Originally Posted by mkguitar

I live in PHX, it's always hot and sitting on top of a 96" makes more heat than my other older Harleys with smaller motors and less precise fuel mixtures.
The 96" EFI also makes more power per cc than the older bikes (the 74" panheads make about 38 HP at the rear wheel).
The motor may be hotter without xieds, but I didn't measure- i bought it in October so had 6 or 7 months before it got hot.

The biggest difference for heat is fairing lowers on the bike decrease oil pan temps by about 25şF ( 12şC ?) measured on a 105ş ambient day. this is a result of increased airflow over the motor.
BUT that removed heat can feel like a blow dryer on the right thigh


performance: the xieds really only affect the ECM under part-throttle cruising conditions. which is about 90% of riding.
When whacking the throttle open ( WOT/ WFO) or when starting a cold bike, they are less active as the ECM is prioritizing input from other sensors.
This means that WOT takes the o2 sensor out of consideration and the rider could get some nasty pinging.


on my bike ( 09 FLHTC, 96"), when completely stock and after break in ( 5000 miles ( 8000 km), my bike would persistently ping under load- 2800-3200 rpms up 6% grades. We have alot of 6% grades in Arizona.

installing xieds solved that- and i ran that way for about 1000 miles.

then I swapped to hi flow exhaust for 1000, still to good result.

and finally to a high flow air cleaner, at which point the increased flow into and out of the motor gave a useable power gain. and still no pinging about 10,00 miles later.

I leave my Harley's at stage 1.

a rider looking to add cams or headwork later could instead look at installing a tuner system which can be adjusted as the motor is modified.

The fixed value xieds on my bike enrichen the mixture about 8%, the rev limit is unchanged.
This approach only affects the air'fuel mixture- as pointed out below by Fabrik8r, many other factors may effect pre-ignition.


how do it do?:

o2 sensors ( once heated above about 600şF) on your 2007 react to the exhaust gasses so as to produce voltage, this voltage from the sensor is read by the ECM and the ECM bases fuel mixture based on that. the Xieds are simply a resistor network which slightly reduces the voltage to the ECM.
The result is that the ECM makes the mixture slightly richer than it would normally be.

Usual voltage produced under stoich is .45 volts DC

if the ECM "saw" .4 volts it would add fuel, if it "saw" 5.5 volts it would reduce fuel.


this can be measured in real time with a voltmeter and i am sometimes seen running around my neighborhood with a big Fluke meter taped to the bars on a Classic and an o2 sensor in the exhaust. my old Cadillacs also get o2 sensor bungs welded in the exhaust when work is done.

slight resistance from bad wire connections from all the sensors ( most run under 5 volts) or at the ECM connector ( or the added connection of a piggyback tuner) can cause interesting problems


mike

Originally Posted by '05Train

No point learning to spell it when you don't know what it is.

Originally Posted by 12hdrk

..or smart enough to not get into a pissing contest about what they teach in high school power mechanics courses.

Originally Posted by '05Train

But wait, if you keep repeating the same thing on the internet doesn't that make it true?