SD tuning for elevation (question)
11-02-2009, 12:06 PM
#1
SD tuning for elevation (question) Okay guys I know I ask a bunch of silly questions that maybe common sense to most of you, but here goes. I am currently in Reno, NV with a elevation of 4,400ft (1,300m) and I have to go to Fremont, CA (53ft) to get my car tuned. Is there a way to tune my car so it would read to run better at my elevation or would it not be a problem? And what would I have to change about the tune as I go up in elevation? More questions will come as I get answers I am just a naturally curious person when it comes to my car. Thanks ahead of time.
11-02-2009, 02:32 PM
#4
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The elevation should be "seen" directly by the MAP
sensor, and not matter (provided that the airflow
is properly / sensibly calibrated past the highest
air pressure you will see). So tuning at sea level
should cover things (provided the tuner tunes airflow
and doesn't just slap more fuel on it to get the "right
answer" on the dyno).
sensor, and not matter (provided that the airflow
is properly / sensibly calibrated past the highest
air pressure you will see). So tuning at sea level
should cover things (provided the tuner tunes airflow
and doesn't just slap more fuel on it to get the "right
answer" on the dyno).
11-02-2009, 04:48 PM
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I've seen your car around. We talked one night over on corporate or something. Who's tuning your car? Synergy? Talk to him about it, he shouldn't have a problem getting the car to run fine at this altitude.
11-02-2009, 06:56 PM
#6
Yea Rick over at Synergy is doing it but I was wondering if something else would have to be done for it. I know whenever I take my bike over into Cali it has some serious heat, it will get up and go and feels more powerful. But I was wondering if it is a SD tune would he need to know the elevation and etc for the computer to read or simulate a tune at that altitude.
Last edited by The Fugitive; 11-04-2009 at 11:44 PM. Reason: spelling
11-04-2009, 04:45 PM
#7
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lets see,, you should be fine, now if your car is tuned @ 4000 ft, then you goto sealevel, then @WOT youll be hitting cells that didn't get tuned. .
now at idle? i dunno.
-Carl
now at idle? i dunno.
-Carl
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11-04-2009, 11:48 PM
#8
yeh that is the only issue I have now is idle after the car has been running for a while. It does the whole "cam install without a tune" idle that wants to die. Every once in a while it does. But I have a MAF very very conservative safe tune (many issues with the people in town not getting me the right parts, not bolting somethings down completely etc etc) but I can live with that until I get my upgrades in sig.
11-05-2009, 10:03 AM
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Having done some experimentation with both SD and MAF at elevation, I will give you a few pointers.
If you run SD exclusively, it is true that the MAP changes due to elevation will normally handle altitude changes. The primary issue is that your airflow table (VE) needs to be highly accurate. I think it is the interplay between the MAP change with elevation and how frequently the PCM does its BARO update. In other words I have done a 6000' climb..MAP falls as anticipated with elevation..pull over..turn off car..watch how the new BARO update affects the new MAP. MAP usually falls even more..which affects fueling.
I have had better luck running closed-loop on big elevation climbs. My Trims definitely fluctuate more on those runs. I may not be doing the best job explaining what is happening, other than saying I have seen it now about a dozen times.
I have settled just using a MAF/SD hybrid closed-loop. But the point is that the VE Table needs to be 100% accurate, or one would anticipate that the Trims would show little to no variance.
Can you tolerate running a closed-loop SD tune for a while until you see what effect the elevation change has?
Hope that helps. Just sharing my high-altitude experience. Yours or others may be totally different.
Good luck..
..WeathermanShawn..
If you run SD exclusively, it is true that the MAP changes due to elevation will normally handle altitude changes. The primary issue is that your airflow table (VE) needs to be highly accurate. I think it is the interplay between the MAP change with elevation and how frequently the PCM does its BARO update. In other words I have done a 6000' climb..MAP falls as anticipated with elevation..pull over..turn off car..watch how the new BARO update affects the new MAP. MAP usually falls even more..which affects fueling.
I have had better luck running closed-loop on big elevation climbs. My Trims definitely fluctuate more on those runs. I may not be doing the best job explaining what is happening, other than saying I have seen it now about a dozen times.
I have settled just using a MAF/SD hybrid closed-loop. But the point is that the VE Table needs to be 100% accurate, or one would anticipate that the Trims would show little to no variance.
Can you tolerate running a closed-loop SD tune for a while until you see what effect the elevation change has?
Hope that helps. Just sharing my high-altitude experience. Yours or others may be totally different.
Good luck..
..WeathermanShawn..
11-09-2009, 12:33 AM
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Having done some experimentation with both SD and MAF at elevation, I will give you a few pointers.
If you run SD exclusively, it is true that the MAP changes due to elevation will normally handle altitude changes. The primary issue is that your airflow table (VE) needs to be highly accurate. I think it is the interplay between the MAP change with elevation and how frequently the PCM does its BARO update. In other words I have done a 6000' climb..MAP falls as anticipated with elevation..pull over..turn off car..watch how the new BARO update affects the new MAP. MAP usually falls even more..which affects fueling.
I have had better luck running closed-loop on big elevation climbs. My Trims definitely fluctuate more on those runs. I may not be doing the best job explaining what is happening, other than saying I have seen it now about a dozen times.
I have settled just using a MAF/SD hybrid closed-loop. But the point is that the VE Table needs to be 100% accurate, or one would anticipate that the Trims would show little to no variance.
Can you tolerate running a closed-loop SD tune for a while until you see what effect the elevation change has?
Hope that helps. Just sharing my high-altitude experience. Yours or others may be totally different.
Good luck..
..WeathermanShawn..
If you run SD exclusively, it is true that the MAP changes due to elevation will normally handle altitude changes. The primary issue is that your airflow table (VE) needs to be highly accurate. I think it is the interplay between the MAP change with elevation and how frequently the PCM does its BARO update. In other words I have done a 6000' climb..MAP falls as anticipated with elevation..pull over..turn off car..watch how the new BARO update affects the new MAP. MAP usually falls even more..which affects fueling.
I have had better luck running closed-loop on big elevation climbs. My Trims definitely fluctuate more on those runs. I may not be doing the best job explaining what is happening, other than saying I have seen it now about a dozen times.
I have settled just using a MAF/SD hybrid closed-loop. But the point is that the VE Table needs to be 100% accurate, or one would anticipate that the Trims would show little to no variance.
Can you tolerate running a closed-loop SD tune for a while until you see what effect the elevation change has?
Hope that helps. Just sharing my high-altitude experience. Yours or others may be totally different.
Good luck..
..WeathermanShawn..
11-09-2009, 09:32 AM
#12
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Macca:
I have done a few higher elevation logs where I lowered the 'RPM Threshold for Airflow Calculation' to 2000 RPM's. I kept it in closed-loop. As I recall trying to do primarily MAF during rapid elevation changes suffered from the same peculiarities as did 'SD' only. 3rd or 4th gear at times would produce identical MAf frequencies..but would result in widely differing Trim Values.
Let me be clear. In no way was I indicating trying to do MAF only was superior to running SD. I think it has to do with the nature of the PCM's BARO update parameters and the BARO offset (assumes linear drop of pressure with altitude). Nothing is perfect.
I am just sharing that I have had better luck keeping it closed-loop with elevation changes. My O2's are healthy enough (with headers) to properly Trim to ~14.7 AFR..which I have logged with a wideband.
Since the OP was concerned about an initial tune at Elevation A, then driving to Elevation B..my only suggestion was to keep Trims active. It would then be easy for him/her to go open-loop at any time. Trims are just a sanity check.
Ultimately Macca, my greater point is that the 'Ideal Gas Law' is just that..Ideal. Both MAF or SD have peculiarities with elevation changes in my experiences. But it still remain opinion. It would take some serious engineering work to prove it.
Hope that clarifies.
Good luck to the OP.
..WeathermanShawn..
I have done a few higher elevation logs where I lowered the 'RPM Threshold for Airflow Calculation' to 2000 RPM's. I kept it in closed-loop. As I recall trying to do primarily MAF during rapid elevation changes suffered from the same peculiarities as did 'SD' only. 3rd or 4th gear at times would produce identical MAf frequencies..but would result in widely differing Trim Values.
Let me be clear. In no way was I indicating trying to do MAF only was superior to running SD. I think it has to do with the nature of the PCM's BARO update parameters and the BARO offset (assumes linear drop of pressure with altitude). Nothing is perfect.
I am just sharing that I have had better luck keeping it closed-loop with elevation changes. My O2's are healthy enough (with headers) to properly Trim to ~14.7 AFR..which I have logged with a wideband.
Since the OP was concerned about an initial tune at Elevation A, then driving to Elevation B..my only suggestion was to keep Trims active. It would then be easy for him/her to go open-loop at any time. Trims are just a sanity check.
Ultimately Macca, my greater point is that the 'Ideal Gas Law' is just that..Ideal. Both MAF or SD have peculiarities with elevation changes in my experiences. But it still remain opinion. It would take some serious engineering work to prove it.
Hope that clarifies.
Good luck to the OP.
..WeathermanShawn..
11-10-2009, 08:40 PM
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Thanks for that Shaun and it confirms what I've always predicted and that is that a MAF is not as great at handling changes in altitude as well as everyone says it is.. Certainly blows the myth out of the water about SD not coping with altitude when a MAF does it too.
11-10-2009, 09:33 PM
#14
Macca:
I have done a few higher elevation logs where I lowered the 'RPM Threshold for Airflow Calculation' to 2000 RPM's. I kept it in closed-loop. As I recall trying to do primarily MAF during rapid elevation changes suffered from the same peculiarities as did 'SD' only. 3rd or 4th gear at times would produce identical MAf frequencies..but would result in widely differing Trim Values.
Let me be clear. In no way was I indicating trying to do MAF only was superior to running SD. I think it has to do with the nature of the PCM's BARO update parameters and the BARO offset (assumes linear drop of pressure with altitude). Nothing is perfect.
I am just sharing that I have had better luck keeping it closed-loop with elevation changes. My O2's are healthy enough (with headers) to properly Trim to ~14.7 AFR..which I have logged with a wideband.
Since the OP was concerned about an initial tune at Elevation A, then driving to Elevation B..my only suggestion was to keep Trims active. It would then be easy for him/her to go open-loop at any time. Trims are just a sanity check.
Ultimately Macca, my greater point is that the 'Ideal Gas Law' is just that..Ideal. Both MAF or SD have peculiarities with elevation changes in my experiences. But it still remain opinion. It would take some serious engineering work to prove it.
Hope that clarifies.
Good luck to the OP.
..WeathermanShawn..
I have done a few higher elevation logs where I lowered the 'RPM Threshold for Airflow Calculation' to 2000 RPM's. I kept it in closed-loop. As I recall trying to do primarily MAF during rapid elevation changes suffered from the same peculiarities as did 'SD' only. 3rd or 4th gear at times would produce identical MAf frequencies..but would result in widely differing Trim Values.
Let me be clear. In no way was I indicating trying to do MAF only was superior to running SD. I think it has to do with the nature of the PCM's BARO update parameters and the BARO offset (assumes linear drop of pressure with altitude). Nothing is perfect.
I am just sharing that I have had better luck keeping it closed-loop with elevation changes. My O2's are healthy enough (with headers) to properly Trim to ~14.7 AFR..which I have logged with a wideband.
Since the OP was concerned about an initial tune at Elevation A, then driving to Elevation B..my only suggestion was to keep Trims active. It would then be easy for him/her to go open-loop at any time. Trims are just a sanity check.
Ultimately Macca, my greater point is that the 'Ideal Gas Law' is just that..Ideal. Both MAF or SD have peculiarities with elevation changes in my experiences. But it still remain opinion. It would take some serious engineering work to prove it.
Hope that clarifies.
Good luck to the OP.
..WeathermanShawn..
11-11-2009, 12:22 AM
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Fugitive:
It all depends on how much reversion your cam has. Some people with a lot of cam reversion prefer open-loop (bypass O2's). But since many, many cars successfully run SD, and if that is your preference..I think it would make sense to keep the car in closed-loop using the feedback from the O2 sensors.
If in the future you have some tuning software it would be very easy to check your Trims..and if you prefer open-loop..would be very easy to do.
Yes, my suggestion is to keep it closed-loop (with O2's).
Let us know how it goes.
..WeathermanShawn..
It all depends on how much reversion your cam has. Some people with a lot of cam reversion prefer open-loop (bypass O2's). But since many, many cars successfully run SD, and if that is your preference..I think it would make sense to keep the car in closed-loop using the feedback from the O2 sensors.
If in the future you have some tuning software it would be very easy to check your Trims..and if you prefer open-loop..would be very easy to do.
Yes, my suggestion is to keep it closed-loop (with O2's).
Let us know how it goes.
..WeathermanShawn..
11-11-2009, 12:29 PM
#16
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Ricks tuned plenty of cars that make good power with a MAF on them. I vote use a MAF but that's where my experience has led me.
11-11-2009, 02:43 PM
#18
I don't think a MAF is the end all and be all by any stretch of the imagination. But they correct better than a SD car. I had a blower on a SD car running 12 psi and I could drive it everywhere no issue whatsoever. Tuned it @ 4500ft above sea level and ran like a champ at sea level albeit a little more lean than I like but that was an easy fix. Had a MAF car running 11psi and it didn't matter if it was at 8,000 ft or sealevel the car ran like a dream. Drive it right to sac and race it not touching one thing.
Ricks tuned plenty of cars that make good power with a MAF on them. I vote use a MAF but that's where my experience has led me.
Ricks tuned plenty of cars that make good power with a MAF on them. I vote use a MAF but that's where my experience has led me.
