VE only tune and Barometric pressure

I am trying to find a way to run a VE only Tune that updates Barometric Pressure when changing elevation. This is for a P01 ecm.

My current configuration has the standard gen3 MAP sensor.

The MAF sensor is dissabled.

I have removed the narrow band O2s.

I am running the VE enhanced OS.

I have found that if I enable the MAF sensor with the VE enhanced OS it will update the barometric pressure as I change elevation. If I disable the MAF it will not update the Baro pressure.

I have searched and searched but it seams there is not very much info on how these ecms update baro pressure, I have read that they update on key on engine off, or when running and at full throttle. I would really appreciate any information relating to how the Baro pressure is calculated on these ecms.

Don't sweat it. The MAPs will handle the elevation changes just fine for you.

The missing NBO2s will hurt you more than any lack of updating BARO data.

I made a thread on here 5+ years ago asking about something along the same lines and got no responses. Here is what I know and my experience-- it doesn't exactly answer your question (I'm curious now too), but hopefully it adds to the conversation.

Back in the day I ran a boosted setup on a EFILive COS. EFI had a couple tables that defined the conditions that would allow the baro to update. I don't have the software installed anymore, but it was basically WOT at low rpm, like below 2500 or 2000 rpm or something like that.

I also discovered that if MAP was higher than previously saved baro value, it would also update (outside the the conditions described above). This makes sense in a NA application, but in a boosted app, first time I went over 100 kPa, baro would update and stay pedded at ~104kPa, which presumably was the max value.

The issue was that this threw off all of my fueling calculation (manifold vacuum) for a fuel system that runs a constant pressure. If you run a MAP referenced fuel system, it shouldn't really matter.

It's possible that HPT killed the baro update code as part of the custom OS patch to avoid the issue I had described above. Or you're just at too high of a RPM for baro to update. In theory this would make sense to kill on a 2 bar or 3 bar COS, but leave baro update logic in tact on a 1 bar OS. Like you also found, I found very little info/documentation on this, so who knows.

I'm running P59 1 bar SD COS (NA car), I log baro normally, I'll peek thru some logs and see if I can see it updating at all.

Small update, I dug up the settings for my current P59, iirc these were the same on my P01. I don't think you'll have a need to edit these, but happy to help with user defined parameters if needed. The question still remains if any of the Custom OSs affect baro updates.

Only post I was able to find with HPT chiming in. Says it's disabled in 2 bar OSs, presumably not touched in 1 bar COS. I'll go dig up those logs now and report back. (edit: just kidding, apparently i removed baro from my log lists awhile ago, I'll have to log it again some time).

What exact OS and custom patch are you running?

https://forum.hptuners.com/showthrea...ht=baro+update

The Baro updates automatically when you turn the key on. Always has since the beginning of the wheel.

Abc, I thought that as well but when I go up in elevation my tune runs leaner at lower RPMs and will mess with idle and low speed cruising. If I log the Barometric pressure, I can see that it does not update. Going from sea level to 7000ft my fueling was off as around %20-%30 in some of the lower rpm areas.

If I enable the MAF sensor the baro pressure updates for elevation and my fueling stays dialed in. I do not remember if I had the ?Speed Density ? Enhanced (RTT)? OS active when I had the MAF enabled.

Aaronc7, wow, that is some great information. Im guessing it is disabled for the SD enhanced OS. Attached is an old log where I turned on the MAF and the Baro updates for elevation, and a current tune file where the baro does not update. I could not find the logs where it was not updating. Next time I take a trip up into the mountians I will have to get some good logs and do some more testing.

Attachment 156859Attachment 156860Attachment 156861

Yep, you can see it updating a few times right around the 51min mark, from ~97 kPa down to 86 or so. I live in florida so this is a bit more difficult for me to test, but I was hoping I could give it high load in that rpm range see if it changes a tenth or something even. Any change would confirm it's updating.

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Originally Posted by SSegal

Abc, I thought that as well but when I go up in elevation my tune runs leaner at lower RPMs and will mess with idle and low speed cruising. If I log the Barometric pressure, I can see that it does not update. Going from sea level to 7000ft my fueling was off as around %20-%30 in some of the lower rpm areas.

If I enable the MAF sensor the baro pressure updates for elevation and my fueling stays dialed in. I do not remember if I had the ?Speed Density ? Enhanced (RTT)? OS active when I had the MAF enabled.

Aaronc7, wow, that is some great information. Im guessing it is disabled for the SD enhanced OS. Attached is an old log where I turned on the MAF and the Baro updates for elevation, and a current tune file where the baro does not update. I could not find the logs where it was not updating. Next time I take a trip up into the mountians I will have to get some good logs and do some more testing.

Attachment 156859Attachment 156860Attachment 156861

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Just had a friend log is 2004 C5Z (P59, 12587603, same setup as my car), he is running the 1 bar Speed Density RTT custom OS, and it DOES update the baro, in both directions (increases and decreases many times in this long log).

Now, that doesn't mean this isn't the case on your OS, but this all checks with what logically makes sense and what Chris@HPT posted a long time ago. Just go WOT around 3k and it should be very obvious if it updates at all.

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Originally Posted by SSegal

Abc, I thought that as well but when I go up in elevation my tune runs leaner at lower RPMs and will mess with idle and low speed cruising. If I log the Barometric pressure, I can see that it does not update. Going from sea level to 7000ft my fueling was off as around %20-%30 in some of the lower rpm areas.

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Then there is something else wrong. When you go up in elevation there is less air/psi available, therefore it will be rich if fueling does not change, which it will via the MAP table. I'm not sure why they reference the baro other than to verify the MAPs is correct at start up. Once the engine starts, the MAP reading is a direct result of the engine's ability to resist the atmosphere entering the intake manifold.

I also do not know but can't imagine they (meaning the oem pcm) put too much emphasis on fueling based on a baro reading.

I don't have any experience changing more than about 3,000 feet of elevation with mine, maybe one of the pro's will chime in with their experience.

It does affect fueling, because some of the injector characteristic tables reference manifold vacuum (baro - MAP), not MAP directly. When baro is not correct, the lookup is wrong. I experienced it firsthand when I had a boosted setup, but kind of the opposite problem of it updating when I didn't want it to.

But I largely agree with that and what someone else said about narrowbands. Fuel trims were able to soak up most of it, but it did affect WOT AFR too. Less than 5% error though, if i remember correctly, but enough that I saw the effects and was just trying to get it at good as possible.

The op probably just does not have the needed sections of the VE table tuned in the areas that are hit at higher elevation. With the MAF enabled the ve is mostly ignored, hence why the problem shows up in SD. I understand that a non return fuel system could be affected a tiny bit, but not to nearly the extremes he is reporting.

ABC, that is what I thought as well and I am still trying to make sense of it. Maby my injector data is bad, I did change my injectors and updated the data a long time ago.

I did some testing. I pulled the MAP sensor out of the intake and put it in a plastic bag and duct taped it to a vacum. I wanted to see if I could get the Baro reading to update with key on engine off cycles.

It seems that in order for the Baro reading to update the SES light must be off with no active DTCs, this whole time I have been running in Speed density mode I have had the SES light on and one of the MAF DTCs active.

These tests were not very conclusive, too many veriables. I couldnt get the SES light to stay off. The Baro reading wouldnt update until I started the engine for a few seconds and the SES light would go out, and I I would maby have to do this two or three times. Durring testing The SES light would keep coming back on I think because a mismatch between the current Baro reading and measured MAP during key on. No codes would come up on the VCM scanner and clear all DTCs would not work. Once the SES light came on the only way to put it out was to start the engine for a few seconds, and it would run like crap because of the massive vacume leak from where the MAP sensor was.

Ill have some better data next time I drive up into the mountains. I will set the MAF errors to SES unchecked and “no error reported” and see what happens.

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Originally Posted by SSegal

Ill have some better data next time I drive up into the mountains. I will set the MAF errors to SES unchecked and “no error reported” and see what happens.

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If you do this, it won't be fueling based off the MAPs alone, it will involve the MAFs also. Do you have the MAFs tuned?

Set P0101-P0103 to "no MIL light"

The DTC must be set for the car to fail over into speed density mode

Hard to follow your test above, but I had a friend run a quick log a few weeks ago-- his car is 100% SD on the 1 bar P59 SD Custom OS, and baro was updating many times

Oh shoot. you guys are rite, it is still using the MAF.

The MAF is tuned as well as i can tune it, Its an LS3 card style MAF. I never get consistent readings with it at low throttle. That is why i would like to run a VE only tune.

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Originally Posted by aaronc7

Set P0101-P0103 to "no MIL light"

The DTC must be set for the car to fail over into speed density mode

Hard to follow your test above, but I had a friend run a quick log a few weeks ago-- his car is 100% SD on the 1 bar P59 SD Custom OS, and baro was updating many times

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Those codes should be set to "MIL on first error" and the SES box unchecked. Not set to "No MIL".

And the Baro updates automatically. You don't have to do anything special.

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Originally Posted by edcmat-l1

Those codes should be set to "MIL on first error" and the SES box unchecked. Not set to "No MIL".

And the Baro updates automatically. You don't have to do anything special.

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No MIL works just the same, it just classifies it as a non emissions related "soft code", either way the code is present and MAF gets disabled

And the baro comment... I was just confirming my first hand experience that baro updates normally in SD during driving-- what this thread is about.

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Originally Posted by aaronc7

No MIL works just the same, it just classifies it as a non emissions related "soft code", either way the code is present and MAF gets disabled

And the baro comment... I was just confirming my first hand experience that baro updates normally in SD during driving-- what this thread is about.

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That is not correct.