MSefi.com read only forum (Jan.15,2018)

Hello,

Ok, so using a Bosch Idle valve, pwm type.

+ Goes to ignition ACC (on when key is turned)
- Goes to MS-II F-Idle output

I am using the 3.57 SMD MS-II ver 2.6 which should not require any board mods to get the PWM idle valve to operate.

My problem is no matter which settings I go to in Megatune the valve gets constant power and just gets warm???? I had the ignition switch on for about 3 minutes and then I had no idle valve activity at all when i went under the hood to check!

Stupid me I did not run the diode across the input of the valve..........Could the drive transistor have been damage on the board? It is to my understanding that the diode prevents back feed of power when the pintle retracts via the spring......Trust me I feel stupid not putting a diode there...........Is this something I can check and replace? While not building the board myself (got a good deal on the SMD 3.57) I could de-solder and replace the transistor is that's all that gets damaged.

any thoughts?

thanks everyone

ok, update. I can turn it either on or off, that's it. Nothing in between!


any ideas? It's like it's operating like a fast idle and not PWM. And in the duty cycle tables i can only enter 1 or 0, turning it either on or off.

Anyone had this problem? Btw installed the diode so i guess there is no real problem with the circuit

thanks

T-,

Make sure you have selected "PWM Warmup" under "Settings/Idle Control/Algorithm". You might also want to post an MSQ file of your settings and a datalog to illustrate the issue.

Lance.

Yes, I have PWM selected under the algorithm. I entered values for PWM% in the table which I thought were reasonable.

OK, will post an MSQ file when I get home tonight. As far as logging, what do you need? I had done a bunch of datalogging this weekend hopefully what you need is there.

One thing I noticed is my embedded code is ver 2.6, looks like it's now up to 2.89? I'm going to try upgrading, but not too confident it will help my issue.

If it were a bad transistor, wouldn't it either be always open or closed (shorted to ground)?

Is there a min resistance value on the ISV valve? Mine reads about 3.8 ohms. Using ohms law it draws 3.15 amps with 12V applied. Do you need to run a power resistor maybe? I've got like 7 different ISV valves from Bosch mid 80's vw's. All read 3.8 ohms roughly.

thanks!

Please see the attached .msq file.

I've tried entering numerous values in the PWM duty cycle table, but as you can see I get it to open (power applied) when I use 0. Off is 1. Nothing in between

Weird.......any thoughts?

I don't have a datalog i can attach.........soon to come though

thanks

Paul

You have set the frequency to -171798691840 in that MSQ. That may be the problem.

Ok, time for a stupid question........

How do I change that? I saw various posts discussing frequencies........but never found where to enter it.

thank you, thank you, thank you!

Set it on the idle control screen.

OK, I think I got it now. So, Frequency=1000/(time step size in milliseconds)

Any ideas on a bosch VW valve, i read 150Hz might work. default is 400 hz in MT which is why I had troubles at first. I put zero in there and everything went to crap.

Not sure why it gave you that -17XXXXXXXXXX number. Maybe that's an error that occurs if you set step time=zero. Like divide by zero or something?

I'll try this soon, not much experience with how the PWM works but i'm beginning to understand.

Well, I tried my theory above with step size but when I select PWM warmup that field goes gray (can't enter anything).

Here is a screen shot of what I see. I don't see any reference to frequency on here?

Do I have the wrong version of Megatune or something? Says 2.25 P3 when I open it.

Please help! Thanks!

Make sure in the Configurator that you have set IDLE_CONTROLLER to "PWM Idle Valve (e.g., Ford or Bosch)".

I have it set to PWM Bosch ford. Could there be any other reason?
Thanks Matt
paul

Paul,

You set the PWM percentage under 'Other Tuning/Idle PWM Duty Cylce' as described here: http://www.megamanual.com/mt28.htm#ep and here: http://www.megamanual.com/ms2/IAC.htm#pwm

Step size is for stepper motor IACs only.

Lance.

Paul,

Also, I think the PWM frequency didn't become user-settable until the the later 2.6xx codes - 2.671 I recall (http://www.megamanual.com/ms2/revisions.htm).

So if you want to adjust the PWM frequency, you will need to use a newer code (and it will appear in the dialog - http://www.megamanual.com/mt28.htm#sd as 'PWM Frequency (Hz)'). You can find the latest code and instructions to install it here: http://www.megamanual.com/ms2/code.htm.

Lance.

Lance,

That makes a lot of sense! I had already downloaded the installer program and had planned on trying to upgrade the code. I bought my MS-II over a year ago (it was used but never actually installed in a vehicle) and it already had the 2.6 code loaded up.

I could have saved myself hours of trying different numbers in the PWM table..........if I had just upgraded my embedded code

You've been very helpful, i'll install and let you know.

Paul,

Yes, let us know how it goes.

Lance.

Thanks for the help, I upgraded to the most recent embedded code and I can now enter the IAC PWM frequency!

Valve works, but 100% turns it off (no power applied) and 0% is full open (power applied)

Any reason for that?

Other than that works perfectly! I can adjust between 100% and 0% to tune the idle.

WOO HOO

Here is a shot of the engine bay, I love MS

100% turns it off (no power applied) and 0% is full open (power applied)

Turbo-VW-ABA-A2,

Different valves have different 'directions' for the PWM%. I suspect yours was done that way so that it draws no power when it is warmed up - i.e. most of the time.

Other valves work the other way, though, and the code doesn't know in advance which way your valve will be. It also depends on the hardware between the processor pin and the valve. If the direction bothers you, you could define a new variable in the INI as new PWM value = 100 - old PWM value, but this would require doing a bit of homework studying the INI file. I wouldn't bother if it was mine though.

Lance.

Lance,

Gotcha. I won't bother modifying the .ini for now. Maybe if I get bored next winter I might experiment. It just doesn't seem worth it. Thanks for all your help.

Paul