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Converting to Megasquirt how to keep a/c functional?

I've got a different 2 wire Volvo iac valve, can't remember the brand but not Bosch, mine is set at something like 217hz, I found adjusting the gain slider smoothed everything out.
 
arsenix said:
It should not be that sensitive, and i dont think you should need the duty cycle that high to idle.
Click to expand...

I'm not trying to be a dick, but do you think or do you know?

I'll keep my eye out for another generic PWM idle valve, one that isn't closed between 35 and 40% duty cycle, thus giving me full resolution from 0 to 100%. I think I will also try to open the throttle plate a bit more in order to use less of the idle valve. (right now it is adjusted as it should be stock for the LH2.4)

But I must also add, this is already in the nitpicking stage for me, my car is already VERY drivable, I could toss someone the keys and they can take it for a spin, no problemo.
 
OkeyDan said:
Yes, I'm running closed loop too, mine needs more work though. And I must say I wouldn't have thought it was so sensitive. I don't know about your car but in mine having a Idle valve duty cycle of 86% results in about 800 rpm and a duty cycle of 88% results in about 1500 rpm. So it sometimes keeps oscillating between 2 duty cycle steps. Does this sound familiar?
Click to expand...

it's not that sensitive. There are a few things at play:

the 2.4 idle valve has minimums and maximums above (and below) which it will default to a set position. call it a failsafe.
also, if you're just about giving it the full monty to get 800 rpms, you may want to evaluate your throttle stop position. I've found that in general, things work best when the car idles between 600 and 650 on its own without the aid of the idle valve.

Also, for closed loop operation, it is fairly normal for the idle dc to oscillate. Other things that also have a profound impact on idle quality and stability include consistency of tune, consistency of timing.
 
^ Oh yeah,I think my valve operates fully between 70 and 85% anything over and it starts to close again. Also as stated make sure your timing is consistent down low, I fought this as well.
 
@ linuxman51: Yes I know, between 35 and 40 % the valve closes again, so the real adjustability is from 40 to 100%. I'm not giving it 100% to get 800 rpm, if I set it to 100% I get 4000 rpm easy, that is what I mean by sensitive, 1 % makes a lot of rpm difference. I do think I now know why this is, while tuning the starting of this engine I found out they like a LOT of air while cranking so that's probably why these valves can let through so much air. Effectually taking away from the precision during warm idle. Like I said in my last post I will indeed try and open the throttle plate a bit more.

But anyway, it's idling ok now, just with a low P and I factor. If it would have more resolution (minimal step is about 0.5%) I could use higher P and I factors and make it quicker to react to changes in load.

@VB242 Wait, that sounds totally different than mine, is it a 940? Yeah I indeed changed the timing and the fueling to be consistent in the idling region, If I lock the idle valve to 1 position it purs like a kitten:p.
 
My car idles at around 45% duty cycle. 1% duty raises it maybe 50rpm. Your setup sounds wonky. Have you looked the idle valve using test mode to see if it opens progressivly with increasing duty cycle?
 
sounds more like incorrect frequency to me. I don't have any of my p&p stuff in front to compare notes for the lh 2.4 valve, but it's nothing crazy
 
I'm using the LH2.4 Idle Motor on my VEMS ecu. Diode across the + - at the motor to gain some resolution.
PWM Freq -75 Hz
P-80
I-25
D-0
Fully closed duty is 44%

Running spark advance idle control in conjunction with IAC. The deadband for the IAC is 20rpm
 
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@arsenix: That sounds like a different IAC valve than mine, at 40% mine is closed. (0% = slightly open, 35-40% = closed, 100% fully open). Yes I verified the positions by using the test mode and looking into the valve.

@linuxman51: I will play around with that, If memory serves me right I have it close to 100 Hz. Currently fitting a new t3 turbo so the car isn't running at the moment, will do this test in a couple of days.

@Homer: I think I have about, 20, 20, 40. And the gain slider at about 350. Not quite sure what a diode would do across the + and - other than flyback suppression, you could elaborate on that? And do you know what your duty cycle is while idling a warm engine? Spark advance idle control, sounds fancy:p, I don't think MSEXTRA has this functionality.
 
OkeyDan said:
@Homer: I think I have about, 20, 20, 40. And the gain slider at about 350. Not quite sure what a diode would do across the + and - other than flyback suppression, you could elaborate on that? And do you know what your duty cycle is while idling a warm engine? Spark advance idle control, sounds fancy:p, I don't think MSEXTRA has this functionality.
Click to expand...

It's just flyback suppression as you mentioned.
PWM: Used with PWM type idle control valves, either two wire or three wire types, for best control apply external Schottky diode flyback.
Click to expand...

Duty cycle on my 5cyl is ~47-48% at 850 rpm and a heat soaked 40C MAT.
It's best to set the reference DC curve to achieve 100 rpm higher than your target idle rpm. When you let off the throttle the idle will settle above the target RPM and then the PID will pull the idle down to the target. Keeps your engine from potentially stalling. Also if you can, add some extra timing in the bins below your idle speed. It'll help when you get sudden load changes at idle.

I'd have thought MS would have that control. :-(
http://vems.hu/vt/help/v3/v3_idle_control_menu.html
For explanation of the PID values.
 
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By the way, the ac doesn't cut off under load.


The problem is that the flaps are vaccum controlled, and it switches to foot and defrost setting when you have boost on the intake, the problem related to that is two small check valves on the vaccum lines that go near the oil dipstick, check them out, pull them apart and check that they only flow on 1 way.

Most likely, they are stuck, I manage to fix mine just by toying with it blowing a bunch of times
 
Homer said:
It's just flyback suppression as you mentioned.
Duty cycle on my 5cyl is ~47-48% at 850 rpm and a heat soaked 40C MAT.
It's best to set the reference DC curve to achieve 100 rpm higher than your target idle rpm. When you let off the throttle the idle will settle above the target RPM and then the PID will pull the idle down to the target. Keeps your engine from potentially stalling. Also if you can, add some extra timing in the bins below your idle speed. It'll help when you get sudden load changes at idle.

I'd have thought MS would have that control. :-(
http://vems.hu/vt/help/v3/v3_idle_control_menu.html
For explanation of the PID values.
Click to expand...

Thank you, no sadly it doesn't, that would be great for fine control of the rpm. Also about the reference curve. MS uses the last value it was idling at, plus something they call dashpot. So lets say my dashpot is 5% and the engine was idling at 50% and you give it some throttle and then back to idle, the valve will initially go to 50+5 = 55% and then follow your pid routine back down to 50%. Must say, this works very well.

Roman_Turbo said:
By the way, the ac doesn't cut off under load.

The problem is that the flaps are vaccum controlled, and it switches to foot and defrost setting when you have boost on the intake, the problem related to that is two small check valves on the vaccum lines that go near the oil dipstick, check them out, pull them apart and check that they only flow on 1 way.

Most likely, they are stuck, I manage to fix mine just by toying with it blowing a bunch of times
Click to expand...

Aaahhhh, that makes so much sense, never knew they were operated by vacuum and not by angry pixies! Thanks! Will check.
 
you'll need to replace a ~$20 or $30 vacuum modulator for the vents going to defrost thing.

and if you're curious about your heater core, that'd be a good time to replace that as well, since it'll only be a couple more hose clamps and like 2 bolts... EEEVERYTHING comes out for that modulator
 
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