FI Tuning - Using VE VS: MAF Calibration

[5_Liter_Eater]

I am just starting out. I'm nearly done with my ATI install and I have what I think is a good baseline tune to start from (IFR scaled for 42# injectors, timing tables adjusted for boost and PE values upped) and when I'm done with my install I had planned to tune the VE based on the LTFTs but a friend pointed out that VE tuning with a supercharger is impossible because the VE table's MAP values end at atmospheric which leaves only MAF calibration to be able to play with. Doesn't seem like a good idea to tune all <= atmospheric values with the VE and then any > atmospheric with MAF calibration. Seems like it would be better to choose one or the other.

Or am I thinking of it wrong? Will boost automatically put me in PE mode? The only factors I find for PE Enable are TPS and MAP which are both set pretty low (~19% TPS and 15 KPa MAP).

I thought I had a game plan and now I'm starting to think otherwise.

Now that I've rambled the question is: When tuning an FI setup is it better to tweak VE or MAF calibration?

[S2H]

YES!!!



LOL....I know people hate it when you answer that way sometimes..LOL

simply put think of PE Enable MAP as an arming switch saying that its ok to use PE
and think of theTPS as to fire and use it

you really need to tune the VE before you tune the MAF as the MAF is only a steady state thing...all throttle changes are done with the VE..
you cant tune the MAF until the VE is correct

I suggest using a wideband,
and you can set TPS to be higher than 19......
even just a small reduction(like 10%-20% lower than stock values)works well...
its up to you in the end on when you want PE to kick in

[5_Liter_Eater]

Well since the MAP enable for PE is only 15 KPa (stock value anyway, I know I could set this) it seems like there are many cells that would hardly ever get hit in non-PE mode since the PE enable MAP is rediculously low and the TPS enable is 19% from 2800 on up. The problem I see in tuning the VE table is there are cells that will never or rarely be hit, particularly in the higher MAP cells. So I guess this is where some smoothing is in order. By tuning the MAF calibration and using this spreadsheet <http://www.slowcar.net/shared/correctedmaf.xls> you redo the entire MAF curve based on the polynomial.

So my new question is; is using the VE table to tune closed loop any different on an FI application than NA? It really seems like using the VE table is better since the MAF calibration table should be based on a predetermined curve but it is not unreasonable to assume that the + LTFTs are because of incorrect MAF readings based on the new intake design. It is also not unreasonable to assume that the volumetric efficiency of the motor has increased with the addition of the blower.

VE or MAF? VE or MAF? Grrrr.... I would have thought this debate would have been settled by now. I have also seen posts indicating to change the IFR to get LTFTs in line but this seems to be an old scool approach. Really they are all interdependent so I don't know how much it matters which table you use...

[S2H]

Well since the MAP enable for PE is only 15 KPa (stock value anyway, I know I could set this) it seems like there are many cells that would hardly ever get hit in non-PE mode since the PE enable MAP is rediculously low and the TPS enable is 19% from 2800 on up. The problem I see in tuning the VE table is there are cells that will never or rarely be hit, particularly in the higher MAP cells. So I guess this is where some smoothing is in order. By tuning the MAF calibration and using this spreadsheet <http://www.slowcar.net/shared/correctedmaf.xls> you redo the entire MAF curve based on the polynomial.

So my new question is; is using the VE table to tune closed loop any different on an FI application than NA? It really seems like using the VE table is better since the MAF calibration table should be based on a predetermined curve but it is not unreasonable to assume that the + LTFTs are because of incorrect MAF readings based on the new intake design. It is also not unreasonable to assume that the volumetric efficiency of the motor has increased with the addition of the blower.

VE or MAF? VE or MAF? Grrrr.... I would have thought this debate would have been settled by now. I have also seen posts indicating to change the IFR to get LTFTs in line but this seems to be an old scool approach. Really they are all interdependent so I don't know how much it matters which table you use...

again...the point you have missed is that you have to do VE before MAF.....This point was settled by people who can tell you exactly how the PCM works...
the MAF is only accrate and is only used in steady state conditions.....at all RPM below 4000 the VE is used for throttle transitions...

this thread...in the stickies of this forum..and even in this section
talks about what the VE does

http://www.hptuners.com/forum/showthread.php?t=687

at a minimum you must tune the VE to atleast 4000 rpm if you plan on using the MAF.

and even more suggested is a 2 bar MAP and a 2bar VCM enhancement for this car and run an SD tune.

IF you tune the MAF first...your fueling will be off because of how the MAF works..and its not 100% MAF or 100% VE..... Its a blend....
the only time the MAF is 100% used on our v8 vehicles is over 4000rpm

if you want to risk it by just doing the MAF first....dont come crying when you fry a piston because of being lean

and you dont need an excel spread sheet with HPT 2.0
all you need is a histogram in the scanner(easy to set up)..and you can use AFR error % to get the MAF corrected

[5_Liter_Eater]

Am I confusing PE with open loop? I know when logging the LTFT's you're supposed to simulate all types of driving while staying out of PE but PE kicks in at 19% TPS. I don't get how to log data to 4000 RPM @ <19% TPS.

I think I am over thinking things. My original plan was to log LTFTs and cut and paste the positive portions of the histogram (special, multiply by %) into the primary VE, rinse, repeat until LTFTs are ~-5 to 0. Then begin WOT tuning via PE table tweaking, all the while looking for KR. Is this plan sound?

[BLOWNZO6]

again...the point you have missed is that you have to do VE before MAF.....This point was settled by people who can tell you exactly how the PCM works...
the MAF is only accrate and is only used in steady state conditions.....at all RPM below 4000 the VE is used for throttle transitions...

this thread...in the stickies of this forum..and even in this section
talks about what the VE does

http://www.hptuners.com/forum/showthread.php?t=687

at a minimum you must tune the VE to atleast 4000 rpm if you plan on using the MAF.

and even more suggested is a 2 bar MAP and a 2bar VCM enhancement for this car and run an SD tune.

IF you tune the MAF first...your fueling will be off because of how the MAF works..and its not 100% MAF or 100% VE..... Its a blend....
the only time the MAF is 100% used on our v8 vehicles is over 4000rpm

if you want to risk it by just doing the MAF first....dont come crying when you fry a piston because of being lean

and you dont need an excel spread sheet with HPT 2.0
all you need is a histogram in the scanner(easy to set up)..and you can use AFR error % to get the MAF corrected

I am not sure exactly what you are getting at with this. Your are obviously a well informed tuner, I have been reading your posts for some time.

I can tell you from experience that when I installed my kit and tuned the car... the kit which the originator now has... I NEVER touched the VE table. I ONLY scaled the MAF using the LTFT's. I am not sure why you would think you would fry a piston? My car has been driven this way for more than a year, 14 months to be exact and made 575/475 tuned this way. I sent him my BIN file for a reference while tuning and the VE table is COMPLETELY stock in it.

I trust that you are correct with what you are saying about the MAF and I agree that tuning with the VE is really the best way to do it.

That being said... I think you are incorrect to when you say that you have to tune the VE to 4000 if you are going to keep the MAF as the ONLY way. Again.. I know you know what you are doing, but I am questioning it as the ONLY method out there.

My car ran fine with his exact kit for 14 months...
1. All LTFT's were between -1 and -6
2. All AFR were below 11.8 for WOT

I never had a single issue from it with respect to driveability, etc. although admittedly I only put about 3500 miles per year on the Vette.

Thanks for listening.

[S2H]

think of it this way....
I probably shouldnt say fry a piston..(but I did have a buddy that did fry a piston because of being way lean on a SC car...).but Only tuning the MAF will lead to inconsistent fueling and usually some very bad fueling in spots.

IF you tune the VE with LTFT you basically only need to go to 4000 RPM because of how the PCM works.

tuning the VE gets proper part throttle fueling and any throttle changes that happen faster than the PCM's set condition for steady state.

IF you tune the VE with a wideband you can tune the entire VE with PE enabled and use it just like normal....
with LTFT you can still leave PE Enabled and not worry if you hit it or not..just filter it out using the filter functions in the scanner [pid.(fuel air multiplier)]=1

I dont know if the PID # is the same on vettes and other vehicles so I just wrote what to use...
doing this will make it so only data that is not PE will show up in the histogram

without a wideband..PE is a shot in the dark.
with a wideband... you set PE to the AFR you desire(example being 1.1704 = 12.5:1) and tune the VE and MAF with PE enabled and just use AFR Error%...extyremely accurate..and guarantees correct fueling for all throttle conditions including WOT
when you tune the MAF with a wideband it is also much better and more accurate(its really amazing how far off most GM calibrations are..even on completely stock vehicles)
same basic principal aplies with LTFT on MAF...just filter it out so you dont get PE data in there.

shooting for 0~-5 is a little bit wide for my tastes...
My car is 0~-2 all the time and I shoot for that on any vehicle I tune, including SC vehicles

and yes..cut paste multiply by %...and sometimes as you get closer to the 0 mark, multipky by % - half

[jimmyblue]

I think you should estimate the VE "trajectory"
even if you don't have the means to tune it in
scientifically. There's no reason to let bad data
sit in the table.

If you look at the VE table, in general the change
w/ the MAP axis is fairly small and consistent, and
the change w/ RPM is the big driver. So if you can
bed in lower-MAP VE rows all the way up you can
extrapolate pretty well the higher-MAP ones, that
you would not want to be in unenriched.

If you suppress PE and decrease timing you will be
able to push further into the MAP range unenriched,
so as to get feedback data for VE tweaking. This is
in fact the only way I've ever done it, keeping the
car open loop and unenriched and with some spark
taken out, and working simply from O2 readings as
high/low indicator.

There are more sophisticated methods people use
now, but you don't -have- to be fancy if you are
more comfortble with cut-and-try, smooth-by-eye
approaches.

[SRPerformance]

I have not tried this on a FI car but this is how I would start.

Read and follow 'speed density' in the VCM help file (FOFF667)

Decide your Open and PE AFR first!

If you dont have wideband or 2bar, perhaps you should stop here!

If you do not have Wideband dont use 'Data Logging' and 'Update HPT file' therefore do your VE table with LTFT, dont worry about PE at the moment. If you get boost and dont have the 2bar the last VE will be used.
When finished VE to 4000rpm then do 'Dialing in the MAF'.

At this point you have been tunning with o2 sensor that cannot really measure past Stoich (AFR 14.7) and you will be getting boost so you will be off your VE table as well

Tune the MAF up to 4000rpm. Now you will need to go put your car on the dyno: do part throttle calibrations above 4000rpm first than WOT, some people adjust PE but that is wrong!

VCM Suite Help

Setting Everything Back to Closed Loop-MAF

Open your Stock file
Copy & paste your new, verified, VE primary & secondary, PE, & MAF tables in.
Save & load the new file

Only changes to this is set your Open, PE AFR as well.

No short cuts, I would use wideband and 2bar.

[S2H]

I have not tried this on a FI car but this is how I would start.

Read and follow 'speed density' in the VCM help file (FOFF667)

Decide your Open and PE AFR first!

If you dont have wideband or 2bar, perhaps you should stop here!

If you do not have Wideband dont use 'Data Logging' and 'Update HPT file' therefore do your VE table with LTFT, dont worry about PE at the moment. If you get boost and dont have the 2bar the last VE will be used.
When finished VE to 4000rpm then do 'Dialing in the MAF'.

At this point you have been tunning with o2 sensor that cannot really measure past Stoich (AFR 14.7) and you will be getting boost so you will be off your VE table as well

Tune the MAF up to 4000rpm. Now you will need to go put your car on the dyno: do part throttle calibrations above 4000rpm first than WOT, some people adjust PE but that is wrong!



Only changes to this is set your Open, PE AFR as well.

No short cuts, I would use wideband and 2bar.

remember tuning your open loop to a value say of 13:1AFR and then setting it back to stock values or to 14.63:1 after will result in fueling being off....
its supposed to be accurate...but IF you tune it different than you drive it...it will be wrong...many have tried it and found out for them selves that you must set it up and tune it exactly as you plan on driving it

[WS6FirebirdTA00]

good thread, gonna be doing my friends with a blower soon so...subscribing

[SRPerformance]

remember tuning your open loop to a value say of 13:1AFR and then setting it back to stock values or to 14.63:1 after will result in fueling being off....
its supposed to be accurate...but IF you tune it different than you drive it...it will be wrong...many have tried it and found out for them selves that you must set it up and tune it exactly as you plan on driving it

Point taken!

The "Speed Density" tune sets Open to 1.0 (14.7) and then reverts back to what was in the original tune. I think Open should be set back to 1.0 or what ever AFR you tuned it too.

[S2H]

I have been working on figuring out an OLFA tuning guide....using a wideband...
when we tune to 1.0(14.63) we do it at all maps...
if you look at the stcok table its not the same from 15kpa up to 105kpa...instead its a bunch of different values...
I have found that by tuning all maps to 1.0 that you can generically use only 1 value for all maps in a temp range..you then just have to work on temperature only...and I have sucessfully done 3 cars with my method...now I just need to have time to make an actual writeup for the public...
but right now HPT has me working on Full Demo's for them..so my time is devoted to paying customers first(I'm building an actual Flash Demo for the Editor and scanner..... and several "how to use this" things for them )

[chrisj6]

sweet, thatll be nice when those get developed. I have a ? though. Wouldnt stoich be 14.681 technically, i see alot of people saying 14.63, but supposedly stoich is 14.7, which hpt takes as 14.681.

Chris

[S2H]

In evry vehicle I have scanned or tuned it has been 14.62857 in the PCM
on diesel it may require slightly different amounts
different gasses burn differently and require a diferent stoich value to properly achieve what stoich is chemically

[SideStep]

I think you should estimate the VE "trajectory"
even if you don't have the means to tune it in
scientifically. There's no reason to let bad data
sit in the table...

I agree with this method of thinking... After pulling hundreds and hundreds of logs I developed a "seat of my pants" idea about where things were headed on my VE table (when in SD) and made educated guess-ta-mates for some values over 4400rpm... A few weeks later I found a lot of empty road and put it to the test and was very surprised how close (5-7) my "guesses" were... I would add that it took me a long time to develop this... MANY hours of logging your vehicle will get you the exposure you need….

[5_Liter_Eater]

Well, now that I have my VE tuned in good and I re-enabled the MAF I realize that my question is moot and soundengineer was right from the get go. Once you re-enable the MAF the fuel trims go screwy again. So a good tune (that will not remain SD) would have the VE dialed in to 4000 and then the MAF recalibrated which I will tackle as soon as I fix the leak my P1 has developed. Then, the oral sex (Holy Grail), I mean the WOT dyno tuning.

I'm not sure the significance of filtering out PE enabled cells. They should lock at whatever the FT was for that cell when not in PE right? I have had my best luck dialing in the VE table by adding up the LTFTs and STFTs for every logged cell and doing a paste special, add, without filtering any PE cells out.

[SRPerformance]

Well, now that I have my VE tuned in good and I re-enabled the MAF I realize that my question is moot and soundengineer was right from the get go. Once you re-enable the MAF the fuel trims go screwy again. So a good tune (that will not remain SD) would have the VE dialed in to 4000 and then the MAF recalibrated which I will tackle as soon as I fix the leak my P1 has developed. Then, the oral sex (Holy Grail), I mean the WOT dyno tuning.

I'm not sure the significance of filtering out PE enabled cells. They should lock at whatever the FT was for that cell when not in PE right? I have had my best luck dialing in the VE table by adding up the LTFTs and STFTs for every logged cell and doing a paste special, add, without filtering any PE cells out.

As well as reading your other thread:

http://www.hptuners.com/forum/showthread.php?t=4421

have you got the WB yet? If not only tune your MAF up to 4000rpm till you get it to the dyno. Otherwise if you have wideband than use 'MAF - AFR error.hst'

You will need to set your VE table for WOT tuning, back to SD again(I can see why a lot of people never go back to MAF, esp if you cannot calibrate it for FI).

[5_Liter_Eater]

I don't have the wideband yet. I need to re-enable the MAF to get a wide range of samples. In SD mode I cannot boost at all or the car shuts down when I run off the MAP table. So I can't use redhardsupras shreadsheet because I would never get any MAF samples in the upper Hz range. That is, unless I can use that spreadsheet with the MAF enabled. I'm not really sure how it's using dynamic airflow to generate the new curve. So I'm going to re-enable the MAF and drive around like I have been while tuning the VE and plug the data into this spreadsheet http://www.slowcar.net/shared/correctedmaf.xls until the LTFTs fall into line. Then I will be ready to WB on the dyno.

[SRPerformance]

So I can't use redhardsupras shreadsheet because I would never get any MAF samples in the upper Hz range. That is, unless I can use that spreadsheet with the MAF enabled.

Yes you scan the values with the MAF enabled.
Then plug them into redhardsupra xls.
Then update you tune and flash the tune back in.

See what values you get to 4000rpm, g/sec if its going of the scale greater than 512.......

but I'm pretty sure you will run out of MAF before you get too far into it...
not that you will hit 14000hz...but you will run out of airflow amounts...
table only goes to 512g/sec max....

Which will mean you need 2 bar and run in SD mode only.