Idle valve min/max duty %
 

I've read into my issue about low RPM warmup idle and idle dip for quite some time now and haven't been able to figure it out. However, I'm starting to understand the closed loop PID settings a bit more and have followed numerous guides to how to find your min/max duty %.

Following Braineak's guide, I did the following to identify my duty % -- but my numbers are VERY off.

1) Test valve setting. Set it to 0. When warm, the car idles at 750RPM at this setting.
2) Raise test valve setting to a number that begins to affect the RPM, this number is 75%.
3) Raise test valve setting to a number that no longer raises the RPM, this mumber is 100% for me.
4) I've read that 90-93s run around 23-64%.

So if these values ring true, I should be setting my minimum to 75 and max to 100%. But again, these values seem crazy high.

What's going on here?

2003 NB Miata (RX8 injectors, CAI, mostly stock otherwise) , MS3 Rev built.

These are the same numbers for Lazarus, we're 100% sure something is wrong with the valve.

Any link to his thread? What did he do to fix it? My idle is fine with my original ECU, although I'm not sure how that translates to the MS3

So far we haven't done anything, our first step will be cleaning it it, after that GreddyGalant has a new valve to install, after that we'll look at our wiring. We're leaving wiring for last because it does work, just in a different range than it should. It also feels like it's sticking. So I'm suspecting a blockage, either of oil, carbon, or gasket. Followed by a slightly sticky valve.

Greatest build thread in history:

https://www.miataturbo.net/build-thr...nothing-75005/

Surprised it's not bookmarked yet bro...

yeah I'm at like 6/28 iirc

28% max? How's it start? Even with properly working ones, I'm around 50% for cold starts.

cold start idle valve settings are 36-46 iirc
I'll have to double check all this on my laptop, but pretty sure that's the ballpark

I know you're not at your laptop, but I'm pretty sure the closed loop idle valve min/max goes for cranking duty too.

And I just found Laz's problem, his settings were set to inverted, where 100%=closed. Oops.

Not on my setup. I can call for all the idle valve on start, but it won't ever naturally go higher than the limit after the afterstart taper has run out.

Something I do to tune vapor lock injectors on hot restarts, or at least in theory. I can have high RPM starts with plenty of valve, but it won't ever rev like mad at a stoplight again and get stuck outside closed loop entry conditions.

For funsies I tested my valve at 100% the other day. Something like 4000 rpm. Racecar idle.

So now that I've tested my car at 75% min and 100% max, is there a reason why I wouldn't enter those as my min/max duty in CL idle?

The logic being that the valve isn't actually opened 75% at min or 100% at max (because all the problems listed above), so it would be equivalent of me setting it to what everyone else has at 23-65%ish. Does that make sense to anyone?

As of now, my idle open duty during cold starts is 80%, which allows me to start the car without throttle. I just need to dump in a ton of gas for ASE/WUE to keep it rich during warmup. However, it prevents my car from stalling when I drive around when the engine is cold. Any reasons why I wouldn't set my parameters like this?

Remember that it's % duty cycle (PWM), not % open.
If you can get decent function, use the values that works for your case.

BTW I had about 5.2krpm at fully open NB valve when I used a flattop, not a quiet test in an apartment garage...

Thanks for that, I wasn't aware of that.

So I took apart my MS3 and measured the diode and found that I get 0.6V when measured the proper way (negative to negative) but 2.5v when measured the other way around. However, I just realized you're supposed to do these readings when the diode is off the board, as these readings may be from something else. So I'm not sure how valid these settings are anymore. I was hoping I would get no reading on my flyback diode as this has been the problem for most people on these boards.

My second question would be about my CL idle. Now that my PWM duty % is set so high (70min// 85 max), do my CL idle PID settings also have to be extremely high? I noticed that when I drop all my PID terms out (all 0), my idle remains the same at 850RPM and idles very nicely- it also returns to the idle after throttle inputs too. So this tells me my PID isn't working? Or do I need to set them in the 100s to get any effect out of it?

I know I'm entering my CL idle as the indicator tells me so. So what's the deal with my PID settings? The only reason I'd like to fix them is that after I throw the clutch in from driving (when cold) the RPMs plummet to near stall conditions, raising the max PWM duty to 85% has stopped it from flat out stalling every time.

Also, the TS reads that my PWM duty is at its max when warmed up, so its always at 85% and never moves from there. I'm not sure if that's proper as I think the PWM value should change when the car is warmed up.

if you're showing the CL ON light, but you're pegged at 85%, that would assume that you're not able to reach your CL target.

75-85% duty cycle range is wrong.

all 90-97 valves operate between 20-60%DC. the NB valves usually run between 60-100%DC.


our idle valves need a diode to 12v, if youre hardware doesn't account for this (ms3pro, or what seems to be the ms labs ms3 basic) you need to wire it in.

Thanks for the input Braineack. I'm sure everything was wired properly, i'm running an MS3 by Rev. What I'm not sure about is whether that Diode is working properly, or another component (identified by Rev -AUIRLZ44- ) might be defective. I checked the Diode and got a 0.6v reading when connecting it neg to neg, but then a 2.5v when pos to neg. But then again, I read that you can't get a reading from a diode when its on a board.

Here's my question, so if I set my PWM min to 60 and PWM max to 100 (although 75 is around what my min appears to be when I valve test). How do I know when I'm able to achieve my CL target? What % PWM duty should I be looking for when I'm idling with the CL light on?

My RPMs are more or less around 850- what I set them to. But I don't think CL is doing anything to get it there.

Warm idle values for this valve should be in the 30-40% range. Maybe in the low 30s if the bypass screw is all the way in. At 50% you should have more than 2000rpm.

So what does it mean to be idling around 75%? That's what Laz does with his MSPNP2, two other MSPNP2s, one on a 94, one on a 99, both idle at a more respectable 25-35%. It's now done this with two valves, should I be looking at my wiring?

I'd expect any 90-97 to idle in the 25-35% idle DC range.

if your valve is operating at 75% you either have the idle speed screw fully open, or the diode to 12v is failed/bad.

How do you suggest I adjust the idle screw? Should I shut turn it off fully (clockwise) then experiment with the PWM idle values? Or should I be backing it off until I hit that 25-35% warm range?

Thanks for the input.

The idle screw is not the issue, but open it (with the idle valve closed or disconnected) until warm idle is raised a little (eg 800).
It's two parallel air channels so you are only moving the balanced valve position slightly.

I have mine totally closed. You use the PWM closed duty percent to simulate the screw, more or less. It should be possible to tune all the RPM drops out, but you can't ever tune that screw more closed and a high idle sure is annoying.

If you have the rest of the car tuned to catch and return low RPMs with timing or fuel it's exceptionally hard to stall the car even if the rpms drop below 700rpm.

Ok, so with the last two posts I'm going to warm the car up (it idles around 850RPM at the moment with little to no oscillations). Turn the idle screw all the way closed (clockwise), my guess is that RPMS should drop to 650ish warm. However, you're saying that my CL idle settings should allow it to seek my target RPM if I set my idle min/max % correctly?

I'll try this when I get home today.

The other thing that was suggested was to disconnect my idle valve. What does this accomplish? Is it just testing whether my car can run solely based on the idle screw? -- my understanding was that the idle screw adjusted the idle valve to a permanent position (open-- close) then the computer fine tunes it from there.

Thanks for all the help guys.. Turbo is being installed this weekend.. Hopefully I can flush out the rest of my MS3 issues before then.

Laz has an NB valve right?

Disconnecting the valve will have it closed, regardless of how flawed your MS is.
Adjusting the warm idle using the screw sets the idle air baseline (mechanically, unaffected by PWM gremlins), and then the idle control valve can raise the idle from there.

The idle screw is nothing more than a needle bleed valve, very unconnected to anything else than it's own air channel.
This is an NB right?
The idle screw is on top of the intake near the TB, the idle air valve is hanging below the TB (you can see it's air channel rectangular openings before/after the throttle plate). Two parallel air paths passing air around the closed throttle plate.

The problem with setting idle via the screw is you've now set your minimum idle in those exact conditions. If your PWM valve is also totally closed at that position, you might get high idle if the weather changes.

If your idle settings are correct when you enter closed loop you should be a few hundred rpm above your target, the valve can then close to bring it where it needs to be but it should not entirely close (close as in reaching your minimum idle duty%.) That little buffer room lets the idle compensate electrical loads and weather a lot better.

...then you can correct things however you want (to high min-idle, close the idle screw until :party:).
But on the hunt of crossing of gremlins, having a non-stalling mechanical idle can help a lot.

How should I go about trouble shooting my idle issue? Yes, it is an NB valve (2003 Miata). You recommend against having the idle valve closed then tuning valve min/max? If so, how do I establish where my idle valve screw should sit?

I'm trying to do everything I can to rule out the fact that my MS3 might be defective (I do not want to send it in for warranty- $$).

You set your idle screw to the position where it gives you the idle you want without additional air through the IAC valve (achieved by disconnecting it).
After that you have a know baseline where you calmly can figure out the duty cycle where you valve start to opens.

You might want to close it a little to lower the unassisted idle for low altitude and colder weather, but that can wait.

But you have already done this according to #1, your unassisted idle is 750rpm.
How non-damaged idle valve deals with high %dc through a funky circuit someone else might be able to answer.

Ok, so let me list out the steps that I'll be trying today.. While the car is running and warmed up I disconnect the idle valve ( I hope its this one.. ISCV valve plug: If you have a 1). If.. 1) the idle doesn't change at all, then I know my MS3 is wonky? and 2) If I do notice a drop in idle, my MS3 is controlling the valve somehow.

After disconnecting it, I adjust the screw to hit 850RPM. Then I connect the valve back on and test valve settings to get my min/max.

That makes sense to me. Thanks for the advice. I'll report back once I get the results.

Does MS3 not have idle valve test mode? What exactly is the problem? Is 75-100% not the correct values for a NB?

I don't know how this can be so complicated. Put it in test mode, set it at 100%, change numbers. Does the idle react? Then the valve works, everything to do with your idle dipping is just poor fuel or spark tuning.

Messing with the idle bleed air screw will screw with all the idle settings you work to figure out and tune. You should never touch the screw after you start tuning closed loop, unless you want to tune it again.

Sounds like he's trying to do this without a laptop, which isn't the right way to test anything.

Because the NBs valve should be around 18-65%. Mine runs at 75-100ish. I'm trying to figure out why, when warm, my PWM duty reads 80%. I do have a laptop and have logs of what's going on. I'll post them once I establish a baseline with my idle valve screw. Part of me just wants to set the min/max values to 75-100 and call it a day, but then I'm thinking MS won't have enough sensitivity or be over sensitive when correcting RPM values.

18-65 is a massive range, I don't really see that being necessary unless you plan to idle the car over 2K for some reason. If you have enough valve to start the car, and you have little enough valve to idle ~850 I wouldn't worry about it. In my case, 10% is around 1k in extra idle...

If anything you might check the idle valve frequency to make sure it matches everyone else.

Ok, so I set my valve to 60% min and 100% max and during an 850RPM idle I get a reading of 83.5% PWM duty. Good news is that my PID settings finally work, I've adjusted them to compensate for lights, heat and etc. It also drives like stock-- for the most part.

My new problem is that SOMETIMES when I lift my foot off the throttle, the RPMS come to settle at 1300RPM before CL kicks in. After CL kicks in, it drops it to the designated RPM. However, this is happening infrequently and there doesn't appear to be a pattern to this madness. I just spent the last 30 minutes driving around to try to trigger this event, and nothing. Also, sometimes my RPMs skyrocket to 3-4k RPM and my CL settings are locked out since my MAP is so low. I had to readjust my map way below my idle so this doesn't occur.

I tried logging this behavior but it seems like the idle valve behaves when TS is logging. I thought I understood what the idle valve did but now I'm just confused as to how PWM duty/idle valve work together. It makes sense to me that before CL is activated, the car should idle at whatever RPM the valve screw is set to (for me: 1300 RPM). However, the last 30 mins of driving would return the RPMs to 850-900 after lifting my foot from the throttle even BEFORE my CL kicks in.

**Although I set my minimum PWM duty to %60, under valve test mode, the valve reacts at around 75% up to 100% (possibly more..)

Attachment 233426

So I was able to log the raising RPM issue after throttle release. The log shows that as I'm driving, the PWM sits at 83.5%. As soon as I lift the throttle, my PWM jumps to 91% and sticks there for a few seconds (this is around 3000 RPM and basically drives the car itself). Once CL idle kicks in, the RPMs begin to move down towards target.

What causes the idle valve to pop open?

Does the car ever need that much valve to idle? Cut the upper limit, play with dashpot settings, tune the lookup table and use it instead of use last value, and a few more things I may be forgetting.

Other than the high RPM upon release problem, the car has never idled better. So I would say yes, the PWM min/max settings are at its optimal. I arrived at the current settings by testing the valve..

I'm not sure that lowering my valve from 100% to say, 95 would help. If the car likes to pop it back to 91% when driving, how would dropping the max to higher than 91% help? -- I might be missing a bit of information on how the idle valve works, so if I'm wrong, feel free to correct me.

Is your dash pot 7.5?

3.9. Where'd you get 7.5?

91-83.5=7.5. Dash pot should be added to the initial value when you let off the throttle, I think until it enters CL idle.

So I managed to correct my problem where the car would rev high after I had input throttle, right before entering CL idle. I lowered my dashpot down to 1.3 and now the car returns to idle-ish RPM after I release throttle.

I now have a more conceptual question/warm-up question. So my min/max values are set at 70-100%. When I start the car, the PWM valve reads 69.9%. The car will crank and catch for the set duration (3 seconds) then shortly die after that if I don't input throttle (when cold: coolant temp of 20C or less).

I've ruled out that this problem isn't due to fueling as when the car is warming up (when I have throttle on and keeping RPM at 1100), I'm seeing AFRs of 11-12, then as the car slowly warms up, 13-14, then at fully warm idle I'm at a solid 14.7- 14.8. This makes me think my WUE and ASE are worked out.

I'm thinking that during cranking, 70% PWM duty isn't large enough to feed the amount of fuel coming into the engine, which is why the car dies. However, even when I set the cranking PWM to be 75% or greater, regardless, during startup, the PWM will remain at 70% and stall.

At the moment, I'll start the car, feed it throttle and keep it at 1100 RPM until it warms up to 30-40C. After that, the RPMs will range from 1200 to 400, constantly oscillating between high and low as it struggles to warm up. Again, AFRs are within the rich side during this cycling.

I'm struggling to figure out how I can get the car to startup when cold and hold a 1100 RPM limit until warm (My CL target table is set to do so, but it never follows this curve).