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2014 Forester 6 M/T
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Hi,

As I promis short report from decarbonization. I was on decarbonization of air intake, injectors and engine. So far I can tell that it has no effect on erratic DPF behavior. Other than that engine runs smoothly and quieter then before. So erratic behavior of DPF isn't fixed as I hoped. Next step would be DPF cleaning. If this didn't help then I just give up. I have no idea what else I could try. Probably I sell the car, but Subaru doesn't have equivalent offering right now. E-boxer is lazy/slow not efficient enough for that price, at least for me...

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2010 Forester Diesel 6MT
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Discussion Starter #322
Did the oil smell like diesel fuel? It is contaminated?
No and believe me, I've smelt the oil when it's got diesel in it previously. It's only been 1000k (maybe 2000) since last service, although it did have a forced regen in there and strictly speaking I probably should have changed the oil after that. Diesel in Australia has got a lot less smelly in recent years and so may not be quite so evident by smelling anymore. It was overfilled to begin with. I will watch it carefully from here and see how/if it climbs. I have a spare filter and oil ready to go.

E-boxer is lazy/slow not efficient enough for that price, at least for me...
Have a look at the RAV4 Hybrid. Several reviews compared the two in Australia (Oz versions). Wheels nowadays doesn't really want to offend any manufacturers...or they won't get cars to review! But they gave the Forester hybrid an absolute caning over its drivetrain basically saying: too noisy and rough (esp restart), too slow, too underpowered compared to RAV4, too expensive... and the kicker.. hardly more efficient than the normal engine- and never than the RAV4. So effectively, what was the point? A few other online reviews make a simiar point, see one here. The Forester may have more ground clearance and all models with AWD but realistically, who goes bush bashing in these nowadays? And hybrids work better economically in town anyway. So Toyota has been clever to recognise this and bring out a 2WD version, dropping the price further.

Numbers tell a story- and this is just on paper:
Motors (petrol + elec in kW)
  • Forester: 110 + 12 (don't say combined output)
  • RAV4 2WD: 131 + 88 : 160kW combined
  • RAV4 4WD: 131 + 88 (F) +40 (R) : 163kW combined
Fuel consumption (avg/city/country in l/100km, reported offical figures- the real world figures differ quite a bit and the Forester comes off worse):
  • Forester: 6.7 / 7.5 / 6.2
  • RAV4 2WD: 4.7 / 4.8 / 4.7
  • RAV4 4WD: 4.8 / 5.0 / 4.8
Battery capacity + warranty:
Forester: 0.6kWh Li-ion, 8yr/160k km
RAV4: 1.6kWh NiMH, 10yr/unlimited km

Servicing costs:
Forester: $2433 5yrs/62.5k km @ 1yr/12.5 k km intervals
RAV4: $860 4 yrs/60k km @ 1yr/15k km intervals

And guess what? No spare wheel at all on the Forester- the battery occupies that space. So much for off-road... And the fuel tank size is pretty weak at 48l.
 

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2014 Forester 6 M/T
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Yeah Rav4 Hybrid 4wd looks prety good and it takes a lot of my attention. It look like a great alternative and for the money I get much more. If DPF cleaning will solve the erratic DPF behavior i will keep my Diesel Forester for 2-4 years and I will hope for better Subaru hybrid ;-)

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2010 Forester Diesel 6MT
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Discussion Starter #324
If DPF cleaning will solve the erratic DPF behavior i will keep my Diesel Forester for 2-4 years...
Good luck with the cleaning. Once it's done 'reinstall' the DPF (i.e. tell the computer there's a new one) and then give it a while before you come to a conclusion as i think the car may 'retune' itself (see below).

Soot control and DPF Regen distance
Another little run today to keep things ticking over, and check behaviour of the soot level. Approx 50km of mostly urban /suburban driving done, left with ~275km since last regent at 5% soot and came back at 325km with 58% soot- in between though the level went as low as 36% with a high of 59%- see below about scaling. It never touched 60%. At 300+km the DPF is almost back to normal behaviour esp considering it's mostly suburban driving. I have noticed a general overall increase in DPF differential pressure whilst driving and this makes sense as the DPF fills. Note these are observations whilst driving, I didn't actually log the data (I really should turn it on again). And of course, the soot level is a calculated estimate.

I think I can more or less confirm that, excluding the normal inexorable soot growth with usage, the following extraneous effects seems to happen, ranked more-or-less in order of effect:

1) Soot scales sharply with accelerator usage- hard acceleration (e.g. full throttle run up to 100km/h, done previous drive) can drive soot up by 10-20% for that short ruin alone. From this I suspect either the DPF full rate flow isn't good enough (either through being a cheap aftermarket and/or damage) and/or there is some miscalibration, esp. as the soot level will come back down under cruise/ light throttle/coast conditions. Gentle acceleration leads to little soot growth. However there is a DPF diff pressure minimum under very small accelerator pressure, as opposed to no accelerator where the DPF diff pressure measured can actually increase- I'm not sure why.

2) Soot scales with engine temperature- The car started at 55% soot from the last run, within ~2km of leaving that value had dropped to 36% whilst the engine was cold, and didn't grow back to higher levels until I engaged in a fair bit of stop-start city driving followed by a strong acceleration up to 80km/h. I guess either the DPF flow or pressure measrement is being temp affected (certainly the DPF differential pressure is a bit lower when cold) or there's a miscalibration of some sort.

3) Soot scales with engine speed- A lower gear for the same engine speed gives a higher soot reading. Note the MAF flow does scale with revs so this also relates to the air flow rate. Keeping the engine around 1650rpm seems to minimise the soot without making the engine lug - so 4th gear at 60km/h OBD speed, 5th at 80km/h.

4) Soot scales with road speed- As speed increases the soot level tends to get higher for the same engine revs. This might be expected as higher speed=more fuel burnt, however the soot level can be brought back down by reducing the speed.

5) Soot level reduction at idle- reduces quickly if you coast in neutral (naughty) and slowly at stationary idle if the DPF differential pressure at idle revs is low (1kPa or less).

The upshot is I am able to manipulate the soot reading somewhat. If I want to initiate a regen from moderate levels, no problem- a couple of accelerative bursts revving the engine out and it will start.
To keep soot down:
  • use gentle acceleration
  • shift up before revs get too high (>3000rpm) but not so the next gear drops below ~1600rpm
  • try and cruise in a gear at ~1650 rpm.
  • use the cold period just after first startup with gentle driving to (ahem) drive the soot level down.
I hoped to get over 300km before a regen, now I'll aim for 350km and 400km if lucky. I'll keep driving to minimise the soot reading, i.e. at slower speeds and with a cold start again for the next run this hopefully this will really 'max load' and 'max distance' the DPF somehow and maybe the computer will learn something from it.
 

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Discussion Starter #325
Well, that was weird. Went out for a drive to initiate the regen. Soot was 59% @~310km when I went out...came back at 46%@337km - no regen in between!

Got to the 100km/h zone which is my 'go to' to drive up soot-100km/h out of a roundabout, uphill. Perfect for full throttle accelerations. Last time it drove the soot up... this time it drove the soot down, albeit slowly. And it stayed down- Go figure!

My guess is the full throttle run 'blew out' the DPF a bit reducing DPF differential pressure just enough to reduce the soot reading. I'd half-suspected this had happened once or twice before, this confirms it. However, if the DPF is really full, the v. high DPF differential pressure this full throttle acceleration generates quickly inreases the soot (as before).

It may also be we have alpine diesel back, that always seemed to help- although I think I topped up a tad early for that- it's only due about now I think.

Looks like a good interval between DPF regens this time, esp. given suburban driving.
 

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Discussion Starter #326
Another drive. Started at ~337km and 30% soot. How it got down there from the 46% above I don't know, but I have seen different soot readings upon a cold startup before too.

Drove around, soot stayed around 30% until I got stuck at higher revs in a lower gear behind a slowcoach on a freeway on ramp- then it went up to the 40%'s, 46% was the max I saw.

Afterwards, gentle cruising brought it back down to the 30%'s, then some strong accelerations- this time the accelerations didn't drive the soot down, but increased the soot which 'makes more sense'.

Back at 415km and 40% soot. Regen dist is now entirely reasonable and not actually near the trigger level yet.

Weird, but good!
 

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2010 Forester Diesel 6sp Manual
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strong accelerations- this time the accelerations didn't drive the soot down, but increased the soot which 'makes more sense'.
Strong acceleration will increase EGT and help burning off soot.
and when going full boost engine does not produce huge amounts of smoke, so that maybe helps keeping the soot down.
Most smoke is generated (this is from what i can see in rear view mirrors driving a deleted DPF) when you give sudden burst of full throttle in low revs - when car builds boost, then there is a puff of black soot. Also going near redline engine starts starving for air because of small turbo and thats where more smoke starts to appear.

In engine ECU ROM there is map that is called "soot load coefficient" that is dependant from Differential pressure and Airmass
535188

And there is map "soot reduction coefficient" that is dependand from Differential pressure and EGT.

535189


I added screen shots of part of those maps (it extends to pressure of 80000Pa)
Maybe it is interesting for you and would give some explanation of soot behaviour.
Actual Airmass PID is 22111A Formula A*10 min - 0 max - 1500 value - mg/st
 

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2010 Forester Diesel 6MT
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Discussion Starter #328
Thanks dieselforry.

I have noticed that the EGR is inactive pretty well all the time at lower ambient temps (<10C), which I am now experiencing in Canberra. This is for both my diesels, the Subaru Forester and a Mazda 3 diesel. Only a slight EGR usage on the Mazda when coasting downhill in gear, and I know my Subaru uses it to assist engine warm-up.
 

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2014 Forester 6 M/T
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Yes I have same experience when ambient temperature is below 10C. Now we have temperatures around 20C, as summer is coming, and DPF getting crazy. I plan to go for DPF cleaning and will see whether it helps. Engine decarbonization didn't helped as I expected/hoped.


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Discussion Starter #330 (Edited)
Infernal car...

* My last drive (last weekend) increased last DPF regen dist to 496.7km at 41% soot. This was some about-town then mostly highway running at night with a couple of full throttle accelerations. The soot level actually dropped when starting- down into the mid-30%'s, and only increased after a some town running holding the revs up a bit for engine braking, acceleration, etc. I think it went up to about 49% before coming down during the highway running, where not even full throttle accelerations could drive it up appreciably anymore. Engine performance was smooth and fine, reported economy good at 6.4l/100km. So... approx 80km for +1% soot...go figure! o_O

* My drive today increased last DPF regen dist to 581.2km at 52% soot. Soot briefly touched 56% due to some city short distance driving (i.e. between several shops). After that I put some diesel in and gave the car a ~50km run in highway conditions, which serverd to slowly bring the soot down to its finishing level. Again a couple of full throttle accelerations made minimal difference. This was a daytime drive with the air temp around 12-13C and the EGR was active at least part of the time. Again, engine performance is good, smooth idle and acceleration, economy remains reported around 6.4l/100km.

I do wonder whether the removal of the excess oil has something partly to do with improving things- it can't hurt! Perhaps excess oil was being aspirated into the exhaust, causing oil pressure issues and affecting e.g. cam timing, or the like.

Coupled with the cleaned DPF ht, removed excess oil, better running conditions, a couple of fixed pipes, the engine retuning/relearning components (injectors, DPF perhaps) etc. may have been enough to 'tip' things in my favour.

So it seems I will achieve the >600km per regen currently. Maybe I really have 'fixed' the overfull DPF... or I've blown a small hole in it :oops: ...see my next post for a bit of evidence regarding that (or not).
 

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Discussion Starter #331 (Edited)
Following on from my previous post about distance since last DPF regen and my last two drives...

I have been wondering whether the DPF has been adversely affected enough by the overfull status to not function properly.

Early on post DPF-rescue it had small regen distances and an excessive response to acceleration which I put down to possible DPF internal damage after the overfull state. Maybe there was a possible partial obstruction, or the DPF was too small for the flow rate in the first place- it is an aftermarket one.

Since then, things have swung the other way to long DPF regen distances. In this case, perhaps the damage was an opening (e.g. crack or hole) being 'blown' or burnt into the DPF core. However this long regen behaviour matches previous Canberra wintertime behaviour accurately which I think is a GOOD sign as it means the DPF, at worst, is behaving similarly to the OEM one of a few years ago. So things can't be all that bad.

So I've trolled back through my thread and pull a few quotes from myself which I think illustrate where, with respect to the DPF it:
  • was at
  • is now
See the below comparison of DPF differential pressures- note these are my 'eyeballs' from Torque Pro whilst driving.

Overfull DPF
...soot level firstly rose rapidly on the drive out of Canberra to the freeway hills, touching ~240%...Returned home, soot at ~162%. Note car in limp mode limiting fuel, boost, revs but also soot production.
DPF pressures ~3-4 kPa at idle, ~14-18 kPa whilst cruising and ~50+kPa worst-case accel.
Preparing for DPF forced regen by bringing soot level down with fuel additive
...soot starting at 90% and not climbing above ~96%.
DPF pressures ~2-3 kPa at idle, 10-14 kPa whilst cruising and ~20+kPa worst-case accel.
Currently at 52% soot level
The DPF pressures are ~1 kPa at idle, 4-5 kPa whilst cruising and ~12-14 kPa acceleration (maybe a little more worst case)

At ~20-30% soot level
The DPF pressures are ~0-1 kPa at idle, 1-3 kPa whilst cruising and ~4-8 kPa acceleration (maybe a little more worst case)

When at 0% soot level, i.e. immediately post-regen
The DPF pressures are ~0 kPa at idle, 0-1 kPa whilst cruising and ~4-6 kPa acceleration worst case

So, it all seems consistent. And you can note that at a steady cruise on a flat road at ~60-100km/h with one person on board, the soot level is roughly 10x the cruise state DPF differential pressure. I can state that if:
  • the soot is at 30% and DPF differential pressure is 5 kPa, the soot climbs.
  • the soot is at 50% and DPF differential pressure is 3 kPa, the soot falls.
This leads me to conclude that at the moment, the DPF seems to be behaving (more-or-less) both as expected and reasonably 'normally' within the constraints of wintertime behaviour for this vehicle. Need to wait a few months and/or go 'North' to test summertime behaviour again- however, even if regen distances are shortened by warmer weather and/or non-winterised diesel, the vehicle driveability seems to be similar to, if not better than, prior to the DPF overfull situation.
 

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Discussion Starter #332
Now 662km at 58% soot.

No soot level instability under hard acceleration or coasting and looks like it's heading for my longest distance between regens ever. Surely too good to be true???
 

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Now 662km at 58% soot.

No soot level instability under hard acceleration or coasting and looks like it's heading for my longest distance between regens ever. Surely too good to be true???
That's sounds great . Would it be possible for you to summarize what you made till you achieve this promising result? Something like check list? Maybe as sticky post at the beginning of this thread.

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Discussion Starter #334
Well I couldn't wait any longer so drove the car until it regenerated. 773km when it finally started a regen, 793 km when it finished. That's by far the most km between regens i can remember, by >100km (I think last best was ~660km many moons ago). I did get >800km betwen regens on my Mazda 3 once, but that resulted in a DPF warning light and a forced regen!

Just before regen, the 110km/h cruising DPF differential pressure was approx 5-7kPa, after it was 1-2kPa.

This time at idle, the DPF differential pressure was 1kPa before regen and 0kPa after. the pre-regen pressure is encouraging, to me that indicated the DPF isn't getting totally clogged.

I still think some sort of recalibration was going on, the last 5-10% of soot seemed to climb more by km that anything else and showed no reaction to acceleration or coasting. Furthermore during the regen the soot dropped sharply then proceeded to sit on 2% for basically the second half of the regen time until the regen finished- I saw it do this a regen or two ago as well.

Oh, and in spite of the relatively low air temp (close to 0C), EGR was active but not until the coolant temp was >90C (and that took quite some time, ~30+mins)

.
 

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Strong acceleration will increase EGT and help burning off soot.
and when going full boost engine does not produce huge amounts of smoke, so that maybe helps keeping the soot down.
Most smoke is generated (this is from what i can see in rear view mirrors driving a deleted DPF) when you give sudden burst of full throttle in low revs - when car builds boost, then there is a puff of black soot. Also going near redline engine starts starving for air because of small turbo and thats where more smoke starts to appear.

In engine ECU ROM there is map that is called "soot load coefficient" that is dependant from Differential pressure and Airmass View attachment 535188
And there is map "soot reduction coefficient" that is dependand from Differential pressure and EGT.

View attachment 535189

I added screen shots of part of those maps (it extends to pressure of 80000Pa)
Maybe it is interesting for you and would give some explanation of soot behaviour.
Actual Airmass PID is 22111A Formula A*10 min - 0 max - 1500 value - mg/st
Hello, i wonder what else is going into the equation that calculates actual soot load? From what i see here is a calculated value from multiple inputs from the sensors.
I am following this thread for a while now. Have the same engine and experiencing similar issues with frequent regens.

Thanks.
 

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Discussion Starter #336
A couple a runs over the past few days - one suburban/freeway and one country- and the DPF behaviour is consistent with the previous regen. In fact I did the driving 'blind' to the soot level, i.e. I didn't monitor the car through Torque Pro whilst driving, only looking at the end or once or twice during driving.

At 80 km since last regen, soot at 8%
At 90km since last regen , soot at 9 %
At ~200km since last regen, soot at 19%

And car is driving smoothly and arguably more tractably than ever before- it revs out cleanly and pulls well from ~1600rpm, although under regen the same acceleration delay/lag issues remain. I am able to 'skip' gears much more than in the past (e.g. 3rd to 5th or even 6th, occasional 2nd to 4th), similar to my petrol vehicles.

During the drive today which was a ~110km round trip Canberra- Yass by highway and back via country dirt roads, we pulled over for me to briefly check the map- and whilst idling the engine went into the 'rough idle' I assume to be an injector relearn. The engine note also changes appreciably, esp. with the door/window open (which it was). It's obvious enough that my daughter in the back seat (who seems to have a mechanical talent) immediately noticed and asked what was going on. It all settled down again in approx 15-30 secs by itself.
 
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