air bleed vs co trim 15m ECU

[xackley]

After dealing with messed up threads on the idle stop screw, i got the base line 150 mV on the left hand throttle body TPS. I set the idle throttle angle between 3.2 and 3.4 according to guzzidiag. In order to get the idle down to 1100 rpm, I had to bottom out the air bleed screws (all the way in).

When I bought the bike it was running lean, then I used gorilla black duct tape to stop the leaks in the boots, then it ran rich according to the color of the spark plugs.
 
On my old R69 BMW bing carbs the mixture screw is actually an air bleed screw, same idea as the guzzi throttle body. But on the R69 I am not concerned with TPS voltage regulating actual mixture and timing throughout the rev range. So turning out the Air Bleed Screws and reducing the throttle angle to maintain a decent idle speed makes no sense when dealing with the air/gas mixture. That would just mess up the  15m ECU calculations by reducing the throttle angle while replacing the lost air with the screws? That would do nothing to resolve running too rich?

So, I am thinking that I should now be using the CO trim to reduce the gas until I achieve a golden brown spark plug. Is this correct?

Thank you
Don

I sure wish that guzzidiag could make the CO trim adjustment in real time. Every change in CO trim requires shutting down the the engine and guzzidiag 47 for the CO trim to take effect.

[guzzisteve]

I set the throttle angle at where ever it idles at 1100rpm not some number. With airscrews at 3/4 turn open.
C/O trim is in real time when it says start your engine to set it.  I use a 'Colortune' in sparkplug hole, change #'s and it gets richer or leaner.  Spark fire color in real time, better than a sniffer in the exhaust at idle.

[beetle]

The trick with GuzziDiag and CO is to wait ~20 seconds between adjustments. Ignore the instructions to switch off the engine after clicking 'finish'. The engine can be running when you open the CO trim menu.

[xackley]

GuzziSteve. Opening the air bleeds and closing the throttle plate is beginning to make sense for leaning out the engine.
The bypass effects all rpm, and throttle angle at idle being below spec doesn't really matter, as a slight twist of the throttle would get the same results through the rev range while the bypass gives it a little more air.

Beetle, so you are saying to just click up or down on CO trim, sit back for about 20 second without leaving by hitting Finish and the new setting takes effect. too bad I can't see the rpm and injection period while in the fuel trim dialog.

Thank you both
Don

Edit $75 for colortune would buy a lot of rubber parts I plan to replace this winter, so I guess I am stuck old school of making a change, and ride, and check the spark plug method. 

[Wayne Orwig]

I do it about like GuzziSteve.
I ignore that 150mv thing. What a waste of time.

1) On the 15M. Set the air bleeds 1/2 turn open. Maybe never touch again.
2) Set the idle trim to zero. Maybe never touch again.
3) With the linkage off, set the idle speed and sync to 1060 RPM.
4) Keep an eye on the TPS, and keep it near 3.6 degrees. Repeat #3 if needed.
5) With the linkage on, set the linkage balance at a higher RPM, say 2500.

If you have trouble, make sure the fast idle cam is not touching.
For step #3, I often set the TPS a touch rich, like 3.9, to keep the idle speed up.
Tweak the trim when done if needed. If the trim really makes much difference in idle RPM, go back to step #3.

[xackley]

I was stuck on the spec of keeping the idle at 3.2 to 3.6 throttle angle. I went with the lower limit as the bike is running rich. It still ran rich with the air bleeds closed to get the idle speed down to 1100 rpm.
Making sure that the throttle plate closed voltage is 150mV still makes sense. The TPS need a base line, and that number is the only part of the equation that seems to be almost universally accepted.
Per GuzziSteve (I think) Today I will be ignoring throttle angle and using the air bleed and idle stops only and tune it like I would a well sorted carb. Turning out the air bleed screws and closing the throttle stops to lean out the mix and maintain idle speed. I will be watching the throttle angle in guzzidiag, but as long  the status reports that it is at idle, I can't see how idle throttle angle really matters.
Don

[Wayne Orwig]

Making sure that the throttle plate closed voltage is 150mV still makes sense. The TPS need a base line, and that number is the only part of the equation that seems to be almost universally accepted.

Nobody with a CARC bike worries about such a thing. Just set the TPS to the idle value.

What idle trim value are you using?
Are the air and engine temp sensors good? Air pressure sensor?

[xackley]

Would CARC guzzis have an O2 sensor, if so the o2 sensor controls the mix in closed loop operation. 15m and earlier ECU do not test the exhaust gasses. Newer ECU appear to also have a mechanism to self calibrate the TPS, if I have interpreted the myriad of conflicting information available on the internet, so manually adjusting the baseline for the TPS is possibly not required as it for older, simpler computers.

All sensors appear to be operating correctly, and the engine performance is impressive. It is just running rich. CO trim on last ride was -2. My next was going to be reducing it a lot more, before reading GuzziSteves opinion, at this point his tuning technique sounds right.
So today a new set of spark plugs, a new twist of the throttle stop and air bleeds, and a ride, hopefully with golden brown spark plugs.
Don

[Wayne Orwig]

Would CARC guzzis have an O2 sensor, if so the o2 sensor controls the mix in closed loop operation. 15m and earlier ECU do not test the exhaust gasses.

You have to set the TPS on a CARC also. The O2 sensor does not set the TPS. Plus they can be run with the O2 sensor off.

[guzzisteve]

You might want to shoot some carb cleaner into the air screw hole just to have things cleaned out.
I look underneath at airscrew and index where closed, 1/2, 3/4 open w/marker. That way they're open the same.

[xackley]

Ok resolved the rich symptom by opening the air screws and lowering the throttle angle.
In fact I MIGHT have over done it. But the important part for me is I may have my mind wrapped around fuel injection on this motorcycle. Now to ride for an hour before it gets dark and then check if it needs dialed in a little more.
It's been an enjoyable afternoon of tinkering.

Thank you all
Don