Installing wideband o2 sensor

Wow! This is a really cool project and I am anxious to see the outcome of the analysis (plus in order to "test" the bikes, you have to ride them!).

Do you have a project thread for the bike you are using for the testing? I am interested in learning more about the mods done as I am thinking about changing mine up a bit.

Thanks kzr750R1. Yeah, I need to make the videos a little more intersting. The text was somewhat of an attempt. But really, it was my own cheapass method of datalogging :laugh: .

Thanks cafekz750, the "testing" is definitely the best part.

Usually I can get out earlier and avoid traffic, but the camera kept giving me a headache and cost me hours of fiddling.

I don't have a thread for the yellow bike, but I have on on the more recent red one, here:

losing the fat

After I'm done getting some baseline numbers from the yellow one, I'm going to hook up the red one. Then after that I have an orange one waiting.

Well, I finally had time to compile the data from several rides. These were done all in the 65 to 85 degree range in air temperature. Air temp, humidity, and barometric pressure did seem to change the numbers a little, but only by a tenth or two.

A bigger difference was seen based on how long I rode the bike. The bike didn't get consistent numbers until I rode at least 10 to 15 minutes at 85 degrees, and more like 20 or 30 minutes in 65 degree weather. Obviously it depends on how you're riding too. My warmups were stop and go city driving.

I plotted a chart based on throttle position. Every throttle position was held steady. As the RPMs changed, the mixture would change. Usually it would get leaner as the RPMs increased. (As would be expected.) So I held the position until the RPMs became steady. This was all done in sixth gear, except idle was in neutral. For throttle positions greater than 1/2, I used the reading near 8000 RPM, as the RPMs never stabilized, they would just increase.

even though I only recorded several fractional positions, I chose them because those positions were noteworthy. I made sure that positions in between the plotted ones followed near the curve.

The results, even though surprising, make sense in hindsight. For me, cruising at 55 to 65 mph was done from 1/16 to 1/8 throttle. That's where you'd want it to be most fuel efficient. Beyond that you start to get into power mixtures. In my opinion, this bike is a little on the rich side, which explains why it runs so nice in cooler weather in addition to running good in hot weather. 3/8 throttle shows a rather rich dip in the graph. 3/4 to full shows pretty much ideal.

Since you don't want to change jetting for every temperature, you naturally have to run a tad rich in hot weather so it won't be too lean in cold weather. The AFR numbers definitely showed leaner when cold. They were nearly a full AFR leaner after just coming off the choke.

Here's the difference a set of pods make on AFR. The blue line is the red bike I've been putting together. (I bought it from a friend named Karl, hence the name.)

Different bike, but motor internals are basically the same.
Exhausts are similar, but not identical.
This is just to give an idea of some round numbers.

EDIT: Notice the AFR goes rich right at full throttle. This is due to the throttle stop being set so that the slide raises farther than fully-open. Thus, the needle lets in more fuel without any more air getting in.

Hey lou, thats cool.I only just noticed this thread but I find that my 650 likes to run rich at idle and also low rpm take off, I run 13,2 afr at hte high load areas and 14.7 at cruise although the 35mm tb's are not open much at highway speeds. I am surprised how well the carbs cope over the entire range, I thought that they would not get to the 14,7 range at cruise speeds.

Yeah, I was surprised at how lean you can run at light cruise and it still is smooth. Doing about 60mph steady, between 1/16 and 1/8 throttle, my red bike is near 16 AFR steadily.

I did another run using different needles, and it was cruising at about 13 AFR. Way richer, but seemed to do well also.

But with both, I still get the occasional pop on decel with the throttle shut. The AFR goes very lean under those conditions.

this is awesome thankyou

School Teacher wrote:

this is awesome thankyou

My pleasure, but a lot of this data needs more explanation and review.

I'm posting it here raw, for now, but it's all subject to change as I get deeper into the project.

This posting is for 550rider since he is doing some jetting right now.

The orange trace is closer to what we're aiming for. However, the AFR readings in the graph do not represent the true goal. The true goal is to control AFR during acceleration. If we make the static-throttle AFR readings match similar to the orange graph, I'm hoping the acceleration while turning the throttle will make the AFR stay in the 11.5 to 13.5 range. The orange the graph actually resulted in slightly rich acceleration in the lower throttle positions (about 10.5 to 12.0), and slightly lean acceleration in the upper throttle positions (about 12.5 to 14).

When opening the throttle, then holding it steady, the AFR starts rich and slowly goes leaner as the RPMs increase. If we therefore open the throttle steadily, the AFR will go to a certain value and stay there as long as we continue to open the throttle steadily. We want that value to be at the richer limit, like 11.5 or 12. This way, when we run out of throttle, and the AFR starts to go leaner, it will end up near 12.5 or 13.

I'm still working out the details on this. For instance, one problem is; how fast to open the throttle? Too fast and the steady AFR will be way too rich and the bike will lack power. On this type of carb, you can feel the engine vacuum pulling on the slide. If you pull it too quickly, the throttle pull loses it's resistance and the bike tends to bog a little. If you crack it way too fast in neutral, the bike may even stall. Ideally, I want the engine vacuum's pull on the throttle to determine how fast to open the throttle.

There's a lot to juggle.