kurtaforesterguy

I have an '09 XT which for the most part works well. However I've noticed some hesitation and "patchy" throttle response. Fuel used is 92 Octane with 10% ethanol.

My local dealers tell me the car is fine. Engine oil analysis revealed no wear and it's had all recommended tune ups.

A reputable tuning shop tells me recent Subaru turbos, by nature of their ECU programming, have some driveability and potential failure issues due to overly lean mixtures. A change in ECU curves correct this problem. A change to front exhaust pipe and cat converter further enhances performance.

However, as my XT is still under warranty, and because I see absolutely nothing offered from Subaru that addresses anything the tuner proposed (no updated ECU curves, no exhaust pipes (not even CAT exhausts like WRX or Outback owners can get)), I'm somewhat leery.

Can anyone enlighten me what I can really expect from the most basic of "retuning" an engine (no parts changes, same fuel)?
Has anyone with these changes successfully completed a pollution control analysis?
And are the results worth the considerable cost?

stan_t

Any altering of the ECU could void your warranty, I believe.

Stan

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'07 XT 5MT, VF43 tuned by FLI
handling > power > looks

linkwpc

I would think so as well!

Subieoutlaw

Sorry to add to the list but anything done to the ECU will likely void the warranty. Your best bet is to tweak the ride with other parts until teh warranty is over. Then go crazy.

__________________
DIY: mud flaps, skid plate and light bracket
My 09 FXT Journal

kurtaforesterguy

Thnx for info. I also believe a reflash would most likely void the warranty. So this mod may have to wait until then.

However, I am curious as to whether or not this retuning actually achieves what is claimed.

The tune shop makes a big point of the portable device being able to reset the engine ECU to factory specs. However, I do not know if this is "complete" or not. Also, EPROMS or other "flashable" parts have a limited number of re-flashes possible before they outright fail.

thefoos

You are talking 100's to 1000's of flashing before you have that issue.

Anyhow, I can't speak to the 09's, but I'm quite familiar with how Subaru tuned from 02-07, and they did some "interesting" things. Remember, that the calibration that Subaru puts on the ECU has to function well in all climates, varying fuels, etc. So there are many compromises in the tuning. I don't know exactly what your tuner had in mind to change, but I know the things that I change to does indeed make it drive smoother and make more power.

With that said, I agree with the others. While it doesn't outright void your warranty, if the service folk could figure out it was flashed, they could deny you warranty work. You would have to prove that a failure wasn't due to the flash, would could be tough to prove if its an engine related failure.

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Scott
04 MT FXT <sold
02 WRX VF43 E85 5 sp

kurtaforesterguy

Can/do these changes improve fuel economy as well? Some tuners mentioned a retune could offer both, which confuses me as getting more power suggests the engine must burn more, not less, gasoline to generate that power.

Still, it is surprising there seems to be that much improvement possible with USA Subaru turbos.

I also wonder if "SI" Capability lurks within Subaru USA ECU's. SI drive, apparently available in Euro and Japanese Subaru Foresters, was offered in some USA Outbacks until '10, when it was dropped.

TSi+WRX

On the BL/BP Legacy ('05-'09), Subaru did implement ECU reflashes in an effort to try to resolve the driveability - i.e. "stuttering/studdering," aka "hesitation, at partial throttle" - issues.

No definitive resolution was ever reached.

Some saw markedly improved driveability overall - others saw the same, only for a very limited time (until the ECU "re-learned," was the general consensus, but no-one could exactly pinpoint if ECU learning was somehow involved, nor if it was a specific number of drive-cycles or other such criteria filled). Yet others saw no improvement, at all, whatsoever.

Whatever re-mapping Subaru tried on the BL/BP, it only partially worked.

For details, visit LegacyGT.com, and search for "stutter" or "studder" or "hesitation." There's plenty of threads there on this issue.

And yes, current efforts on resolving it, in the BL/BP crowd, is heavily focused on the ECU:

Lurching ride on acceleration between 2000 to 4000

Sadly, kurtaforesterguy, as the others here have said, any ECU work is going to leave a trace of some kind that, if the technicians tried hard enough, will be able to detect.

Will your dealership somehow search for such work, secretly, when you drop your car off for an oil-change or, say, a warranty repair for a blow strut? No, not likely at all.

But can they find it, if they wanted to?

Certainly.

Given your reluctance, in terms of warranty preservation, then, sadly, you'll either have to bear with it or, alternatively, hope that enough SH-FXT drivers notice an issue that Subaru themselves are forced to look in to it further - i.e. to try to address it via an official remapping, as with the BL/BP turbo-Legacys.

In the meanwhile, it would, nevertheless, be nice to try to confirm, for yourself, that nothing is askew or otherwise not completely up-to-par.

I would encourage you to look in to how to datalog the vehicle (start with the RomRaider website, and go from there), so that you, yourself (including with the help of fellow community members who are knowledgeable in reading datalogs), can see that it's truly fully healthy, and that you're not somehow noticing the manifestation of something which may be just ever so slightly wrong enough that it makes a difference in terms of driveability, but not so much as to raise the CEL/DTC flag.

At the same time, I would have a knowledgeable local enthusiast or if none are available, if finances allow, have a reputable independent shop (which is knowledgeable with Subarus) give the vehicle a quick mechanical once-over, just to be sure, so that you can rule out, once and for all, potential mechanical concerns.

__________________
Me: '05 Legacy 2.5GT
Wifey: '09 Forester XT

stan_t

FWIW, my car has this hesitation issue as well. It had it stock, at Cobb Stage 1, Stage 2, and it still has it after the turbo swap and tune. I've learned to live with it. I wonder if it is a hardware problem (head port design, etc) vs. an ECU logic issue.

Stan

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'07 XT 5MT, VF43 tuned by FLI
handling > power > looks

kurtaforesterguy

TSI, thanks for info. Perhaps Subaru will offer revised '09 tuning via a TSB or other info invisible to customers. Still, it's surprising they had so much trouble with the Legacy.

Stan, I wonder if you saw any other benefits from the tunes? The '09 got a revised air intake system and turbo.

Also, wrt COBB PASSPORT device....
This claims to be able to change engine maps "on the fly" without reprogramming the ECU.
Is this true?
So that if I decide not to use a new engine curve programmed into the PASSPORT, I simply disconnect the PASSPORT, at which point the engine ECU reverts to its unaltered original factory curves?

stan_t

Anything you consider that will alter ECU in any way may void your warranty, period. This includes the Cobb AccessPort, open source software -- anything, except for whatever your dealership wants to do to the car using their own equipment.

The AccessPort supports "on the fly" map switching -- basically, certain ECU parameters will be changed without having to stop the car and reflash a new map. Your maps have to be compatible with each other for this functionality to work. Forget this though for reasons listed above.

I absolutely saw benefits from the tunes since I was tuning to compensate for hardware changes I've made to the car -- exhaust, turbo, etc. Hesitation still remains though. The '09 turbo is same as my stock one was -- TD04 -- and the intake should be identical as well.

Stan

__________________
'07 XT 5MT, VF43 tuned by FLI
handling > power > looks

kurtaforesterguy

If the Passport simply allows users to run a different map (sort of like an aftermarket Subaru SI system), that's one thing, assuming the user goes to a reputable shop and __carefully__ dyno tests the car to get a useful curve.

But if doing AP's "on the fly" curve changes also _modifies_ internally stored ECU in any way whatsoever, for now I'll pass on the device.

stan_t

The AccessPort has to be "married" to the car. This means, it rips the original map off your ECU and stores it, then replaces it with it's own map. From then on, you can flash your ECU with other maps you get for the AP. When you "unmarry" the AP, it will re-write the original map to the ECU, but the checksums will not match up, so the dealer will know it was flashed.

If you want to stay true to your warranty, you have no choice other than the Subaru dealership re-flash.

Stan

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'07 XT 5MT, VF43 tuned by FLI
handling > power > looks

kurtaforesterguy

Thanks Stan.
The tuning shop said the same thing - the Passport must write its map to the ECU before it can do anything, thus opening the can of worms I was hoping could be avoided.

If Subaru offers a re-flash, I'll be happy to take them up on it.

Otherwise my XT's ECU stays stock for now. Thanks for the info!

TSi+WRX

^ Unfortunately, like I said above, to-date, there is still no ECU-based tuning solution available that would leave absolutely no trace, and this includes the AccessPORT.

I guess you could take it to the extreme, get a replacement ECU and re-encode your anti-theft to-match, then either go with either one of the popular aftermarket ECU reconfiguration devices, such as the AccessPORT or ECUTeK or a standalone tap, or re-tune via Open-Source.

Then revert to the factory ECU (and re-pairing the anti-theft to that ECU), whenever you take the car in...but that would require some serious investment in a SSM-III, to re-do the ECU/anti-theft pairing, without the intervention of the dealership.


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My wife's '09 FXT did not and still does not show this symptom - not with the first engine, and also not with the replacement longblock.




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What we know from our collective experience on LGT.com is that the 510N ROM image on the turbocharged 5MT BL/BP-chassis Legacy somehow was found to correlate - mysteriously on some vehicles, but not others - with the "stuttering/studdering/hesitation" issue. Subaru then introduced the 521N as well as 522N ROM images, offered as a reflash for those affected, as a "fix" - which itself was variably successful.

My Legacy, when new (and thus still on the earliest ROM), never exhibited such symptoms.

It also did not exhibit the problem after my first tune, in 3rd quarter '05, which utilized ECUTeK.

Mysteriously, my re-tune, also via ECUTeK, in '07, saw the emergence of this problem.

Sadly, with ECUTeK "locking down" the ECU, I don't know which ROM image I was using, nor which one I'm currently using.

As you can see with the BL/BP crowd, we're seeking resolution based nearly solely on ECU tuning:

Pulsing Hesitation at Constant Throttle - Subaru Legacy Forums

- which, as I mentioned to The Rookie, I found rather interesting, when compared to what the SF.org community is doing, in looking almost solely at the hardware side.

My personal belief is that it's likely an interaction of hardware/software (including unique-vehicle variability, and, now that you've mentioned it, also perhaps even factory component shortcomings! good thought! ), and that both sides of the equation needs to be pursued in order to find the true cause and cure.

From searching here, on NASIOC, and on LegacyGT.com, this seems to be a pervasive issue that spans both the 16-bit as well as 32-bit ECUs and multiple generations of Subarus.

Hopefully, someone, some time down the line, will have a more definitive answer for us.

__________________
Me: '05 Legacy 2.5GT
Wifey: '09 Forester XT