How can the OCV affect idle?

My idle is a bit lumpy and I want to perfect it. So far new plugs, no vacuum/boost leaks/clean maf. I am debating replacing my ocv's I have a log but at idle they basically are inactive I do not see how they can affect idle? Check out the ocv log let me know if you would advice them being replaced. Thanks!

romraiderlog_eric_20130906_005630.csv

I am a noob when it comes to this but interestingly enough, I have been investigating the same thing this week on my car. My OCVs duty @ idle are both exactly the same ~9.41%. I see these values on your log between time-stamps ~7.5-15s. Other than that, you can see how one of your OCV duty is varying compared to the other which looks pretty much stable (see plot below). There are at most like 10% off. I don't know if this is OK.

FWIW though, both of my OCVs while cruising are only like 2% off at most (see second plot).

 

On another note, have you tracked your AFR at idle? I've been noticing an interesting behavior where apparently target AFR @ idle is not 14.7 but more like 14.2 which may affect idle a bit. see http://legacygt.com/forums/showthread.php/interesting-afr-behavior-idle-213454.html

You can see the RHS OCV is oscillating, it cannot match the LHS OCV.

 

I'd recommend replacing both OCV's, at a minimum the RHS, or remove and clean both, activating with a 9v battery.

 

Replacement OCV's are available widely, in AU we source them from Celtic Motorsport and Flatirons.

 

We havent been able to find filters in AUDM postFL AVCS banjo bolts...

But its mandatory to sort the issue on preFL's. (because the blocked filter can starve the turbo of oil)

 

Massive thread here:

AVCS VVT angle out of sync diagnosis MY07 GT B

 

 

http://legacygt.com/forums/http://www.flickr.com/photos/bigbadbenny/9682658869/

Heard from several folks that OCVs are basically an 80-100k item. They can sometimes be tough to pop out. You could log more data, pop them out, clean them, then swap them and log again to see if the issue follows a certain OCV. That's free diagnosis and you can then determine if you need to spend the coin on one or both.

I understand that both OCVs should always be in sync regardless of load, rpms, etc... (correct me if I am wrong)

 

-->Now, we know nothing is perfect. So I'd like to know how many degrees out sync is tolerated.

 

In OP's case though, it looks like one of them is clearly acting up IMHO.

I already tried cleaning them made no difference on the log. the rhs is passenger correct?

and the AFR is 14.7.

the rhs is passenger correct?

 

I think it is driver side.

Rhs = turbo side

As in RHD or LHD car....

 

Please correct me if I'm wrong

 

Also good OCV's will be around 99% synced.

Oscillation and lag are good indicators OCV's are bad.

What I know for sure is that the 'famous' OCV codes are p0011 referring to 'bank 1' and p0021 referring to 'bank 2'; the former is for the passenger side and the latter for the driver side. So it's like looking at the engine standing in front of the car.

So I am assuming that left OCV in romraider is passenger side and right OCV is driver side. *BUT* I cannot confirm that (a few Google searches led to nowhere).

So I could be wrong.

Left and Right are normally in the travel direction of the car.

 

Both sides shall normally have the same behavior, so if there is a difference it's a good start to look at the valves, but also check the oil pressure.

 

Notice that the duty cycle is for the control valve, which means that you shall also make sure that the camshaft timing itself is right and not one tooth off.

 

If possible you shall also look at the Intake VVT Advance Angles (If that info is available)

 

I found the following quite interesting:

http://www.uotdealereducation.com/repository/course/groups/%7B0FFBA7D5-DFB6-41B3-8F07-A27C1098BDF1%7D/swf_content/2_80.swf

Bank 1 = passenger side (LHD) = cylinder 1(f) & 3® = RHS OCV /VVT angle = turbo side

 

According to google

Bank 1 = passenger side (LHD) = cylinder 1(f) & 3® = RHS OCV /VVT angle = turbo side

 

According to google

 

Which definitely means it's a good idea to look at that darn banjo bolt then.

My idle is a bit lumpy and I want to perfect it. So far new plugs, no vacuum/boost leaks/clean maf. I am debating replacing my ocv's I have a log but at idle they basically are inactive I do not see how they can affect idle? Check out the ocv log let me know if you would advice them being replaced. Thanks!

 

Lumpy. Can you see it in a log?

Or is it just felt.

My idle is a bit lumpy and I want to perfect it. So far new plugs, no vacuum/boost leaks/clean maf. I am debating replacing my ocv's I have a log but at idle they basically are inactive I do not see how they can affect idle? Check out the ocv log let me know if you would advice them being replaced. Thanks!

 

Lumpy. Can you see it in a log?

Or is it just felt.

 

Warming up only or when warm too?

Another known issue for a bad idle is the donuts at the TGV:s - they shrink when they get old and starts to leak.

I'd like to know how many degrees (max) can the OCVS be out of sync and still be running OK.

 

Bump.

I logged mine out of curiosity after reading this thread; I never saw more than 1 degree of difference between the advance values. This included a variety of driving conditions, including some WOT pulls.

As regards "how far out of sync" question, AVCS is implemented in the stock tune mainly for emissions and economy.

 

So the car will run OK-ish, have difficulty maintaining steady revs just off idle (1200-1500rpm) and fuel economy will suffer.

 

If undiagnosed, your tuner will struggle to get consistent results, especially if they favor aggressive AVCS tuning.

 

IIRC on the 2.5T 40 degrees is the normal maximum angle, I saw up to 51 degrees before I replaced my OCV's.

I've plotted difference plots for both cruise and idle conditions. I got at one point up to 3 deg off during cruising. I'll post one during a WOT session.