First off i will admit as far as ezpert in this field goes , im not :-( i wish i was though :-)

I have one question i would like to ask all here who have managed to get their current vehicle runnning/driving/idling decent.............

I do understand the arguement stated many times by grumpy that u should set the inj size as close as humanly possible to what the actual inj's size is (#). (im running 24#svo at 48psi)

their are many merits to this which he regularly mentions, cold start enrichment, power enrich, tip in, etc (and i may be wrong in mentioning some of these but please let it be for the sake of the questions contained herein) and a host of other functions i havent even managed to begin to understand yet...

in my particular combination(lt4 hotcammed, vortec headed, headers, converter(everything ported out to some degree) 350, 730ecm) I ran into the simple problem of running the numbers in my VE tables on TC over 100, which automatically knocks them down into the upper 90's usually.... at this point i was forced to change the inj constant and as of current prom version im clipping mostly mid 80's and a few upper 80's on my ve table ..

But i have all the small issues i am slowly dialing out(or trying to) the little off idle stumble, the acceleration enrichment. Whether any of this remained the same had i been able to run the correct inj size i do not know..

Im trying to work out a post that can hopefully help myself and others to better understand the consequences involved when having to stray from the "correct" inj sizing due to ve table or other factors and what the trouble areas are.. (and yes im working on this and have the .bin to prove it)... ive printed somewhere in the neighborhood of 1200pages or roughly thereabouts on attempting to fully understand each tc table (code and hac i cannot read yet) and then work it thru once im done

So anyone willing to share their ideas that have proven useful or stumbling blocks u have found that i had not mentioned or not encountered yet let me know

PS anytakers who can post my bin so the big guys can check out my madness?

thanks for a hopefully sticky post eventually(hoping)
Jeremy

 

Jeremy,

You should try to stay close to the real value regarding the injector flow. However, it is a little more complicated than just plugging in 24lb/hr for 24lb SVO injectors at 48psi. You must calculate the new flow at the pressure you are running as compared to the pressure that the injectors were rated. The new flow for your situation is close to 27.5 lb/hr. Deviating from this real true flow rating is OK in my book as long as you don't stray too far. I like to stay within 5%. Why? Honestly - the only reason is because I have found that this works very well. You want to try to achieve a VE curve that closely approximates the real Volumetric Efficiency of the engine (for SD cars). If the injector constant strays too far then the numerical VE numbers will be wrong (not that it matters that much).

Most people tend to start changing the injector constant without REALLY examining their BLMs across all RPMs and all loads ... and without calculating / using the REAL flow rating for the injectors. You need to also make sure the car is in a good state of tune so that you can rely on the BLMs. Fairly new O2 sensor, good plugs, wires, cap/rotor, etc. In my experience - if the car is in a good state of tune and you use the correct flow rating, cylinder size, etc. then the VE tables will not max out. They will approach the mid 90's or so.

Tim

 

I understand that traxion and sized my inj constant as near as i could while still maintaining correction factord in the VE table on TC under 100... depending on where the fuel curve was on the ve i was encountering several values off over 100% and was forced to richen things overall thru the inj. constant change to a point in which my previous 100 or more numbers in the VE table are now in the mid to low 90's range and i can account for needed tuning changes without exceeding 100 in the VE tables.....

i am trying to keep the IC as close as possible to tuning requirements and keep values max in the lower 90's , down the lines of the stock fueling tables

thanks for the 2 cents
jeremy

 

i have the same prob........ when i bought the ford racing 30's out of summit i didn't know the psi rating was different....... i put 31.5 for the psi difference in my inj constant.... hopefully that change alone will let me get some miles on her......... maybe not...... good luck on tuining..... it's obvious you have alot more understanding than i do......

i just can't get a straight awnser from no one here on where to start tuning more.......

 

You are talking about the values listed for 100kPa correct? Those are the values that will have the greatest VE. My question is:
How did you know that you needed to increase the values to over 100%.
The answer to that question will force the real answers to the question at hand.

Tim

 

You want to start with a 33.0 lb/hr constant. Then tune the VE tables (if you have SD) according to the sticky article above.

Tim

 

Actually i was referring to the actual table entries in the VE table on TC , as far as i know of and can tell u are limited to a number that is under 100 and hitting 100 usually automatically forced me down to the upper 90's when i jclosed and reopened it. this was turning off my PE or limiting it to 75% or so throttle in what im figuring to be my peak torque range and then i adjusted my IC richer and went back and retuned to accomodate...

hoping u follow what im trying to say
and thanks again
jeremy

 

Again...

How did you know that you needed to increase the values to over 100%?

What I am trying to get at is this ...
The values for the 100kPa vs. ALL RPMs is a value that should yield 14.7 AFR in closed loop. So - how did you determine that you needed a value greater than 100kPa? Did you lock out PE mode and drive up a rediculously steep hill? Did you apply the brakes while applying the gas pedal to create an artificial 100kPa load?

I'm just trying to figure out why you think you need 100kPa values greater than 100%.

Tim

 

i dont know how he did it but if i need to figure out if the VE tables are coming up short i usually lock all the PE stuff at 0 or 14.7:1. if im lean and next to 100% ve then i know that the injector is to small or the IC need to come down to richen it up a bit. unfortunately injector flow isnt perfectly linear at longer pw it may actaully flow more/less fuel then expected. tis is the only time i mess with the injector constant or bump the FP a bit.

 

i think we're on the same page now, just not on the same line :-)
lol

i think funstick is getting what im trying to say is when i moved my tuning efforts into my peak torque range(going by best estimates ,cam, etc) i had several values that when accounted for in the VE table of TC that would put me over the limit , ie .. over 100 in the stock VE tables , which it will not let me do...this was with a basically tuned VE from idle to about 2400...i had to pull tons of fuel from the lower kpa's/rpm as u could imagine...it was when i stepped into attempting to tune the 2400+ range and mostly in the 3k+ range(maybe all their ) that i encountered values that would need to be in excess of 100 in the VE tables on TC to correct them (was running stock inj at this time) @ 22.1 IC w/ 48psi fp....


like i said what i did, after the engine blew(no, not detonation, heads incorrectly machined grrrr) was replacing the inj for 24# ford which i know are flowed at a lower psi than gm equiv.

lowering the IC was the only way i could find to make the VE tuneable thru all rpm/load ranges...............

i've done enuff of this now(working on 4 tpi setups all sd, auto and stick) that i know i wont claim to be an expert whatsoever..
just wondering what tables incur the largest penalties when your forced to lower/raise the IC due to the VE curve....got the basics down just trying to discover what else im missing

got 3 binders full of the hac and articles from here and diy-efi...i end up researching what changes i think(educated guess) and from scanner data...

easiest way to say it : When forced to lowerr the IC to cover the VE tables when tuning, what are the major after effects and what tables are most affected by this?

thanks, hope that gets us on the same line
jeremy
PS will post my .bin up later or t'row so u can take a look at my madness personally :-)
bye for now

 

im not so sure that fudging the injector constant is really so harmful. as its my understadning that the PE AE and OL tables are all derived from the VE% becuase its assumed to be 14.7 at any all load ranges represented in the tables. so as long as the VE table actually represents 14.7 then all your other adders should be fine. this is speculation on my end cuase i have not had time to read the $8d hac and go throught the calibration summurary to reflect and understand it all. however for good sd reading download the turbo4 pdf form the diy-efi website in the incoming are and read thru it. not everything will apply but it opens up ones eyes to the way it calculates fueling etc.

well i put in my 2cents peace out.

 

but isn't that what you said not to do is lie about the sizing?

i have 30lb ford racing injectors rated at 38psi... the psi difference between gm will equate to a 1.5lb change, so at 43psi i will actually have a 31.5lbhr injector...... lying and saying 33 will be leaning things out a little and i don't want to chance it on a new 5000$ buck motor.... and i have a arap maf car........ which compliates things more....... i don't mean to be an *** but as you can see i have a long tuning road ahead of me.....

 

sweet funstick :-) thanks for pointing out the turbo4.pdf to me ....due to my wondeful eyes computer monitors give me headaches(swear to *** been that way since i can remem) especially the busier sites lol i grunt everytime i go hunting at dyi-efi lol .but tons of info packed in their just takes a loooooooooooong time to wade thru it all . checking out that summary/hac/documentary? there looks to be some amazing info in there on how all the tables interpolate with each other....gonna print that out at work t'row(not wasting my paper and toner) :-)

thanks for the inputs

just for giggles and i did a rough count of my actual pages of info sorted and numbered in binders with the turbo4.pdf /8D hac/and diy-efi and prom board articles i think im close to about 900-950 pages and it doesnt stop :-P

thanks again jeremy

 

thats nothing i have filled up 8 CD's with text documents alone and i have at least 4 cds of gif pics etc. but yeah data accumulation is part of the game. the hard part is keeping is organized. i have most of it sorted by code ecm etc. some of it is by car. the turbo4 pdf is just a great refernce tools thats about it. itll give you insite into the terminology and how thing tend to interminlge.

 

Your out of injector.

There's a final answer explaining injector sizing as it pertains to the stock GM ecms. And that's different from the .5 BSFC equation folks have been throwing around.

 

I have 24 Note books, and 3 drives devoted to EFI stuff. And a stack of CDs several inches high. And that doesn't include the various sites, that I google around reading obscure stuff from.

There is ALOT to grasp.
For most of the deeper thought threads, you could easily write a Thesis on it. There is just that much material. You have to consider GM, and Ford hire teams of engineers and they all have years of time in on very specific items. What takes 4-6 guys a life time to lean, about injector sizing and how it relates to code ain't going to ever be covered in one thread.

The trouble with the way things are going now, is that there are alot of folks that have read a few things, and think that covers it all. Then with a min amount of experimentation think they have it figured out. It takes LOTS of work to get past the surface stuff. While having a command of what appears at the surface is an excellent start it shouldn't be taken as having a real grasp on all the subject matter.

 

wow grumpy replied to me :-) j/k your the fountain of truth in here.. and i appreciate the words, yes i know ive barely dug into the surface but luckily being a jaguar techniican and a decent amount of playtoys and side work, semi fast stuff:-) i do have a pretty good understandinf of what the engine is tryio tell me and try to isolate as many variables as possible... ive prolly done about 200-250 chips on 4 diff sd cars total now (not an expert yet but figured out quite a few things and had a few go way wrong )

yes my binder number 3 is nearing the overbulge point so number 4 is on the way i have tons of threads from here printed along with a few good ones i found at dyi and the turbo4 is now added to the list ,....PIA for me to understand completely but i can glean enuff from it to prove useful it appears

i prolly have 20-30 bins not done by me just to see what people did/tried with there own combos in certain situations and the like to see if i overlooked something or just trying to pick up a new trick

when im at home later i will post my bin up so u big guys can see if my madness if making sense
thanks and later
jeremy

 

badgta,

Traxion's answer was based off the assumption that you were running 48psi fuel pressure. If you were, 33 Inj Cnst would be ther correct answer. In your original post you didn't state what psi you were using.

new flow rate (#/hr) = SQRT[new fuel pressure/rated pressure] * rated fuel flow


Tom

 

Since we got quite the replies including the heavy hitters here(thanks guys)....i managed to find a few new sources, ie documents etc to help me out and managed a few more small things to make sense to me in the world of prom burning

early on in this thread i would post my current bin up for the knowledgeable guys here to critic and/or admire(i can dream rite?)

only part driving me semi-nuts right now is cold start ? ive added and taken away fuel in the startup enrichment vs coolant temp table and gotten it better a few times and lots worse on others but cannot quite managbe to get it for a nice easy cold idle open loop drivability after cold starts. i know these tables are derived from the VE tables(my understanding that they are at least) and when warm my car exhibits BLM from 124-130 when warm pretty much all the way thru about 3600 rpm... and even when coming to a stop when warm, putting car into gear etc anywhere near the idle range i have consistent blm of 124-128 under all conditions that i have seen so far? anyone shed smoe lite

and please let me know if this bin is avail. as a zip tp u guys first tie doing this



and please give me your opinions on my bin even if it is a what the @#$% did u do that for? lol i have my reasons for almost all of what i have done(once again, i think i do)

later and thanks

 

try: open loop change to fuel/air vs coolant temp. i looked in the bin and the values from 20c-150c are all .9% which is most likely not enough enrichment at those colder engines temps.

good luck.

 

thanks funstick i was trying to get as much info as possible on there but havent delved into yet so im heading there on the revision jpc17.bin im working on along with sorting more scan data. i changed the startup enrichment tables back to where i had a fairly decent(not correct, but better) cold start and will see if its possible to dial out the rest thru open loop change to a/f vs. coolant temp ....


only thing thats scaring me here is most of the hard and heavy idle oscillations i get seem to be due to rich condition vs. a lean one and that is what im experiencing....being open loop and no wideband laying around :-( i cant really put my finger on it but i will try it and see what happens within the next day or so

thanks again
later
jeremy

 

alot of time a lean miss fire will smell and act rich. still looking at those table values i ct imagin that the engine isnt lean. treat that table like a choke. thats bascially what it is. cold engines need a good bit more fuel to run smoothly. try adding a bit of fuel if it gets worse then i have no idea what to sugest.

 

funstick u hit it dead on the head

i was just o blind to see it i was always waiting for oil pressure and tmepo to stabilize before i started taking readings and paying attention etc....

had the scanner out t-nite (20 degrees or so) with me latest revisions and finally found my stinking stutter when cold start and first driving :-) knock was going off like a geiger counter aroundish 2k with any moderate acceleration......

so now the lean part and the rolling cold idle when in gear and the flutter when in park on cold start are all making sense to me now :-)
now the question is,
#1 will the startup enrichment vs. coolant temp or:
#2 the a/f ratio enrichment vs. coolant temp fix my problem?

hmmm looks like jpc 19 and jpc 20 are on the boards for later t-nite or after work t-row :-)

*** i hope this helps :-)
later and thanks a million
jeremy
PS we need to work on a sticky for idle related issues, such as how to attain as smooth as idle as possible, and the stall saver paraameters(havent had to touch mine yet just looking to get her smooth as possible) and iac counts vs.coolant(helped me out alot)
my humble 2 cents :-)

 

both tables can affect idle fueling im not sure which one has the largest impact glen91gta should bve able to pop in as well as traxion these guys are the in house $8d guys. i think even rbob know a chunk more about it then i do.

if the $8f,$58,$42,$6e,$32,$32b stuff i have is any indicator stratup fuel is timmed out in 1-2 seconds.

a/f vs coolant is a constant setting thats based on coolant temp.this should stay on till the ecm hits closed loop i think it even function in closed loop.its based on ve and is a calculation from 14.7:1 to whatever you have as a percentage change which i beilive goes rich not lean.

 

Maybe slight off topic, but if you are using 24lb. SVO injectors, 42lb's fuel pressure (with vac line on), Speed density .bin, and AFR in .bin set to 14.7, then what should I use for injector constant in the .bin? Right now I have it set to 25 lb. and it still smells pretty rich. I couldn't tell you the BLM's cause I don't have a scanner yet. Would 27 lb. injector constant be too high and cause the car to run too lean? Would I be safe with 26 inj. con.? I do have an adjustable regulator, so what would you guys set the pressure to?

Thanks,
Mike (1bad91Z)