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Bad fuel mileage

2K views 14 replies 7 participants last post by  lh4x4 
#1 ·
I have a 07' road glide with the following mods:
Thunder header
S&s .570
103"
Very mild head work
K&n filter
Power commander

The problem is when I run about 80 or so my mileage drops to 30 or less. Never above 40, even with going slow.
My mechanic seems to think the problem may be the exhaust. Any ideas?
Any shared wisdom is appreciated!

Thank you.
 
#8 ·
There are a few ways to look at this. 02 sensors should be used in today's motors. Without the sensors it's all guess work. That being said, it all depends on where you want to run the motor. Closed loop will run .977 lambda, maybe .974 if you have a very good sensor location. That's 14.3 afr, if you want to run it richer, you will need wide band sensors and a head pipe/exhaust that has the bungs for those sensors.
You can get sensor bungs welded to your pipe fairly cheap, just make sure they are put in the right place. You can use a PV with a target tune setup, or you can go with the auto tune pro setup also. I used TTS for 3 yrs, it's a good tuner, but now I am experimenting with the PV and Target tune. Dialed in really quick, very easy to use. Easy to make adjustments.

Give Fuel Moto a call, I believe they have a promotion going on for trading in your tuner and upgrading. Great company, and provide you with a good base map, and unlimited support. Hope this helps
 
#9 ·
I am running a 2012 103 with a thunderheader. air cleaner and Fueling 574 cams with a Cobra tuner,mileage runs about 39 around town and 42-45 on the highway at about 70.
 
#10 ·
Get you a dyno guy that uses TTS or Direct Link and get a good tune. He should tune the throttle positions and rpm's for cruising speed and the rest of the areas tuned for max power. With this you get the best of both worlds and a bike that should get from 41-46 mpg cruising. Nothing beats a dyno tuned bike.
 
#12 ·
BTW, for fuel economy run the motor in closed loop mode in the cruise section of the map, and open loop when you want the AFR to drop for power. If you really get into how the ECM operates you can actually keep it in closed loop and just add fuel and advance the timing through various ECM parameters.
 
#14 ·
I forget the exact parameters but basically you tell the ECM set the fuel AFR to 15.x (I have to look up the "x") and that tells the ECM to stay in closed loop. Anything outside of the 15.x setting is open loop. To get the true AFR you want there are bias tables you adjust. It's kind of a screwy setup on the 07s because you are really tricking the ECM into thinking that "X" 02 reading is 15.x AFR but you are going after the AFR you really want whether you are targeting fuel economy or power. The beauty of the system is you can actually build the map in such a way that it produces excellent power and gets good fuel economy. If I kept my hand out of the throttle I would get between 40 and 50 MPG all day long, but if I had my hand in the the throttle well it was a 25MPG bike, but man hang on to your shorts because it ripped.
 
#15 ·
My 12 RGC with a Cobra FI2000R-CL, iridium plugs, SE wires, Ventilator breather and stock exhaust runs 52 mpg at 70 mph.

Combined with the above was a slow three K run in after doing 12 heat cycles. My dealer leaves them for me as they come off the truck with >1 mile.

I have had some long local runs at 55 mpg on the 55 mph speed limit local roads.

Just traded it in today at for a 16 RGC CVO Ultra. Some one should go get it.

Another factor with the mpg is that it uses 87 octane only. Except in the mountains when it uses 85 octane.
 
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