I think there's a fundamental misunderstanding about Long Term Fuel Trim being discussed here, and in fact a misunderstanding of the entire nature of the ECM's "ability to adjust". The LTFT is not in any way meant to be some sort of automatic tuning or ECM adaptation for adding performance parts.

Closed Loop is an accommodation made to the EPA for emissions control systems. It is not some magical autotuning capability, it is a nanny system that keeps emissions under control for idling and lower-RPM cruising, and is only active in those scenarios. And can only do so when working within very narrow parameters. The stock O2 sensors can only report in a very narrow band from around 14.2 - 14.9, approximately. If your air/fuel reads outside that range, you would need wide-band sensors to read it. And you don't have them. Because narrow-band O2 sensors and the accompanying STFT and LTFT trim values are not the ECM accommodating for performance parts, it's minor ECM adaptation to keep the emissions low.

The short-term fuel trim (STFT) is a calculation based off the O2 sensor's reading of the air/fuel mixture by sensing the amount of oxygen in the exhaust. If it reads a little high or a little low, the STFT is calculated to represent the amount of change the injector needs to either add or remove a bit of fuel to return the stochiometric ratio of air to fuel. The STFT adjusts rapidly and continuously, and has a limited range in how much it can adjust.

The LTFT is a calculation made based off the recent STFTs. If the STFT is ranging up and down around a very small deviation, then the ECM is going to look at maybe the last 30 seconds or so of STFTs, average them out, and then assign that to be the new LTFT. Example: let's say your injectors are old, and they're only squirting about 95% as much fuel as they're rated for. In a case like that, your air/fuel ratio would be about 5% lean, and so the STFT will constantly be saying that the engine is running a little lean and the ECM would then increase the injector duration to add a little more fuel. So in a case like that the STFT would be constantly asking for 5% more, and as the ECM gathers that info, it would eventually assign a LTFT of 5%. That way, 5% more fuel will be added to the entire map, and the STFT can go back to zero. That's the idea here; that the LTFT is designed to help accommodate for things like a faulty injector or maybe a slight vacuum leak or whatever. It is NOT an auto-tuning system for adjusting the entire open-loop map!

I mean, understand this: the LTFT is calculated from the STFT. The STFT is only ever used in Closed Loop, which means idling and cruising, and only ever calculated in a very narrow band. The STFT is never used in Open Loop; it cannot be calculated during Open Loop, there's no provision for that in the ECM. The ECM literally has zero idea what the air fuel ratio is, or should be, whenever you're at a more-open throttle or high rpms or heavy loads, when you're stoplight racing or passing on the highway, etc. No clue. In all those cases, it draws the appropriate fuel value directly from an internal map, not from O2 sensors and adjustments. And that map that it uses was designed around a stock intake with stock A/C, stock injectors, stock header, stock catalyst, and stock mufflers.

Do you see the problem now?

There is no "automatic compensation" happening at anything other than idle/cruising! Is the LTFT even applied to the open-loop area of the map? Not sure on that; some cars and bikes may do that, some may not, we'd have to ask Steve Cole if the M8 does. And even if the LTFT were to be applied to the whole fuel map, that isn't auto-tuning or the ECM "adjusting" for your performance parts! Instead, applying that LTFT would be an attempt to compensate for (for example) a perceived faulty injector, or a slight vacuum leak, or some other consistent, persistent defect that would be affecting all injection circumstances. The bike's ECM cannot, and will not, adjust and tune the whole rev range. Period. End stop. It only can do minor adjustments related to emissions during very light loads; if you put the bike under load (again, opening the throttle up more than halfway, revving up above about 3750 RPM, etc) then there is NO ADJUSTMENT HAPPENING by the ECM.

Can you extend the ECM to cover all the RPM range and all the throttle ranges etc? There are products offered for sale that claim to do just that, but you'd need wide-band O2 sensors, a tuner (such as an SEPST or PV), and that tuner's autotune module (for the SEPST use Harley's Smart Tune Pro; for the PV use DynoJet's autotune kit). And leave it all attached all the time. Does it work? Opinions vary, but Steve Cole (who knows the Harley Delphi ECM better than all of us put together) questions it in his post #12 and #14, so I'll take his word for it. But the point of even bringing it up is, this combination is what everyone seems to think the ECM is already doing, but the very fact that you have to buy this set of parts and install them is proof that the ECM is most definitely NOT automatically adjusting and adapting for your new Thunderheader or drag pipes or ram-air intake or decatted headpipe or velocity stack or whatever else.

As always, it's your engine, your money, your choice. If you were to choose to not get a tune, and something bad happens, then it's all on you. If you rarely ever open the throttle up, you're much less likely to run into an issue. If you like stoplight racing, you're begging for something to happen. Getting the bike properly tuned by a tuner who knows what he is doing will ensure the best performance and the best long-term reliability for any given equipment combination. Slapping on new headers and going to the dragstrip with no tune (just assuming" the ECM will compensate") is a case of "you pays your money, you takes your chances". No way I would do that.

To the OP: I would (obviously) recommend don't put on new pipes if you're not going to tune it. If you're going to wait until you get the cam upgrade, I would say wait on the pipes. If you want the pipes on now, do as $toneCold said, buy the tuner now, and at least put on a canned tune designed for your combination. Get a PV from FuelMoto and they'll get you a canned tune that should be reasonably close. If you're getting a camshaft, you're going to need a tuner anyway, you'll just be spending for it sooner rather than later but the plus is that you can at least have that canned tune in place, which is vastly preferable to just hoping that the ECM will adjust in a way that it was never designed to. And as always, if your bike is still under warranty, using a PV will void any remaining warranty you have on all powertrain components, so factor that in too.

 

The above it pretty much completely false, there is no such thing as Auto Tune and this is just why I have never used those terms. None of the tuners or ECM's Auto Tune, it is pure advertising hype and always has been, The process for using the long term and short term to trim fuel to the pre set values in the ECM has been in the ECM's for many years long before HD ever introduced EFI! So what do people think is really happening versus what is happening are worlds apart. The Thundermax ECM, SEPST or PV have NEVER AUTO TUNED ANYTHING and they are incapable of doing so, always have been always will be. The ability to tune using the stock O2's or WideBands O2 sensors was first introduced to the HD world by TTS way back in 2008, TTS has never called it Auto Tune for one simple reason, it's not autotuning! What it will do is adjust the system based on the feedback from the sensors to remove any measured error by the ECM. So what is really going on is the system is being calibrated for what is being asked for, An ECM is real stupid, it only does what you ask it to and does not care if you asked for the correct or wrong thing at all. So if what your asking it to do is wrong, for your combination of parts it will gladly work at doing it wrong all day long.

Auto tuning is believed to be something that is properly tuning the bikes engine and as you can see that is NOT what's being sold or used.

 

Steve, I agree with you that constant airflow monitoring is not "auto tuning", in the same way that knock control is not properly tuning the ignition timing. Closed Loop is not "tuning"! It is an EPA emissions control system. I never said those devices were actually automatically tuning; I can't help it if that's what the companies have chosen to call their systems, that's literally what Dynojet named the product. What I was saying is that if you wanted the sensors and ECM adjustment to work over the whole rev range, you would need to buy all these additional components, and the fact that you'd have to buy all those (just to extend the ECM's "closed loop" operation across the full rev and throttle range) is proof that the ECM cannot and will not adjust for performance parts. I have edited my initial post to hopefully make it more clear about the difference between a proper tune and a half-baked EPA emissions control system being extended across all RPMs.

So do you agree that a proper tune is required for proper performance, and that the concept of "the ECM adjusts" is fallacious?

 

Problem is that the false/misleading advertising has you and others convinced that they will Auto Tune and they do not, plain and simple. Since you bring up Dynojet let's use them as an example. Their add -on systems for WideBands will not Tune a damn thing on a HD EFI system. As a matter of fact all you have to do is a simple test to prove it out. If you set the mixture in the ECM to be 15:1 AFR it will gladly try and make the 15:1 mixture just as the stock O2's do, so it's not tuning a damn thing and there claims that it does are just as false. I could get into a long discussion on how these systems do not work and do not tune the engine but I would get banned from the site if I do, so let's just leave it, that I have informed you and others for now.

 

Okay, I revised that paragraph in my initial post again based on your above post, because when it comes to what the Harley M8 ECM can do, I consider you the definitive authority. Thanks.

 

Looks like I opened a can of worms. lol
I think I'll just wait until I get a cam kit and do it all at once.
This my first fuelie bike.

 

Not really; you just asked an innocent question that is very common, that happens to be flooded with urban legend, misunderstanding and myth -- "Do I need a tune" is right up there with "What oil should I use". And that second one got so pervasive that they opened up a separate forum just for it, and then it got so out of control that they shut down that forum!

 

Well that is about as vague as one can get?

Since I sold the OP the exhaust set I can say without a doubt the GNs worked perfectly fine in the bike as a stock 114", a stage 2 114", both with and without the torque/quiet baffle; I have dyno sheets for both. The mufflers do perform better down low where we ride with the inserts and absolutely require a different tune with and without them. You can't swap the inserts in and out with the same tune. The mufflers also had an ear piercing rasp to them when wide open so I used packing in the large stock baffle to get rid of that. I also put it back on the dyno to verify the tune was still good with the packing, and it was.

The only reason I sold the exhaust is I found an awesome deal on a used Khrome Werks full exhaust that I could not pass up. I went to a 128" over the Winter and I feel the Khrome Werks are better suited for the larger bore.

 

Well that's all good to hear,Im leaving the baffles in as I don't want another loud raspy exhaust like the Rinehart true duals I had on my last bike.
I just want a little more rumble and hopefully a bit more power than the stock header and CVO slip ons I'm running now.
I'll wait until I get a cam kit then get a tune with these pipes.
I'll probably leave the bike a 107,it gets the job done just fine touring two up as is and I have an FXR build project for a hotbike to ride solo.
Thanks all,I have a game plan now.

 

Doesn't a Tmax with wide band O2 sensors tune to the AFR that is requested of it? It can't adjust timing so isn't that where the tuning is required & both RPMs & throttle position is what is required to get the correct tune?