Bink

#1- I've learned ALOT around here asking questions and more questions. It's a very helpful group. A GREAT bunch of guys.

#2 - I was not mad. I stated the current beliefs, here and now, on this board. FWIW- IFR is less global than MAF, I was trying to save you future headaches. Reread your posts.

#3 - I am Joel (Bink).

joel

87_ta

My bad, I ment Gameover for posting that skit about code.
It helped alot.
I never said these were not a good bunch of guys , everybody seems friendly mostly .

But I now see what influence VE has which comes as a big relief to me, and I am sure that you can agree with some things I have said concerning people scaling all load/kpa ranges of the VE. Even though high KPA (wot) areas are not referenced during PE or above 4000 RPM.
But it will be referenced if MAF fails. I think people should know that
Just trying to save an engine or two.
Just remember please that your PCM though far advanced was spawn from my ECM. I have had alot of experience scaling MAF tables and VE as I have had both in my car over the years.
Also agree that IFR is an easy change for "global" changes . - scaling the MAF tables properly would not.
I also do not think a MAF table should really need to be touched unless you have screens removed or tons of overlap, agreed about the headaches.
And Now I have found my answer on Primary fuel source.
Thanks far your help Bink (joel) , I am just trying to help a little on my own.
You should visit DYI-EFI pages , There is alot you can learn there from the guys who first began to hack before their ideas and work got pirated
Not to mention it started out as freeware, go figure.
See maybe we can actually help each other, Just speaking from experience.

Bink

Cool.

I've visited DYI- EFI before. Nice site. Alot I don't understand...and don't have the time to learn. I once considered learning more about LT1/OBD1 tuning - Camaroholic advised against it if I would not be using it. I took his advice.

Scaling the VE works very well, in the idle RPM range, for reducing pulsewidth with larger cams. It's been used by countless guys here.

My car runs open loop so the VE table is very important. Stock CI but bigger cam 0.570", 239/251, 106 LSA. Whole VE table was recalculated using NoGo's original VE equation. Before it ran like **** at idle and part throttle - now it has very nice manners. NoGo coached me through it (the tuning) - he is The MAN.

Some good tuning info can be found here: http://www.ls1tuning.com/iboard/

Anytime I can help let me know. Good Luck.
joel

87_ta

Thanks Bink,
I know the troubles of forced open loop with all that overlap purging so much raw air that o2 can't smell anything but air. My previous cam had 120 degrees total. I have since switched to much faster ramped solid with only 96 degrees total alowing me to return to closed loop. Kinda sux tuning blind huh.. I did not have the luxury of a VE calculator Just alot of plug reading and EGT readings.
During that time I was thinking of using TPS voltage output inplace of MAP sensor being they both range 0 - 5 volts and both are directly related to manifold pressure, That would have allowed much more usage of the whole VE table.

Thanks for the link, Ill check it out

Cal

iTrader: (1)

87 ta, I'm confused . . . did you come here to learn or to tell others how to do it? Anyway, what bink said is absolutely correct; you've got to forget your past tuning methods for a LS1; PCM works completely different. VE doesn't do what you think it does on an LS1. Keep in mind what happens inside the PCM is purely up to the people that wrote the PCM firmware; they may have their own definition of what the old familar parameters such as VE and PE should do.

You have two options: you can use the tried and true methods from this board; or you can re-invent the wheel develop your own methods based on your own ideas. The second method may be time consuming and expensive in terms of engine parts.

87_ta

If you can tell me something in the last 2 post I have said that is wrong or un true please do so
Now i'm confused , I already said I was here to learn....
What makes you so sure you may not have something to learn....
What make your methods soo tried and trued in just 4 years or less?
Did you know up until last year most people thought it was unacceptable to rescale the MAF tables of the 1987 165 ECM and it would be certain death....
They just accepted the fact you were either lean at idle or rich midrange and just did the best they could with inj. constants table and inj pw vs battery voltage tables. Now its the standard for people using that ECM?
Did you know that tunercat still adds tables for the 7730 /747 / 165 monthly?
Wow after 15 yrs + people are still finding new tricks......
Did you know that it was just found that in the 7730 it offsets the 02 swing reference points for the air pump and nobody knew?
Fact is did these things arise because people did not ask why or doubt things?
Do you really think this is all that new? IS volumetric effeciency still what it say? Are MAF tables still giving a certain Pulsewirth for A certain Grms/sec of air that passes through it?
In this thread you told a guy to scale his whole VE by 60%-80% , that to me sounds like a good way ruin a good investment especially not knowing what his fuel trim is..
Did you know that some of the fastest LT1/LS1's are running MAP only? Sorta makes our ECM's alot alike doesn't it? With the exception one is sequential and the other a batch fire.
Fact is its a device to give a certain Pulse width at a given load/RPM
Do you watch your pulse widths ? Thats what it all come down to.
I don't think I know everything about mine or your ECM, Do you really believe that you do?
Just trying to help and learn, again if you see something that is untrue let me know.

Cal

iTrader: (1)

87 ta, my apologies, I have a nasty habit of not noticing that there is another page of posts besides the one I'm on. The last posts are much better.

I'm not going to try and address all of those questions, but I'll say this much: the tuning method used on this board was not derived from trial and error or X years of experience; it came directly from a person that worked at GM.

87_ta

Understood Cal,
Actually alot of ours did too - I was never saying they were wrong.
Bink was trying to help me out think I was more new than I am by suggestion IFR tables, which is also very understandable and used widely.
The part I brought up about people scaling the whole ve under 1200 RPM or wherever was comming after reading some of the code. Stating VE above 4000 RPM or when above 84 KPA is not used.. "unless" there is a MAF failure which Is why I stated, If that should happen your gonna be really lean @ wot or above 4000 RPM. Which after installing a nice cam or heads those areas are going to be lean anyway because you have made the car More Volumetric effecient in the higher RPM.

PewterZ28

iTrader: (1)

I have a headache.

BAD XXX

Great discussion guys. I have been running very rich since the header/cam install, so I have been using the IFR table to lean it out, but I was loosing power in the process. After reading this post, I copied the LS6 VE table to enhance high rpm operation (it worked) and started to reduce the VE table at rpm's where I was running rich. If I went too far, the car would hesitate. The result is a car that runs great and no more black exhaust tips. I am still trying to fine tune the table, but modifying the VE table did the trick!

Bink

Here is gameover's post from the HP Tuners site:
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Mar 22nd, 2004, 8:52pm

HP Tuners Bulletin Board « Airmass Calculations (MAF & SD) »

Author Topic: Airmass Calculations (MAF & SD) (Read 210 times)

gameover
Administrator

Posts: 435
Airmass Calculations (MAF & SD)
« on: Mar 9th, 2004, 10:59am » Quote | Modify

--------------------------------------------------------------------------------
something i had been working on awhile back thought might be of interest...


LS1 VCM Main Airmass Calculation
=================================

A very important calculation the VCM must make to ensure correct fuel mixtures under all driving conditions is the dynamic airmass calculation. This is the main calculation the VCM uses to determine how much air it should use for the Base Fuel Calculation (Inj PW). The airmass calculation is not simple and uses various combo's of MAF and SD inputs depending on engine operating conditions such as current engine RPM. It may also make decisions based on whether the engine is in a steady load state (steady MAP) or unsteady load state (Unsteady MAP). Note, that these thresholds change with RPM and MAP. eg. at higher RPM or high MAP readings you have more leeway before the VCM decides that you have an Unsteady MAP condition. This unsteady MAP defintion is basically there to decide if a throttle transient has occured (or other) ie. the MAF input is known not to be accurate under these operating conditions.

Under normal conditions (ie. all sensors working properly) in the code i'm looking at it is like this:
(caveat: many of these thresholds may vary between code revs and vehicle type)


RPM > 4000
----------
trust MAF completely and ignore SD calcs (apart from MAF sanity checking purposes)

RPM < 4000
----------
if RPM < 2400 and MAP < 84 kPa then
Steady MAP threshold = 0.0 kPa
else
Steady MAP threshold = 0.8 kPa

If (SteadyMAP) then
Calculate MAFAirmass/SDAirmass ratio (used for Unsteady MAP operation)
Correction Airmass = MAF Airmass (filtered)
else
Correction Airmass = SD Airmass x MAF/SD Airmass Ratio (calculated during Steady MAP conditions)

Transient Corrected Airmass = previous Final Airmass + proportion of Correction Airmass

Final Airmass = fn(MAF Airflow, previous MAF Airflow, prev 3 MAP readings, prev 3 TPS readings,
Transient Corrected Airmass)


There are 9 coefficents to this filter (and a total of up to 16 diffent sets of coefficients depending on operating conditions). It is worth noting that the previous value is weighted heaviest followed by the 2 MAF terms, so MAF dominates IMHO).

There are also a number of checks at the end to make sure things do not exceed certain limits


To summarise:
1. High RPM behavior is totally based on MAF
2. Mid RPM behaviour has an allowance on Steady MAP behaviour before it switches to Unsteady MAP
3. Low RPM behaviour (where the bulk of the fuel cells are) is dictated by unsteady MAP behaviour that is still mostly dominated by the MAF input with small tweaking from SD)

If the VCM decides that a throttle transient has occured (unsteady MAP), the airflow incorporates a "correction" from the SD calculations. This value is the SD calulated airmass multiplied by the previous ratio of measured MAF airmass to calculated SD airmass (this normalises it, since you are worried about the transient deviation from MAF airmass only). The way i understand it is this, imagine you are cruising (MAP is steady), you have a decent vacuum in the manifold and you change the throttle position quickly. Air rushes into the manifold to service the change in air demands from the engine itself but also to try and fill the vacuum. The result is that the MAF reads higher than it should at that point in time (spikes). This is more pronounced at low RPM where the engine airflow is smaller and the relative proportion of extra airflow due to filling vacuum is higher, also the MAF is known to be more inaccurate at lower RPM and more non uniform airflow. IMHO, the SD correction is to account for filling and emptying of the manifold during throttle transients and also to smooth the MAF's spikyness at lower RPMs.

The bottom line is that if the engine is at a steady load state or operating at high RPM then the airflow is 100% based on the MAF once you get thru all the filters and calculations. And the SD calcs only get used for transients and smoothing lower speed operation.

At no stage does the MAF get ignored completely in these calcs (the dominating terms of the main filter calc are always MAF based).

An interesting point to note is that removing the MAF basically bypasses the whole system and directly sets the Final Airmass value to be the result of the SD lookup (it also disables things like knock learn and a few other nice things). Most have taken to calling this "Backup SD Mode" which is as good a name as any i guess and i meant to allow the engine to run with a failed MAF (although it is quite possible to tune usuing this mode (eg. HSV GTS 300kw comes factory this way). There is another way to disable the MAF system completely (ie. without setting the DTC's) and by tuning of the thresholds and other flags you can get a fully functional SD tune happening, the so called "True Speed Density Mode"... maybe more on that later...

Since i haven't had time to step this out in painstaking detail and i haven't yet qualified for my guru pin, please feel free to correct any errors that are in here. i'm sure there are some.. as things have been a little busy around here lately

gameover...

« Last Edit: Mar 9th, 2004, 11:05am by gameover » IP Logged

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moehorsepower

iTrader: (3)

I know this is an old thread but here is some data I recently discovered for LT1's anyway. Like Chris B said changing the VE tables all across the board does not affect A/F in anyway, only in the start up mode. I Lowered my VE tables all across from single digit numbers at the lower KPA and at the upper to low double digits i.e 12.0. This did not affect the WOT A/F at all. On a wide band o2 my A/F still remained constant. IT DID though cause starting problems, so I increased the VE at the 0-12 and this corrected the hard starts but that is about it.My problem was at idle and low rpm cruising my car was running very rich, The VE did not correct this, What I did is scaled the MAF by first 90% then another 10% and this cured the problem, I have not had it back on the Dyno to check the A/F but I am sure this will have an affect.Hopefully when the targer A/F is back in order the same symtoms will not return.......

TwoFast4Lv

iTrader: (8)

I also was one of the Guys that did VE testing on LT1s. I had same effects. This has always made me wonder if we were even looking at the right tables. Were they a secondary table? As mentioned we may not know for years.

I must admit Joes tunes are un-real to look at...and took out a local motor fast. Was the Owners fault. He had NO idea what Knock sounded like and beat the bearings right out of the car.

Waht is have found interesting after looking at hundreds of factory files is GM it self used the so called "band Aids" to tune there cars! MAF tables to lean out the car and offset tables to fine tune the VE.

I do believe the VE tables are key on ALL sets of code...or they would not be there.

As noted they over all effect can be a major impact or have no impact at all.

I Look at it this way. The MAF is one hell of a tuning tool. why get ridd of it

87. All those table they are finding I have been looking for! I knew they had to be there but Ken is usually less then interested in finding The transmission stuff I am looking for. There is SO much more to that silver box that runns our cars then meets the eye

moehorsepower

iTrader: (3)

Here is an update on what my results were. Again the VE tables DID NOT do anything for rich idle and low RPM driveability and of course scaling the entire MAF did affect the A/F at WOT. So this is what I did. I returned the VE back to stock, I did some data logging on at what RPM did the bucking stop. I then compared the Gms/Sec vs RPM vs mghz and map load, I went and change the MAF frequency at the appropriate parameters, Results.... NO more rich smoke at start up and smooth cruising at the lower RPM, TO ME, I would leave the VE alone and data log where your problems start and stop and adjust the maf at those points. All I can say is that it worked for me and my WOT A/F is back to where is should be...Happy Tuning

Bill Bowling

iTrader: (6)

Is ls1tuning still around?

Bill

Bink

I don't think so. I believe it was Jes' site and he shut it down. Not sure, though.

Cheers,
joel

Nine Ball

iTrader: (38)

TTT for new forum