Road tuning VE's different route - different results

[a2wheeler]

I have to drive south 20 miles to get below 6000 ft in order to get the 80kpa column filled in. I have made the same basic route for 8 times, and the final 2 vtunes show a couple of new changes in the low kpa columns. So I decide to go ahead a do a couple of last vtunes in my neighborhood of 7000-7500 ft. I find it wants to change many 50kpa and lower cells now, mostly increases and mostly in the rear.
I had no idea driving at different elevations would effect the VE value in a cell. I thought it would just affect whether I could reach it or not. This looks like it shifted all the VE values towards the left cause many want to be increased.
This just is not making sense to me.

[98fxstc]

the calculated air flow thru the heads are determined from sensors telling the ECM about O2 in the exhaust,
ie testing for rich or lean burn
So O2 in atmosphere changes with altitude and will affect the burn
more O2 at lower altitude so leaner mix when going down
ecm has predetermined VE but thinks more air is flowing and would increase VE
Would expect some difference
no idea how much
my .02 , may be wrong

[a2wheeler]

here are some visuals. The first two are the last two runs at normal location/route. Then the last one is using a new route.

[98fxstc]

Go back to your normal location/route with the map that you last used there and see if your VE's return to previous values
ie Confirm nothing else has changed

Just as well riding is fun 

[a2wheeler]

Yes, going back to normal route is my plan now. I have not loaded the new map because of the amount of change. Something else might have changed. The new route only takes 20 minutes, the old route is 1.75 hours. I definitely get a lot more hits on the old route as well. Maybe it is a better collection, but the bulk of the area that changed on me was blue in the VE histogram of datamaster - meaning enough hits.
I guess it just depends on what altitude I want to use as the base map. Trying to use both routes appears to be an endless battle.
I just have not read any one else running into to situation before. I may have to wait for the weekend now.

[whittlebeast]

You really need to plot MAPxRPM vs Duty Cycle at each altitude and see if the code is compensating for the altitude change.

The Duty Cycle should be a little higher at high altitude for any given MAPxRPM.  The average o2 readings should be no different for any given MAPxRPM if all is working per the books.

Andy

[1FSTRK]

Timing

[98fxstc]

The Duty Cycle should be a little higher at high altitude for any given MAPxRPM.  The average o2 readings should be no different for any given MAPxRPM if all is working per the books.

Andy

Wouldnt the duty cycle be lower at higher altitude ?

[whittlebeast]

That rule is left over from the old TPS based systems from the 70s.  Carbs did need smaller jets as the altitude increased.

Andy

[whittlebeast]

All we need to test this is have someone set a bike up in closed loop in Denver and drive over Loveland Pass and back to Denver with the loggers running.  Denver is at close to 5000 foot and Loveland Pass is like 12000 feet.

Andy

[a2wheeler]

Timing

The timing is pretty much done. There was only a couple of akr's in this last run up at 5000 rpm. But yes, back in the 70's when I started in Leadville at 10,152 ft, half way down to Denver I had to pull my GTO over and dial my timing down a little or I would fry the motor running to high a timing.

[a2wheeler]

Got a good run using the old route. This comes in just like the run before from this route. I still have a couple of areas that want some change, but I am going to call it good for VE tuning at this point. I the auto-extend again as well. I am guessing that while during the Vtune process, the altitude does make a difference. Once I set this map into place with regular main lambda table, then the bike will simply be adjusting for the altitude.

[98fxstc]

Got a good run using the old route. This comes in just like the run before from this route. I still have a couple of areas that want some change, but I am going to call it good for VE tuning at this point. I the auto-extend again as well. I am guessing that while during the Vtune process, the altitude does make a difference. Once I set this map into place with regular main lambda table, then the bike will simply be adjusting for the altitude.

I'd think about bumping the first autoextend column to match the columns either side
Hasnt been any discussion about this but I cant see a problem with it

[a2wheeler]

yes, good idea. I was going to go around the edges of the VE tables and blend to the ends. Not that I will ride in those cells, but it will look pretty - LOL.

[98fxstc]

 

[HD/Wrench]

 

[glens]

The Duty Cycle should be a little higher at high altitude for any given MAPxRPM.

Wouldnt the duty cycle be lower at higher altitude ?

That rule is left over from the old TPS based systems from the 70s.  Carbs did need smaller jets as the altitude increased.

Andy, Andy, Andy...

Think about what you're saying.  Less O2 molecules requires more fuel?  Really?

[whittlebeast]

Glen

You missed that I said for any given MAP and RPM.  Think about this. Say you are were riding are 60 KPA in the intake at 5000 feet below sea level.  The air pressure at the end of the exhaust would be about 120 KPA  because you are so low.  The exhaust system would be terrible at scavenging at this very low altitude with this huge back pressure.

Now you go up to sea level.  The back pressure is now 100 KPA at the exhaust tip.  Still at 60 KPA in the intake.  The motor is running a little better.  The exhaust is starting to work as intended.

Now you go up to Denver and the intake is still at 60 kpa.  Granted you are a little deeper into the throttle but still 60 KPA.  The exhaust back pressure is now at 82 KPA at the exhaust tip.  The exhaust is really starting to work.

How you go to the top of Loveland Pass at 62 KPA atmospheric pressure.  You are at WOT at 60 KPA in the intake.  That is all the power you can get at this elevation.  You are still working out of the same VE table.  Guess what happens?  The motor is running the best it has ever run at 60 KPA as the exhaust is almost sucking the exhaust out, by comparison.  Wow, you need more fuel at 60 KPA and 12000 feet to get the AFR the same.

Keep in mind that at every one of these examples is at 60 KPA and the original RPM.

This came up when we were doing Alpha-N calibrations for motorcycles doing the annual Pikes Peak Hillclimb and we had data logs off the closed loop bikes.  We could watch the motor change are it went up the hill.

Glen, Glen, Glen...

Andy

[whittlebeast]

Here is the baro pressure at each altitude.  I was guessing based on experience on the previous post.  I was close...



Andy

[glens]

Andy, you're right; I did neglect your pressure stipulation.

Yet are you sure the AFR was actually changing?  Maybe it was staying the same but the O2 sensor wasn't responding the same so merely reporting differently (after all, they do tend to lie lean, right?).  Think about it.  The number of O2 molecules in whatever volume of air at 60kPA is going to be the same at Death Valley or at Red Mountain Pass (at the same temperature, of course).  The same AFR should be achieved either location with the same injector duty cycle.  Math is math.

Maybe there were merely "busts" in the tune

[whittlebeast]

O2s are sensitive to temperature and pressure.  I have no idea to what degree as you climb a mountain pass.

The speed of sound sound changes with temperature and I have no way to know how that would affect the scavenging of any single header but with a wobble fire motor, I can see things getting strange from front to rear and have different results in the long term fuel trims.  Notice that the OP was about the trims were being leaned on more on one cylinder than the other.  That has a ring of an exhaust back pressure / exhaust timing issue as altitude changes.

Keep in mind that the factory ECU has baro correction built in.   What all those control is all in the Harley Hidden Tables.

Cranking PW, ignition timing tables, VE corrections, even the effective fuel pressure could have a table in there for altitude compensation.

Most ECUs I have played with for example have at least two VE tables.  High altitude and low Altitude.  Most hacked ECUs only deal with the low altitude one and the other one gets ignored.  Like the pink elephant in the room.

Andy

[a2wheeler]

you guys are way over my head, but what I saw what that no matter what altitude I'm running at , the front cyl is lower VE's than the rear. The change I saw when running at the higher elevation was that the VE's were being increased in the lower kpa and descreased right of 60kpa.  That matches the shift of kpa which is a result of being higher in elevation.
There was discussion in a long thread with Steve Cole regarding the multiple VE tables that the automotive has to handle elevation, even some discussion on how the TTS VE's get set in the base cals, with high, low and medium altitude simulation. The point was HD does not have those multiple tables in the ECM. I'm still looking for that link.

[Admiral Akbar]

Glen

You missed that I said for any given MAP and RPM.  Think about this. Say you are were riding are 60 KPA in the intake at 5000 feet below sea level.  The air pressure at the end of the exhaust would be about 120 KPA  because you are so low.  The exhaust system would be terrible at scavenging at this very low altitude with this huge back pressure.

Now you go up to sea level.  The back pressure is now 100 KPA at the exhaust tip.  Still at 60 KPA in the intake.  The motor is running a little better.  The exhaust is starting to work as intended.

Now you go up to Denver and the intake is still at 60 kpa.  Granted you are a little deeper into the throttle but still 60 KPA.  The exhaust back pressure is now at 82 KPA at the exhaust tip.  The exhaust is really starting to work.

How you go to the top of Loveland Pass at 62 KPA atmospheric pressure.  You are at WOT at 60 KPA in the intake.  That is all the power you can get at this elevation.  You are still working out of the same VE table.  Guess what happens?  The motor is running the best it has ever run at 60 KPA as the exhaust is almost sucking the exhaust out, by comparison.  Wow, you need more fuel at 60 KPA and 12000 feet to get the AFR the same.

Keep in mind that at every one of these examples is at 60 KPA and the original RPM.

This came up when we were doing Alpha-N calibrations for motorcycles doing the annual Pikes Peak Hillclimb and we had data logs off the closed loop bikes.  We could watch the motor change are it went up the hill.

Glen, Glen, Glen...

Andy

Not sure any of this is correct.. You state that the ambient pressure effects scavenging.. Isn't cylinder fill pressure measured at close to bottom on the intake stroke and pressure in the intake during overlap the piston is just starting the intake stroke?   At tdc wouldn't the pressure be close to ambient? 

I'll agree that the pressure range that the motor runs in is higher at higher ambient pressure as you can never go below 0 absolute pressure.. That can effect how the whole system operates..

[whittlebeast]

I am talking about pressure on the exhaust side of the motor.

[Admiral Akbar]

I am talking about pressure on the exhaust side of the motor.

Understood.. If that's the case why do you compare to the intake pressure?