Does HP Tuners Offer Access to These Engine Parameters???

[DrkPhx]

The ZL1, CTS-V andd ZR1 all have the Estimated MAP Max value set at 190 kPa from the factory. The intake manifold volume on the V and ZL1 is 13487 cc and 10327 for the ZR1. Hopefully that helps you guys.

[cc-rider]

There must be some incredibly complex equations that GM uses to control aiflow and fueling in these ECU's. Would probably be a really eye opening experience to get a GM engineer to explain some of this.

[jsllc]

I have a request in for this and 22 other parameters missing from HPT on e67 ECUs that other software allows for tuning. These all relate to fueling and airflow.

[jsllc]

What [ECM] ID value is the Estimate MAP Maximum in your tune?

[sssnake]

Does the baro update above the max setting you put in durring full throttle boost - this is granted your not running an enhanced OS patch and your boosted...

Yes the MAP sensor reads accurately during full boost. It is just the cylinder air/dynamic airflow values that appear whacked.

What [ECM] ID value is the Estimate MAP Maximum in your tune?

It was 105KPa and now is 235 KPa. The change made a difference but did not eliminate the issue. I am still investigating. Has anyone played with the MAP prediction filters? I suspect this is a two step problem. We fixed the first and now other data values are limiting the estimate during large MAP swings.

[GHuggins]

I meant if the barometric update will cap itself at a lower setting if you lower the max map. Sorry should have been more clear.

[jsllc]

I have spent days on prediction coefficients for my ZL1. Never could make them work. Eventually just zero'd them out like everyone else to get the car to fuel correctly. After the mods the stock settings for TPS, MAP and others just would not blend to create a usable situation. Just 2 days ago I tried again starting with the stock values. Using MAF only car starts runs at 14.6. PE engages on the throttle as it should and tapers to 11.2 at 17psi of boost. All works great. Disable MAF and run SD and AFRs follow the MAP. WOT 17psi and 11.2. Put back the predictive coefficients and AFRs went to 13.9 and stayed. Pulled them and 11.2. Just do not know the math behind them.

[GHuggins]

I don't think we have all of the tables needed to adjust them anyway...... I know efi will supposedly give you a couple more, but still believe there are some in the background used for calculations. I really didn't care much about the prediction coefficients - I've been more interested in finding out if max map will "cap" the baro update - a must for sd tunes!!! Otherwise fueling gets thrown into way left field...

[cc-rider]

Can one of you guys that knows explain exactly what this baro update issue is? I've read it here a few times...but I really don't know what it is...

[sssnake]

I meant if the barometric update will cap itself at a lower setting if you lower the max map. Sorry should have been more clear.

I guess I am not sure what you are asking... I did read a couple of posts on the baro update. They seem to focus on the E38s. I am on an E67 so I may not have that field. If I do I haven't seen it...

[GHuggins]

All naturally aspirated engines "as far as I know" will update the barometric pressure reading durring wot... HPT fixed this in their OS upgrades by making it to where they only update key on engine off in the software itself. This also only applies to platforms using the intake manifold air pressure sensor for it's baro referrence - E67's have the ability for external stand alone baro sensors... Basically if you don't have access to the OS upgrades and running something like an E38 with baro referrenced from the map, everytime you go wot, baro will go to it's max of 105kpa - since ALL base fueling is devised from the baro readout for altitude corrections, this can and "will" throw fueling off - more so if your at higher altitudes - baro is normally 90 where I tune at 3400 feet so you can imagine what going to below sea level will do to fuel calculations - it throws fueling off 15% for me!!!

SD tunes seem to take the brunt of this while MAF tunes will somewhat compensate for it - MAF may only be thrown off 2 to 4 percent vs. the 15 percent... Makes tuning sd setups very aggrevating...

[sssnake]

Thank you! That I understood. I have not been keeping an eye on baro as I always thought it was based on KOEO measurement right before cranking. Looking back through my logs I am seeing the baro change. Not just a WOT but at low RPM sometimes as well. I am right around sea level in my location so not a big deal except that I like to make a trip to NC to run the Dragon at least once a year. I thought the elevation change along Cherohala Skyway would cause issues (4000ft altitude change). But in looking at pressure vs altitude charts that looks to be only around 12KPa difference. I am seeing half that in my logs already just running around at roughly sea level. So something is wrong...

This makes me really want to go to another ECM and just ditch this one. The later CTS V ECMs have provision for IAT 2, won't have the issues I am seeing with prediction coefficients (at my boost level), and appear to have provision for a baro sensor as well. I just hate to have to redo the wiring harness (add the additional wiring) and connectors (lots of things to re pin). I wish I could just swap the OS on this thing (I don't think you can as the pin outs for the V1 and V2 ECMs are different).

Again thanks. One more thing to put in the to do list.

[GHuggins]

Did the max map limit it at all? Say if you changed it to 100 or 95 or something like this? Was really hoping for something there.

Yes the only way I found to tune SD setups is to stay out of boost for drive-ability and then tune boost only independently. Makes everything a pain.

[cc-rider]

Just so I'm clear...does the E38 2 bar custom OS have this baro update issue as well? Where it only updates baro when key on/off?

[GHuggins]

The OS upgrades fixed this problem by keeping it from updating during wot - in other words they only update the baro during key on - engine off... Just one of the reasons everyone would go to the OS upgrades...

[NotSure]

Sorry to dig up this old thread but I noticed that my baro reading updated from 98 kpa to 103kpa after a WOT pull (gen4 6.2L with a Whipple). I have the GM 3 bar MAP installed, and the max setting at 255 kpa, but it wouldn't matter anyways, looks like maybe it is capped at 103 as far as what it will allow to be recorded. I am seeing about 160 kpa in boost.


Anyone see any issues other than if I travel into some high elevation? There is no 2-bar OS upgrade for my controller.

[5ft24]

Sorry to dig up this old thread but I noticed that my baro reading updated from 98 kpa to 103kpa after a WOT pull (gen4 6.2L with a Whipple). I have the GM 3 bar MAP installed, and the max setting at 255 kpa, but it wouldn't matter anyways, looks like maybe it is capped at 103 as far as what it will allow to be recorded. I am seeing about 160 kpa in boost.


Anyone see any issues other than if I travel into some high elevation? There is no 2-bar OS upgrade for my controller.

Baro is the air pressure outside. you won't see your 160KPA boost on the Baro reading.

[NotSure]

Not 160 Kpa but it did change from 98 to 103 after a wot. So I think the 103 may be an internal cap on the baro update. No OS update available for me, not sure if I can do anything for it. Per calculations it is like going from 900 ft to -500 ft elevation. Wish I paid attention to this earlier, may explain why my fueling seems spot on at times and then it changes, mainly at idle and low load.

[griffincox]

I am seeing the same Baro update issue with my 2008 E67. Barometric pressure for me is typically 82 kPa here. As soon as the MAP goes above this 82 kPa the barometric pressure moves up and stays until a restart. Does anyone know what this is affecting in terms of airflow estimation? Can a barometric sensor be added to E67 easily? I don't see any way to enable in the calibration. Maybe by turning on "Supercharger fitted"?

[pannetron]

Also see this issue on my crate engine E67. I have a supercharger and have "Supercharger fitted" set to yes. My average barometric pressure at home is 75 kPa but my logs usually show a steady 90 kPa.