E Throttle - Duty cycle

[zek]

I recently swapped my 68mm BMW electronic throttle body for an 80mm version. It works, but I have an issue with the revs hanging when at 0% TP.

It happens when the ECU applies a duty cycle of less than 50% with the throttle closed (0% TP) - this causes the butterfuly plate to not seat fully against the bore causing a vacuum leak.

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I assume the difference in position is too small for the throttle position sensor to pick up, so it thinks it is at 0 but is not.

I have spent some time experimenting with the PID settings, which has helped a little but not solved the problem and I am afraid to mess things up.

Is is possible to request a feature that prevents the duty cycle from going under a set level at 0% TP?

Not sure what else to try.

Ben

[Dave Kriedeman]

When you calibrated the TPS, did you physically push the throttle blade fully closed and set that as your closed value.

Most DBW throttle blades will set in a slightly open position.

Which isnt really the closed value or position.

Try doing the DBW setup and physically close the throttle blade all the way with your finger.

Be VERY CAREFUL when the throttle blade opens,these things can do horrible things to fingers.

[zek]

Thanks Dave,

I pushed the throttle closed before I started the calibration and this has helped, but as the E throttle calibration process is automatic I could not find a way to set the closed value individually.

[Dave Kriedeman]

When i setup DBW,

I disconnect or turn off the power to the DBW motor.

I then hit the OPTION Tab at the top of the screen and do a TPS CALIBRATION manually.

Fully closed and WOT position.

Reconnect or turn on the power to the DBW

Carry out the DBW calibration setup,

Remembering to push the throttle blade closed when it does the closed setting.

[lemmy01]

Do you use DBW for idle control or do you have a idle-valve too?

I have a TP of 2.0% when the engine is warmed up to idle at 750-800rpm.

So your tp must be at (real) >2% when the target is 0 to have idle problems.

If so there must be something wrong with your settings.

Test your TP calibration:Remove the e-throttle fuse and move the TP with your fingers and look at the reading.

if you get only a 0% reading when the TP is fully closed your calib is good.

[zek]

Thanks guys,

Over the past week I have had fun messing around with this.

Unfortunately the calibration is still proving to be a pain as if I do a manual calibration and press the throttle closed at points during calibration it will then cause the E throttle to go into safe mode later on.

The only method that works is to perform several auto calibrations and choose the one that is most accurate after road testing. I also tried various PID combinations, but there is a small margin that If I go outside it will not calibrate.

I am going to try another throttle body to see if I can get any improvement. If not I don't think I am going to fix this unless there is some kind of semi auto calibration mode available.

Ben

[zek]

Do you use DBW for idle control or do you have a idle-valve too?

I have a bosch 3 wire ICV.

I have a TP of 2.0% when the engine is warmed up to idle at 750-800rpm.

So your tp must be at (real) >2% when the target is 0 to have idle problems.

Being an 80mm throttle and having an ICV It only has to stick open a fraction of a percent to cause idle problems.

Ben

[Dave Kriedeman]

Be careful when adjusting the PID parameters,

you nneed to make very small changes to the values.

I used to get impatiant when adjusting PID's and make large changes to the values.

Only to discover i was creating more issues, when doing so.

A work around for your idle problem, is to disable the ISC and use your DBW Target table to control your idle.

I had a similar idle issue with a twin throttle blade DBW setup on an engine with aggressive camshafts.

I managed to get the idle spot on with a combination of the DBW Target table and the Idle Ignition Timing values.

However to have success here the DBW must be functioning correctly.

Maybe post up your settings for the DBW so we can have a look for anything unusual.

[zek]

Thanks Dave -

I will try more subtle PID adjustments, I think this will be the key to cracking it.

My throttle settings are:

P = 8

I = 0.145

D = 30

Max Clamp 90%

Min Clamp -90%

Frequency 10000 Hz

Deadband 0.1%

Good to know there are other options, I will do some more experimenting. I have got it calibrated to the point where it only occasionally hangs a few hundred RPM over target now so not terrible.

Ben

[FIS]

I had similar problem, I leaned and reduce ignition timing on idle area cells, problem solved

[zek]

I swapped the Siemens throttle body for a Bosch 84mm and things are looking better - Will know after the weekend once I have made another adaptor plate.

I don't think it was possible to tune this problem out as the throttle would not close at the same position all the time.

[zek]

Well the Bosch DBW throttle is installed and my initial thoughts are that I like it much better than the Siemens unit.

It has a weaker return spring, so feels more responsive and seems to track more accurately.

One thing I had to do was put the deadband to 0.4, otherwise the throttle would try and close too much causing the Min DC limit error. (the exact opposite of my last problem )

Ben