ChrisB

Kevin - The closed loop/open loop explanation definitely wasn't aimed at you, just at this post in general - if you look up over some of the previous post there did seem to be some confusion.

I am actually out of the country now for the next few months, and don't have a car handy. If anyone here on this thread has the time, it would be interesting to see what the effect is. You could multiply the VE table by 300 from 2000rpm on up (to avoid starting issues). Log the RPM, TPS, MAF Raw, Maf Flow (G/sec), MAP, Avg BPW bank 1, Avg BPW bank 2, Spark Advance, Calculated Load, L-trims and S-trims. If a decent amount of logging is done this should be able to show any difference objectively.

Honestly I have tried this out on a LS1, though I will still be suprised if there is a difference (there definitely isn't on LT1's).

Bink

Hey Guys - not trying to flame or be a smart a** . Everything I've read says a MAF can't respond quickly to Pressure deltas. If that is the case ,then what does the PCM use for rapid Kpa changes (deltas) ??? Newbie here ...trying to understand function. Thanks! Great discussion.
joel(Bink)

z28man

ok, i finally messed with the tuning last night. no luck! i changed my ve table from 400-1800 rpm and mult by 60%, then 70%, then 80%, then 108%. all of these setting gave me a miss/hesitation when i hit the throttle at idle. so i changed it back to stock. i also mult my maf table by 107% and this seemed to help the miss/hesitation. auto tapped and my iac's are around 55 to 45 & my lt's are around 3 to 4 when crusing around. with the only changing the maf by 107%.

Cal

iTrader: (1)

z28man, you aren't supposed to change the VE above 1200 rpm to address startup and idle.

Ed Blown Vert

iTrader: (2)

Well, I seem to agree. When I modified my VE table to lean-out my idle in open-loop (cold-start)when I lowered my IFR. The car runs rough even in close-loop (hot-start).

If this is the case, how would I lean out the idle in open-loop (cold-start)?

ChrisB

If someone who is experiencing this can log the parameters before and after a run then perhaps we could figure what what change is being made (if any)?

NicD

iTrader: (7)

This I fully agree with.

Cal

iTrader: (1)

Kevin, I can verify this. I just tried scaling my VE table by 60%. The car had no stumbling or hesitation problems before, but it sure does now! And this is in closed loop as shown by EFILive5. I think I'll try 80% next or just put it back to the stock setting.

Joe Overton

VE isnt ignored its the base fuel map ..any changes to the VE are permanent ones,hence relearn wont affect it...MAF,pe (map enrichment) tps and o2 correction etc are only variables added or subtracted from the VE table...not to discredit some of the tuners out there..but if added/subtracting fuel through maf,PE,or i seen even some use injector offsets is whats considered tuning, it isnt..Its a bandaid for a problem in the VE table itself....being its a flash only and you cant tune real time..need to pinpoint the area kpa(load,map) and rpm area and adjust those numbers only in that area since the numbers around the certain problem cell its in will be used also to derive what the finally outcome will be..

Cal

iTrader: (1)

Thanks Joe, that was a very useful comment. Is there anywhere I could get a list of what are the permanent parmeters and what's not? I assume the main IFR table is another permanent parameter that does not require a relearn? Also, what is the "Crank VE" table for?

Joe Overton

crank ve is the pulse width added to VE used to start the vehichle there will most likely be a different requirement for what the engine temp is at...warm up enrichment is % of fuel added to the VE accompanied by a decy rate up to a certain operating temp or number of revs...

Cal

iTrader: (1)

So is Crank VE the table people really should be changing to address hot startup problems rather than the Main VE table? I think Main VE is the one everyone is using for this.

Bink

Cal- Ken Kelly addressed Crank VE a while back .He said essentially what Joe says.Only used during cranking.
joel (Bink)

Bink

Joe - this sounds like "Speed Density" Tuning. From what I've gathered here, and on the LS1 Edit list and archives , we can't use VE tables for tuning with a MAF- Based system . LS1 is MAF- Based. No argument here -just trying to understand.BTW your "bandaid" comment was right on the money. It seems like we're missing a huge part of the overall equation (Rosetta Stone????. Hell, I can't even get the airflow (gms/sec) tables to jibe, mathematically, with various parameters.
joel(Bink)

Joe Overton

Well to clarify a lil I've tuned 3 different ls1's with ls1edit and all the tuning was done in the VE tables and timing 1 in particular recently being larry01ss from Va. maybe you know of maybe not, but he dynoed 435 rwhp cam /heads on TEA's dyno before he ran at bowling green... a/f was almost dead on all the way across the board ...I knew there was disbelief about what VE truly is and the reason I posted here.. I'd love to see a ls1 run with just MAF and no VE that would be a trick.. what is speed density?,,,,load versus rpm scaled with a pulse width for a particular cell at a certain rpm...so we go to MAF this aids in calculating the airflow to arrive at actual airflow entering the engine ..hence MAF compliments a speed density fuel map or VE in laymans terms..by usuin multipliers to cover transitions in sudden airflow changes and more accurately determining total airflow.PE also covers transitions but uses change in kpa or load to cover light load transitions in fueling....basically every other sensor revolves around the VE table...the car will run with just VE,but it wont run with just MAF...

Freak

so, in otherwords, are you saying "dont screw with the VE tables if you dont know what you are doing"?

Or is it OK to lower them to deal with the hot start problem?

I have a hesitation at 2000 RPM with light throttle after messin with VE, which is why I have been paying attention to this post, but I only edited up to 1200RPM, so Im not sure that its the VE table. Is there some way the 2000 RPM area could be affected anyway?

Joe Overton

Freak it shouldnt if you didnt edit in that area that you know of.My guess your stumble maybe came from another table maybe you've changed.....as for the first question NO!! you shouldnt unless you have some idea of what your doing....I almost feel bad posting now,I dont want to see bunch of guys crap shooting with there VE tables thnking they have a handle on it.Thats not my intention I just wanted to clarify what the VE table is.Which is the "heart" in the fueling...changes in MAF,PE air temp or any offsetting variable is doing nothin more than adding/subtracting fuel or covering a hole in the VE table itself.. does it revert back to s/d? yeah kinda just think as MAF as another variable thrown into the mix..can ls1 ditch ther MAF all together and run s/d ? most certainly...

ChrisB

In a true MAF based system, VE isn't needed at all (in MAF mode - again, it has nothing to do with open or closed loop). LT1's are like this. Setting the VE to 0 or 100, etc. across the board makes no difference.

Judging by the comments above, it does sound like the VE is used even in MAF mode, making the LS1 some sort of hybrid system. (*If* it works better though, who cares).

The questions then become

1) How is the VE utilized - is it effecting fueling only, or is there some change on timing.

2) Does it apply to transitional fueling, or steady state fueling, or both?

3) How are the numbers actually used? (The numbers in LS1 edit don't mean anything in and of them selves in any classic VE sense) - are they working like an accelerator pump shot.

4) If different modes are causing VE referencing, what are the parameters for these (e.g. is it a TPS threshold, operating all the time, etc).

I am still suprised that they seem to be referenced at times other than cranking, but if they are (as it sounds like), it will definitely be intersting to find out why, and what they are effecting. (The log files mentioned above would go a long way towards that Since everyone seems to have tried it does anyone have any logs of those tests?)

Joe Overton

chris heres a question back at you maybe it helped you understand better without answering all the questions..looking at your MAF table in edit ...how is it comin up with a pulse width? think about it how is it going to be the same amount of airflow at the many differet throttle angles and load at 2000 rpm or any rpm for that matter..the table only has 1 entry for every certain rpm..it has to have a lookup table for map/load to derive at a pulsewidth for steady state .. if the MAF was the all tell tale of fueling then PE wouldnt even be needed in way...PE acts as a fuel adder also for map changes ...to smooth transition if you will..now hypothetically speaking if the throttle angle was 100% all the time..i can see the maf table being linear to rpm..but knowing this is outrageous for me even saying this..its a good example to maybe help someone understand...I do know however changes in VE does affect fueling in closed loop..being ls1edit is a factory ecm tuning tool theres alot of tables that are not to be gotten to...unless the cars I done recently just all of a sudden fixed drivabiltiy problems steady state driving without adjusting nothin but VE..I'd say the VE is the lookup table for the MAF... or atleast has some function as far as fueling load vs rpm..wish i could explain it better but this the best i can do....

Joe Overton

oh and to add one other note VE also affects lt1 not just with lt1 edit but tunercat as well.. just tuned a cam heads lt1 car made 402rwhp on stock tuning with offsets for 30# inj. and then made 452 rwhp by the final pull ..same tuning procedure only adjusted VE/timing... if anything maybe this will open some uncharted waters for you guys..but as I said before I just hate to see someone just go into VE and go the wrong way with something...