Explain this to me. Knowing that an O2 sensor's job is to read the amount of oxygen and send that to the ECM for adjusting air/fuel ratio. So, when you change the exhaust system out, why do you need a tuner and dyno tune to get the air/fuel ratio right? Why don't the O2 and ECM take care of it?

Thank for your thoughts.

David

 

If all you change is the exhaust system, you don't need to do anything. However, if you change the exhaust system AND add a high-flow air cleaner, then you have introduced more airflow through the motor and you will need to enrich the AFR a bit.

By the way, the O2s on the HDs are 12mm "narrow band" sensors. They are able to make slight changes over a very restricted range, but not quite enough to keep your AFR where it should be if you switch out the input and output hardware.

There is a gob of info on here relating to this subject...closed loop vs open loop, what kind of tuner, do I need a tuner?, dyno tuning, performance gains, etc. Try the search function to ferret it out or use Google to do some searching.

Edit: I will also put a plug in for Fuel Moto, our sponsor here on the touring forum. Give those guys a call and they can answer any question you might have and help you to decide on any performance upgrades you might be contemplating now or in the future.

 

Deleted!

 

They do compensate for changes. If you add some insane setup that they cant compensate for itll throw a code and the check engine light will come on. They are better then theyre given credit for. People are so scared to death theyre bike is running lean they throw tons of money at these tuners and dynos before even trying their setup without it and investigating how their bike is reacting. Usually its just cause the last guy told them to and that guy didnt have a clue.
Im running bub jug huggers and an se intake with no tuner and it runs great, plugs look healthy, has a slightly gassy aroma, and leaves a little soot in the pipes like its supposed to. Some people relly do have problems that theyre ecu cant make up for and a tuner does the trick for em. Youre bike will almost definitely run as good if not better than it did stock, the 02 sensors will see to it.
If you take you're stock pipes off and put open ones on it there will be more grumbling and noise then there was, that is what they do, thats what you got them for. Anything short of shotgun blasts is nothing to worry about. Sometimes the ecu may take a little while to adjust and find a happy spot too.
All im saying is give it some trial and error first, make youre own educated decision and dont be a mindless drone follower. Some people will not even mention the word intake around their bike before they give the stealer thousands to install it at the same time they get a tuner and dyno run.
Now if youre after high performance thats a whole nother story. A tuner and dyno run can give some pretty impressive results if done right. Good luch with whatever you decide.

 

I've had private email conversations with the Nightrider guy (maker of XIEDS) and he will tell you that the ECM will most certainly compensate for AC and pipes. (says Harley engineers have publicly agreed)

In fact the 5% gain you usually get from the stage 1 upgrade is almost entirely from the new AC and pipes, not the tuner and not the Dyno tune either. We all have and are entitled to our opinions but I think most people dont understand what they are getting (or not getting) for all the money they are spending on fuel management systems and dyno tunes.

I know I was not able to tell much difference after I spent nearly $1K on a SERT and a dyno tune.

Personally I'm getting XIEDS an AC and slip ons and will run that way until I see evidence that it isnt running well.

 

they do...but you get 14.7:1 AFR which is hi heat, low emissions, low power, high fuel economy.

 

Correct, thats why I'm going with $120 FL-VIEDS which will richen it up, vs a $1K sert plus inexpertly done tune (because most of the techs at the dealers dont have very much experience tuning anyway)

 

I would have to say you're on the other end of the spectrum without a clue, telling guys they don't need a tuner cause your plugs look healthy, gassy aroma, and sooty pipes. Thats some real precice validation methodology ya got there. Without some sort of exhaust gas analysis you have no idea the condition of your tune. The O2 sensors are an additional input to assist the ECM with keeping the AFR closer to the base map target, they work within a very narrow range, and they will not compensate for changes. Believe what you want, but I gurantee ANY intake or exhaust change effects your tune, and the ECM will not self adjust to optimum performance.

 

x100.

EGR temps or sensor readings with dyno results, etc are needed to optimize it.

Sure you don't have to tune, but never know your hp potential, how hot you're running, etc.

The stock ECU also doesn't have the code to optimize what bolt-on modifications allow for.

 

K. The Harley tech here told it to me like this. If you put a high flow air cleaner and pipes on a fuel injected Harley the ecu recognizes there is more air going in and out so it adjusts and adds more fuel HOWEVER it is still trying to maintain a 14.7-1 a/f ratio which as we all know is good for emissions but not power. He suggested unless I was going to get into the motor(cams,headwork,etc) a simple enricher(fuel pak) is all that's needed to get the a/f ratio into the 12s where max power is found. Or you can buy a 12 cent resistor from radio shack,install it inline from the o2 sensor and fool the ecu into believing that it's maintaining it's 14.7-1 a/f when in reality it's in the mid 12s. It made sense to me therefore I will accept his explaination as fact. Think about it b