RomRaider

In several articles posted on the Romraider website, the authors note that the IAM will be reduced from the ideal "16" or "1" (depending on the ECU bit rate) if 87 octane fuel is used. For example:

(source: http://www.romraider.com/RomRaider/HowT ... ockControl)

and

(source: http://www.romraider.com/RomRaider/IAM)

Am I correct in understanding that the reference to use of 87 octane and the impact it would have on IAM is only in relation to engines such as the turbo and H6 3.0 that require higher octane fuel and not, for example, to the normally-aspirated 2.5 that requires only 87 octane?

In other words, would the IAM for a normally-aspirated 2.5 that requires only 87 octane typically be less than "16" or "1" (depending on the ECU bit rate), or should it still optimally be at "16" or "1" despite the use of 87 octane?

Adding a couple of Learning Table Value readouts from my 2007 2.5 normally-aspirated Outback.

The two are Apr. 26 and May 6, and were recorded Key On, Engine Off.

In both the IAM is at 0.68. In a Romraider log I have going back to November 2011, the IAM, during highway speed cruising was at 0.75.

(The battery was replaced in Dec 2013; I presume the IAM would have been reset to the default 0.5 at that time.)

I haven't been able to find any IAM data from another 2.5 n/a, that, like mine, otherwise seems to be performing well, and has been well maintained.

Anyone able to provide comparison data, or comment on these reports?

The answer depends on the tuners preference.

Some prefer max IAM.
Some prefer a lower IAM so that the ecu is always trying to add more timing in case of better conditions occurring than were tuned at.

The second situation I wouldn't allow in higher hp setups in high load areas.

If you are not tuned, this is simply how the OEM ecu operates due to incredibly varying conditions all over the region.

Thanks

I guess I should have mentioned that the ECU is stock, not tuned.

Also, I had read the linked articles to be implicitly saying: An IAM of "16" or "1" is good/ideal/target; anything less is not good and should be looked into.

But if I understand you correctly, this is only if the ECU is tuned, and the tuner is looking to maintain an IAM of 16 or 1. If a stock ECU is showing less than the maximum, it's not necessarily unusual or indicating a problem; that's what it's designed to do. Is this correct?

(I'm trying to better understand what the logger data is telling me, and how it can help in identifying problems or troubleshooting.)

What the numbers are saying is that the ECU is compensating for the environmental conditions under which it is running.
This includes fuel quality, temperature, and possibly wearing components such as dirty air filter, old spark plugs, dirt MAF sensor, aging AF and/or O2 sensor. How many km on these components?
Have you had any DTC show up lately?

Car has about 134,000 kms, and is running fine, as far as I can tell. There are no DTCs. (It only had the CEL come on once, in 2011, due to a few moments of misfiring on a very damp, cold morning start up. Ignition wires and coil were replaced.) All "scheduled" maintenance has been done (e.g. last plugs etc., at ~94,000 km). Some, such as the air filter, which are easy enough, I just do annually, well before the scheduled intervals. But, granted, I haven't cleaned the MAF sensor, and the A/F and O2 sensors are original.

I generally use Petro-Can regular, but occasionally fill up at other major "Top Tier" brand stations. Both the 2011 logs, and the recent checks might have been with "winter" fuel, if that might be a factor.

Other than the IAM, the LTV data is showing fuel correction that is noticeably progressive with air flow. I haven't focused on this but it is something I'm wondering about as well.

All this data is generating lots of questioning and learning on my part . . .

(Still wondering, and learning . . .)

Been looking at the A/F Learning levels, and at the ROM file (opening in Romraider Editor).

The ROM has a table for base ignition timing, against which, I understand, all the other tables relating to timing adjustments are applied.

There are also tables of adjustments to fuel, but I don't see a table of "base" fuel settings, as there is for timing.

I can understand that in a closed-loop system, the fueling will simply be determined by the feedback and any base levels become redundent. But then, how does open-loop work? There is a table for "primary open-loop fueling" that looked promising, but it's mostly filled with 14.70 A/F ratio cells.

I did some searching in the forums for a thread that might deal with this (like the very informative ones on knock control), but didn't spot one. If there is, I accept the rebuke (along with a link, perhaps?). Otherwise, any insights on this question?

Not much progress in the past while, but there's updates on what I've done in the time since my last post in my thread on subaruoutback.org http://www.subaruoutback.org/forums/66- ... -have.html.

I am noticing that the Knock count/sum parameter moves up even under light throttle, and sometimes even when the throttle is released, or off, (as when coming off a freeway). On a typical city/freeway drive it's not unusual for it to run up quite high, and sometimes reaching 34 after which it resets to zero and starts over.

Intake has been examined several times for leaks, new MAF sensor has been tried, and exhaust has been checked for leaks at the manifold. Also, fuel pump pressure has been tested.

Is there any causal relationship between knock control and fuel correction? Could detection of knock events (including sounds like it) result in the ECM adding fuel? (Granted, seems an odd approach, but I reaching out for ideas.)

I'm not discounting the possibility of a skewed A/F sensor, or something I haven't even identified as a possibility. But I wish there was a reasonably reliable way to test the sensor without the costly replacement approach (and no refund if it doesn't prove out).

I'm still puzzled by the long-term consistency of the data -- pretty well unchanged since I started with Romraider in late-2011. Whatever it is, it isn't something that is "wearing" or would likely deteriorate over time.

Here's a odd question: When Subaru does a reflash recall, does it replace the whole program and tables, or is it a narrowly-applied patch? The car had the WVU-31 reprogramming done in early 2011. This supposedly was to change the A/F Sensor heater control function. Is there a possibility that with the reflash, I could have ended up with a ROM that is for a different engine/build etc? How would/could that be checked?

Lots of uncertainties and questions . . .

Keeping it alive in the hope that something might just trigger an explanation if not a full resolution.

I have not really tuned any NA subaru.

Have you check exhaust leak pre 02 sensor?

Have you ever changed you CAT?

What is your oil consumption like?

Carbon Build up on top of the piston can cause detonation.

Thanks

I appreciate that normally-aspirated 2.5s are not usually the subjects for tuning. In my case, there's no trouble code or apparent symptoms other than the data that I happened to observe some time ago, and have returned to now to try to determine if it's "normal" or odd, and if the latter, why. Because few have logged identical or near-identical engines that are otherwise performing well, I have little for comparison.

Yes, we've checked for an exhaust leak at the manifold gasket and flange area, and the rest of the pipe. The pipe appears to be in good shape -- no perforating rust or visible damage -- but the area approaching the cat and the cat itself are surrounded by heat shields and we haven't removed them (yet). There's no obvious leaks as might be identified by exhaust sound or pulsing air from under the shields, although I recognize that there still could be a crack or a pinhole that's being muted by the shield. It's probably one of the next things to get more attention. The cat is original (135,000 km), as are both the A/F sensor and the rear O2 sensor (there's only the two).

Oil consumption hasn't been a problem. There is some loss, but not unusual for the engine, based on others' experience.

Carbon build up is a possibility. I've owned the car from new, and its use pattern, fuel, oil, and maintenance cycles haven't changed. As noted earlier, the low IAM and the somewhat high fuel correction has been consistent now for about 4 years (this goes back as far as I have been observing parameters, but might have been the same even before). It could explain the knock, but would it also explain the higher LTFT?

I have reset the ECU on several occasions, and noted that before any LTFT levels are set, the STFT tends to increase as soon as the engine is brought up off idle, even with the transmission in neutral, (little real load on the engine). Eventually, of course, these STFT levels are memorized as LTFT corrections in the LV table. So the correction is rooted in something that affects the AFR even at relatively low rpm and engine load.

Earlier, I asked about the ROM tables, and whether or not there should be a table of CL "base fueling" that's expressed in terms of injector "on" time (e.g., injector pulse width). As a tuner, what have you observed in the tables that you've worked with? Is the base fueling table only the one showing the target AFR.