Bosch 2 wire idle valve setup help

[kd7jmy]

Hello all, Ok I have a VW 2.0 ABA Turbo Setup, I'm having a huge time with tuning the idle. I was wondering if anyone can walk me through a good way to set the throttle plate and the settings with in Mega-squirt 3 for a starting point. The car originally had a servo controlled throttle plate. My current settings verified by me looking at the valve is like 74 % for it to be closed and about 90 % for open. if its before 74% the valve is open about 20 percent. any ideas are welcome. I'm willing to chat with anyone on any chat service or even on the phone. Also car has 288 Cam and very loopy idle.

[Matt Cramer]

We have an article on idle tuning advice here:

http://www.diyautotune.com/tech_article ... uning.html

[elaw]

Just to add a little to what that very good article says: start by setting the idle control algorithm to "PWM warmup", then go into the "Idle PWM duty table" and put numbers in there that get the idle speed close to correct as the engine warms up. Use this opportunity also to make sure your PWM idle settings (valve mode, port, 3-wire mode, and frequency) are correct.

Then... don't do anything further with the idle valve control, instead focus on getting your fuel and ignition right in the idle area. You can go in and fool with the PWM idle values to raise and lower the idle speed to make sure your timing/fuel settings work well.

After you've done that, then you can start getting closed-loop idle working. Reset the algorithm to "PWM closed-loop". On the closed-loop idle settings screen, set the open and closed duty to the numbers you mention above, "Min duty for PID" same as the closed duty, and "RPM with valve open/closed" to the engine speeds you see with the valve open and closed (if the engine stalls with the valve closed, just enter a low number like 400).

Leave the other settings at their defaults except set the target RPM table to the idle speed you want over temperature. Set proportional and derivative gain to zero, and integral to a low number like 20. Also at this point if your default dash in TunerStudio doesn't have a gauge for "Idle PWM%" I'd strongly suggest adding one so you can see what the idle valve is doing.

Then start the engine and start tuning the integral and proportional gain (leave derivative at 0 for now). Raising "P" will generally make the engine hit the idle speed target faster, but can cause it to "hunt" (overcorrect). The "I" term works similarly and increasing it can get the speed closer to the exact number you want, but again too high a number will make the engine hunt.

There is more info on tuning and some of the other settings here: http://www.msextra.com/doc/ms3/Idle_Control.html

Keep in mind that with an aggressive cam, the idle can only get so smooth and you don't want the idle valve constantly trying to "chase" a varying idle speed that it has no hope of keeping up with. Keeping the "P" value low can help with that situation.

[prof315]

2 quick questions..... 1: Which valve are you using? The stock OBD2 valve that is a part of the throttle body or the remote OBD1 valve? 2: What frequency are you trying to run it on?

[elaw]

Well I'm not using an ABA engine so I have no valve as part of the throttle body! I've actually got an Audi with an AAN 5-cylinder engine.

This is the valve I'm using, it's one of the skinny VDO/Siemens valves off an older VW (MKII Golf or Jetta, I don't remember the exact car it came from):


And unlike most people I'm using a very high frequency: 1021 Hz. Although that shouldn't matter much.

[prof315]

The question was directed at the OP. @ elaw the idle valve you are using is from a digifant car. Just curious, how wide of a duty cycle range do you have operating at ~ 1000hz? Those valve usually work best around 100hz.

[elaw]

Well the valve is very voltage-sensitive which has really been a PITA getting it to work with MS. But in general with the engine warmed up and system voltage = about 14.5, 15% duty will give me 700 RPM and 30% duty will give me 1500.

I started out running the valve at a low frequency... around 100 Hz I think. But at idle you could hear a "humming" noise coming from the air cleaner and it quickly became obvious the source was the idle valve. So I kept increasing the frequency until the noise went away and ended up at ~1000 Hz. The frequency seems to have little effect on duty cycle - at 100 Hz it idles around 18-20% and at 1000 it's about the same.

[prof315]

That makes sense. And yeah I've noticed that the VW/Audi 2 wire idle valves are rather voltage sensitive.

[kd7jmy]

I wish I got emails on this all of this info is good info.. I got my idle fixed turns out most of my problem was my huge cam and fueling .. once I got the fueling right the engine idles fine. on the ms3 build. but to further this topic. I just did a mk2 jetta 16 valve conversion to ms1 extra. and I'm having a hella time with the idle hunting on a stock engine.. currently I just have a breather filter attached to the valve and the valve is plumed factory after that. Does anyone have a good set of values to use and on top of that does any recommend a plumbing method. The two things 'm noticing with my current values are this.. the valve is going under the minimum DC value... so I have a bad number somewhere and I'm thinking the way the idle valve gets its air is a determining factor due to flow threw a pipe vs an open hole. any suggestions?

[radics1]

Hi,

i have similar problems with Bosch idle valves: As you stated,there is only a small window between closed and open valve,in general,my car idles around 20% when warmed up,and only 0.4% (wich seems the smallest step it makes),makes a noticeable difference in idle speed,so it starts hunting sometimes.

Its not the fuelling nor the ignition. With 20% idle is below target,it starts to raise,next step us 20.4 and it is over the target.

I use relatively low PID numbers also,but it still hunts sometimes. How can i improve the resolution of the valve? I am running on 4x30,5Hz. Originally this valve works on 156hz,but digifant ecu has some kind of current limiting system.

What is the relation between frequency and resolution?

[duxthe1]

Other than the #s, it sounds like you are describing my Mercedes/Bosch 2 wire PWM idle valve. (Thinking of starting to call it the oscillation valve) I have struggled trying to idle smooth but the thing is determined to oscillate 1-200 RPM when in closed loop idle. For now the best I've done is use GSlender 2.7 code to enable adaptive PID. I set the "APID" so that there is 0 valve control 100 RPM on either side of the target and a steep return to PID after crossing that threshold. It doesn't get me very tight to the target but helps dampen a lot of oscillation. It doesn't control all oscillation. I still have a wild variance when idling without load on a cold engine but warm and in gear its acceptable.

[radics1]

Well,i tried also PWM warmup,it is fine when cold,because it doesnt matter if it idles around 1200 or 1300 when CLT is 20°C,but at 90°C i dont like to have either 1000 rpm or 800,depending on if Fan or headlights are on.

I checked some current limiting circuits found on the MSextra,but there are hard-to-get components and i dont like to spend more money on the postage than the real value of the package.

[kizzoalfa]

Hi,

do you have the antiparalel diode installed? If not than you can have the same errors like you are describing.

You need to solder the antiparalel diode. Use an 1N4001 from the lowside output to +12V. Best if you solder it into the idle valve harness side header.

With the diode installed try to test the valve in output test mode it should work fine.

Zoltan

[radics1]

Of course,the diode is installed.

Once i forgot to install it in an earlier project,the Tip122 was fried in a very short time.