my 2019 rgs (114ci), i changed the ugly stock ac for the hd ventilator. i also replaced the stock exhaust for the full flow se exhaust system. ran it without 'tuning' for over a year. no issues, it did not run any hotter, did not sputter, backfire, pop, gurgle, etc.

after that year, i go the se pro street tuner and installed the stage 1 tune on the bike. ran a few auto tune sessions and updated the map. i think about the only difference that i could noticeably feel, was that the throttle response seemed to be a little 'snappier'.

the stock ac is already, technically, a high flow system. you could put a better flowing one on there, but the bike will only flow so much and if you're already at that point, it doesn't matter what you put on there, you've already maxed it out. and you're not really changing the air flow out much with just a set of slip ons. i don't think you're going to have any problem. if you do notice a degradation in performance, then you can look into the myriad of stage 1 tuning options.

 

There are a lot of people out there, for whatever reason, have endless budgets when it comes to these modifications. Then when it's time to ensure the bike is running correctly, they want to close the wallet. I will never understand it.

Personally, I'd do things right and have it tuned. Even a bone-stock bike can benefit from a tune.

 

WOW, and that was with a full exhaust swap also, very interesting.

 

I bought my 17 Road King, I wanted the stock air box gone before I took it, they gave me the Ventilator air cleaner, it required the SE tuner, this was thrown in as part of the deal. If it wasn't necessary, do think the dealer would have absorbed the cost & labor for a freebie? Think about that.

 

I'm no expert but here is what I have gathered about the M8 Engine from posts here, on Facebook groups, and internet videos from DK Customs and others.

Air filter only - No tune needed. The M8 can adjust for that.
Slip-ons only - No tune needed. Same here for the M8.
Air filter AND Slip-ons - No tune needed, but you could optimized with a with a tune. Many have done both with no issues.

Full exhaust - Tune would most likely be needed to run optimally. Many have done this without a tune with good results (see above posts)
Cam or other Engine change - Yes a tune is definitely needed.

This is for M8 only. Older models are not as forgiving or have the ECM ability to adjust for minor changes.

 

My thoughts exactly

 

"I don't know why you guys bother opening your eyes when you cross the street. I've crossed the street hundreds of times and I always do it with my eyes closed. I've never been hit by a car yet! Y'all may get all worrywart negative-nancy on me, you do you, but my way works for me and now I can keep staring at my phone and know that I won't get hit."

If you're asking for personal opinions, you'll get those, and they'll vary all over the place.

If you want to know the actual truth, that's a different story. Referencing the fictional quote above, I don't care how many times someone's crossed the street successfully without looking, they're still a damn fool and reality will catch up to them sooner or later.

So, some non-opinion data for you:
If you put on a free-flowing air cleaner like a Heavy Breather Elite or even a Ventilator, Harley says an ECM calibration (aka "getting it tuned") is required. Not optional, required. I would speculate that they'd be within their rights to deny warranty service if someone put on a free-flowing A/C but didn't update the tune appropriately.
Secondly, if you put on freer-flowing slip-ons (like Screamin' Eagle Street Cannons), Harley says an ECM calibration is required. Required.

Okay, back to opinion:
So what do you think should happen if you put on aftermarket parts that outperform the Screamin' Eagle stuff? Is a tune necessary then? Duh. If just changing the A/C requires a tune, surely changing both requires a tune, and changing them to higher-flowing units would absolutely require a tune.

Now, back to the crossing-the-street-guy: if he only ever crosses the street in Los Ybanez, Texas, then you know what, he's right -- there's only 28 people in that town, the risk of getting hit is probably so ridiculously low that his opinion might be perfectly valid, for him, in his circumstances; but if you live in San Francisco or NYC and try to take his advice, you'd be a dead man within a day. In that same vein, if you NEVER get on the gas, you only ever mildly cruise and you putt around under 3,750 RPMs, then you may not need a tune. But if you ever plan on getting on the gas, you'd damn well better have it tuned, at the bare minimum by something like an SE stock tune or a FuelMoto-supplied tune for your equipment. For more on that story you can read the way-too-long post I made explaining the situation a few months ago.

 

Not sure how crossing the street with your eyes close is an analogy to tune or no tune, but I do like your posts Fat Bob 2018 and respect your opinion, especially as a fellow Fat Bob owner!

Hundreds of thousands of us have modified hundreds of thousand Harleys and every other brand of bikes over the last 50 years and have not had any adverse events. That's not to say it won't happen, but it's up to each of us to decide what works for us. Of course HD would say it's "required" because it would be required them to do it (and charge for it). Lol

Plenty of internet videos saying "you must tune" by companies (including Harley) that sell tuners or are tuners. Just as many actual bike owners who chose not to. If I was looking for absolutely every ounce of horsepower I would definitely tune every time I stopped at a different gas station with slightly different octane levels, or any mod I did to the motor. If I'm a normal Joe that rides between idle and 4,000 rpm then maybe not. From what I've seen in the used Harley market most bikes sold are under 20,000 miles and the majority of those are under 5,000 miles so long term data on the effects of tuning or not tuning is probably hard to find.

To use the term "required" and to prove harm to the motor without tuning, I would think we would need a "actual comparative study" to determine the effects of tune vs no tune.
Bike 1 = Aftermarket air cleaner/ventilator and Slip-ons WITHOUT a tune.
Bike 2 = Same aftermarket air cleaner/ventilator and same Slip-ons WITH a tune.
Bike 3 = Stock bike (this is our control group)

All 3 bikes would have to be brand new with zero miles and running on the same dyno, over the same miles. They would run those bikes for say 30,000 miles, tear down the motors and see what each one looks like. Like what they do for oil comparisons.

So you are correct in that a tune would for sure "optimize" performance with any aftermarket air cleaner or slip-ons or both. But the real question is it "required" for each of us and our individual bikes and riding styles.
As far as warranty, Harley would be required to prove my slip-ons caused the defect they are trying to deny warranty. My transmission did not fail because of my slip-ons.

 

My 17 RK came with the SE tuner, found it recently and played with things a bit just to see what it was all about, had no hands on with EFI other than riding them. AC and fuel moto slip-ons, the last added after I had the bike a while. Did the update the program called for and flashed the stage 1 canned tune. Riding I did notice the throttle response was a hair perkier, idle was a bit more stable, didn't fluctuate as much sitting and the EITMS was kicking in again. That said I'm a middle of the road rider on the RK, I do tend stay on the higher side of the RPM range per gear, old habits and I like the more aggressive feel. Honestly see zero reason for a dyno tune with this package or even a mild cam included and honestly with low end grunt these things have I don't see slip-ons and the average AC change affecting the ridability of it without a tuner.

Think Fat bob has it called pretty accurately. BUT, and a big BUT, CARB and the new EPA emission regs the last year is playing merry hell with doing anything to these machines now. Looking for another ignition for the shovel, sorry we don't ship to California now, same with a mild cam for the M8, nobody is shipping out here unless it's brutally marked up and no warranty through a questionable 3rd party.

 

What bike? TC were reported to be lean from factory. M8 are reported not to be lean like the TC were. M8 software is reported to be more flexible than the TC bikes were. But I am not not sure of the limits. Say...a stock bike goes from sea level to the mountains, the M8 can probably adjust fine. With different air intake and mufflers, the M8 may auto adjust well in some places, but not others.

I am surprised a tuner has not chimed in if there was a simple answer.