|Posted on Friday, February 25, 2005 - 10:46 am: ||
Your engine is an "air pump"... The physical properties of your motor (eg, intake, head, exhaust design) dictate the engines air flow properties, or it's Air Flow Curve. If you change the physical properties of the "air pump", you change it's air flow characteristics and it Air Flow Curve.
The Fuel Supply Curve needs to suit the Air Flow Curve and dictates the fuel map. You add fuel to the combustion chamber as required to maintain your A/F Ratio.
So, deviating from the factory air flow characteristics by changing your muffler, adding a high flow air cleaner, etc, requires adjustments be made to the factory fuelling system...
DDFI does this to some extent.
The DDFI on your Buell stands for Dynamic Digital Fuel Injection... Dynamic referring to the fact it corrects Air:Fuel Ratio to suit changing conditions.
There is the Adaptive Fuel Value, or AFV. The AFV is the factor by which the DDFI has adjusted, measured as a percentage.
However, DDFI cannot change the shape of the Fuel Supply Curve, but it can adjust the entire Fuel Supply Curve up or down. This is only a problem with some intake or exhaust modifications that can change the shape of the Air Flow Curve, meaning the OEM Fuel Supply Curve is no longer correct.
How does DDFI know when to adjust?? It's called Closed Loop Mode. Your DDFI enters Closed Loop Mode when the bike is used at mild throttle settings and constant speed, ie, cruising...
So, if you are cruising at 3,000rpm, the DDFI moves the Fuel Supply Curve up or down to suit the air flow at 3,000rpm. This sets the A/F Ratio to be correct at 3,000rpm.
If the Air Flow Curve is a different shape to the Fuel Supply Curve, then this may cause a lean or rich mix on either side of 3,000rpm.
Fortunately for us, the DDFI enters Closed Loop Mode more often than many of us give it credit... In fact it spends a good deal of time in Closed Loop Mode, so these adjustments are being made very often.
Also, soon we'll have access to ECM Control Units, so we can adjust the shape of the curve to suit our air flow needs.
You can see the A/F Ratio data on the Dyno... You can have a separate curve plotted under the power/torque curve that will clearly display the A/F Ratio across the Dyno test
|Posted on Friday, February 25, 2005 - 02:30 pm: ||
Thanks BuellMan, that is some good info.
|Posted on Friday, February 25, 2005 - 04:18 pm: ||
Very soon (maybe next week)I will have my rolling wideband O2 sensor A/F datalogger hooked up to my 9. Then we will see what's really going on in a real world situation. I'll finally be able to set up the Teclusion box to my satisfaction. I sprung for an accelerometer as well. I can also log 3 other 0-5 volt signals going to the ECU. It should be very interesting.
|Posted on Friday, February 25, 2005 - 06:40 pm: ||
jerseyguy........ i for one will be very interested in your findings....keep us posted
|Posted on Saturday, February 26, 2005 - 02:54 am: ||
soon we'll have access to ECM Control Units
Buellman that sounds very good, where did you find that out from? I agree with your interpretation of the DDFI and AFV and closed loop, from memory my bike is still in closed loop at a steady 90 mph.
|Posted on Saturday, February 26, 2005 - 09:41 am: ||
Rigga - I just finished reading the hardware and software manuals. I think I'm going to set up the system to record RPM, A/F, Acceleration, TPS & temp. inside the airbox.
Opto - should we be blessed one day soon with programmable ECMs, I'll be ready.
|Posted on Saturday, February 26, 2005 - 10:53 am: ||
Jersey, Once before I mentioned the Veypor unit for measuring HP and TQ. This unit works with accelerometers similar to the G-Tech. Problem is they claim that a meter in one single direction will not yield good results on a motorcycle due to vibration. Just something to consider. You might have to run more than one accelerometer and do some software to calculate acceleration in the horizontal plane.
Anyway, very interesting, good luck on your endeavors.
|Posted on Saturday, February 26, 2005 - 12:23 pm: ||
If you have your race license you can already buy a programable ECU from Buells racing division. It may take a little searching a some connections but they are out there.
|Posted on Monday, February 28, 2005 - 09:50 am: ||
Jim, I'm more concerned about vertical acceleration than vibration at this point. The manufacturer says to keep the accelerometer within 3 degrees of horizontal as well. I'm mounting it roughly over the rear axle to minimize the vertical travel during hard acceleration.
The absolute number isn't critical to me at this point since I will be making comparative runs. Consistency is more important. It is purported that Torque and HP can be calculated from acceleration, but the jury is still out on that in my mind considering all of the variables. Plus I don't know how a calculated HP from an "on the road" run might stack up to what a particular brand of Dyno might claim as HP.