EFI conversion on a Gen-1

[Jack Hammer]

Good to know. At the moment I don't need this but maybe in the future.

 

[RempageR1]

Hi,

I`m putting the bike back together for another year of fun, and there is one thing I still need to fine-tune. If you open the throttle slightly as shown in the video, the bike backfires slightly. If you open the throttle quickly, it`s just fine . What could be causing this? Too rich or too lean?

Thank you.

View attachment Vmax.mp4

 

[Jack Hammer]

Have you tuned AF independently on the cylinders or all the same? They are not the same. I've used independent O2 sensors and independent exh Temps. Your problem seems to be only one cylinder based on that video.

 

[Jack Hammer]

You are targeting leanest possible clearly. Your cylinder temps vary. You need to compensate with extra fuel. Running a bit on the rich side clears things out and whether you want to stay on top of it then that is exactly what open/closed loop is about. An engine is not a human heart, it cannot follow as far as your mind, you need to define parameters before it can learn by itself.

I know, sounds arrogant. If you want to know how I know then ask yourself : What are the two strongest ways to learn? Mistakes and time.

 

[RempageR1]

Thank you Jack Hammer, the pops happen at multiple cylinders, although more often on the rear ones. I`ll first try and lean it out a bit and see if that helps. The fact that it starts popping when I add a little more air might mean it was perhaps a bit rich. The O2 is on the rear right so I`ll check the values there a bit more closely once I got it ready to run again. Doing some changes on the EFI computer so that also takes some time to get right.

 

[Jack Hammer]

If you lean it out more, my quess is that the situation worsens. Take an IR gun to see the exhaust temps right where the exh tube begin before the first turns to get consistent results. Make sure you measure from spots of equal material thickness and surface.

 

[Jack Hammer]

Other thing with open loop is that throttle response programming requires you to understand certain definitions of the dimension of fueling vs air vs time. Over-airing (big TBs or carbs) mean aggressive over-fueling to create the intended result, simplified. Best results up-high compromise the results down-low unless you control the throttle electronically. You get the point.

I'm assuming ignition advance is good and not causing the symptoms. Ignition in fuel injection charts is the easy part.

 

[one2dmax]

I was going to mention that it needs to probably go richer to compensate for the sudded increase in air. Much like an accelerator pump would do on a regular carb to help with that transition.

 

[RempageR1]

In the end, the problem was twofold. I did lean it out a bit, but the main problem was that I was using TPS (throttle position sensor) with the VE (fuel) table. The thing is that a TPS is not really able to distinguish between 0 and 1% throttle. So with normal riding it`s fine but off idle, it`s not ideal. Below is a bit of telemetry showing how the TPS (after the bike has warmed up) hangs at 1.5%. I could set the reference value a bit lower but then it would say 0% even though the throttle was _slightly_ opened.


During the winter, I modified the Throttle Bodies. Before, the MAP sensor was connected to one TB, but as shown below it`s now connected to all four:



So with that, I have a much faster reference for the manifold pressure and the MAP value is averaged out over all four cylinders.

Since the manifold pressure _does_ rapidly change if you slightly open the butterflies it`s a much more precise way to measure the butterflies` small movements.

Today, I started out driving the bike which now was way out of tune since I had to rebuild the VE table. After an hour of driving with the laptop on my back, the bike was running well. Below are the differences between how I started out and what it was after an hour. 'Cell weighting' measures how long a cell has been tuned, 'Cell change' shows how it was tuned. Red is leaner, blue is richer.



And below is the proof that the problem is now solved:

View attachment WhatsApp Video 2023-03-11 at 17.43.35.mp4

Cheers!

 

[joksi]

Wonderful job! Unbelievable how much work you put in your project. Genius.

 

[Jeff Jarquin]

Fantastic!

 

[BrianB.]

Great work. Really impressive stuff from where I sit.

 

[lajo666]

Looks awesome fair play hell of a bit of engineering should see a mild power boost and better fuel economy

 

[Woody]

Snappy throttle.nice work!