08-02-2014, 06:40 AM
(08-02-2014, 03:45 AM)CBXBob_imp Wrote: In search of improving the small but present low throttle (lean ?) surge and better sound, economically, I have done the following mods.
1) added a 1.3 k ohm resistor in the IAT Sensor circuit.
2) blocked the pair valve air supply hose
3) installed an O2 Bypass resistor plug
4) drilled 25mm ( 1" ) holes into the baffles in the muffler at both
ends. The 'Walls' you see at both ends looking into the or inlet,
offset a bit inside.
Results are seat of the pants, no dynos nearby and not that anal about this.
Better throttle response, even down to below 2000 rpm in top( 5th)
gear. throttle stumble,hesitation or whatever between 2500 and 3000 rpm is 99 % cured.
engine is more responsive to throttle inputs and 'eager' to accelerate.
Mld to moderate sound increase at idle and hearable to about 40 mph when helmet noise blocks it out. The sound is like stock, only louder, not a deep rumble or loud bark like an after market exhaust.
Mileage appears to have increased about 2 MPG. 48 mpg on freeway, expressway keeping up with the faster traffic and 52 MPG,spirited riding on secondary roads. Just my results after a 338 mile day test ride.
If 2 semi mechanically skilled owners PM me their mailing addresses I will mail them a home made sensor resistor kit to install and try for their own evaluation. Locate IAT sensor plug under left side cover, unwrap tape, cut and strip one wire and screw resistor/ posilock assy on to wire ends. I will include pics.
So I take it that the added resistor fools the Intake Air Temp Sensor into thinking that the air temp in the air box is cooler than it really is, thereby causing the ECU to richen the Air/Fuel ratio.
The other way to accomplish the same thing is to relocate the IAT to a cooler location. This was a common mod on my previous bike (Vulcan 1700).
You might want to keep an eye on your plugs for fouling, especially now that you don't have a closed loop system with an O2 sensor, but you likely are not richening the mix much beyond optimum anyway. The only drawback to this mod that I am aware of is that on some bikes the ECU may have trouble if you make some drastic elevation changes.