You have not remembered about a pressure wave and the returning wave as it bounces back? What happens in the exhaust chamber to the gases? When flow from the cylinder stops, what remains in the exhaust chamber that represents what flowed from the combustion chamber?

 

1. Absolutely.. Why you think I stated:

??

The exhaust flow is in the form of waves which are pressure differences.

2. Still haven't seen what you mean by exhaust chamber.. Is the hole exhaust? Head pipe to the collector? Are you thinking of a specific exhaust topology?

3. I would say it depends on what the answer is to #2 plus RPM, and amount of exhaust gas flowing.

 

Steve- I appreciate the attempt to make us think about what's going on with the exhaust pulses. I'm thinking though that it would be more beneficial to the masses if you would just tell us out front what you are trying to get at. This is just the beginning of a very large subject and I personally feel we might be better served with direct statements rather than "riddles" (for the lack of a better word) to make us guess at the answers.
Thank you very much for what you are bringing to the table for us all.

 

OK, the exhaust travels from the cylinder in pulses, it is NOT steady state. The frequency of the pulses varies as engine speed changes as does the pressure. The O2 sensor is in the exhaust chamber somewhere. The exhaust chamber pressure rises and falls depending on what is going on at the time. The shorter the exhaust in general causes the chamber to empty faster and any pulse that travels down through it also causes a reverse pulse to travel back in the opposite direction. This reverse pulse can and does pull the air from the atmosphere back into the exhaust chamber. There is NO way for the ECM to know what any of this is going on other than what it is programed for, which is a STOCK exhaust. Change the characteristic of the exhaust system and guess what happens?

Each various exhaust is different as are just changing the mufflers! The HD motorcycle exhaust range is about 3 1/2' to 6' long depending on model. Typically made from 1 5/8" dia. tubing plus a muffler. A car/truck exhaust is 15' to 20' long! Typically made from a manifold, 2 to 3" dia. tubing plus a muffler. The car/truck typically feed 4 or more cylinders into one exhaust pipe with one O2 sensor. The HD one cylinder to one O2. One exhaust pipe to one cylinder for the most part.

What works in a car/truck, doesn't work for a HD, and a simple look at the exhaust is why. The problems of O2 sensor placement and exhaust reversion have little to no effect in the car/truck world but have huge issues in the HD world for the above reasons. It has nothing to do with the sensor being used, it is what the exhaust causes the sensor to read! NB O2 sensors do not much care what the exhaust pressure is doing but WB sensors very much care about it. Since the car/truck is feeding multiple cylinders into one exhaust chamber with one O2 the pressure is much more stable and revision is pretty much none, due to the overall length involved what little there is never gets to the O2 sensor measurement area.

So in the HD world with the short exhaust and pressure waves traveling very short overall distances through the exhaust chamber it's very easy for the exhaust chamber to become diluted. We have pressure problems to deal with if using WB sensors, and dilution problems along with poor placement/mounting locations for the all sensors that need to be dealt with. These are mechanical problems, not electrical problems and need to be fixed or accounted for and with hundreds of aftermarket combinations for exhaust with as many problems cause by the manufactures of them, you can begin to see why you cannot compare to the car/truck world.

So now how do you want to deal with the issues?

 

Since this is a powervision thread, how would you identify this happening in a powervision log?

Apparently this is a situation that comes up when you have a poor combination of sketchy designed parts. What combinations are the most common to come across?

What percentage of the bikes you see come along have this as a show stopper for trusting the 02 sensors?

What is the typical work around?

 

Move the sensors closer to the exhaust port? Use a longer exhaust or possibly one with a bigger silencer?? LAF exhaust guys won't like it tho.

You won't get much argument from me that most HD exhausts ain't all that hot..

 

There will have to be a thread on what "Target Tune" means next ...is it a tuner or is it a piggyback wideband feedback controller for when your bike has been tuned and you are running up and down the road ...although that won't fit on the box either

 

this would be better in Steve's other thread but...

Given this appears to be another fact of life in the HD environment we should presume that HD have a way of dealing with it ...or they would never have put O2 sensors on in the first place. The obvious assumption I got to a while ago was that was what the CDE/EGR tables were for.

That, presumably is how we address the issue. However other than the apparent very few that know how to tune CDE or the TTS which has a tool that can apparently calculate it from some logs ...it seems to be a bit secret squirrel.

 

Why anyone would want to find a work around, fix the problem! No one should want to do a work around, it is just dead wrong! You should want to learn to fix the problem, not find a poor excuse for a work around. As for how many have the issue, just read the internet about all the people complaining and that should give you a pretty good idea, that it is a real issue. Anyone who complains about Tune drift or issues at low engine RPM and light load have the issue. The part throttle performance will suffer as well. Get the engine RPM high enough and or the load high enough and there will not be an issue, in most cases.

As for identifying it in a PV log or a PV-TT there is not enough data present and it comes in too slow, to see it directly. Any amount of trying to use data when you have no idea if it is any good or not, will not cut it. If you try to average BAD data all you get is an average of BAD data. The data must first be sorted and the BAD data tossed aside, then work with the balance of the data. Once that's done, look at the rate of change in the data to see if it is where it should be. At 3 frames per second on a PV or PV-TT J1850 without the extra necessary data being provided it's a tough task and the CAN PV or PV-TT at 12 frames per second is still limited to about 1400 RPM before it gets over-run. So you must feel how the engine is running and look at the data, over the same area to identify it, in these cases. One of those things when you really go and work on a HD engine yourself, you will learn. Slow acceleration down to the point you give it time to catch up, as you would on a Dyno allows for much better data to see it.

You yourself have complained about it but you never were able to figure it out, you blamed everything. "Bust in the Code", "Harley Hidden Table" " NB O2's no good" "O2 switching issue" "PID" and on and on.

 

I have been involved with the Code that runs TT for a long time before they ever tried to use it. So my answers here are from that knowledge and three sets of calibrations I have from TT units. One set from DJ and two sets from an internet provider and they all have the same issues. The code in the ECM was never designed for doing what has been claimed with TT. There is NO code changes from stock by TT, only limited calibration changes. This was also confirmed by the VP of DynoJet in another thread on this site. In the three calibrations I have the settings are such that the adaptive learning is turned off and the short term limits have been turned way way up. IMHO that is NOT a good thing. This allows the ECM to run wild and not be able to tell when something is going wrong. Since the short term has to step along over time if the calibration is not close to what it should be, it's never going to be correct and if you have a close calibration to start with, why then, would you turn the limits way way up and defeat the whole limit check?

The applied correction from TT is stored in the PV itself and not applied real time, so it is sort of in-between how other tuner products work. Yes, if you hold it steady state long enough the short term value will chase the correct in provided it does not get to the new limits and stop. The main issue is that once it learns what it need at one point, if you change the engine operation it has to go from that point to the new one again and again as nothing is stored in the ECM. Not a problem if the base calibration is close to what it really should be, but what if it is rich in one area and lean in another? The short term correction is down at 85 at one point then it has to step from 85 up to 135 for another point and that takes time. Then each and every time the engine changes it has to do it all over again.