The Harley website says adding the 2 into 1 Screaming Eagle 2 into 1 exhaust requires and EMC update. Other manufacturers that offer a 2 into 1 exhaust for Harley bikes make no mention of an EMC update. I realize the EMC can make some degree of F/A mixture adjustment on its own (riding from sea level.to 5,000 feet probably requires some adjustment). Do the other manufacturers of 2 into 1 exhaust simple ignore and don't tell buyers an update is required or is Harley simply trying to force you to take the bike to them to swap out the exhaust?

 

Anytime you increase air flow out You will also be increasing air flow in which will change AFRs which will need a new map....

 

As 98hotrodfatboy said above, any time you change the exhaust, you will change the airflow through the engine, which will affect the AFR (air fuel ratio) of your tune. A retune (adjustment) is always a good thing to do whenever you change the airflow through the engine.

Short answer:
The ECM can make real time adjustments to the tune, but they only happen in the closed loop portions of the tune. Without an ECM retune (update) you will be running lean in the critical open loop areas of the tune. Depending on your riding style, and habits, it could be damaging to the engine.


Longer answer:
The debate has raged for years on whether an ECM retune (update) is necessary for a change in exhaust only, intake only, and /or for change of both exhaust & intake change.

You didn't say what year bike you have, and the M8s are a little different than the Twin Cams. Twin Cams came from the factory running a bit more lean than the M8 engines.

The Harley OEM ECM tunes are partially closed loop (adjusted in real time by the ECM) and partially in open loop (no real time adjustment, AFRs based on algorithms in the tune). The closed loop portions of the tune are in the cruising and low-load areas of the tune. The open loop areas are in the high load, high RPM areas of the tune.

IF you DO NOT retune (update the ECM) then the critical areas of the tune are based on algorithms with the old exhaust, and you will be lean in the tune areas where AFRs are most critical. As mentioned already, depending on your riding style & habits, it could leave you critically lean at times, that could lead to engine damage.

Many aftermarket exhaust manufacturers will suggest or recommend that you retune when adding their exhaust, some won't warn the consumer believing if you are changing the exhaust you should know and understand the tune issues, and others don't care as long as they sell and exhaust. I won't go as far as to say that HD cares about your bike more than the others, just that they never miss an opportunity to market one of their products or support their dealers...

IMHO.... I always retune (update) the ECM any time I change the airflow through the engine. As long as you get a good tune (another totally different discussion) you will ensure you have a safe tune, an efficient tune, and get the best performance out of your mods (new exhaust).

 

Thanks for the comprehensive answer.

The bike is a 2022 Lowrider S. My thinking was the EMC has some ability to adjust the AFR, riding from Denver (low atmospheric pressure) to Miami (high pressure) but apparently not enough to account for a change in exhaust.

Is going to Harley the only way to remap the EMC or are there other ways that a NOVICE can accomplish this on their own (over the counter tuner)?

 

On your 2022 M8 Softail there is no need to do a tune when going to a free flowing intake and/or exhaust.

Below is a video on the subject, and here is a LINK to a written report with dyno charts and AFR charts on the subject.



And here is a video you may find interesting on how the ECM adjusts-



Kevin

 

So if I’m understanding all this correctly the M8 ECM has adaptive fuel management that can handle the change of swapping out an exhaust, up to 20% according to this individual.

Also to clarify, I’m 71 years old and my need for speed left me years ago. I don’t race with friends anymore or feel the need to test the top speed of the bike. My normal cruising in FL is 70-80 mph, short 1-2 hour pleasure trips to clear my mind.

The Harley 2 into 1 exhaust for my bike is $1,500. I see 2 into 1 exhaust from other manufacturers that are half that price. I don’t want anything super loud (I’m sure I have hearing loss from riding around with V&H slip ons) but something you and vehicles near by can hear while. Any suggestions would be appreciated.

 

Technically, not really....

Both Twin Cam engines and M8 engines both have the partial closed loop & partial open loop OEM tunes. They both only make real time changes while in closed loop, the cruising rpm range, and they rely on algorithms in open loop for heavy load and high rpm operation. With increased airflow, you will still see a difference in AFRs in the open loop areas, but the M8s don't get lean to the point of being possibly dangerous to your engine like the Twin Cams did.

The difference is that the M8 OEM tunes are different and NOT as lean as the Twin Cam OEM tunes. Therefore, when you lean out in the open loop portions, their algorithms don't drop you into dangerous AFR conditions for the high load/rpm like the Twin Cams will.

As Dennis mentions in his video, with an M8 engine you DO NOT NEED a retune. You engine won't be in possible danger like a Twin Cam may be, but your M8 engine WILL RUN BETTER if you retune.

Again, IMHO, I always retune when I change the airflow through my engine. It gives the best, most efficient performance from the mods you make....

In your case, with your current riding style, you will be fine either way... Enjoy the new bike...!!!

 

AFR goes something like this:
11.5 AFR is acceleration loads.
12.5 AFR is best rich torque.
14.7 AFR is 02 assist.
16.5 AFR is best MPG.

There is a pre-fueling or the telemetry computes the best overall input.
Post-fueling is what is read at the sniffer or gauge of an AFR.

If system uses a PAIR assist, meaning fresh air into the exhaust system, it runs around 16 AFR. No PAIR shows close to 14.2 AFR (open loop).

6000ft and above is to lean out the low speed screw one full turn in. 02 is automatic for high altitude. Visiting (passing thru) Denver's high altitude does not need an adjustment carb wise, unless permanently living there.

So you are safe PRE wise with a map setting from sea level to 5000ft or a little above. Being a closed loop system, it will adapt to the 2 into 1.

To verify the tune, run a new set of plugs and read the results at the porcelain, meaning, no gray pitting of pre-ignition at the porcelain nose, or too white at the nose. The real reading is at the base of the porcelain-needing a plug reader. Best overall is 'lean is mean,' meaning not too rich, not too lean.

A spark plug read will give you the answer.

 

I recommend wearing earplugs when riding.

 

In addition to what hattitude wrote, the ECM has LTFT (long term fuel trim) which does make adjustments to the open loop, based on what it sees happening in closed loop. So you will not be dangerously lean with swapping out to free flowing and not doing a tune. It will run stronger with a tune, but it is not necessary for the health of the engine.

I would go withe the 2-1 header that you want, for looks and price, since you are not looking for the absolute most power. Don't worry about the loudness, that is much more a function of which slip-on muffler you use.

Here's a video we made with some hints on how to pick the right exhaust the first time.



Kevin