The ECM can make adjustments within the closed-loop area, i.e. the operating range where the O2 sensors can work. For most bikes this is up to approx. 3500rpm and 80KPA (Lambda calibrations) or 60% TP (AFR). What this means is that as you roll the throttle there's a point where the O2 sensors can't physically operate and aren't programmed to do so, and that's the area that will require a tune if the bike indeed needs one.

The HD Stage 1 "download" does little except to make some tweaks to the calibration, mostly if you swap the AC, as just changing mufflers typically doesn't make enough difference in airflow to require a change of tune.

In stock form the ECM will dictate 14.6:1 AFR in the closed-loop area, so swapping mufflers typically won't matter, but you won't be able to set AFRs richer in that area without a tuner, if that's what you want to do. That is primarily a move to reduce heat and perhaps increase throttle response a bit. Also, in the open-loop area (e.g. WOT) the ECM won't adjust for changes in airflow, like swapping mufflers, AC, cams, increasing displacement, etc. However, even though in most of the stock calibrations I've seen the AFRs specified in the AFR table are below 13.0 at WOT, like 12.4-12.8, it would seem to give you a bit of leeway in avoiding a tune. Although 13.0 is considered ideal for WOT power it might appear to give you a built-in fudge factor, but not always, as it depends on the bike and the mufflers you install. What's more, if you change anything in the hardware setup, including only mufflers, you are changing the airflow characteristics, and even though the O2 sensors can compensate up to a point in closed-loop, they will have to work harder since the VE tables won't be as efficiently tuned. All that said, IMO all Harleys that have even a muffler change will benefit to some degree from a tuner and a good tune or map.

In a well-intentioned plug, I would call Fuel Moto for advice--as they sell a number of tuners and will give good advice on selecting the right one at a good price. If you go with one of the DynoJet tuners (PV or PCV) you will also get a good map or tune for your bike's configuration.

Be careful in selecting tuners or quasi-tuners, however. Some are limited at best, others are dead-end options that won't allow you to make future changes to your setup and maintain an acceptable tune, and yet others may be overkill for many riders. For example, IED's and their variants (XIED, etc.) will make changes to the closed-loop area only, so if you plan on going further than just changing mufflers in the future you may need to purchase a real tuner at that time. Thus, the $125 cost of the IED's will be lost unless you can unload them on Ebay or somewhere. Some tuners, like the V&H Fuelpak adjust AFR only in broad areas and cannot alter spark advance. These limited devices do have a place in the marketplace, however, and will fit some niches.

 

I put a Power Commender on my bike after a year of running it. Started with a stock 96 and put a S&S dual runner intake, a 103" kit with 255 cams and D&D fact cat exhaust. Ran fine, but with the power commender it lifts the front wheel in 1st and 2nd now... I do however, get popping on deccel now.... and this was after it was dyno'd and the maps modified for best air/fuel mix.

 

Best advice I've seen here so far (and yes, I'm plugging, too) is to call Jamie at Fuel Moto and have him explain it to you and make and informed decision. I have heard the guys who say they do certain things and their bike runs great. Great is subjective, maybe it does maybe it doesn't run great. Great to you might not be great to someone else. Also, as Iclick said, depends on the situation. The one thing that amazes me sometimes though, the guys that will buy $2,000 worth of chrome for a $20,000 bike, but try to find a way to skimp on things like a tuner or other performance modification, I think because you can't see it ..............

 

There you go! This is one of the most accurate answers you'll get here.

iclick's post is pretty accurate, and thorough too.

Now my two cents... You own a Harley? You can benefit from a tuner! Even if it's completely stock otherwise.

 

Captain Itch's Crotch Cooler

OK - you got me - actually 4 words!
It's quick - It's EZ - It's relatively cheap and IT WORKS!

 

[QUOTE=TUCCI;9553175]Or remove the catalyst from the stock header like I did, right side heat went bye bye. Put a VIED to add a tad more fuel and ride boddie ride![/QU

 

Did you core drill the cat if so where did you get the Bit from ?