TPS voltage offset with engine running

[Cliff]

I would set 100 also.

[Ryland3210]

That is an interesting theory, I should be able to verify that easily. If you're right I'm amazed it's so consistant and stable. I'll watch it under really hard decel too, it's should be worse then.

 

 

Thanks, that confirms my figures are not much worse than others. Maybe that supports Cliff's theory.

 

I've also studied the schematics and real world grounding. Even a severe grounding issue should not affect the 5V circuit much as long as it's not inside the ECU. And I'm pretty sure it's not.

 

I'll make some field studies!

On better A/D converters, the analog input has an independent ground, which would also be the ground reference of the precision 5 volt reference voltage.

How is the ground of the TPS connected to the ground of the ECU?

[dlaing]

On better A/D converters, the analog input has an independent ground, which would also be the ground reference of the precision 5 volt reference voltage.

How is the ground of the TPS connected to the ground of the ECU?

Good Question!!!

Looking at Carl Allison's earlier diagram it connects with the air temperature sensor and does not directly ground out.

Which is not likely correct, and a correction was made to it in a later version that connects the TPS ground with the air temperature sensor, the 3 way diagnostic connector, a ground point, and the 23 and 24 ports on the ECU.

Looking at my shop manual, it connects with the air temperature sensor, the engine temperature sensor, and port 22 on the ECU.

The port 22 could very well be the same ground as used by the 5V reference. Given that all three are 5V devices, it seems likely. But Carl's could be correct too.

We could try checking the TPS using the frame or battery negative as ground, to verify...

[raz]

On better A/D converters, the analog input has an independent ground, which would also be the ground reference of the precision 5 volt reference voltage.

How is the ground of the TPS connected to the ground of the ECU?

WM 1.6M does not provide separate ground on its connector so I guess Cliff couldn't improve that either. On Carl's latest Sporti diagram, which I believe is right, the TPS has three own wires all the way from the ECU connector. That is, the common ground is at the ECU ground pins. From that point, a not too heavy wire (maybe 1 or 1.5 mm²) also connects with ECU chassis at one of the mounting bolts. At that latter point, another not too impressive wire goes up to the battery ground strap. Inside the ECU, the PCB ground is screwed against chassis too.

 

My My16M (Mk II) does not internally separate analog ground but as far as I can see the heavy currents are routed directly to that same ECU connector ground joint so they shouldn't interfere internally.

 

The ECU does not require much 12V current. But it sinks ground for the coils and injectors (that gets their power directly from the power relay). So the ground requirement for the ECU is much higher than the 12V input current (and, for example, its real fuse requirement, 3A will do fine instead of the stock 15A).

 

The way I see it, the first thing to check is that tiny ground strap between battery braid and ECU chassis.

[v11cafe]

Don't know much about a bike's electric system,(...just the basic), so I consider as an axiom the remark of raz that

tps at idle is different than tps with with engine off/key on, and I see that most people here confirm it.

Since I cannot explain in theory why this happens, I thought how it affects setting the tps when I tune my bike.

Tps value at idle is a cumulative value, resulting from base tps(150mv+-), plus the value given by the

left or right idle throttle screw, plus the alterations happening to this value by synchronizing throttle bodies

with connecting rod, and bypass screws.

 

Guzzi and logic says that best point to set tps is where less components are involved, that is key on/engine off

....let's you worry only about the state of your battery, provided that all electrical components are OK (ECU, relays,..etc).

Right idle throttle screw is the best choice for setting the tps , because you get rid of the inaccuracy of connecting rod.

Some numbers.... Cafe sport 2004

 

key on engine off everything disconnected

Run 1 / base (0 angle) 152mv / right idle throttle body screw 0.472V

Run2 / 152mv / 0.472V

(instructions say 465+-5mv, I choose upper limit and added 2mv to compensate that base tps was 152mv(not 150mv)

 

engine running/everything balanced

tps idle / Run 1 / 0.483V / Run 2 0.515V

 

I could end up with any idle tps number ( within certain limits) with cylinders balanced , although start values are always the same, check how the bike goes on the road and if I decide that this is the best number for my bike,

then I have a shortcut to tune it without disconnecting anything.

With voltmeter check tps idle, and if you see the magic... number ....all ok.

What I mean is, that there is not exact tps idle for all v11, exact is only the initial (+- "value" mv) tps number

(set by right idle throttle screw) that Guzzi gives for the V11 model changes.

[Dimitris]

Bike is running fine! through the VDST I saw the followings:

 

TPS (engine not running) 2.8 degrees

TPS (engine running) 3.0 degrees

Trim -92

[dlaing]

engine running/everything balanced

tps idle / Run 1 / 0.483V / Run 2 0.515V

That is strange.

At first I thought Cliff's vacuum explanation made perfect sense, but this may fit in better with the 5v ground theory, or the air temperature sensor(not because of air temperature), another sensor changing the reading, or a drain from fuel pump and injectors.

Key on, engine off, the fuel pump primes than stops. Engine one, the pump goes.

Something is happening in the ECU to do this.

But if something changed the mV with Cliff's ECU, he would know about it, or maybe not, as it is a small change relative to the 12v system???

[docc]

The voltages would all certainly be somewhat higher running versus key-not-running.

 

Perhaps the higher running figure is just more voltage in the system? I wonder if the TPS reading would change from key-on to key-on with a charger hooked up.

[raz]

The voltages would all certainly be somewhat higher running versus key-not-running.

 

Perhaps the higher running figure is just more voltage in the system? I wonder if the TPS reading would change from key-on to key-on with a charger hooked up.

The 5V comes from a regulator that will give a very accurate output regardless of battery health or charging voltage. Even if the battery only put out 8 volts, the 5V should be almost unaffected. And likewise if an overambitious rectifier put out 18 volts. That's what got me started in the first place!

 

Today I finally confirmed that, by establishing the fact that my TPS voltage is not affected

at all

if I connect a charger with engine off (voltage went from 12.6V to 13.5V, TPS output at idle remained at 414 ±3 mV).

I'm currently putting my money on Cliff's theory. Not that the butterflies are sucked open in the normal sense, but I think the whole shaft is moving (due to wear) enough to affect the TPS sensor. I.e. the butterflies are not rotating but they are moving towards the cylinder! This may be a pretty small amount and maybe it's nothing to worry about other than I have to tell the ECU where the deck is.

[Cliff]

I don't think I've noticed any variation on my Sport.

Here's an experiment for someone - see if adjusting the bleed screw has any impact. If I'm right then screw in will give greatest suck effect and more deviation.

[dlaing]

I don't think I've noticed any variation on my Sport.

Here's an experiment for someone - see if adjusting the bleed screw has any impact. If I'm right then screw in will give greatest suck effect and more deviation.

And the balance could throw it off even more.

I have not set my balance in a few months, so it could be well off.

Time for a valve adjustment and a full tune up.

Will try to do that experiment this weekend.

[v11cafe]

The voltages would all certainly be somewhat higher running versus key-not-running.

 

Perhaps the higher running figure is just more voltage in the system? I wonder if the TPS reading would change from key-on to key-on with a charger hooked up.

Guzzi manuals suggest that Axone should be powered by the vehicle's battery,...think it means that they have observed variations

in numbers if you use different power sources, so a charger hooked up might not be a good idea,

...speaking for myself I don't tune anymore the bike if the battery is not 100% ok.

I have done it in the past and results were not good.