Down on power?

[Dropz]

Good to see its sorted. After a long drive UEC is a good idea as cruising speeds is when the pcv opens, causing all the shitty gases to go into your intake.

[jslayz]

BP98 and all good, glad to hear its back to booting hard

J

[al_cam]

Good to see its sorted. After a long drive UEC is a good idea as cruising speeds is when the pcv opens, causing all the shitty gases to go into your intake.

Dropz, could you explain please - about the PCV? Is it the low revs coupled with a long time? I do a 330km Country trip about once a month and this would fit behaviour I've observed.

Thanks,
Al.

[Stomps]

BP98 and all good, glad to hear its back to booting hard

J

Yeah, a tank of 98 and ecu reset...

The main difference I see now is in 2nd and 3rd...

When it was running shit, it would actually slow down as I shifted up gear at 50% throttle.. would bog down.. now it just keeps going again...

Can't wait for the rest of the exhaust and tune.. that will help a lot..

[Dropz]

At cruising speeds like 2-3000 rpm under light load the pcv valve opens to burn the crankcase ventilation gases. It wont do it at low rpm, high rpm or heavy load because it slightly lessens the engines performance (not noticeable), which is where catch cans come into play. All these gases get vented.

[al_cam]

Thanks Dropz.

It was only a little hijack.

[TheFirstEskimo]

Yeah disconnect battery, pump brakes about ten times to discharge all voltage and leave it for ten mins then reconnect battery

Your iam will default to 0.5 once you reset the ecu.

Try to baby it after the reset cos the knock sensors are quite sensitive and if it picks up any knock it won't advance the iam from 0.5.

Drive it sedately for 5kms or so and it should be ok

Then give it a squirt and see how she goes

Good luck

Just a quick one on this... Ive had my ECU re-flashed and had a tune.

Will disconnecting the battery remove the effects of the tune?

Surely the info is stored permanently on the computer?

[dr20t]

No you have nothing to be concerned over

The ecu has three types of memory:

Volatile - this is the fuzzy logic part of the ecu that learns certain behaviors and adapts to new situations (eg closed loop fueling)

Semi volatile - I'm not too cluey on what entirely or exactly falls within this category, but I know that for eg subaru's knock detection and correction strategy will kick in and be applied to the parameters logged into this type of the ecu's memory. I really don't know how to adequately explain this but for eg when you have a bad batch of fuel (like stomps' example above), the knock sensor may detect knock and pull timing as I described a few posts back. The knock conditions are stored in this part of the memory, and the ecu deducts timing and makes other adjustments to work around these conditions or until they disappear.

Non volatile - this is where your tune is stored to the hard rom. The ecu will compensate for things like timing and open loop fueling correction to some degree by using the functions of the semi volatile stored ram settings and adjusting, all the while however trying ultimately to get back to the parameters in the hard ram.

[TheFirstEskimo]

Cheers Mick,

Thanks for the reply, and thanks for confirming my suspicionsthat in detail

While your feeling helpful, could you explain the reason for driving sedately after ECU reset?

I was always told to drive hard after reconnecting battery.....

[dr20t]

No problem - just repeating what I've picked up from romraider forums and a couple of tuners

The reason for driving sedately after ecu reset is due to the knock sensor in the boxer motors being so sensitive, especially in the 2.5.

After an ecu reset, the iam defaults to 0.5 (out of 1). The iam is a multiplier as I said earlier, which is applied to the entire timing table. If it's set at 0.5, it means your entire hard ram/rom timing table (which the tuner has optimized to extract max power/torque and efficiency when he tuned your ecu) is being effectively halved. I'm sure you could understand that this would not be ideal for performance. Once you understand the ecu knock control, you will know that an iam reduction is the ecu's last port of call to reduce knock by cutting timing across the board.

So basically your ecu reset has just reduced your timing to what is hopefully the lowest common denominator (unless something is majorly wrong with your tune or engine - ive seen iam of 0.31 on an ecu which you could read as the ecu sending an s.o.s out to say fucking help me cos I'm fked!!!). There is no more likely adjustment possible because this is the last of three knock control elements the ecu will use to reduce knock.

Using this logic, and taking into account the sensitive knock sensor, you basically want to baby the motor around until the ecu breathes a sigh of relief to say "ok everything is cool let's slowly advance timing in reverse order to how timing is usually pulled". Therefore, first your iam will try to climb closer to one if there is no knock, and once it safely thinks a 1 times multiplier is ok to apply, will revert back to the other two knock control mechanisms, by elimination, to control it.

So think of it like this. There are three modes of knock correction:

1. Feedback knock
2. Fine learning knock
3. Iam (rough correction)

If everything is cool and in ordinary circumstances, the ecu will use 1 & 2 to make adjustments to timing to control knock (and without confusing things, number 2 can also increase timing if it senses it's safe to do so, but only up to the maximum hard timing values set into the ecu rom when it was tuned)

If knock is severe enough and not being controlled by 1 & 2 above, then it will use method 3.

Only when things are ok again will it go back to using 1 & 2.

So when you reset the ecu, it has pretty much defaulted to using number 3 method (the most severe), and therefore you want to do your best to assist the ecu going back to "normal" modes. By babying the motor you're giving the ecu the best chance to do this and revert to your stored hard tune parameters

That's the simplest way for me to put it from my limited knowledge

There is a HELL of alot more to it but that is a basic run down

For more info I highly reccomend reading the romraider forums and maybe even making a donation for the great work the developers there do in assisting the Subaru community

Hope this hasn't confused you more and has been of some assistance

Mick

[Kekotic]

Really good info there Mick and well explained, and +1 on reading romraider.

[Kekotic]

Anyone interested in learning should have a read of A Subie Newbie tuning guide.
Old mate Bruce told me about this, looks pretty good. Have only read a few pages but it's a good starting point.


https://sites.google.com/site/asubienew ... de/ver-1-0

[rooby]

So I'm guessing the volatile part is gone after losing power and the non volatile part is safe unless deleted or overwritten, but what is semi volatile?

I'm not aware of semi volatile storage and when its data might be lost.

[mynameisdaniel]

Anyone interested in learning should have a read of A Subie Newbie tuning guide.
Old mate Bruce told me about this, looks pretty good. Have only read a few pages but it's a good starting point.


https://sites.google.com/site/asubienew ... de/ver-1-0

Just finished reading the whole thing a few days ago, really simplifies a lot of stuff but having said that there's still no way I'd change anything myself. Although good knowledge if you want to check your tune and monitor the car to see what's going wrong.

[dr20t]

So I'm guessing the volatile part is gone after losing power and the non volatile part is safe unless deleted or overwritten, but what is semi volatile?

I'm not aware of semi volatile storage and when its data might be lost.

Yeah im not entirely sure on how the semi volatile works but I know it's there

The ecu uses this to make instantaneous decisions and then if the conditions disappear it wipes itself

Mick