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Making sense of Wideband O2.

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This is my first attempt to "tune" a carb engine with a wideband O2 sensor, and I'm finding it's not that easy. Instead of uploading a map over USB to some PowerCommander, I'm looking at a voodoo analog computer with orifices and needles, jets and slides..

I'm hoping someone could sketch out their "here's what I do" pattern for checking Air/Fuel and interpreting the results. It's one thing to do a full-open runup in fourth gear, but how do you check the A/F across the throttle?

Is it normal for A/F to have a lot of noise? I'm sampling it 100 times a second, and the readings (from LC-1) seem to change rapidly. I've confirmed it with tha second unit and second analog output, so I don't think this is communication noise. What does the Wideband Commander output look like?

Here's an example of moderate RPM with just "maintenance throttle" at around 40mph:

part_throttle.gif

Since the throttle is just cracked open, is it normal for the A/F to be so lean (15)?

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I just look at the gauge while I'm riding and note the reading

and my throttle position (15 is way too lean obviously)... should be between 12.8 and 13.2. When I was adjusting mine the needle was good, 1/4 to 3/4 throttle, but the main needed adjusting since it was rich at WOT around 12.

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thats why i prefer the wideband commander.the readings are much easier to decipher.

is there a "smoothing" or "slow rate" logging option?

you need to put the bike in 4th gear and do steady throttle readings at different rpm/throttle positions.

your graph looks like that becuase nto only did you shift,but your not holding the throttle steady.

light load steady throttle can be as lean as 15 some times.but ideally i like to see it 13.5 to 14.0.

what jetting?

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Here is a wide-open pull in 5th gear (uphill) from 55 to 85mph. I'm most puzzled by the two periods where the A/F stopped bouncing and settled into a solid 14.7 for a few seconds! That makes me think something may actually be wrong in my carb. The mixture is just so erratic, it doesn't seem right.

wide_in_5.gif

I've doubted the sensor quite a bit, but it was recently tested against reference gas, and has a solid dialtone when the engine is off.

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thats why i prefer the wideband commander.the readings are much easier to decipher.

What kind of graph do you get from the WBC? (I already had the Race Tech DL1, so adding the LC-1 seemed like an easy way to go. If I had it to do over again..)

is there a "smoothing" or "slow rate" logging option?

There is, but I'm not applying very much now.. 0.2 seconds smoothing. I can thicken it up to make the readings more stable, but I thought I'd look at the fast numbers first.

you need to put the bike in 4th gear and do steady throttle readings at different rpm/throttle positions.

your graph looks like that becuase not only did you shift,but you're not holding the throttle steady.

You're quite right.. I need to go for a more purposeful ride and hold some steady states.

light load steady throttle can be as lean as 15 some times.but ideally i like to see it 13.5 to 14.0.

what jetting?

It's an SM with 160 main and a stock 'E' pipe on it. 2nd clip on the DJ needle. 4x4 :applause: airbox mod.

I thought I'd open up the airflow as much as possible, then work on the jetting to make it all okay. Clearly I've made some work for myself..

4x4.sized.jpg

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On the E header.. like this:

IMG_0357.jpg

Yes, it's filthy, unworthy of a new bike, and in need of a sound sandblasting..

IMG_0387.jpg

S'alright?

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FYI this is from Uncle Bob who uses the LC-1 (in case you wanted to use a gauge instead of the computer).

"the LC-1 does not come with a gauge, but you can program one of the output wires to convert to a traditional narrow band signal, which allows you to buy any cheapie NB gauge and use it with the LC-1"

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"the LC-1 does not come with a gauge, but you can program one of the output wires to convert to a traditional narrow band signal, which allows you to buy any cheapie NB gauge and use it with the LC-1"

Yeah, I'm thinking of doing that. The digital (proper) gauge is $229, so a cheapo narrowband 'disco light' is sounding pretty good. I didn't think I'd want a guage, but I was wrong.. sure would be nice to see the data in real-time.

Even just a 0-2v multimeter will do me fine. I think I'll go strap my Fluke on the bars to see.

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Okay, I went out and did some :applause: in the name of science.

First, a few steady partial throttle spans:

steady_3x.gif

The moral of this story is pretty clear -- more throttle makes it much richer. I'm lean at the bottom and rich on top. Call it the west coast cappuccino..

Then the full-open throttle pull in 4th gear:

4th_1run.gif

This is a steady ride at 60mph around 35% throttle.

legal_60mph.gif

And the same at a more zesty 80mph (5th gear, 50% throttle):

50percent_5th.gif

I'm guessing I have to give up the 160 main jet and go back to 155, then take the needle out a clip or two to richen the low throttle? I could also tape up part of my enlarged airbox hole, but it's not clear to me how this is impacting the part throttle more than the full throttle where I expected a bonus and got none.

Thoughts?

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I'm guessing I have to give up the 160 main jet and go back to 155, then take the needle out a clip or two to richen the low throttle? I could also tape up part of my enlarged airbox hole, but it's not clear to me how this is impacting the part throttle more than the full throttle where I expected a bonus and got none.

Thoughts?

definitely a good start....I'd leave the box alone personally

Kinda cool seeing the time line with speed....man! 20 seconds from 55mph to 85mph or so. Its depressing seeing the numbers on paper (nothing to do with your tune....just not what I'm used to)

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155 main is a good move.you could also just open the air box a little more.

retest steady throttle again after the main jet.

1 change at a a time.

what pilot jet are you running?what is the a/f reading at idle?

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Doh.. I need to take better notes.

I opened up my jet kit to find the 160 sitting there, surprisingly.. present!

I just opened the carb to find the 155 in already.

I dropped it down to 150 just now. I was hoping to get more fuel through the stock E pipe, but I guess 155 was just too fat. (I have to wonder, would a corked Yosh be any better?)

I'm running the 25 pilot jet that I put in with the original 3x3.

My (warm) idle reading is currently 12.2 at 1500rpm. I optimized for good smooth idle, needing just a little choke for morning starting, and quick off-idle response. No complaints there. (87oct)

Here's a long idle with a hot engine, and one small throttle blip in the middle.

idle_blip.gif

Good point about the "one change at a time". I'll leave the needle (and box) alone for today, but I expect unbearably lean midrange. Fortunately, it's easier to get to than the main jet. :applause:

Thanks again for the helpful comments!

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I rode with the 150 jet, and no other changes (Still the enlarged 4x4 hole and second needle clip)

The bike is nearly unrideable at partial throttle. It sputters and bucks like it needs to flip to Reserve fuel. It's super-lean (17.1) at part throttle and higher RPM (6k), which is the reason I started this whole thing in the first place.

Full-throttle is more promising, with 14.2 readings low RPM, and richening up to 13 at max RPM. Here's a 4th gear pull:

4x4_150_wot.gif

Given that max throttle is in the right range, and partial throttle is not -- does that imply I need to back the DJ needle out a click or two?

I guess I'm just surprised to see the increased airbox hole actually impacts mid-throttle more than full-open.

I taped up half the airbox hole to try tomorrow, since it's easier than pulling the carb again.

I'm still not convinced that all this vacillation between readings (swinging 0.7 Air/Fuel or more) is normal. Is is it possible my slide isn't functioning correctly? It's almost like it's too fast and the needle is flying back and forth.

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a single cylinder is taking big gulps of air with lots of time between pulses. Its a much different situation compared to multi-cylinder engines.

severe derestriction of the air box on just about any bike, will usually have a large effect on the low speed. You are doing something simular to removing the entire air box completely.

You're giving up awfully fast on this....why use the WBO2 if you're not willing to use the data???

you could try raising the needle, although I suspect that would enrichen the mid range too much, you might be stuck putting a different needle in it, or changing the pilot. Since the needle is easy to get to without pulling the carb, why not start there?

This is how carb jetting always goes, WBO2 or no.....you gotta be prepared to pull the carb more than twice! Heaven knows, I've had my carb out dozens of times

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severe derestriction of the air box on just about any bike, will usually have a large effect on the low speed. You are doing something simular to removing the entire air box completely.

I see. I perhaps got a little excited with the dremel, and should have done more measurements first.

You're giving up awfully fast on this....why use the WBO2 if you're not willing to use the data???

Oh I'm not giving up anything yet! I just didn't get a chance to tear into it tonight, so I thought I'd tape up a bit of the airbox for the commute tomorrow -- just to collect some supporting data.

you could try raising the needle, although I suspect that would enrichen the mid range too much, you might be stuck putting a different needle in it, or changing the pilot. Since the needle is easy to get to without pulling the carb, why not start there?

Roger that. I'll give that a shot on Saturday.

What can you tell me about how the Pilot jet influences the midrange? I know it's King of Idle, but how far into the powerband does the Pilot Jet play a role?

I've only done electronic mapping before, where RPM and throttle are distinct axis, but here it seems there is more interaction. High RPM cruising with small (20%) throttle twist -- what jet has the biggest part here?

This is how carb jetting always goes, WBO2 or no.....you gotta be prepared to pull the carb more than twice! Heaven knows, I've had my carb out dozens of times

Yup. I didn't think this would be easy or quick, but I'm still looking to make some kind of logical sense of it all, and correlate the adjustments to the readings. Carb School for Geeks.

Believe me, I'm reading Your Other Thread with boosted interest. :applause:

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its not fuel injection.the fuel curve will never be completely flat.

you will end up with a larger main jet.

on this particular motorcycle the slide is fully open much earlier than you think.

i cut the top completely off the drz air boxes.the only difference in setting is the main jet.

when you raise the needle it will make it to rich at small throttle oepnings.

the pilot jet only effects idle and super small throttle oepnings.

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Was wondering which carb this is. Looks like it has a TPS and you hooked it up to the sensor.

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Was wondering which carb this is. Looks like it has a TPS and you hooked it up to the sensor.

Exactly -- stock S carb, with the wiper of the TPS pot connected to the datalogger. It's around 0-5v with some fudge:

Throttle % = (100 * (100/62) * (Volts / 5)) - 22

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