it fits on all bikes and trikes that have lower fairings. 


This next chart shows the difference between Stock and the 636v A/C with the Monster Round Filter Element.

It give just a touch more performance than the Oval Element, but not enough that it would even be felt in daily riding, so it would just come down to which look is preferred.



This last chart is an interesting one. We get asked all the time "how much air does XYZ air cleaner flow"? 

As you can see from the chart below, free flow of air is only one, of many, important aspects to designing and manufacturing a top performing Air Cleaner System.

This shows that without a filter element there is substantially less torque than with a filter element. It also shows that there is less horsepower, all the way up past 4500 RPM, and even after that, it is a very small increase.


These Charts showing normal operating temps are Directly from the Harley Manual:






Other interesting info-

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.

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.