What would this be in HP Tuners Scanner?

[Cyclone Chris]

Any Idea what PID's this would be in HP Tuners?

CALC.AFR_LC11*GM.INJFLOW*GM.IBPW1*GM.DYNAIRTMP_DMA/SAE.MAP

I can't seem to find INJ FLOW RATE and DYN AIR TEMP (Blended temps for SD - ECT & IAT) on the LS2's

Thank you
Chris

[EC_Tune]

To get Calculated Cylinder Air. Some vehicles don't report Dynamic Cylinder Air so HPT calculates it for you.

[Cyclone Chris]

What about Injector Flow Rate on LS2 (E40) PCM's?? Can that parameter be scanned. The option is available on the LS1, but can't locate it on the LS2.

Thanks

[S2H]

that looks familiar.....cant put a finger on it though...
what does that calculate??

[EC_Tune]

CC - not there on the LS2. Bummer... So much data so rapidly but sooo much "missing" from the LS1 days... LOL

[Cyclone Chris]

that looks familiar.....cant put a finger on it though...
what does that calculate??

VE Calculations from what I was told. It comes from EFI Live, which has the capability to get DMA (Direct Memory Access) values.

There is no way to tune VE correct on the LS2 unless these PID's are available. I've been spending the last month or so tuning the VE, but noticed that there is a huge difference in AFR % Error from morning to afternoon scans.

50* Ambient temps yield -2% AFR%Error
75* Ambient temos yield +8% AFR%Error

I noticed as IAT & ECT rise, the fuel mixture goes lean and the colder it get th fuel goes rich.

We need the guys from support to chime in on this. Just wondering if reading the required PID's is even possible in HPT. I emailed Chris, but haven't heard back from him yet.

TIA
Chris B.

[PurplePiss]

Dude, welcome to my world. I've been trying to tune for 6 months. My car isn't radical and I probably don't even need to VE tune, but I thought it would be fun to try and wring everything out of the car possible and hopefully get a little more MPG out of it. We seem to be on the list after every possible manufacturer and DOD application is supported though. I could see if this computer was only used in the GTO, but its in so many other vehicles. I can't understand it. Simple things like transition filters would be useful for everyone but everytime a new version comes out I get excited and there's nothing in there for LS2's.

Wouldn't this all go away if we could just dump the LTFT's out of the computer? Can't that be done?

[Bill@HPTuners]

We seem to be on the list after every possible manufacturer and DOD application is supported though. I could see if this computer was only used in the GTO, but its in so many other vehicles. I can't understand it. Simple things like transition filters would be useful for everyone but everytime a new version comes out I get excited and there's nothing in there for LS2's.

In their defense they did just add 185 new parameters for 05 GTO's for 2.1.16 which is the last public version. You basically saying they haven't done anything for you is just wrong.

[redhardsupra]

just dumping more pids doesn't do diddly squat until we know what relationships govern them. no one ever said how to tune E40.

[EC_Tune]

RHS - The E40 has the same issue as the LSx series in regard to IAT offsets. GM needs to fix it.
BTW: The E38 has the same problem but inverse. Go figure...

[Cyclone Chris]

What if we minimized the span of error while VE tuning. Basically adding a filter in the AFR%Error Histo to only scan between IAT: 80-95*. Then make another for 95-110* and so forth.

I'm assuming we can create these filters and have multiple SD tunes depending on ambient temps/IAT temps. A problem I have is that when I get to a light my IAT's go up to 130* and once I start moving again they drop to ~85*.

[PurplePiss]

What if we minimized the span of error while VE tuning. Basically adding a filter in the AFR%Error Histo to only scan between IAT: 80-95*. Then make another for 95-110* and so forth.

I'm assuming we can create these filters and have multiple SD tunes depending on ambient temps/IAT temps. A problem I have is that when I get to a light my IAT's go up to 130* and once I start moving again they drop to ~85*.

Filter everything out below 16% TPS, ECT > 175 and < 185, IAT <90 or whatever. You could also filter out map below 20 I think, which would help filter out when you lift. TRANSITION FILTERS WOULD BE NICE.


The question is, if your VE tuning and you plan on turning the maf back on, what do you tune the VE to and at what ambient. Do I have to wait until 75* weather to tune, then turn the maf back on and let the car trim when it gets hotter and cooler? How does everyone else work this with a permanent SD tune? Are they constantly logging and adjusting for ambient or is it because the LS2 VE is different?

[redhardsupra]

the idea behind GMVE is that it is a normalized airmass table, describing airmass at given conditions. this way the real airmass gets calculated precisely for current conditions, courtesy of various sensors. this is also why the VE tuning with narrowed down conditions (that's what your filters do) works well, because you've 'normalized' your GMVE values by simply ignoring other conditions. the problem is that then it will only works for these conditions.

this is starting to get complicated folks :/

i'm doing experiments with Chris where we're trying to get that normalized GMVE table directly, without corrections. it's finals time for me, so i wont be able to publish it for a while, hopefully it will give us more time to test it out.

[Chris@HPTuners]

I have given the guys the PIDs they wanted for the E40

For everyone elses benefit the GM SD calcuation on the E40 is basically the same as the LS1.

g/cyl = VE * MAP / AirChargeTemp

where VE = gK/kPa

As you can see it follows the ideal gas laws where the pressure & temperature relationship is assumed linear. The usual error is the estimate air charge temp or IAT measurement error (the IAT sensor is not perfect and is subject to heat soak itself etc.)

There are a number of assumptions to this formula such as:
- everything is linear
- the IAT and MAP sensors are accurate
- ignores flow dynamics to the cylinder
- the loading of each cylinder is equal

These are big (huge) assumptions and exist for the LS1 as well.

The biggest issue is the estimated air charge temperature (or the manifold air temp as i named the PID). It is a predictive filter that account for heating of the air charge as it makes it way past the IAT sensor in the intake pipe or the MAF till it reaches the cylinder. If you were to model this in reality you would have a much more complex arrangement than just a simple first order filter. At minimum you would have heat transfer coefficients for each section of the intake path, after all some of it is plastic (manifold) and some is aluminum (heads,TB) and some is steel (TB, intake valve).

GM's assumption is that all the engine parts are at the same temperature (ECT) and that a single flowbased heat transfer coefficient (filter coefficient) will do the job. At that at the end the air temp is somewhere between IAT and ECT depending on the airflow going into the engine (for SD this airflow is calculated from the VE itself so the value you calculate feeds back to the IAT estimation...) Maybe it's okay if its calibrated correctly, maybe its just too simple.

I've never done the test to see what the dominating effect is on this...
- is it IAT heatsoak?
- is it poor calibration of the estimation filter?
- is it some other non-linear effect?
- is it some temperature dependance of the injectors, fuel or some other thing that causes the fuel to go leaner for higher IAT's. An easy test is to just log the dynamic cylinder airmass when in SD mode (eg. if you see a trend to lower numbers at higher IATs then it must the airflow related.)

I have seen heatsoak as an issue in s/c applications (with the IAT in the manifold on the boost side) before.

Chris...

[Cyclone Chris]

Yes... thanks Chris... we're experimenting with it. Results soon to come.

[S2H]

I have given the guys the PIDs they wanted for the E40

For everyone elses benefit the GM SD calcuation on the E40 is basically the same as the LS1.

g/cyl = VE * MAP / AirChargeTemp

where VE = gK/kPa

As you can see it follows the ideal gas laws where the pressure & temperature relationship is assumed linear. The usual error is the estimate air charge temp or IAT measurement error (the IAT sensor is not perfect and is subject to heat soak itself etc.)

There are a number of assumptions to this formula such as:
- everything is linear
- the IAT and MAP sensors are accurate
- ignores flow dynamics to the cylinder
- the loading of each cylinder is equal

These are big (huge) assumptions and exist for the LS1 as well.

The biggest issue is the estimated air charge temperature (or the manifold air temp as i named the PID). It is a predictive filter that account for heating of the air charge as it makes it way past the IAT sensor in the intake pipe or the MAF till it reaches the cylinder. If you were to model this in reality you would have a much more complex arrangement than just a simple first order filter. At minimum you would have heat transfer coefficients for each section of the intake path, after all some of it is plastic (manifold) and some is aluminum (heads,TB) and some is steel (TB, intake valve).

GM's assumption is that all the engine parts are at the same temperature (ECT) and that a single flowbased heat transfer coefficient (filter coefficient) will do the job. At that at the end the air temp is somewhere between IAT and ECT depending on the airflow going into the engine (for SD this airflow is calculated from the VE itself so the value you calculate feeds back to the IAT estimation...) Maybe it's okay if its calibrated correctly, maybe its just too simple.

I've never done the test to see what the dominating effect is on this...
- is it IAT heatsoak?
- is it poor calibration of the estimation filter?
- is it some other non-linear effect?
- is it some temperature dependance of the injectors, fuel or some other thing that causes the fuel to go leaner for higher IAT's. An easy test is to just log the dynamic cylinder airmass when in SD mode (eg. if you see a trend to lower numbers at higher IATs then it must the airflow related.)

I have seen heatsoak as an issue in s/c applications (with the IAT in the manifold on the boost side) before.

Chris...

for the LS1 its fixable in the IAT/ET bias balance...
amazingly the magical number is around 1.0(which happens to be an even blend of IAT/ECT as teh LS1 minimum is 0 and maximum is 2)...and slight variance for each car and each airflow...not always 1.0 exact...but its a great starting place and it takes small amounts to make the IAT/ECT blend behave properly in all temperatures...and makes for an incredible stability in fueling from day to day weather#1 to weather#2..whatever changes in the environment

the hest soak issue isnt so much an external heating issue as its just a general engine bay heat issue getting sucked through the intake....which is why the IAT/ECT bias works so well when set up better than stock...I say this from actually measuring the heat inside and outside of the intake thanks to some nice fancy probes from my dads work

I would assume since GM is still doing the same basic thing that it would work on the other vehicles with this same basic balance setup...
figure out what the middle is...start there..

you will have to add a bunch of air to the VE and MAF tables...cause it changes the calculation some....I saw about 10% added on to my VE on my LS1 camaro when I did this... but my actual fueling that came out of the Injectors and into the engine remained the same....it wont change the actual amount of fuel you need..it just fixes the calculation and makes it much more consistent

[PurplePiss]

I set my bias to 1 on my LS2 when I started a few months ago. I am seeing large swings IMO. 0 at 32* and -6 at 50*. What will it be during the summer? I can't have the car trimming that much. Why is this so damn difficult?

I turned the maf back on today just for grins. I knew my VE table was about -3% fat. I was seeing -6 to -8 on the maf histogram. So I stopped and redid the maf curve really quick with the copy paste multiply %. Rinsed and all of a sudden it was really really fat. -10's. The curve did go down when I pasted, meaning in my mind that I'm telling it there is less air so don't spray so much fuel. The opposite happened.

If the VE table is the middle of the road for airflow at say 70* on the ls2's, then they are counting on swings of -10 to +10 depending on the weather?

I'm about to put the stock VE, bias, and maf curve back in and scale the maf to force it where I want.

[Chris@HPTuners]

the thing is, both methods have measurement error, for the SD calculations its the IAT and the MAP sensor, for the MAF its the MAF itself. Each of these things can easily introduce 5-10% error. The MAF is no panacea either...

You have to remember the engine is a HIGHLY non-linear environment, there are fluid dynamics effects, wave dynamics, thermal effects and also turblence in the intake path and combustion chamber and supersonic shockwaves in the exhaust. In addition not all the combustion products in the cylinder actually exit on the exhaust stroke and just take up space on the next cycle. Furthermore, some of these gases go up into the intake path and contaminate the intake charge. The there's the fact that the fuel injected doesn't actually get a straight shot into the cylinder, it is fired at the intake valve where it evaporates off and into the cylinder in a certain way, so you can't even count on the fact that all the fuel you inject makes it into the cylinder, evaporation rate is obviously a temperature dependant effect.

If all these processes were well defined and "mathematically nice" there would be no need for closed loop feedback mechanisms (O2 sensors) to reduce the error. We could all just run open loop all day.

As one of my physics professors used to say, "The difference between a physics formula and an engineering formulae is around 5 pages and 5% if you know what you're doing." In regards to a mathematical description of an internal combustion engine the book isn't even finished yet becuase there are just so many departures from well behaved processes and so many individual processes themselves, additionally confused by years of folklore and myth.

Before HPT began i used to write some engine simulation software (among other things), fluid dynamic and acoustic intake modelling, cylinder chamber temperature and burn model, exhaust temperature, fluid dynamic and non-linear turbulent shockwave model etc. etc. and i can tell you that it used to run one engine cycle (4 cylinders) in around 20-30 secs on the fastest pentium cpu you could buy 4 years ago. By comparison the PCM has to work out some kind of answer to this stuff in real time (of course it actually has sensors to measure stuff that make things easier).

GM isn't gonna replace a $2 IAT sensor with a $200 sensor in a better place to gain 5% accuracy that very few care about.