Altitude Issues

[Onthefence]

While on a Trip out west I found my bike ran pretty crappy at high elevations.  8k and up.  Ran a few PV AT Pro sessions and it got better.  Noting that my cruise area was in the 30kpa range, I am curious how that is accounted for on a dyno.  Can you hit those areas or is it a matter of a good tuner knowing manual adjustments.

It seems on the street anything I would log in 30kpa would be in decel.

[FLTRI]

While on a Trip out west I found my bike ran pretty crappy at high elevations.  8k and up.  Ran a few PV AT Pro sessions and it got better.  Noting that my cruise area was in the 30kpa range, I am curious how that is accounted for on a dyno.  Can you hit those areas or is it a matter of a good tuner knowing manual adjustments.

It seems on the street anything I would log in 30kpa would be in decel.

If decelling is 30kpa how could you cruise at 30kpa unless you were going downhill?
Bob

[rageglide]

Less air to work with at altitude - the kpa values will be lower.   WOT might only be 70kpa at 8k feet where it would be 100 @ sea level.

The ECM must scale/correct accordingly for the change in MAP.  This is where EFI with Closed loop shines.   Just like a CV carb will handle altitude better than an S&S E.  Running open loop puts you in the same class as the S&S carb.   

Getting the <30kpa VEs dialed in perfectly for technically unrealistic RPMs at Sea Level would probably not help at altitude because the ECM should now treat 30 as a running pressure vs a decel.

[FLTRI]

Getting the <30kpa VEs dialed in perfectly for technically unrealistic RPMs at Sea Level would probably not help at altitude because the ECM should now treat 30 as a running pressure vs a decel.

Makes no difference where in altitude you are, 30kpa is 30kpa and tuning is exactly the same.
The problem comes when trying to get the 100kpa cells when you are at altitude.
No problem tuning low KPA at altitude.
Bob

[PoorUB]

While on a Trip out west I found my bike ran pretty crappy at high elevations.  8k and up.  Ran a few PV AT Pro sessions and it got better.  Noting that my cruise area was in the 30kpa range, I am curious how that is accounted for on a dyno.  Can you hit those areas or is it a matter of a good tuner knowing manual adjustments.

It seems on the street anything I would log in 30kpa would be in decel.

I just ran into this too. My Ultra was tuned well for 900 feet, but ran poorly at 5,000 ft and up. The easy answer is to add to the VE's at the lower MAP. If your engine runs good at 40 MAP, just extend the settings in the 40 MAP column to the lower MAPS.

[Onthefence]

While on a Trip out west I found my bike ran pretty crappy at high elevations.  8k and up.  Ran a few PV AT Pro sessions and it got better.  Noting that my cruise area was in the 30kpa range, I am curious how that is accounted for on a dyno.  Can you hit those areas or is it a matter of a good tuner knowing manual adjustments.

It seems on the street anything I would log in 30kpa would be in decel.

If decelling is 30kpa how could you cruise at 30kpa unless you were going downhill?
Bob

For clarification, I meant that at 500 feet above sea level, I only see map readings in the 30kpa range during decel.  My assumption originally was that a dyno at the same altitude would produce the same results making it a bit difficult to hit those low map areas.

[rageglide]

Getting the <30kpa VEs dialed in perfectly for technically unrealistic RPMs at Sea Level would probably not help at altitude because the ECM should now treat 30 as a running pressure vs a decel.

Makes no difference where in altitude you are, 30kpa is 30kpa and tuning is exactly the same.
The problem comes when trying to get the 100kpa cells when you are at altitude.
No problem tuning low KPA at altitude.
Bob

I agree 30 is 30.  But if cruise 65mph level ground cruise shows 30kpa at 8k and 50kpa at sea level, and the 30kpa is not tuned for the same conditions (rpm and tp), how can the engine demands be the same?   

At 10k feet if WFO shows 70kpa You will never be able to hit 100kpa without forced induction.   Less air, Less pressure.
Just like you can't hit 120kpa at sea level.  100kpa is 14.7psi it only goes down with altitude.

That's how I understand air and naturally aspirated internal combustion engines.

[FLTRI]

...65mph level ground cruise shows 30kpa at 8k and 50kpa at sea level, and the 30kpa is not tuned for the same conditions (rpm and tp), how can the engine demands be the same?

30kpa IS the demand. The ECM only knows KPA. If an engine is properly tuned (calibrated) at 30kpa it makes no difference what altitude.
That's the way I understand it.
Also, I don't think 30kpa is a realistic number for a land yacht to maintain 65mph level ground no wind. I may be wrong.
Bob

[a2wheeler]

Yes, kpa is the load factor, but that combo of rpm and kpa is all over the map. At idle 1000 rpm, kpa is 31.8 here at 6000 ft.  Decel, I can be rpm 3000 and kpa is 17. Accel, 3200 rpm and kpa is at 28. It climbs fast though. You just have to get the cells filled in the best you can. A dyno would fill them in better. I just got back from a sea level trip and initially, the 6th gear accel was a dog, but the ECM seems to learn enough that after 4500 miles it ran ok. I think it could be better. But I just guessed at those cells.

[Coyote]

but that combo of rpm and kpa is all over the map.

   Pretty sure it's only in one place (cell)

[FLTRI]

Yes, kpa is the load factor, but that combo of rpm and kpa is all over the map. At idle 1000 rpm, kpa is 31.8 here at 6000 ft.  Decel, I can be rpm 3000 and kpa is 17. Accel, 3200 rpm and kpa is at 28. It climbs fast though. You just have to get the cells filled in the best you can. A dyno would fill them in better. I just got back from a sea level trip and initially, the 6th gear accel was a dog, but the ECM seems to learn enough that after 4500 miles it ran ok. I think it could be better. But I just guessed at those cells.

Just keep in mind I doesn't matter what you and I think is happening. It ONLY matter what the ECM does based on its rules not ours.
What I mean is there is only one cell for a given KPA @ rpm, as Coyote mentioned.
If you will accept that fact you will be able to find and tune where needed. No need to guess at cells you can't collect data for.
I do a bit of blending, smoothing, and other subtle changes to the tune based on my experiences with particular builds and how they react to different exhaust systems and cam profiles.
Common sense approaches to tuning helps too. Give the engine what it likes.
If you get plenty hits you prolly can use the data. If you don't either it's too lean or rich...or something mechanically is wrong.
Bob

[Onthefence]

I am still not clear if a bike on a dyno at or above sea level could run at those low map settings to take the measurements to calculate good ve numbers.

[FLTRI]

I am still not clear if a bike on a dyno at or above sea level could run at those low map settings to take the measurements to calculate good ve numbers.

The only issue with high alititude is getting to 100 KPA. Not sure why you think low KPA is unique to high altitude.
The key is to leave some low KPA stuff in open loop so the ECM doesn't rely on the sensors for that area. It's knowing when to hold 'em and when to fold 'em so to speak.
Bob

[Onthefence]

So it's common for a bike to cruise in the 30kpa area at sea level? I didn't know that. Mine is far higher than that and must be uncommon.  Thanks for the information.

[a2wheeler]

but that combo of rpm and kpa is all over the map.

   Pretty sure it's only in one place (cell)

Yes, poor choice of words. yes it is one cell for a given rpm/kpa, but the variable is you might be decel, or accel, or high altitude or low altitude. My point was even at idle I see 32 kpa at 6000ft and at sea level, idle will be different.
And I equate blending VE cells that I can't get enough hits in as guessing. I have read several different expert opinions on how upper kpa columns should blend up, and some say blend down, or blend even. Or maybe I got all those confused with blending of the timing tables. If you get close, then the ecm fills in as you ride in those new cells - for what ever reason you end up hitting them.  That was the case with mine. I'm happy with what it learned in a short period. However, I now want to change my target main lambda table to get a bit better mileage. And when I reload the map, it will reset all those learning. I wish I could see what it learned, I have no different guesses.

[FLTRI]

So it's common for a bike to cruise in the 30kpa area at sea level? I didn't know that. Mine is far higher than that and must be uncommon.  Thanks for the information.

Ok, show us a data log that shows 30kpa while cruising at 65mph on level ground.
Maybe it takes less KPA to produce the same power at high elevation as at sea level to maintain 65mph?
Air's thinner maybe that's why less KPA necessary to maintain 65mph?
Bob

[a2wheeler]

That is definitely easier on a dyno. But I'll give it an attempt. I doubt that 30 will be seen at 65 mph, but I'll try several speeds to create a pattern of high altitude. This will most likely be in the 7k ft range. What I have been seeing in general is that the cells I can hit at 7K ft are a shift left about 3 columns that folks can hit at sea level. I can not hit 90 + kpa, I have to go down to 6k ft and go through strange driving styles to even touch 90 and then it is not often enough to use it. I fill cells in 25kpa to 80kpa and I hit 15kpa and 20 kpa but TTS does not keep track of those.   

[FLTRI]

... I'll give it an attempt. I doubt that 30 will be seen at 65 mph, but I'll try several speeds to create a pattern of high altitude. This will most likely be in the 7k ft range. What I have been seeing in general is that the cells I can hit at 7K ft are a shift left about 3 columns that folks can hit at sea level. I can not hit 90 + kpa, I have to go down to 6k ft and go through strange driving styles to even touch 90 and then it is not often enough to use it. I fill cells in 25kpa to 80kpa and I hit 15kpa and 20 kpa but TTS does not keep track of those.   

Sea level calibrations look just like yours, no difference. The fact is you cannot get to the high KPA due to altitude. No shifting to the left.

It's very easy to hit max KPA, whatever it is, just put it in high gear and add throttle. If you are in the lower rpms you can hit max KPA with as little as 15% throttle.

And finally, anything below 25-30kpa is decel and if running an open exhaust, air reversion can cause erroneously lean mixture only to have the system dutifully and accurately compensate.
Ya learn to guess good on the decel numbers to control behavior like popping and backfires.
Different exhaust systems react differently to decel fueling and timing strategies.

If I've learned anything from tuning it's the ECM will always win and no matter how smart I think I am the ECM easily outsmarts me.

I've learned how to work with the system (a lot of thanks to SC of course) in an endevour to better understand why it does what it does. That way hopefully, I will make more informed tuning decisions in order to produce a better running bike.
I learn something new every day too.
Bob

[rageglide]

   The conversation isn't about producing the same power.   It's about the engine running best at altitude when the engine has been tuned to run best at close to sea level.  30kpa at sea level is decel (closed throttle) but at 8k feet, it's going to translate to throttle being open a fair amount. 

There is less air at altitude, therefore there is less pressure.  Cruising at 65mph at same RPM will not be using the same TP as at sea level.  It's not the same.

http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

If 50kpa at WFO at altitude is ALL the pressure you can get. That's it, without forced induction you will never get to 100kpa at that altitude. 

[glens]

25-30 kPa is decel even at 9 kft?

You, mount a large fan in one wall of your booth, have it blow out, but don't allow enough makeup air to the room.  And you, mount a large fan in one wall of your booth, have it blow in, but don't allow enough exhaust air from the room.  Problem solved: extend your tuning range. 

I think the biggest issue is when AE and DE running modifications (exiting closed-loop) are disabled for the purpose of collecting data while road-tuning.  These really are, or least can be, irregular conditions which should not be used as a basis for establishing VEs.  Especially so when they're present in an inordinate amount within any log file.  A certain amount (at least type) of accel enrichment will be built into the VE tables from the presence of a sufficient amount of such conditions during a run, for example.  AE/DE stuff would certainly influence the lower usable pressure range at the sea coast, generating data really not pertinent for more "normal" operation that will certainly be encountered at altitude.  Perhaps that's what's happened in these two recent examples?

Refer to paragraph two.

[a2wheeler]

My head hurts now, but this grasshopper is still processing on all that you guys have shared.

Glens,  early TTS instructions said turn off AE and DE for vtune data collection. Newer versons say leave AE and DE on during vtune data colleciton. I got confused with your comments - are you saying that having AE and DE on during collection may adversely affect those low kpa columns depending on what altitude you are at during the collection? So I'm am thinking you suggest turning AE and DE off during collection?

[rageglide]

my head hurts too...

As Bob said, (and I did too) the ECM is going to try to deal with the situation regardless.  That's it's job. 

Less Air, Less pressure.  ECM deal with it.   (Best if it's in closed loop)

[harleytuner]

Not to get the Topix off course, but on the dyno I tune deceleration manually. It's really quit simple, I usually go in 3rd gear, get the bike up to 5k then start the record, slowly let off the throttle while watching the kpa keeping it at your target all the way back to idle. My dyno is at 80' above sea level but 35 miles west of me is over 3000'.

[Onthefence]

So it's common for a bike to cruise in the 30kpa area at sea level? I didn't know that. Mine is far higher than that and must be uncommon.  Thanks for the information.

Ok, show us a data log that shows 30kpa while cruising at 65mph on level ground.
Maybe it takes less KPA to produce the same power at high elevation as at sea level to maintain 65mph?
Air's thinner maybe that's why less KPA necessary to maintain 65mph?
Bob

By my observation, the map readings were shifted left throughout the operating range.  It seems 75-80K was all I would see at WOT.  Idle was in the 20s maybe.  Most of the cruise below 3000 rpm was in the 30s. 

I am not all that surprised by the map readings or questioning those.  I was only trying to figure out if a sea level dyno tuners regulary replicated those conditions for measurement or if you have to manually fill in those areas based on experience? 

I will look and see if I still have the logs.

[glens]

early TTS instructions said turn off AE and DE for vtune data collection.

I'm pretty sure it wasn't the "official" guide that said to disable AE/DE, and I took some issue with the issue back then.

Newer versons say leave AE and DE on during vtune data colleciton.

Good!

I got confused with your comments - are you saying that having AE and DE on during collection may adversely affect those low kpa columns depending on what altitude you are at during the collection? So I'm am thinking you suggest turning AE and DE off during collection?

No.  That's backwards from what I'm saying.  Leave AE/DE up and running while vtuning.  The instances they're needed will be disallowed from later consideration by the software (plus some few seconds after they happen, so things return back to normal).  Let me try to say it a different way.  Say you don't want any running time disallowed from data collection, so you disable AE for vtune logging.  That's just like disabling the accelerator pump on your carburetor back in the day.  When you're steady throttle then open it some, the engine needs a little extra fuel so it won't stumble any during the transition.  But you've disabled it so it does stumble a little and this event gets recorded as something that requires VE changes to correct it.  But it was in fact a transient change which should be handled by something other than VE correction...

Think of it like this.  You're recording your buddy's band to make a demo disc.  You mix it down using your favorite speakers which really make a lot of good bass, plus you've got them in the corners of the room which increases bass response even more, relative to higher frequencies.  So you adjust the bass on the recording so it don't sound quite so "boomy".  Now the next person to play the recording, if their speakers don't make exaggerated bass and/or they're mounted in the middle of a wall, will wonder why there's no bass in the recording.  Does that make any sense?  It'd be a case of using a non-flat-response system as a reference and making adjustments to the content so that the response is then flat.  Later, when a flat-response system is used to play that recording, the result is the opposite of the condition that existed when making the recording.

That same sort of situation can happen when developing VE tables for a calibration.  And this is likely why it's evidently now recommended to leave AE/DE enabled while vtune logging on the road.

The reason I brought this up was it's likely that lower-kPa (like where you're idling or even slightly lower pressure) will get recorded as a disproportionate amount of AE/DE activity at lower elevations.  If that "abnormal" activity is allowed to influence the final VEs it won't really much matter while at lower elevations, but it will come into play pretty heavily high up in the mountains.  I was just wondering aloud about it maybe happening in this case.