I have been looking at many different pipes and air intakes for my 2009 street glide. All of them advise remapping of the ECU. I thought that if it was a closed loop system the O2 sensors would make up for any difference. Am I not correct in saying the reason we have O2 sensors is to measure rich or lean conditions and correct them. If you buy a K&N setup and a cat back exhaust for a 4 wheeled vehicle you don't need to update the ECU. So why do we need to program the ECU for our bikes when essentially we are doing the same thing? The only thing I can think of is adjusting the ignition part of the system for an even better performance gain.

 

You are right to a point.

Now this is my understanding which is not too far off I hope.

When you just do things to the engine to improve Air flow, or Volumetric Effeciency (VE) There will be more air going ito the engine. Exhaust pipes usually not too much alone, cause the intake is the biggest block.

You improve both, just those though, and the O2 sensors cannot, may not, adjust far enough.

The O2 sensors used by HD and also just about every other Motorcycle or Automobile Manufactor on earth arer simple switching units with a +- range of about 0.50% in closed loop. They get to their spot and they switch back and forth, +- up and down. This is also slightly adjustable in the ECM. (BIAS ) And they do a real good job. Just gotta give them good numbers to work with.

They cost below 50 dollors a piece mostly. The other O2 sensors people sometime talk about can cost much much more and are very sophesticated. Used for testing mostly.

The ECM calculates using the VE tables in the ECM program. If you change too much on the engine you get out of range. Not from the O2 sensors, they dont care about range but the ECM got to know what it is, cause outside of open loop it is all calculation.

The Factory sets the VE tables and the closed loop areas very lean anyway to comply with the EPA. Closed loop it WILL go to 14.6 AFR. OK for cruising and some other times. Outside of that the ECM uses calculations to get the AFR. If the calculation it uses, the tables, are too low, you will be lean all the time. All this can be adjusted particularly the closed loop areas which from the factory are mord that wanted. (no choice for them)

Air cooled its harder to do (temp is all over). Liquid cooled, (temp is controlled) which as far as the engine and engineers go, is much simpler to tune for.

This is not just HD or Motorcycles.

I figure the lawn mower has or will have a ECM soon.

Cams and headwork and bigger engines is just the same but in spades.

There I did it again. Got too long

Hopes this helps some. Not really complicated, it is a process like a lot of things and you gotta study on it awhile. Just like everything else.

There are a lot of folk do this fro a living and know much more for sure.

 

The reason HD installed the narrow band o2 sensors is to keep the EPA happy and the air fuel mix at a lean 14.5 to 1 or close to that during closed loop operation. Increasing the airflow leans an already lean condition even more. Remapping the ECM / ECU by using a SERT or one of the after market controllers of some kind allows you to reconfigure the air fuel ratio and richen the mix. (It will also allow a wider range of control over the many other tuning variables involved.) The stock ECM settings and narrow band o2 sensors do not have enough range to compensate for the increased airflow that a stage one will allow. Or at least that is the way I understand it.

 

Yeah. The HD download isn't really good enough. It still must comply with the EPA mandates so it's still too lean. The best bet is a Something like a SERT, SEST, or TTS. The stock ECM is a good unit and allows for some great fine tuning. To the get the best results it must be dyno'd. I'm not a big fan of the piggy back units but some people have had good luck with the XiED's. Don't know if they have them for your year and model though.

 

Thanks for the input. I started wondering about this when I was putting a slip on exhaust for a friends sport bike and it came directly from Yamaha. Yamaha did not recomend any changes for the ECU with their own pipes. I does make sense that when the bike is in open loop mode it will be lean. I also must agree I am not a fan of the Piggy Back controller. Just something about tricking the ECU worries me.

 

Just so you know; with HD its called an ECM. Electronic Control Module.