Can someone please explain to me why the M8 engines lack the typical Harley sound? I have seen people remove the catalytic converters and literally run straight pipes and they still dont have the sound that the Twin Cams have (or any other Harley engine for that matter).
What in the design makes them sound different?

 

8 valves up top, different head port design, dual counter balancers(in the softails), cam design, and other factors.
Remember when the TwinCam came out people said it didnt sound like a harley. Now there's people who swear it was the end of HD when the twincam and dyna was discontinued.

A stage 2 cam certainly brings a nice true harley lope to most M8 engines. It's definitely still more aggressive and angry sounding over previous Harley engines.

 

Thanks, that makes sense. I appreciate your knowledge on this subject!

 

Stock, they don't lack the sound any more than stock twin cams do. People have been modifying their engines to get that "lost Harley sound" since the advent of the shovelhead.

 

I think you need to get the idle RPM below about 900.

 

No overlap in the cams.. In fact they stay closed longer at TDC than say a latter TC. Add a cam with some overlap and you 'll get the sound back..

 

Lots of "pros" in the industry advise against this on the M8. I dont remember the reason why, but pretty sure harley even bumped up stock RPMs after the first year or so of M8 productions because of the same reasons.

As said already, good aftermarket cam and exhaust will make a huge improvement in sound. Still the M8 wont sound like a TC as the TC didnt sound like the Evo and so on. ALso the M8 is much more sensitive to cam/exhaust combos.

 

IIRC it was shortly after initial M8 release they changed from 850 to 950 rpms on production bikes. The SEPST Stage Calibrations updated to 950 from the start. Some of the issues / concerns with 850 were as follows;

1. Charging System Performance
2. Lower Oil Pressure
3. Complaints about clutch performance during low speed operation (this might have been the catalyst for HD making the change)

 

Sounds right. When I bought my 17, it initially had the lower RPM. Very shortly after purchase, I did the stage one upgrade and remember the RPM being higher. Seems like it might have even been 1050 at idle until I did a stage 2 aftermarket cam and tuner a year later. That put it back down to 950 or so.

 

same here, my 17 went to 950 after ECM calibration, and 1050 with EITMS activated, as designed and as stated in the OM