SD Altitude tuning.

[TimbrSS]

411 P01 PCM running 3 Bar OLSD OS: 1263016.
Procharged LS6, large cam, low vac at idle (72 Kpa at 100kpa baro).
Tuned VE to under 3% error at 700'. Runs excellent all around at that altitude.
Problem this weekend: Drove from 700' to 6000'. With the altitude change, Fuel was showing 15-25% lean part throtttle/out of boost. I'm seeing Kpa levels at altitude with some throttle that I'd only ever see at no throttle decel at sea level.
Is there a way to add correction for barometric changes? Any strategy to pull baro from the map sensor would just max out to 105kpa whenever I get into boost.

[Alvin]

"I'm seeing Kpa levels at altitude with some throttle that I'd only ever see at no throttle decel at sea level."

I think this is your whole issue.. The VE table had spots that you couldn't get to near sea level.. Now that your at altitude you are in spots you had to fill in with good guesses before.

[TimbrSS]

"I'm seeing Kpa levels at altitude with some throttle that I'd only ever see at no throttle decel at sea level."

I think this is your whole issue.. The VE table had spots that you couldn't get to near sea level.. Now that your at altitude you are in spots you had to fill in with good guesses before.

Sure, I did get to some new spots, but a lot of them I did see before. It's that I didn't have as much (or any) load on the engine. After adding in all that fuel at the top of mountain, it was rich at the bottom of the mountain.

[68Camaro]

this is a problem with P01 and P59 ECU's because there is no built in baro correction in SD - these ECU's do fine with altitude changes as long as you keep the MAF which is not possible in a big boosted application

the solution in your case is ditch the factory ECU and step into something better for what you are doing like Holley HP or Dominator (Terminator X is an option as well but I prefer the HP or Dominator platforms)

[murfie]

P01's should have VE correction factor under airflow> dynamic. This is a ECT vs Baro table that does VE correction for altitude.

VE correction factor.jpg

Is there something not working correctly with your cars baro sensor? I don't think it should need to have 15-25% added on top of what it already adds(4-8%).

[TimbrSS]

P01's should have VE correction factor under airflow> dynamic. This is a ECT vs Baro table that does VE correction for altitude.

VE correction factor.jpg

Is there something not working correctly with your cars baro sensor? I don't think it should need to have 15-25% added on top of what it already adds(4-8%).

There is no separate baro sensor. I'm using LS9 3 bar MAP sensor. I assume the only way pcm would know baro is that it would take the reading from map at KOEO for initial, then possibly recal the "baro' value at WOT, which would max out at 105kpa as soon as I hit boost.

I do have the tables you posted, with those values in them.

[TimbrSS]

this is a problem with P01 and P59 ECU's because there is no built in baro correction in SD - these ECU's do fine with altitude changes as long as you keep the MAF which is not possible in a big boosted application

the solution in your case is ditch the factory ECU and step into something better for what you are doing like Holley HP or Dominator (Terminator X is an option as well but I prefer the HP or Dominator platforms)

Yes, I know ultimately I'll end up with aftermarket stuff to get all the features. I'm leaning Haltech 2500, or Nexus to future proof my needs, but would also consider Dominator.

Haltech does this, which seems to be helpful in my scenario:

MAP Correction
The percentage correction table for changes in Manifold Pressure. Up to 3D mapping is available with this table. When the Tuning Method is set to VE and when the load source is TPS, the Manifold Pressure is automatically corrected for, as part of the VE fuel calculation. In this case, the table should initially be set with all values at 0% (default). The table is then used as a correction for any error in the automatic calculation. When the Tuning Method is set to Injection Time, there is no VE calculation auto correction, and all values need to reflect a raw correction with changing Manifold Pressure. This table should not be enabled when you are already tuning with MAP as your load source. (Default = Disabled)

[Alvin]

Sure, I did get to some new spots, but a lot of them I did see before. It's that I didn't have as much (or any) load on the engine. After adding in all that fuel at the top of mountain, it was rich at the bottom of the mountain.

Are you sure you just didn't maybe over shoot? I do things like this all the time and have not had a issue.

Sidenote.. odd that the custom OS didn't fix the baro stuff. You are right that it reads at KOEO and doesn't update unless it sees a pressure higher than that. Which would be the best way to work if you started on the mountain and made your way down but not right if boost is an option.

[murfie]

There is no separate baro sensor. I'm using LS9 3 bar MAP sensor. I assume the only way pcm would know baro is that it would take the reading from map at KOEO for initial, then possibly recal the "baro' value at WOT, which would max out at 105kpa as soon as I hit boost.

I do have the tables you posted, with those values in them.

P01 baro sensor.jpg

Mine has a barometric pressure sensor that updates while I drive.

[TimbrSS]

P01 baro sensor.jpg

Mine has a barometric pressure sensor that updates while I drive.

Is it an actual separate sensor, or a value derived from the MAP sensor?

[TimbrSS]

Are you sure you just didn't maybe over shoot? I do things like this all the time and have not had a issue.

Sidenote.. odd that the custom OS didn't fix the baro stuff. You are right that it reads at KOEO and doesn't update unless it sees a pressure higher than that. Which would be the best way to work if you started on the mountain and made your way down but not right if boost is an option.

I'm going to log Baro sensor value and VE correction to see if that is doing anything.

I'm working mostly in my normal cruise areas and got this lambda % error with the low alt map.

tuning.jpg

[Fast4.7]

P01 baro sensor.jpg

Mine has a barometric pressure sensor that updates while I drive.

Seperate Baro sensors have not been used since CCC Carb cars with GM. It is calculated off the MAP using a lookup table that references RPM and TPS for correction. Basically it takes a reading everytime you open the throttle heavily at lower rpm.

[murfie]

You are right it is not a sensor and its some calcuated value (all pid's are sensors to me), but it updates under normal driving conditions, and is fairly accurate.

I was curious and wanted to display this and needed to test a new fuel regulator on my car (heads/cam LS7 in a 99 c5). I cold started it at 2500 ft elev. then rolled down to 2000ft elev.(take note of all the DFCO). It then updates under light throttle as I changed roads. I then rolled down to 500ft elevation and turned around, again it updated under light throttle. I then came back up the hill much faster with much heavier throttle, it did not update faster.

Either way point is, these ECUs compensate for elevation just fine.

Barometric pressure update .jpg

[Fast4.7]

You are right it is not a sensor and its some calcuated value (all pid's are sensors to me), but it updates under normal driving conditions, and is fairly accurate.

I was curious and wanted to display this and needed to test a new fuel regulator on my car (heads/cam LS7 in a 99 c5). I cold started it at 2500 ft elev. then rolled down to 2000ft elev.(take note of all the DFCO). It then updates under light throttle as I changed roads. I then rolled down to 500ft elevation and turned around, again it updated under light throttle. I then came back up the hill much faster with much heavier throttle, it did not update faster.

Either way point is, these ECUs compensate for elevation just fine.

Barometric pressure update .jpg

The problems I have run into on Baro updates are on engines that either have a restrictor plate for class racing where power is limited or a much larger throttle body then stock. The calculations will be off resulting in high or low baro readings. Its not an issue unless the throttle body has drastically changed airflow from stock.

[murfie]

The problems I have run into on Baro updates are on engines that either have a restrictor plate for class racing where power is limited or a much larger throttle body then stock. The calculations will be off resulting in high or low baro readings. Its not an issue unless the throttle body has drastically changed airflow from stock.

It would have to be a very big throttle body change, maybe even dual plate or oval style. My point is you don't need to go WOT or anywhere near boost to get a baro update.

[TimbrSS]

So the more I look into what is happening at altitude, I really think I need a "VE Multiplier vs. TPS vs. RPM table" that is offered with the 1 bar SD OS. I think if that was tuned in properly, I'd only be off by the actual change in altitude air conditions, which should require me to add fuel. I'm saying I'd be off because there is no way for the MAP sensor to give accurate updated BARO info other than at KOEO for a boosted engine.

[Alvin]

The problems I have run into on Baro updates are on engines that either have a restrictor plate for class racing where power is limited or a much larger throttle body then stock. The calculations will be off resulting in high or low baro readings. Its not an issue unless the throttle body has drastically changed airflow from stock.

Thats interesting. I was doing a lot of that for a while for some local racing. Gen 3 and 4. I never did have a issue with the baro update changing the tune the best I could tell. Honestly never really paid too much attention to baro until the GEN 5's... Well old chip cars would do it too with boost also but I don't even think that was a huge deal.

Gen 5 baro stuff is critical to keep right.

[murfie]

What throttle body do you have on the car?

There are calculated MAP max/min tables under engine diag> airflow that if you don't have HPT support could add those for you. They determine the p0106 diag code, but calculated Baro would be based on calculated MAP vs actual MAP. I could see how going into boost would quickly throw the BARO off. It should quickly fix it's self once under vacuum again tho.

[TimbrSS]

Stock LS6 Throttle Body.

[murfie]

Stock LS6 Throttle Body.

How about manifold, stock or is it some heat soaking sheet metal deal?