Uh oh - IAM dropped to 0.375

Well that's all I need Fingers crossed for a pre-turbo vac leak. Guess I'll try a boost test this weekend.

 

One thing I have noticed changing slightly is I seem to be running a little leaner lately (see LV). And logging shows A/F at WOT to sometimes get as lean as 11.8 - wonder if that would have an impact on this?

 

 

http://www.btssm.com/scrnshots/scrnshot9iamDrop.png

Oh man. That's strange cause your LV doesn't look that terrible at all. Any misfire? oil level good? MAF voltage OK? O2 sensor reading OK?

Have you been keeping track of your knock events?

 

Yeah check for leaks. Although I'd doubt a vac leak would drop the IAM that much with such little effect on A/F trims.. weird.

It is weird indeed. Prior to the screenshot above when the IAM dropped, i did have some learned timing pull in the rightmost column. It was typically -1.4 or -2.8, then jumped to -4.2, and blam... IAM drop. I believe that causes the FLKC table to get reset to all zeros, and it pulls timing across the board. Then it starts experimenting by putting positive values in there. If no knock is seen for a while, it increases the IAM a bit, clears the table again, and repeats, hopefully until IAM is back up to 1.000

 

And yes, I have been capturing knock events. This morning had quite a few until the IAM drop, then I backed off the throttle a little

When that happened, did you notice the car go into "limp" mode?

 

For the past week I've been chancing down a leak, as my car was going in/out of limp mode (no CEL), and it stumbles between 2k - 3k rpms. Checked all the connections, everything was connected and tight. Then decided to changed the plugs, thinking 1 or more plugs were failing. At the same time pulled both OCV out, looked ok, cleaned and reoiled.

 

As I was putting everything back together, I noticed on my air box that the bottom connections weren't connected properly and the air filted was moving around quite a bit. Thinking this could be the cause as air was bypassing the filter causing the MAF to recalcute until the turbo kicks in and sucks the filter back into place. Yup, that was the problem, after connecting the air box back together and sealing it tightly, the car felt strong again.

I will check the air filter box today, thanks. I really HOPE it's something like this. Already had a short block project this year, I don't want another project just yet!

Yeah. I'd check 'simple things' first. Airbox, vacuum leak. And then MAF, o2, etc..

How's your oil consumption? and roughness at idle?

At the same time pulled both OCV out, looked ok, cleaned and reoiled.

 

I was thinking OCV too. I logged their activity this morning to see if they are in sync, and found that they basically are - see 2 teal lines below. The left OCV/VVT is a little lazier than the right, but probably not enough to account for this issue.

 

 

http://www.btssm.com/scrnshots/scrnshot10_graph_vvt.png

Yeah. I'd check 'simple things' first. Airbox, vacuum leak. And then MAF, o2, etc..

How's your oil consumption? and roughness at idle?

 

Just checked airbox and it seems fine. Can't really dig in too much until this weekend, but looks securely closed. Re-seated it anyway. Still same. Oil consumption is fine, dipstick hasn't moved from the high mark for a while. Regarding idle, it's never been butter smooth, but I think it has become a little rougher.

OK. Next will be vacuum leak then.

Have you monitored cylinder misfire closely during idle?

Argh. No vacuum/boost leaks. Holds pressure really well.

 

I ordered a fuel pressure gauge to see if maybe that's an issue. Plus, I always wanted a fuel pressure gauge

Well, LTFT at max of +6.00 doesn't look like a leak to me. That means the system is trending lean but the compensations can still keep up. I'd reset the ECU and take frequent LV shots to see where the FLKC is building up enough to drop IAM that low.

yeah fuel isn't *that* lean. it's just trending that way, which is a red flag for me... maybe just a yellow flag

 

regarding when/where flkc is happening, i have a log or two. it is mostly at wot, but sometimes at low/med load too.

Yes, I don't like positive numbers for any length of time.

 

Please post your logs. How's your oil consumption? Have you checked for rattling heat shields etc.?

have you monitored cylinder misfire closely during idle?

 

 

+1.

Yes, I don't like positive numbers for any length of time.

 

Please post your logs. How's your oil consumption? Have you checked for rattling heat shields etc.?

 

Oil consumption is fine, dipstick has remained at high mark for a few weeks now. I have checked heat shields, they seem fine. I think it's "real" knock. At one point yesterday I actually *heard* the knock for about 1/4 second while at WOT on the highway. I thought "well, I guess this isn't false knock".

 

I've attached a log from yesterday which may have actually been the IAM drop. Unfortunately at the time I wasn't logging the IAM field itself, but other important fields are present. Also, here is a graph of the attached log. I put the vertical bar on a curious point where it may have been the IAM drop. Also note that the A/F is 12.2:1 at that point, a bit leaner than I've tuned it to be.

 

http://www.btssm.com/scrnshots/scrnshot11_WotKnock.png

BtSsm_20140919_092031.csv

+1.

 

Hah, you +1'd yourself

 

Sorry, yes, I've looked at those. The misfires general hit 1 or 2 occasionally on any of the 4 cylinders during idle. This seems just a little higher than it has been before. Usually before this incident, it was more rare to see it hit 1 on any cylinder. Now it's just a bit lumpier (not much), and the misfires are a bit higher (but also not much higher).

 

Also, these slight misfires don't seem anchored to any specific cylinder, they're spread out more.

Um, what fuel are you running and is the AFR data from a WBO2 or the stock O2 sensor?

Um, what fuel are you running and is the AFR data from a WBO2 or the stock O2 sensor?

 

Fuel is 93, and O2 sensor is stock but relocated to DP bellmouth.

 

Engine mods: straight UP, catted CNT DP, 3" midpipe/Y, BNR 16G, EBCS, TGV delete. Recent shortblock due to bad acl main thrust bearing in previous build.

Okay, about your log...

 

You start knocking at pretty reasonable AFR and timing advance for the revs and load you're pulling.

Your timing figure from full spool through to about 4k8rpm looks a bit high to me, even though you already have so much timing pulled via FLKC. Even on your B25 heads I'd only be targeting about 13* in the saddle and getting up to 16* or so at 5k6rpm on a 16G and 93RON fuel.

 

Your fuel curve is also pretty daring. Even the so-called 'rich dip' only falls to 11.3 AFR and the factory O2 bottoms out at 11.2, so it's probably not too linear down there.

 

You can see your knock event is over at the time you bounce up to 12.2 AFR, so I don't think those factors are related. I usually see real knock being related to overly aggressive timing, not lean AFR. I like to run at around 11.2 AFR at full load but I've gone out to 12.2 before without seeing knock. Running too lean causes high EGT rather than knock, IME.

 

黑車?

Okay, about your log...

 

You start knocking at pretty reasonable AFR and timing advance for the revs and load you're pulling.

Your timing figure from full spool through to about 4k8rpm looks a bit high to me, even though you already have so much timing pulled via FLKC. Even on your B25 heads I'd only be targeting about 13* in the saddle and getting up to 16* or so at 5k6rpm on a 16G and 93RON fuel.

 

Your fuel curve is also pretty daring. Even the so-called 'rich dip' only falls to 11.3 AFR and the factory O2 bottoms out at 11.2, so it's probably not too linear down there.

 

You can see your knock event is over at the time you bounce up to 12.2 AFR, so I don't think those factors are related. I usually see real knock being related to overly aggressive timing, not lean AFR. I like to run at around 11.2 AFR at full load but I've gone out to 12.2 before without seeing knock. Running too lean causes high EGT rather than knock, IME.

 

Thank you for taking the time to analyze the log and provide feedback. I guess I will update my tune with less timing and see how that goes. Sound good? Funny that I've been running basically the same tune for quite some time, I wonder why it picked last week to act up?

 

黑車?

 

Yes. 黑車 = hei che = black car

Had a sudden change in weather recently? If for example your tune calls for a large shifts in global timing via IAT comps, and the ambient temps dropped a lot since you tuned the car, you can end up with a lot more timing than you expected.

 

When did you last change your plugs? If you still have stock shielding on the header and especially the up-pipe, think about pulling that off, even temporarily.

 

我開白色車但'baiche'不是什麼好名

Had a sudden change in weather recently? If for example your tune calls for a large shifts in global timing via IAT comps, and the ambient temps dropped a lot since you tuned the car, you can end up with a lot more timing than you expected.

 

When did you last change your plugs? If you still have stock shielding on the header and especially the up-pipe, think about pulling that off, even temporarily.

 

我開白色車但'baiche'不是什麼好名

 

It did get a little cooler last week (55F rather than 70, 80, etc), but I've driven the car with this tune in much cooler weather as recently as this past spring.

 

Plugs? Changed them about 6K miles ago.

 

Shielding? Yes, I do still have the same shielding on the header. I did wrap the UP during the shortblock project though during the summer. Could that make a difference in the perceived timing tolerance?

 

And regarding your white car, thank goodness for google translate!

And were you targeting those AFRs or did that just happen lately?

I was targeting low 11's, and getting them. The log above shows them to have crept a little leaner.

Mmm. Have you upgraded your fuel pump? Are you still using the original FPR? First sign of a failing fuel system is leaning out under load.

 

Also, are your load figures where they were when the tune was healthy? If you're running at the same boost pressure as before, in the same air density / IAT range, and then you notice load and airflow dropping... you could have a MAF signal that's reading low. That will account for timing being high and fuel leaning out. Try cleaning the MAF sensor or swapping it for a known good one.