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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #1
The engine feels way nicer to drive when IAM is higher so I set up Tactrix Open Port to log to SD card continuously. I’m learning slowly about AFR, knock and IAM. Typically IAM on this car settles on around 0.5 or 0.6 a few days after ECU reset but it sometimes drops lower. The rom raider learning view should be attached.

This is a stock 2007 JDM import normally aspirated H6 3.0R at 100k kms. The air filter has been changed and diff oils, engine and transmission oils changed at the local Subaru dealership recently. We’ve been running the same fuel brand for a month or more which is 98 octane, the closest we could get to the 100 the Japan models expect.

After an ECU reset then a 50km trip we looked at the 50km return trip log and saw IAM went through 0.50, 0.28, 0.50, 1.00, 0.75, 0.37 and finished up on 0.50. I guess it’s meant to keep learning but it always seems to settle on a low value.

The AFR trims seem to show fuel is being added to bank 1 could this mean a vacuum leak ? I read somewhere that trims < 5% are ok but am not sure. Also for the knock readings I checked that there are no loose items around the engine.

I’m keen to figure out what’s happening here but am kind of new to this and would appreciate any advice towards getting it fixed thanks.
 

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Registered
2005 OBXT Ltd Obsidian Black 5MT
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1,079 Posts
Typically IAM should be at 1.

FLK or Fine Learning Knock Correction typically indicates an air leak of some sort, either on the intake or exhaust side. But just merely the presence of it isn't necessarily bad, but when, how much ignition retardation, and how often it occurs is more important. But in your case, I believe you have lots of leaks.

When I was in the process of getting all the bugs out of my engine, I also had a low IAM around .5 or .6. Once I got all the intake leaks fixed, the IAM has stayed at 1.
 

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Registered
2006 Outback 2.5i Auto
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417 Posts
We’ve been running the same fuel brand for a month or more which is 98 octane, the closest we could get to the 100 the Japan models expect.
You should be aware that Japan uses a different octane rating method to the US - Japan uses RON, while the US typically advertises fuel as AKI = (RON+MON)/2. 100 RON is about 94-96 AKI, so 98 AKI is plenty sufficient for your car.
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #6
Did the MAF get cleaned when the air filter was replaced? It's pretty simple and can't hurt.
good point i did clean up the MAF sensor with maf spray cleaner. not sure that it's completely happy it could be the next thing to check up on.

You should be aware that Japan uses a different octane rating method to the US - Japan uses RON, while the US typically advertises fuel as AKI = (RON+MON)/2. 100 RON is about 94-96 AKI, so 98 AKI is plenty sufficient for your car.
i should have mentioned we are in new zealand where RON is advertised at the pump. interesting about the AKI i hadn't heard of that system so was good to read up on. as an aside our pumps are displaying 2.22 NZD/litre for 98 at the moment
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #7 (Edited)
following the smoke test we changed out the cracked intake air resonator. the engine seems a little smoother and the dash fuel economy reading is jumping around less.

however the IAM is still very low even after ECU reset and a couple of weeks of daily driving.

we found a local mechanic had put in the wrong air cleaner 16546AA090, replaced with 16546AA120. some folk mentioned this could affect the engine performance.

now logging (kind of) the knocking sensors using Rom Raider and Tactrix. the low logging frequency means we could miss heaps of these fleetingly fast events so the results are not quantifiable but with enough data a pattern could show. anyways so far knock sensor 1 hasn't reported any and knock sensor 2 sees knock on every trip.

next steps ? probably to replace the spark plugs
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #8
A quick follow up on this after the dealerships 100K km service.

The IAM has been up around 0.8 for the last couple of days and the car drives much nicer. The key related things here I think are the new spark plugs and upper cylinder cleaning.

I'm not sure if IAM should be any higher as the JDM ECU is not getting it's expected fuel RON (100) as my countries premium fuel (98) isn't always the highest quality.

Anyways the improvement is good and will keep an eye on this. Will try the Rom raider learning view to see what is happening over the weekend
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #9
I spoke too soon! A few weeks on IAM is down to 0.58, it's less responsive to drive and has clunkier gear changes.

There are no CEL codes although last week on the first start of a summer day the check engine light flashed fast. I think it was checking for misfires but ran OK after that.

The main difference on Rom Raider learning view (attached) seems the fuel trims have gone from positive to negative and more so on bank 2.

This means the ECU is decreasing fuel supply. I'm working through a bunch of articles on negative fuel trim being affected by fuel regulators and injectors and such.

The car had a smoke test a few months back that showed one air leak on a cracked airbox behind the throttle body which was replaced.

I’m scratching my head on how to troubleshoot this and what to do next, any guidance is appreciated
 

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2005 Legacy GT wagon 5MT Limited
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320 Posts
I recommend going ahead and starting an e-tune. Those fuel trims are close enough for them to start you on a base map, and their job is to replace the inadequacies of the stock tune, which are what are causing your timing pulls. This is certainly true if your available fuel is not up to the standards for which that tune was written.
It's possible the tuner may identify hardware issues during the process, saving you a bunch of time trying to diagnose them yourself.

Also, with those IAMs, which are pretty scary, having an experienced tuner address whatever's going on as soon as possible may avoid potential engine damage.
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #13
yeah I agree and will get back in touch with a tuner i know. keen to get this sorted.

also looking at the romraider logs i can see the bad knock is usually in 4th or 5th gear, will try to attach a chart
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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16,144 Posts
yeah I agree and will get back in touch with a tuner i know. keen to get this sorted.

also looking at the romraider logs i can see the bad knock is usually in 4th or 5th gear, will try to attach a chart
Yep....she's pinging alright....
 

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2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #15
IAM has stabilised around 0.7 with the 100k km dealer service with new spark plugs, also EGR valve was replaced. It's nice to drive compared to before now I'm curious to figure out a lean situation on bank #1 as much as I can.

RomRaider logging shows bank #1 is running consistently leaner than #2. Ran smoke tests on the intake and exhaust with no visible leaks. I wonder if this is fuel pressure or injector related. I've attached graphs from cruise control - the downstream O2 sensors difference between bank 1 and 2 is noticeable although strangely the upstream AFR sensor values don't seem so different unless the difference is data scaling.

I am (no pun intended) enjoying learning about this and appreciate the help here.
 

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2008 JDM Outback 3.0R, 5EAT
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Discussion Starter #16
There's currently a physical issue with my car, a very mild shuddering at all speeds, even deceleration and coasting in neutral. No noises, no CELs and not so worried about it at this stage. Now this could be a complete random coincidence but when I rotated the tyres IAM stopped bouncing around. Out of curiosity temporarily reversed the rotate and the changing IAM problem came back so that's another story.

Anyway setup Tactrix to log FLKC, load, RPM, base timing, etc.. to SD card via fast CANBUS over a week of mixed driving styles and a few pulls for good measure. The knock is definitely worse with high AVCS and when lugging the higher gears. I tried the RomRaider 'reduce global timing' feature with no luck.

So I'm running analysis with SQL to figure the knock hot spots against each base timing table and reducing the cells with obvious knock (my ROM has base timing tables A through H - would love to know which scenarios they represent). Currently on the first ROM of reduced timing, IAM and drive ability have improved a little so I'll run several iterations and report back.

There's a very interesting read from hmhaga in Australia who tuned out similar issues over @ "Tuning" the 3.0R (BP) ? club.liberty.asn.au seems fuel octane, lean stock maps and slow CL/OL transition were causing detonation and his IAM to drop.
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #17
OK after installing the new front axles I decided to log weeks of data to SD card with Tactrix OpenPort.

I watched for roughness correction (IAM dropping) and large fine learning correction changes (FLKC) and noted the engine load and rpm conditions these occured.

I pulled timing from these areas using RomRaider whilst attempting to keep the maps as smooth by interpolating changes and then logging all over again.

IAM has been at 1.0 around a month, the engine is happier and the gearbox is running smoother. I guess my timing issues were due to running lower octane fuel that it's expected JDM 100 RON and also online research shows the factory tune runs lean by design.

So now I finally feel some progress has been made, albeit slowly :)
 

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Premium Member
2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #18
OK there’s an update overdue here. Finally, I can say IAM is at 1.0 and the car drives better after de-tuning. I now believe the factory tune has over ambitious timing and runs too lean. This post shares what I’ve learnt from the Subaru community from those who arrived at this conclusion ages ago (links below), here’s how I got here.

I gotta say early on that this isn’t a USDM or ADM model. It’s a JDM JDM – born and driven in Japan for 8 years before relocating to New Zealand. The car is designed to run on 100RON premium unleaded fuel.

I'm running the best gas I can get in my country which is 98 RON. IAM was slopping around anywhere between 0.3 and 1.0 we could feel the drivability change with IAM, so it became kind of addictive to get the car running optimally. As another post mentioned it sometimes felt like driving a 1500 rather than a 3000cc vehicle and the 5EAT transmission is happier when the engine isn’t knocking. Did try adding octane booster to the fuel whilst it did reduce knock wasn’t so comfortable pouring this stuff into the tank and wanted a longer-term solution.

Of course, IAM isn’t just a number but reflects the amount of knock detected so we’re really figuring out optimal timing (and other parameters) for the engine.

My local Subaru dealership didn't seem to think low IAM was an issue. Guess it will move around with a tank of bad or cheap gas and they didn’t want to get involved or perhaps other models of Subaru don’t have this problem.

After reading various articles and wanting more zoom I found an e-tuner who showed me the car can be optimised to run max IAM. However, I purchased the e-tune early on, pretty much after buying the car before replacing plugs and parts and before I knew enough about tuning and engines to get the best result.

I then spent some time trying to stabilize IAM with the stock tune re-installed and a hardware approach. Replaced a bunch of stuff but always OEM or the Denso direct equivalent products. Spark plugs, EGR,PCV, in tank fuel filter, injectors and seals (after having them professionally cleaned made things worse) and the air intake chamber due to the typical crack appearing behind the throttle body, transmission mount and so on. Oh, and one AFR sensor was clipping its output so replaced both. Idler pulleys needed replacing too but you’ll know that most of this is general maintenance that needed doing anyway.

Back to tuning with RomRaider where I continue learning as much as possible (links below) and tweaking the tuning parameters little by little. I won’t go into the details here as the tuning forums are a great place to figure out the world inside our car’s engine computer. But basically, decreased open loop AFR around 0.5 and reduced timing after analysing lots and lots of files logged with Tactrix to SD card. AVCS angles can be smoothed over to reduce knock but this diluted the accelerator response for me … nah.

The logs now show IAM at 1.0, no FLKC and only occasional FBKC. Sure, the car uses a little more gas but that’s inevitable with a lean starting point and using 98 RON gas which is lower than the 100 they have in Japan but I’m reasonably happy.

https://tactrix.com
https://romraider.com
"Tuning" the 3.0R (BP) ? club.liberty.asn.au
Tuning the Subaru H6 engine - Engine/Electrics - UK Legacy Forums
https://www.romraider.com/forum/viewtopic.php?f=15&t=15341
 

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2008 JDM Outback 3.0R, 5EAT
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424 Posts
Discussion Starter #19
OK so the detuned maps ended up using way more fuel and the car never really felt awake so back to the drawing board with the stock ROM installed in the car.

Had Tactrix log full time to SD card awhile and loaded it all into a database to analyse parameters when the worst feedback or rough knock correction happened. Lugging highway gradients in 5th would trigger changes but other times it would jump around in benign driving conditions.

IAM's been higher but importantly more stable and driving better with recent fixes however it's just a month in since the fuel system work. Also Autumn here so things could change as warmer or humid weather arrives, or before. Most of these helped with the knock ;
  • Cylinder compression & leak down test. Just for sanity and to prevent spending time or money on a no good engine.
  • Regular servicing. Good fluids, genuine filters & parts as I didn't know what the previous owners did & this car is fussy!
  • Checked the plastic air chamber that sits behind the throttle body. There's a known vertical crack that ca open up front and centre. Also the join seam that runs around its circumference can peel open a little. This can cause vacuum leaks but easily filled with JB Plasti Weld. Subaru have issued a revised design of the chamber tho its not cheap.
  • Checked the catalytic converter covers, they are made of mild metal and should have a couple mm gap around the pipe at the forward and rear openings. Mine were rusted around the bolts & the ends pushed up onto the exhaust pipe plus small stones trapped inside. These factors can make a vibration that the knock sensors shouldn't hear .
  • Changed the in tank fuel pump & filter - also reflected on the knock logged.
 
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