Negative knock correction under light throttle & vacuum

[05pearl]

My advance multiplier has been dropping steadily until eventually the ECU limits the boost to 10psi. An ECU reset allows me to get back to full boost.

 

Under WOT 3rd gear pulls, logs look pretty good.

 

When I am driving around 40-50 mph in 3rd or 4th gear, under light throttle (3% to 17% opening) and slight vacuum (-3 to -6 psi), I see negative knock corrections ranging from -3 to -9.

 

Are these negative knock corrections the cause of my advance multiplier dropping and eventually limiting my ability to make full boost?

[Legend]

Are these negative knock corrections the cause of my advance multiplier dropping and eventually limiting my ability to make full boost?

 

No, but knock does cause the IAM to fall. A lower IAM will give you less advance and result in lower timing. Post some logs and a Learning View. Is your FMIC piping free from rattles/vibration?

[05pearl]

I am using an AVO Top Mount IC. I have an ecutek delta dash log csv, but cannot seem to attach it successfully. Advice?

[Legend]

Ugghh ecutek? The only advice I have regarding ecutek is to get rid of it. (Not that it's your problem today, however). Will ecutek let you log with romraider? Did you get it tuned/dyno'd at Super Rupair? Those are good numbers. Can you list your mods?

[05pearl]

Ugghh ecutek? The only advice I have regarding ecutek is to get rid of it. (Not that it's your problem today, however). Will ecutek let you log with romraider? Did you get it tuned/dyno'd at Super Rupair? Those are good numbers. Can you list your mods?

 

Thanks. Yes, tuned and dynoed at SuperRupair. Mods (cut and pasted):

 

E85 Tune

Cobb DP, MP, Y

Stock Cans

Perrin UP/DP

HKS SSQ BOV

Subaru short shift

AVO Fuel Pump Upgrade

AVO TMIC

NGK One Step Colder Plugs

Deadbolt TD06H-20G Zilla

DW 850cc injectors

AVO Intake

Snow Performance WI kit running washer fluid

Labonte WI safety monitoring

Defi boost gauge

Momo shift knob

Tuned at 5200' altitude

 

I was told that -ve KC will cause the ECU to limit boost eventually. Is this true? If so, is it true when not under boost but vacuum?

[Legend]

Colder plugs and E85 isn't a good combination... but again, that's not your problem now.

 

How low is your IAM getting? Low IAM (caused by excessive knock) can limit boost. Can you post a Learning View?

[05pearl]

Colder plugs were installed before I considered E85.

 

Sorry for being ignorant. IAM, learning view??

 

IAM - Advance Multiplier? If so, when my boost was cut to 10psi, the AM was at 0.13, I reflashed - it started at 1.0, then dropped to 0.88, 0.63. At some threshold I don't know about, it will cut the boost. So, I reflashed it this morning again. Again, I was told that -KC will cause the AM to drop which will in turn wil limit boost at some point as it continues to drop.

[Spec B]

I think you should log Knock Sum..this will tell you when there is a knock event (what RPM and load). I was/am having a similar problem to you with regard to "knock" at low load and low RPM. Turned out to be my FMIC piping rattling enough to trigger the knock sensor and ultimately lower the IAM. Althought a long shot, make sure nothing is rattling under the hood.

 

Post some regular driving logs, log Engine speed, Load, Knock Sum, throttle opening and relative manifold pressure. Some of the more experienced tuners will be able to help you out.

 

Learning view is a program that takes a snapshot of the ECU's knock correction learning, it will show where the ECU has learned to pull timing (under what load and RPM).

 

IAM = advance multiplier - I know as it drops so does the amount of timing that can be added. I am not sure if it ultimately cuts boost, but I do know it is gets too low it goes into a failsafe mode.

[Spec B]

btw..you can download the learning view tool here: http://www.romraider.com/forum/topic2772.html

[05pearl]

Thanks.

 

I am using a TMIC and everything seems to be pretty secured.

 

Is learning view compatible with Ecutek cable (probably not)?

[05pearl]

Ok, here is the log I took. The worst KC occurs at ~414125 - 416422 ms. Hope someone can shed some light on whether or not these -ve KCs are the cause of my eventual boost cuts.

DeltaLog-aj17B-6815-Fri Oct 24 2008 11-33.40.pdf

[mwiener2]

Colder plugs and E85 isn't a good combination... but again, that's not your problem now.

 

 

 

nothing wrong with colder plugs

[Infamous1]

If it is enouh knock to cause your IAM to drop to 0 that is not a good sign. Can you here any audible tappin when idling? If your certain nothing is banging around and this issue is new I would opted for a compression/leakdown.

[05pearl]

If it is enouh knock to cause your IAM to drop to 0 that is not a good sign. Can you here any audible tappin when idling? If your certain nothing is banging around and this issue is new I would opted for a compression/leakdown.

 

IAM had dropped to 0.13 before the reflash. I do not hear or log any tapping at idle. It only seems to happen between 2700-3700 rpms in 3rd or 4th gear when accelerator is only open between 1-10%. I don't see anything loose, but I wonder if something is hitting a natural frequency at these rpms?

[Spec B]

That is a big drop in IAM..I think something must be making noise. Other than loose items, I would also make sure everything around the TMIC is tightened down, it could be something rattling at that RPM range.

 

What about your drivetrain, are you running a lightened flywheel? Sometimes the chatter trips the knock sensor.

 

Also, how long have you had the issue? Did it pop up overnight?

[05pearl]

That is a big drop in IAM..I think something must be making noise. Other than loose items, I would also make sure everything around the TMIC is tightened down, it could be something rattling at that RPM range.

 

What about your drivetrain, are you running a lightened flywheel? Sometimes the chatter trips the knock sensor.

 

Also, how long have you had the issue? Did it pop up overnight?

 

It took a few days for the IM to drop that low. No light weight flywheel. But, I have heard the exhaust rattle sometimes at start up. I wonder if the stock cans are the problem? Sounds more and more like a rattle issue (no pun intended), but I don't want to take any chances. Bad thing is that is is hard to track down rattles.

[05pearl]

Can someone who is used to reading logs open my file on post #11 and tell me if it looks like a rattle, or an actual engine problem? Is there anyway to tell from a log? Thx.

[LittleBlueGT]

Can someone who is used to reading logs open my file on post #11 and tell me if it looks like a rattle, or an actual engine problem? Is there anyway to tell from a log? Thx.

 

That is a big file.

 

Log these (if you can do so with RR)

 

-rpm

-throttle

-g/s

-MRP

-AFR

-knock sum

 

 

Post up the log in a spreadsheet format so it is easier for us to modify/look at it.

[05pearl]

Little Blue, attached is a small section from the log of one area experiencing the problem. Any help from someone familiar with log reading would be appreciated. I want to know if the negative knock correction is a result of rattling vs. a real engine problem. Most everything on the car seems to be secure, but my stock cans do seem to rattle at times. I am going to put my cobbs back on and re-log too. FWIW, no knock problems under any boost or WOT.

 

Thx

short.kc.log.pdf

[Spec B]

There is no definitive way of knowing if it is knock or just noise by reviewing a log. But looks like noise to me.

 

I would help a lot if you can log Knock Sum using Romraider (not sure if you can). This will give us a better idea of when the ECU hears the knock event and how many are occuring.

 

Take a look at my log..very similar to yours, I logged Knock sum and you can clearly see the knock events as they increment (not just the resulting timing being pulled). Look at knock sum 15, 16 and 17, those occured with the hood up and my tinkering with the FMIC piping.

 

http://www.romraider.com/forum/download/file.php?id=6138

 

My point is, if you can log knock sum, we can get a better idea of exactly when it is occuring and how frequently.

[LittleBlueGT]

Little Blue, attached is a small section from the log of one area experiencing the problem. Any help from someone familiar with log reading would be appreciated. I want to know if the negative knock correction is a result of rattling vs. a real engine problem. Most everything on the car seems to be secure, but my stock cans do seem to rattle at times. I am going to put my cobbs back on and re-log too. FWIW, no knock problems under any boost or WOT.

 

Thx

 

+100 on the knock sum

 

Any perceived knock at less then 0.5 engine load seems unlikely to either be real, or be worth stressing over.

 

Everything in that section of log was around .25 load.

[05pearl]

Thanks guys. I don't have knock sum on ecutek and I don't think I can use romraider right now. I just put the cobb cans back on and I will log again shortly and let you know if that helped or not.

 

L'l Blue, even if it is just noise, I still need to stress over it because the ECU pulls back timing and eventually cuts boost when the IAM gets too low. So, I still have to figure out what is causing the noise - if that is the problem.

[Spec B]

LBLGT, as far as I know, there are 2 rough correction ranges (RPM and LOAD). Rough correction is what causes the Drop in IAM (if the knock is bad enough).

 

Do you have to be in both ranges in order for rough correction to kick in and IAM to drop, or just in one? In other words, do I have to be in the load AND RPM range specified in the tune or just one or the other?

 

One solution to the OP problem may be to raise the rough correction ranges?

[LittleBlueGT]

LBLGT, as far as I know, there are 2 rough correction ranges (RPM and LOAD). Rough correction is what causes the Drop in IAM (if the knock is bad enough).

 

Do you have to be in both ranges in order for rough correction to kick in and IAM to drop, or just in one? In other words, do I have to be in the load AND RPM range specified in the tune or just one or the other?

 

One solution to the OP problem may be to raise the rough correction ranges?

 

 

I don't know what options 05pearl has.

 

The engine has to be on both ranges.

 

I just adjusted the ranges for all (FBKC, FLKC,rough correction) up to about 1.0 load as the minimum. I could look at exact numbers if someone wants.

 

Basically just adjust the numbers high enough so that your learning table and DAM does not go crazy, then you should be fine. But before you do that double check everything to try and get rid of the noise.

[Spec B]

^^ Thanks.