Author Topic: hard to start, erratic idle fluctuations / stepper issue. log inside.please help  (Read 18807 times)

Offline ZoLtaR

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I have changed the topic title.

I have a problem with huge idle rpm fluctuations. It looks like IAC it's not working at all. When I'm disconnecting plug from there is no change at all.

It's "B02" Magnetti Marelli 4-wire stepper IAC from Fiat Marea 1.6 throttle body.
Does anyone know how should I configure those tables? Is it negative or positive? How should I set IAC sequence?











How to check if electrical connections are ok? Is there some possibility to do some tests with VemsTune ?


Valve look like this
« Last Edit: May 18, 2011, 08:16:54 pm by ZoLtaR »

Offline Sprocket

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Re: how to set 4-wire Magneti Marelli B02 stepper IAC
« Reply #1 on: May 16, 2011, 09:28:03 pm »
Simple things first. Are you also using the Fiat throttle body? Or, are you just using this valve on its own?

Aslo, is your box is fitted with the stepper chip?

OK

Set 'max steps to extend' to something like 180. This is basically the stroke of the valve.  You can do some testing to find the stroke by playing with the max steps to extend value and keying of and on again, but you must set both the IAC steps while cranking values to the same value as the max steps to extend (don't forget tho change them back again)

set the stepper speed to 70 for now to slow it down a bit, you don't want it to fast, like wise you don't want it to slow.

I assume the polarity simply changes the direction of the motor.

The step sequence needs a diagrmatic explanation in that dialog, but if you look at Phat Bobs instructions, you can see how the sequences are worked http://www.vems.hu/wiki/index.php?page=MembersPage%2FPhatBob%2FUserGuide You should be able to determine the two seperate windings in the motor easily with a multi meter. From memory the windings for this sort of valve are on pins 1/2 and 3/4. The raw step sequence 216 greyed out at the bottom I know will work the valve one way or the other as long as the wiring is correct. 201 will reverse the direction of the valve. This value will change as you change the sequence. The raw value is good to see as you can work out whether the motor is configured correctly or not.

These newer firmwares allow you to wire the stepper windings to any stepper outputs in any configuration, and then set it up in the config, but it can become a mind f$@k. Follow the diagram below and you wont go far wrong. pin 1-A-EC18/4, pin 2-B-EC18/10, pin 3-C-EC18/5, pin 4-D-EC18/11

accepted step sequence D-B-C-A (216 raw) and D-A-C-B (201 raw)



I don't see much wrong with the values for 'IAC position while cranking' but these are usually engine specific and may need tuning. I personally used 80 for warm and 160 for cold

The coolant refference curve is a bit bumpy. Try smoothing it out a bit. In reallity this curve will need tuning using the IacInt gauge, as the engine warms up, and logging is a godsend in this area and it will take several cold starts to get it right. The last point is used as the refference position for idle, again using the IacInt guage. Set the last value to 40 and tune the throttle stop/ throttle bypass screws while watching the IacInt guage at warm idle.

The max temp for cold idle speed is a little high, try 40c in there and 75c for min temp for warm idle speed. Again, these are dependant on the engine and the normal temperature it runs at. The max temp for cold idle speed is the point at which the idle speed starts to ramp down from the cold idle speed towards the warm idle speed. The min temp for warm idle speed is the temp at wich this ramp down finishes. The wider apart the two temperature settings are, the smoother the transition from cold idle to warm idle as the engine warms up.

Afterstart RPM may be a little high, but might be dependant on the engine. I would say 200rpm should be enough. 4 seconds is ok, again dependant on the engine.

The PID settings are explained better by others elsewhere on this forum.

what you have not shown is the 'idle control ignition advance' settings which includes settings for how the IAC is controlled with the 'igniton based idle control' enabled. Set advance change max advance, advance change max retard, advance rate of change and threshold for activating IAC all to 5 degrees.

See how you get on with that lot.  ;)
« Last Edit: May 16, 2011, 09:33:47 pm by Sprocket »

Offline ZoLtaR

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Re: how to set 4-wire Magneti Marelli B02 stepper IAC
« Reply #2 on: May 16, 2011, 10:10:06 pm »
Thanks for fast reply.
I ordered assembled ECU fully equipped with IGBTs/EGT input/Wideband and so on so I think stepper chip is there:)

And yes, this is whole throttle body housing with tps and stepper inside from Fiat Marea. It is in one aluminium housing that i used on my intake manifold.
It looks like this.


If I understand correctly after turning the ignition on , stepper should pull out the rod and then go back? Even without cranking the engine. I think such a situation does not have place in my configuration, I haven't seen that stepper is "alive" somehow after the ignition is on. Wiring is ok, I used connection diagrams from phatbob user guide as in the pic above.

So the stepping sequence is the most important hardware settings? What about stepper polarity "positive/negative" , and IAC float/normal options? How to set them?

But the worst thing is like the vems doesn't drive the stepper at all. Stepper looks like dead after ignition on. No movement or any sounds. May this be some vems hardware issue? How to check if the stepper chip is alive and ok ?

Offline Sprocket

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Re: how to set 4-wire Magneti Marelli B02 stepper IAC
« Reply #3 on: May 16, 2011, 11:31:50 pm »
Check in the menu 'Outputs' 'Assign Output channels' to see if there is anything else that is configured to use the stepper. Also check that there are no ignition channels configured for stepper.

Offline ZoLtaR

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Re: how to set 4-wire Magneti Marelli B02 stepper IAC
« Reply #4 on: May 17, 2011, 09:20:44 am »
I don't have anything assigned to stepper channels. I'm using 4x IGBTs for coils, 5xFETs for injectors and boost control and few spare P259 low current to drive fuel relay/tacho/shift light. And that's all. Look at the screenshot below.



Is there some fast method to check if hardware is ok ? I mean to measure something with DVM? I hope stepper chip is ok and it's a configuration issue. But why stepper don't move the rod after the ignition on  ???

Offline ZoLtaR

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Re: how to set 4-wire Magneti Marelli B02 stepper IAC
« Reply #5 on: May 17, 2011, 09:58:44 am »
Ok I checked with another 4-pin stepper just connected to loom plug and it moves the rod so I guess hardware/stepper chip is ok. But car is still not tuned, it's hard to start it without blipping the throttle, looks like IAC is in close position and there is no additional air to start the car and idle well. When I release the throttle it starts to fluctuate 1000-1500 rpm or even dies at all.

Offline ZoLtaR

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Re: how to set 4-wire Magneti Marelli B02 stepper IAC (now log inside)
« Reply #6 on: May 18, 2011, 04:41:58 pm »
I made a log of engine fluctuations. I'm starting to doubt if it's stepper motor issue. Look at the log, engine is reving 1000-1500-1000 rpm and so on.

here is the log
http://www.ital-performance.pl/temp/vems/v3.3_n003546-2011.05.18-17.10.14.vemslog

Maybe something in configuration is bad? Now I really don't know what is going on  ??? ???

Engine is Fiat 1.4 T-Jet with 60-2 and camsync.
- 60-2 pattern
- camsync
- 380 cc bosch injectors
- GT2056 turbo
- original bosch COPs running via IGBTs
- 46mm Fiat Marea throttle body

Here is some basic config that I want to start with but those fluctuations of rpms are so annoying that fine tuning of idle and so on is impossible  :(
http://www.ital-performance.pl/temp/vems/v3.3_n003546-A-2011.05.18-17.25.03.vemscfg

Offline mattias

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The fuel injector pulsewidth = 0 and the flickering of the idle air control status "IAC on/off" is a dead give away. Lower your idle rpm (adjust throttle stop), or disable overrun fuelcut by setting the values to unreasonably high values.


« Last Edit: May 18, 2011, 08:25:11 pm by mattias »

Offline ZoLtaR

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I can't adjust anything because of such a fluctuations. I tried a lot of times to adjust all IAC settings, but the engines does not respond at all. Anything I set , nothing change in engine behaviour. It also don't want to start without open throttle. With throttle closed, it starts for a second and dies. Cranking/priming parameters also doesn't change anything. I really don't know what to do now  >:(

I set overrun as you said:


and then started the engine. (with throttle opened, otherwise it starts and dies). I tried almost all settings, and nothing. Nothing change in it's behaviour. Here is the log.

http://www.ital-performance.pl/temp/vems/v3.3_n003546-2011.05.18-21.11.23.vemslog


In higher rpm engines works well I think. Only starting and that erratic idle problem.

Offline mattias

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Set the pressure based fuelcut to to 0 kPa. Your idle is lower than 40 kPa, so it will cut fuel when your TPS is below idle threshold.

If you just kept it at 12 kPa from your last log it would've worked just fine.
« Last Edit: May 18, 2011, 08:51:10 pm by mattias »

Offline ZoLtaR

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Ok, so I should it set to 0 kPa and fuel cut rpm to 25500 and fuel resume rpm to 25500 and leave it like that? If I understand correctly, 0 kPa means flames from exhaust when I go to redline and release the throttle? fuel won't be cut when engine brakes the car in the gear with released throttle?

With above 0 kPa/25500/25500 , then start to try setting the stepper motor IAC to get correct idling speed?

Offline gunni

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You never reach 0kpa so no flames ,,

Offline Sprocket

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Make sure the valve is operating in the correct direction. The majority of this type of valve close off air as the valve stem extends out, and opens up the air when the stem retracts into the valve body. If at key on the valve extends, then retracts, it is working in the correct direction.

Offline ZoLtaR

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You never reach 0kpa so no flames ,,

I was wondering if there is some possibility to make some flames when braking by the engine with released throttle?

Make sure the valve is operating in the correct direction. The majority of this type of valve close off air as the valve stem extends out, and opens up the air when the stem retracts into the valve body. If at key on the valve extends, then retracts, it is working in the correct direction.

Thanks for your advices!
I think I got it to work. But with very strange step sequence "30" = A-B-D-C. Is it normal ?
I still have a problem with cold starts. I have to crank it for a pretty long time until I get it started. With warmer engine it starts even pretty well but it takes 10-15 seconds until I get stable idle. Here is the latest config file. What should I change to get it working better?

http://www.ital-performance.pl/temp/vems/seicento_config.vemscfg

Still looking forward for help of vems-masters  ;)

Offline gunni

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Why does everybody want flames , I don´t get it.

anyway what you need to do is have no fuel cut when you close the throttle and retard the ignition ALOT.