What can a constant - number on fine knock learn mean

[Dalee1104]

So I'm basically seeing numbers in the negatives in both fine knock learning and knock feedback. I think I saw a positive of 1.35 once but since then it's nothing. Arent these guys supposed to rest around 0. Every time I hit boost it increases. Doesnt matter what gear or what rpms but I get a feedback knock of around -2.4 to -4.0 and a fine knock learning ranging clear up to -12 sometimes. What does this mean? I've tried checking for vacuum leaks and rattling items. Downpipe has been replaced with an aftermarket setup so I can eliminate that as well as the rest of the exhuast system. I have factory exhaust manifolds still in place. Car runs and drives nicely. No rough idle or anything of that sort

[awfulwaffle]

Means your car has learned to pull a hell of a lot of ignition timing in response to knock, and is still knocking. Pull a learning view, and it'll show you a snapshot of every condition where it's adjusted timing in response to knock.

 

Feedback knock correction occurs during transient events, fine learned knock correction occurs during steady state. Read more about it here:

 

http://www.romraider.com/forum/topic1840.html

[Mr-C]

Does it also occur in neutral/park while revving the engine ? AFR look good?

[Dalee1104]

Okay that's a very informative write up. So now understanding what the ecu is doing in scenarios of knock and how its pulling timing, the question I have for my car I guess is why. Knowing that its knocking upon load no matter what, why is it knocking? What's a common cause and what's some ways to remedy this?

[Dalee1104]

It doesnt occur in neutral or park while revving but weirdly it does occur on a downrev which I thought was pretty odd. AFR seems to check out okay. 14.7 at idle, then as I step on it it starts rich low rpms, mid rpms are around the 14ish range, and then towards the very end with full boost about 18psi itll go up to about 16ish which I believe is a little lean but I think I've heard that engines lean out slightly in the higher rpms

[awfulwaffle]

There's very little load on the engine in neutral, so you wouldn't see any knock correction. 16 AFR is extremely lean in boost. If you keep pegging it while it's that lean (assuming it's actually that lean), you're going to pop your motor in short order. I've never seen an AFR over 12 at WOT on any of my turbo cars.

 

I'd start by checking long term fuel trims, and troubleshooting MAF, front O2 sensor and fuel pressure.

[Keyan]

It doesnt occur in neutral or park while revving but weirdly it does occur on a downrev which I thought was pretty odd. AFR seems to check out okay. 14.7 at idle, then as I step on it it starts rich low rpms, mid rpms are around the 14ish range, and then towards the very end with full boost about 18psi itll go up to about 16ish which I believe is a little lean but I think I've heard that engines lean out slightly in the higher rpms

 

you have major fueling problems. check your fuel pressure. at WOT you should be at 11-12AFR

[Dalee1104]

Oh damn really? I thought ideal afr was 14.7 so I'm supposed to be a little rich in boost not lean. Okay so I can clean the MAF or should I replace it? Same for the 02, test or replace. Can the accessport measure fuel pressure? i have a little dial gauge that you can hook up to the fuel lines but cant really be in boost with load while holding still. I can look at injector duty cycle and those usually get up to about 70%, highest I've ever seen is 77% should I be seeing higher percentages at WOT.

 

Also if I'm super lean shouldn't I be getting an engine light for extreme lean? Reason I ask is I actually have a warranty on the car but they usually can't take action until I have a check engine light. On top of that the warranty isn't aware that the car isnt stock so I cant be like "hey so I was getting improper readings on my accessport". What should I do? Warranty is the very nice, zero deductible that covers pretty much everything.

[Dalee1104]

just kidding i was looking at the wrong gauge, afr stays below 12 in boost.

 

 

first time trying to figure out how to upload a data log but heres the one on the way home from work. the drive is pretty short but about halfway through that drive i switched the car into sport sharp mode

8-26-19 stg 2 spec b.csv

Edited August 27, 2019 by Dalee1104

[Mr-C]

I'm no expert at this but in looking at your log your AFR are way too high while in boost....at 14-16 psi your showing 13-14 AFR fuel correction is also high and your DAM at 0.5 and 0.75 is NOT GOOD !! When you switch to sport sharp seemed to have helped a little bringing your DAM back up to 1 where it needs to be.

 

Is this a stock set up? What's been done to the car, has the fuel pump and/or filter been changed recently?

 

With some of the issues I've gone through in the past year I'm inclined to say there's a fueling issue but again I'm no expert at this.

[Dalee1104]

Interesting in my accessport it didnt display any changes in the DAM and in boost it showed the highest afr at 12.7? That's really really weird to me, if the car is in fact making these changes why isnt it showing me a drop in dam or something?

 

The car is stage 2 with a 3 inch catted downpipe and 3 inch piping from there back and a k&n drop in panel filter. Other then that shes bone stock.

 

As for the fueling i thought these cars didn't have fuel filters? At least not one accessible? The car has about 127k miles and I'm the 3rd owner, have only had it for a year so no idea how other owners have treated it. I change oil at 3k or sooner depending on the condition and always keep up on maintenance when I can. I'm actually a Subaru mechanic, just starting out so I've only been doing easy stuff like pulling engines out of the NA rigs, still trying to learn. But yeah that being said i try my best to take care of my cars to the best of my abilities because I'm going to want to have fun with the car.

 

As far as my knowledge goes I believe the fuel pump and filters are running the same stock ones from the factory, never been replaced

[awfulwaffle]

Agreed with what Mr-C said. Way lean under boost. When you're at WOT, you should be seeing an AFR of 11-12. Ditto DAM being too low.

 

These cars have an in-tank fuel filter. You have to remove the rear seat bottom, pull off the passenger side cover plate, and remove the entire fuel pump bucket from the tank. The filter is a cartridge which forms part of the bucket assembly - look it up on a dealer parts list. Not difficult to replace, but gassy. Do it on a near-empty tank if you do, or you'll get gas everywhere.

 

That said, I've had two LGTs with way more miles on OEM fuel filters than yours, and when I replaced them for posterity they were still in OK shape. YMMV.

 

I'd get a fuel pressure gauge on the car before buying any parts. It's pretty easy to splice in a tee into the fuel send line to which you can connect a pressure sensor. I went with a 3-way NPT block, two barbs for the fuel pass-through and an electronic sender, but you could just as easily put a Schrader valve on there for a mechanical gauge you could borrow from your local parts store. IIRC the lines are ~5/16.

Edited August 27, 2019 by awfulwaffle

[Mr-C]

Yea,

 

Not sure why your AP isn't displaying the data in real time like your log....that would definitely concern me. If it persists, contact COBB.

 

If you work at a Subaru dealer, you must surely have a kit to test your fuel pressure and FPR....if you do, as awfulwaffle said....start with testing the pressure and go from there. I'm also assuming your putting in 91 octane or more when fueling the car?

[Dalee1104]

Actually just work at a smaller shop called subie solution's. I have been putting 92 octane in it. I know some people are particular about what brand gas they use? I just get shell gas because it's near my house

 

I have a fuel pressure test in the form of a psi gauge so I'll have to run that but nothing to test the regulator, I'll take a peak and see what happens

[Mr-C]

For the FPR test I recall the FSM saying to unplug the vacuum hose to see if there is a spike in psi. If you do a little searching here you should be able to find a link to download the fsm.

 

If not, send me a PM with your email and I'll send you a copy

 

 

Good luck!

[Dalee1104]

Okay so found a really rattling heat shield on the up pipe. Got thay fixed and now it seems my numbers are better but still there. -2.81 is the highest number I've seen up to 3rd gear. After 4th then I saw a -4.21.

 

My boss also checked my fuel trims and fuel pressure while i was busy and said with the uppipe fixed that the numbers seem to be okay. I might take a datalog just in case. Are these numbers average? Should I still consider replacing my fuel pump sooner rather than later?

 

And that brings me to my next point, can I upgrade the fuel pump to a walbro of some sort as a supporting mode and run the car as is or will it require a tune? Does the ecu dictate how much fuel gets to the injectors? If it does require a tune is an E-tune a decent option? No dynos near me

[awfulwaffle]

Those are still problematic IMO. I don't see much FLKC over -1.41, and when I do it pulls back down to zero within a few minutes driving in that range. The fact that you see FLKC consistently means your car is maintaining an adjustment for persistent knock. I'd keep digging - check for loose/rattling hardware closer to the knock sensor maybe. It would also be good to know what engine loads and RPMs the FLKC adjustments are being made at.

 

You can upgrade to that fuel pump without a tune - the stock FPR will set the pressure seen by the injectors

[Dalee1104]

Okay I'll definitely keep digging then, still learning all the acceptable parameters in these cars when it comes to tuning. I might upgrade the fuel pump in the meantime considering its cheap and easy and might eliminate some of the lean issues I'm having. I do still hear some rattling on a down rev so I'll keep searching but I'm confused what to look for, all the exhuast and heatshields and such ate tight and squared away

[awfulwaffle]

Do you know what the measured fuel pressure actually was? Replacing the pump won't help you if it was within spec.

[Dalee1104]

I think it was this little fancy computer thing you plug in to obd and look at everything from there, he was doing some equation with the fuel trims so thats a little beyond me. I guess my thought process with the fuel pump was that it's cheap, and to build more power in the future I should upgrade it, and if the fuel pump doesn't do anything then I'm looking at the regulator and injectors next correct?

[Dalee1104]

On a side note that kinda has me thinking it could be fuel pump is lately I've noticed sometimes the car doesn't accelerate as smoothly as it could. It's only sometimes so it could be me over analyzing it or its completely in my head but the other day I went to accelerate in 2nd gear and right when your about to build boost and accelerate its like the car hesitated. I didnt get that pulling feel of boost and I glanced at my AP and at that exact moment the car showed a -8 on the feedback knock so I let off the gas and babied it. Not sure what that could be but it only happens occasionally, instead of smooth accelerations theres hesitations in it

[awfulwaffle]

Well, there's no way that he measured fuel pressure with any kind of OBD2 device, unless your car has a fuel pressure sensor added aftermarket and wired in to an open port in the engine bay. More likely he looked at long term fuel trims and decided that they look good. However, you should make sure that he looked at trims in every airflow range, and that he was looking at the long term and not short term trims.

 

That is, there are trims stored for 4 different airflow ranges, and there is a short term trim that adjust on top of the long term value. So, you can have a zero short term trim at idle because the long term trim on top of which it is making an adjustment has already made the necessary changes.

 

Again, the best thing to do IMO is to pull a learning view. This will show you all the stored long term timing and fueling adjustments, in every engine load/airflow range.

 

I recall you having a VAG-COM cable? If so, you can use this to pull a learning view:

 

http://www.romraider.com/forum/topic2772.html

 

The hesitations you're feeling could well be due to the fact that the car is pulling a bunch of timing in certain engine load/RPM combinations, or due to a boost/vacuum leak due to which timing is being pulled. It's really hard to intuit what's wrong with these cars in situations like this, and you'll end up pissing a bunch of money down the drain chasing ghosts trying to do it.

 

I reaaaaaally don't like spending money I don't have to, so I would be looking into all this before deciding on a fuel pump or injectors, etc.

Edited September 1, 2019 by awfulwaffle

[Dalee1104]

Thank you for the info, I kinda thought he might have kinda half assed it tbh. I actually do not have a vagcom cable, I'm still very new to all this world of tuning.

 

To add on to the hesitations, if I had a boost or vacuum leak wouldnt I see that in boost levels?

 

Update: today on driving in normal condition I'm noting a lot more of these hesitations and lack of power, they are now happening very frequently. Is there a chance my fuel pump might actually be crapping out on me? They dont really feel like a vac leak and my boost levels read normal

[awfulwaffle]

Fair point, I don't know what normal boost levels were for your tune and there wasn't a boost error in your logs (unless I missed them). Again, if your fuel pump is crapping out and not supplying enough pressure, that'd show up in your long term fuel trims.

 

Just realized, if you have a means of datalogging you have a means of displaying the currently applied long term fuel trim. Not as good as pulling a learning view, but will tell you which trims are in effect while you drive. I see you had an AF Learning in your last log, but it was zero at all times - had you recently reset the ECU?

[Dalee1104]

Actually yes I did, I reset it for replacing the ocvs which I recently had an issue with. Sort of a semi update tho, pull on to my road and have a straight stretch I usually like to let the spec b stretch her legs a bit and she didnt feel as great. So I slowed down and started paying attention, you must be right with the boost like because now I can't peak past 15psi. Stock is 16psi and on stage 2 I'm usually around 18psi. On top of the that my DAM was all over the place so I pulled her in and left her alone gonna drive it subtly tomorrow. Im not sure if I'm getting hit with a double whammy or just one thing and over analyzing.

 

I dont have time to check tonight but tomorrow i can take a datalog on the way home from work. Which items should I log? I know (at least I think) you can change what the catalogs actually record? If that's the case I'll log those and then upload them tomorrow evening. My issue is time, I'm not sure if I'll have time to pull my intercooler and look for this boost peak tomorrow, any tips other than starting fluid?