I've had my 2019 SGS for a few months now and have added all the basics, bars, floor pans mirrors, etc. I'm about to add a Rinehart full exhaust, air filter and thinking about a stage 4 screaming eagle kit, I know the basic idea behind that would be more torque and hp, but I'm curious as to the effect on the overall fuel economy. My bike is rated at 43mpg, will the kit kill it completely on the Milwaukee eight 114?

 

I'm not sure. You might get a better response to this question in the M8 forum.

 

 

I somehow think the OP already knows the answer to the question.

 

Floor Pans ??????

 

I can tell you about a 2018 and a stage III and the answer is...not so much. The increased efficiency of the engine takes up some of the increase in fuel usage, BUT, the increase in fun factor will decrease the fuel economy by a great deal. Twitchy wrist syndrome will cost several MPGs as well as a few speeding tickets, but if your putting a stage 4 in a 114 M8 I imagine you already know that yes?!

 

Before you decide to do the Stage 4 make sure you study all the affects of the update. More power, absolutely....but at significantly higher RPM.

There are other cam changes that boost the torque in the the low RPM range that make an impact on the riding RPM range without having to rev it. If you want the Stage 4 that is fine but just saying... Check the torque curves that HD puts out for the various engine updates and pay attention to the torque curves and the torque peaks. While the torque 'number' and the HP 'number are significant I know for a fact that I would not be happy with where those peaks occur.

 

Aboslutely agree with Dceggert. While there is no replacement for displacement, you can get considerable performance bump with a cam swap. There are a lot of build configs out there for the M8. Do your homework and go with the right one for you. Be careful when comparing dyno charts and only use them as a rough idea as to what the end result will be, as these vary widely depending on many factors. The M8 heads have a great fill rate and would not need much, if any porting except maybe to clean the rough raidiases. They are showing to be very sensitive to exhaust back pressure: so choose your exhaust system accordingly

 

If you were really concerned about fuel mileage,whether the cost or the miles between fill ups, you would leave engine in basic stock condition. Considering the cost of your 2019 SGS with the special paint and the accessories already on the bike and plans for a stage 4 upgrade,cost of fuel isn't a problem. Also fuel range with a six gallon tank probably won't be a problem either. So you really don't need to worry about fuel mileage. Upgrade engine and enjoy it. JMHO

 

I went with the stage III kit on the 107 stock motor for the cam profile difference in the stage IV. I feared I'd be putting around at 4500 rpm and dead flat at 2500. I can use some fuel if I want. Running down the hiway at 70-75 seems to provide a pretty good range. I don't take MPG calc, just don't care.