FWIW, I pulled the inserts on my TTS tuned 124” build with the FM Outlaws and had to put them right back on cause the bike ran like crap, sputtered and back fired. I think the tuning on my setup is spot on, and the increase in airflow really affected it in a yuuuge way!

 

We've noted this effect many times, these motors are very sensitive to exhaust especially when you change out the stock cam. When you have a baffle or muffler core that is larger than necessary you lose velocity and this causes issues with low RPM performance & response, having an exhaust system that functions properly with your combination is key.

 

If this was reversed how would it affect the tune, by reversed I mean if the bike was dyno tuned with open mufflers (2.5 baffle)and you then put a more restrictive muffler on like your street outlaw, would it need a retune or would the ecm compensate?

 

Interesting. When FM built and tuned my 124, they only put the insert in the right side muffler and left it out of the left side. That could possibly? explain the slight flat spot I can see near the beginning of your torque curve.

 

If you are changing the flow characteristics considerably its going to greatly affect the tuning, this is also going to be proportional (i.e exhaust tuning is affected to a lesser degree on a stock engine than an engine with aftermarket cams, big bore, etc..) Also note the ECM can only adjust in closed loop, this does not include any of the higher load, upper RPM areas or at wide open throttle.

 

Thank you sir!

 

which flat spot are you referring to?
btw, this was tuned with both inserts IN.

 

I'd like to know all about this. Bike, year and parts used, and where you bought them.
Please and thank you.

 

You couldn't ask for better results than that!

 

Sure, here is my list:

S&S 124" kit 11:1 comp.
Fuel Moto/ Ward ported S.E. throttle body with 5.5 S.E. injectors
Fuel Moto/ Ward ported Level A cylinder heads.
Fullsac header
Fuel Moto Outlaw muffs.
Woods 408 cam and Woods Alpha lifters.
H.D. latest oil pump with new backing plate to cure the sumping issue (which so far it has).
AIM SDR clutch with S.E. 1275nm springs (stock 9 plate clutch plates)
TTS tuner