Altitude Issues

[Onthefence]

I looked back through real quick but did you post your calibration?  It would be nice to take a peek at it.

Calibration or log?  My tuning at elevation was done using PV AT and I did not create a log for it.   I have plenty of logs at 500ft, but didn't think those are in question.

[Onthefence]

This guy is making similar claims as I am.   According to him engines idle at different manifold pressures depending on altitude.   By his example, there is a significant difference at 10,000 feet.  Less at 6,000 but still measureable different.

http://www.underhoodservice.com/diagnostic-dilemmas-the-pressures-of-intake-manifold-vacuum-tests/

When testing manifold vacuum, it's important to remember that if an engine idles at 22" Hg at sea level, it will idle at about 17" Hg at 5,000', 14" Hg at 8,000' and 12" Hg at 10,000' altitude. Variations from the calculated standard, of course, are the weather conditions, the engine design, and how well the engine management system adjusts spark advance and air/fuel mixture to correspond to a change in barometric pressure.

[Coyote]

This guy is making similar claims as I am.   According to him engines idle at different manifold pressures depending on altitude.   By his example, there is a significant difference at 10,000 feet.  Less at 6,000 but still measureable different.

http://www.underhoodservice.com/diagnostic-dilemmas-the-pressures-of-intake-manifold-vacuum-tests/

When testing manifold vacuum, it's important to remember that if an engine idles at 22" Hg at sea level, it will idle at about 17" Hg at 5,000', 14" Hg at 8,000' and 12" Hg at 10,000' altitude. Variations from the calculated standard, of course, are the weather conditions, the engine design, and how well the engine management system adjusts spark advance and air/fuel mixture to correspond to a change in barometric pressure.

I think your example is using Gauge Pressure. Not the same as what the MAP sensor measures.

[joe_lyons]

The calibration that you are using in the ecm.

[Onthefence]

This guy is making similar claims as I am.   According to him engines idle at different manifold pressures depending on altitude.   By his example, there is a significant difference at 10,000 feet.  Less at 6,000 but still measureable different.

http://www.underhoodservice.com/diagnostic-dilemmas-the-pressures-of-intake-manifold-vacuum-tests/

When testing manifold vacuum, it's important to remember that if an engine idles at 22" Hg at sea level, it will idle at about 17" Hg at 5,000', 14" Hg at 8,000' and 12" Hg at 10,000' altitude. Variations from the calculated standard, of course, are the weather conditions, the engine design, and how well the engine management system adjusts spark advance and air/fuel mixture to correspond to a change in barometric pressure.

I think your example is using Gauge Pressure. Not the same as what the MAP sensor measures.

Ok so a 22"hg differential would mean manifold pressure of  7" hg.
And a 12" hg differential against 20.6" hg at 10,000 feet = 8.6"hg 

Doesn't that make the map increase in his example if we are calling that guage pressure?   Does that make sense that MAP would increase?  That would be like 5kpa increase.

[FLTRI]

The question is how to tune a bike at altitude.
The answer is the same as at sea level.
The question is how to get to low kpa cells at sea level to tune for altitude.
The answer is the same method as tuning for sea level.

Bob

[Onthefence]

The question is how to tune a bike at altitude.
The answer is the same as at sea level.
The question is how to get to low kpa cells at sea level to tune for altitude.
The answer is the same method as tuning for sea level.

Bob

And along the way, a disagreement popped up as to whether at altitude you will see lower KPA settings during operation. Is it not fair to finish that discussion? 

I am not sure I have a handle if it's even possible to get those lower KPA at sea level on the street.  You have confirmed that it can be done on the dyno.  Care to share what gear to use to hit the 30 and 35 area's between 2000 and 3000 rpm?  I'll give it a try and see if I can do it on the street. 

[Onthefence]

Here is another claimant who saw idle map drop at elevation.

http://www.motor.com/article.asp?article_ID=1354

[FLTRI]

I am not sure I have a handle if it's even possible to get those lower KPA at sea level on the street.  You have confirmed that it can be done on the dyno.  Care to share what gear to use to hit the 30 and 35 area's between 2000 and 3000 rpm?  I'll give it a try and see if I can do it on the street.

Sure. Pick 3rd or 4th gear. Run along at 3000+ rpms and reduce the throttle to achieve 30 and 35 kpa.
Bob

[Onthefence]

The calibration that you are using in the ecm.

attached file is after tuning at the higher elevation.  Assuming that is what you are requesting to see.

[FLTRI]

The calibration that you are using in the ecm.

attached file is after tuning at the higher elevation.  Assuming that is what you are requesting to see.

Was this calibration, virtually as is, provided to you from Fuel Moto?
This calibration doesn't look like the ones I've got from Jamie.
Bob

[joe_lyons]

Whats your whole motor combo?

[whittlebeast]

All it would take is hooking up a PV to a fully tuned bike tuned in Denver.  Log that bike on a ride with the wife on the back from Denver, over Loveland Pass at 12000 feet to Avon and return to Denver.  Take highway 6 for part of the ride to get lots of different riding conditions.

Get a hotel room at Avon as the wife will love the ride.

Post that 4 hour ride on here and I should be able to show you guys all this cool stuff happening on the fly.

All I need in the log is

Timing
MAP
RPM
TPS
STFT I forget what they call it
LTFT I forget what they call it
O2
Baro if it is there, I think it is
Knock channels
VE
VE New

You may be shocked what you see.  I have racers that tune and practice  at 4000 feet and race at world finals at 400 feet.  We deal with it every year.

Note that the Baro pressure on Loveland Pass will be about 63.5 KPA

Andy

[whittlebeast]

We will also be able to see the timing compensation tables (if they exist) as you climb the hills.

Andy

[DrumRunner]

I delivered a modified 120r to a customer in Colorado, and we went riding for a couple of days. I tuned the bike at Sea level and did some flight recordings at higher elevations. I know for a fact the map values shift to the left. decel on this 120r was 20-26 @ 60ft above sea level decel at 6000 feet was in the teens. Idle also shifted down. I don't know if it is a linear scale that can be predicted  or not but elevation effects the whole map value not just wot.

[FLTRI]

I delivered a modified 120r to a customer in Colorado, and we went riding for a couple of days. I tuned the bike at Sea level and did some flight recordings at higher elevations. I know for a fact the map values shift to the left. decel on this 120r was 20-26 @ 60ft above sea level decel at 6000 feet was in the teens. Idle also shifted down. I don't know if it is a linear scale that can be predicted  or not but elevation effects the whole map value not just wot.

Not quite sure why you say anything shifts in either direction. Again the ECM wins no matter what we think is or is not happening. IF the ECM see map as load, does MAP (load) go down as elevation goes up to make enough power to drive the vehicle through the air?
Note: Since air is thinner at altitude the vehicle will go through the air a bit easier so a bit less load to maintain a given speed.
Anyone willing to post their 5k-up elevation logs showing steady-state cruise at 60-up speed?
Bob

[DrumRunner]

These are in no way perfect examples but it should at least show you that map does change across the board to some degree as elevation changes. It is not a consistent change,meaning if you loose 20 at barometric you don't loose 20 at cruise but you do loose some. The easiest to duplicate and verify is idle. At seal level idle is around 42 kpa and at about 8000 ft it is 33. the cruise is less than ideal since there is no way for me to tell of the bike is going up hill down hill with 100 percent confidence. The two examples I found have a constant steady speed and constant map range and tps but they are in different gears so it screws the comparison up. If this doesn't give you enough info ask Steve Cole. He gave me a crash course for a bike that I had to tune at sea level and deliver it to Colorado.

First pic is idle at sea level second is idle at about 8000 ft.

[DrumRunner]

idle @ 8000 ft

[DrumRunner]

cruise sea level

[DrumRunner]

cruise @ 8000 ft

[FLTRI]

Thanks for posting DrumRunner.
Now that we have data to refer to let's make sure we are comparing apples to apples.
We note the vehicle speed is right at 60 mph at both altitudes.
So next we look at the KPA and see far less KPA at 8k feet.
So we then go to engine rpms and we have a big discrepancy between rpms 2500 vs 3000.
So now we know the bike was in 2 different gears at 60 mph.
Now here comes the other foot....Compare the 5%tp @ 2505rpm (5th) @ 8000ft to the 9.1tp @ 2983 (4th) @ sea level.
This begs the question... why would it take almost twice the throttle in a lower gear to maintain 60 mph on flat no wind road than the same bike at 8000ft?
With the wind, against the wind? Slight uphill or downhill?
The bottom line is we don't have apples and apples.
Bob

[glens]

I predict 40% available kPa at idle will be 40% of available no matter the driveable altitude and it'll all scale from there.

[DrumRunner]

Yea I know we don't it's the best I could find on my limited flight recordings. I was to busy enjoying Colorado. But idle is apples to apples.

[glens]

Idle at sea level is 0.427 of available.  At 8k feet it's 0.433.  Close enough...

[FLTRI]

Note the 8k idle data is still in warmup mode (still adding .3 AFR) which has different desired.

Sea level idle desired = 1008 vs 1006 actual vs 8k alt desired = 984 vs 1084 actual.

This means the load on the bike will naturally be a bit different depending on different idle speeds with different fueling. VE accuracy really counts here as fueling may be good at idle but not above...as in warmup mode or visa versa. If the VE is incorrect the engine will increase load trying to get to desired rpm.

One last point... if you were to move the cursor just a bit to the right in the 8k alt graph you will get a different (higher) KPA reading as the engine is trying to hold desired rpm so KPA fluctuates as engine load changes occur.

I realize air is thinner at altitude but to think a bike cannot be tuned at sea level to run good at altitude is, well just not true...UNLESS the VEs are off and/or targets are significantly different between desired idle and warmup idle (higher rpm) cells.

The real challenge is to tune at 8k alt for a bike that will spend most of its time at sea level.
Since at 8k alt a tuner cannot get to 100kpa he must extrapolate/extend the VEs through the higher MAP cells. This method may be adequate but not as good as tuning at sea level.

Bob