injector constant - issues and a theory - Tuning Forum

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injector constant - issues and a theory
Thursday, June 26, 2014 10:19 PM
so I've been struggling to tune my car with ID1000cc injectors the past few days and despite following the typical pattern of tables this time around the car is acting all kinds of screwed up.

at first it would not start with the injector constant calculated from the scaling formula.... 0.04507 (in the area of depending on what numbers you use with which stock constant... they weren't all the same)

the car refused to run, and was trying to idle at a 19:1 AFR.

after messing with the constant (and using one that was for the 60# injectors) I got the car to idle and drive with light throttle input happily.
however, whenever I'd try to hit boost the car would fall on it's face

I'm using my IPW table as a coarse fuel adder... so whenever vacuum hits 0 (boost) the car will multiply the pulsewidth calculation by a factor from 0.0-2.0
I've been hanging around 1.5-1.6 with the 60# and a 60% VE offset.

so I went back and used the proper injector constant, then just went crazy raising my VE tables WAY up
I took VE offset to 80% and jumped everything up.

car ran a lot better. But the more I added fuel with the IPW multiplier (and eventually reaching a full 2.0... DOUBLING the pulsewidth calculation when in boost) the car hated me. It was chunky, it was mean, and my AFRs were still on the lean side.... mid 12s.

I filled up with gas and when I went to restart the car would absolutely NOT start.
I tried logging with HPT scanner, but came to the conclusion that the IPW multiplier @!#$ up your starts because before the engine can pull a decent vacuum the IPW adds a ton of fuel and chokes the engine out.
I kept making changes as I was stuck at the gas station, and when I lowered the IPW multiplier, the car fired back up.

so here's my theory as to how to possibly sidestep this problem.
keep in mind, I have yet to try this out but I plan on it tomorrow at some point.

it seems that whenever the injector constant gets very low (big injectors), the calculations get a little... effed.

also, you run out of room to increase fuel. VE tables are maxed. multiplier is maxed. drivability is garbage and still not enough fuel.

So, I'm thinking... say you set your injector constant for an injector HALF the size of what you're packing.... 95.2# for the ID1000s, and I reduced it to 47.6#

I think did the calculation for the Halfed constant using 45# injectors as the starting point...

42 / 47.6 = 0.88235

I then multiplied this by my injector constant for 42# injectors

0.88235 * 0.10215 =0.09013

so our constant is 0.09013 for 95.2# injectors.

so the PCM thinks the injectors are half the size. so for a given calculation, we can assume (I HOPE) that the pulsewidth is going to be double what we actually want.
how do we take this away?

the IPW multiplier.

set the IPW multiplier to 0.5 across the board, and it'l half the PW and hopefully give us a well-behaved car off boost
then, just simply start adding to the 0kpa cell as you normally would with smaller injectors, only now you are already below 1 and have plenty of headroom to add more fuel without completely destroying the VE tables to try and force the car to work.


the reason I believe this will work is because even though the PCM thinks the injectors are half the size, they can still physically perform to the level we need them to... we just need to bandaid tune our PCM because it is incredibly weak and does a bunch of random @!#$ that makes no @!#$ sense.

I plan on trying this out sometime this weekend to see if it works.
the only thing I could see happening is the duty cycle calculation will get screwed up and read double what it actually is.... but if we know that, just chop it in half or change the function string to compensate and voila.

the other thing that could happen is the car runs exactly the same... completely screwed the F up.


any thoughts from my more seasoned tuner friends?






Re: injector constant - issues and a theory
Friday, June 27, 2014 1:54 AM
I my honest opinion, it will probably work fine. Like you said, it's a weak pcm, and anything done at the level you're at (tvs, huge injectors) is a bandaid.

One thing that confounds the results is warm starts on a supercharged car with this pcm, that's always gonna be bitchy.

Nice work in explaining what you are going to do and why, it's easy to follow and anyone who can understand tuning can make sense of it. I'm definitely curious on how it'll work for ya. Also, I'm by no means suggesting a 2.5bar fake, but when people run the fake, the ve tables are essentially 2.5 times more sensitive. In other words you rarely see the need to bump the ve offset on a 2.5 bar fake car. Just food for thought.
Re: injector constant - issues and a theory
Friday, June 27, 2014 3:27 AM
pj, go megasquirt and document it step by step so I can get mine wired up this winter

all kidding aside, i hope you get it figured out.



Re: injector constant - issues and a theory
Friday, June 27, 2014 4:18 AM
I ran a 0.1000 w 80's in my 01 that put down 488 and drove like a stock car. PJ hit me up in a pm I'll be glad to send that tune to you via email.


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4 Cams...32 Valves...5 Liters...This Could Get Fun!


Re: injector constant - issues and a theory
Friday, June 27, 2014 5:09 AM
Interesting.. sub'ed for the update on how this turns out.



"In Oldskool we trust"
Re: injector constant - issues and a theory
Friday, June 27, 2014 6:48 AM
Essentially you are doing something similar that the LD9 SC reflash does, and what a lot of us do on other PCMs requiring bigger injectors than 60's (double stoich/half IFR), With this being said, it makes it much easier to tune in lambda instead of AFR...



P&P Tuning
420.5whp / 359.8wtq

Re: injector constant - issues and a theory
Friday, June 27, 2014 3:55 PM
QWK LN2 (P&P Tuning) wrote:

Essentially you are doing something similar that the LD9 SC reflash does, and what a lot of us do on other PCMs requiring bigger injectors than 60's (double stoich/half IFR), With this being said, it makes it much easier to tune in lambda instead of AFR...


Lambda vs AFR...well duh. That's the true measure that AFR is calc'd off of anyway. Most modern pcm's don't see AFR anyway...they use lambda. My 09 cobalt and now the 11 mustang both are lambda...makes tuning for e85 much much easier because regardless of fuel type 1.00 is ideal for normal driving and depending on application 0.80-0.85 is ideal for wot. The lnf has a commanded 0.88 at wot iirc and that's also where I take the mustang at wot again due to the massive reduction in chamber temps from running e. My max egt @ wot is roughly 1300 degrees. I've got matt's constant set @ 0.1500 and that car has been running 80's and e85 for well over a year...


---------------------------------------------------
4 Cams...32 Valves...5 Liters...This Could Get Fun!


Re: injector constant - issues and a theory
Friday, June 27, 2014 4:34 PM
Skunk wrote:

QWK LN2 (P&P Tuning) wrote:

Essentially you are doing something similar that the LD9 SC reflash does, and what a lot of us do on other PCMs requiring bigger injectors than 60's (double stoich/half IFR), With this being said, it makes it much easier to tune in lambda instead of AFR...


Lambda vs AFR...well duh. That's the true measure that AFR is calc'd off of anyway. Most modern pcm's don't see AFR anyway...they use lambda. My 09 cobalt and now the 11 mustang both are lambda...makes tuning for e85 much much easier because regardless of fuel type 1.00 is ideal for normal driving and depending on application 0.80-0.85 is ideal for wot. The lnf has a commanded 0.88 at wot iirc and that's also where I take the mustang at wot again due to the massive reduction in chamber temps from running e. My max egt @ wot is roughly 1300 degrees. I've got matt's constant set @ 0.1500 and that car has been running 80's and e85 for well over a year...
While I agree with you that the Bosch/LNF PCM and the most Ford PCMS give you lambda tables, not "all modern PCMs" have tables for lambda. Most GM/Delphi PCMs still use AFR calculations for Stoich (E67/E40/E38, ETC......) Using lambda calculations (1.0 for Stoich regardless of fuel) is definitely the way to go as far as making life easier, but you need to make the proper changes/calculations in your scanner to make it correct.







P&P Tuning
420.5whp / 359.8wtq

Re: injector constant - issues and a theory
Friday, June 27, 2014 4:41 PM
I wish I were smart.



"In Oldskool we trust"
Re: injector constant - issues and a theory
Friday, June 27, 2014 6:49 PM
I like what I am reading here. I need to get better at this tuning stuff.



Re: injector constant - issues and a theory
Friday, June 27, 2014 11:54 PM
so I experimented a bit today with the tune.

I tried the half injector constant and 0.5 IPW multiplier.

it worked fairly well. I also bumped up the VE tables like hell.

car was running lean, but pulling pretty strong.


after adding fuel, the car would fall on its face in boost.
a little insight into how I work the IPW multiplier...

I leave everything the same except the 0 kpa cell. I use that and that alone as my value to change.
I feel that the PCM hitting a "wall" of injector pulsewidth is probably bad practice, but it worked fine for the 60s with the M62 and the TVS.

so the IPW multiplier, 0kpa cell being too high does a few things:

starts are long and hard (yup.. pun intended)
the engine bogs, stalls, stumbles in to running, etc. It doesn't "snap" to life like a factory car does.
reducing the VE tables for cranking and increasing the VE tables for idle helped a bit, but I still needed throttle input to get the engine to run.

also, when flirting with boost threshold, the car will surge like @!#$ crazy.

if you can punch through the surging, the car pulls decent, but AFRs are still lean.
VE tables are pretty much maxed, and anymore IPW multiplier will make the car impossible to start.


so here's my new method of tuning that has the car driving and behaving like stock, albeit with a bunch more power (even tho she's still lean)

injector constant set as 50% actual injector size (1000cc injectors programmed as 500cc)
IPW multiplier set as 1.0 across the board
VE offset at 60%
tables manually adjusted for decent range (histograms used to fine tune them)

now, I can still use the IPW multiplier, but not as much as I was before. with the injector constant set for half size it makes the IPWx twice as sensitive

I then bring down the VE tables and my AFR is in a much better spot (still needs tuning tho)









Re: injector constant - issues and a theory
Saturday, June 28, 2014 4:16 AM
I have never tuned 1000cc injectors. 80lb being the largest I have worked with so far. That was on a 2 bar fake map. Car runs like stock, starts like stop. It did require me playing with the cranking VE some. I'm also using the IPW, but only a little. VE offset stock.

I have found that if the fuel system is up to the task then VE offset does not need to change and little IPW needed.



FU Tuning



Re: injector constant - issues and a theory
Saturday, June 28, 2014 11:10 AM
right now I'm no longer using the IPW, but if I do I want to keep the numbers low.

if I need to bump my fuel a lot, I'm going to use a skewed injector constant in order to get a lot more injector then use the VE tables to bring it down and keep my VE offset to a minimum as well.


tricking the PCM to fueling boost
tricking the PCM to run 1000cc injectors

I wonder how many more tricks are gonna be needed





Re: injector constant - issues and a theory
Saturday, June 28, 2014 11:19 AM
DaFlyinSkwirl (Pj) wrote:

right now I'm no longer using the IPW, but if I do I want to keep the numbers low.

if I need to bump my fuel a lot, I'm going to use a skewed injector constant in order to get a lot more injector then use the VE tables to bring it down and keep my VE offset to a minimum as well.


tricking the PCM to fueling boost
tricking the PCM to run 1000cc injectors

I wonder how many more tricks are gonna be needed
Do you have your table scaling to nearest tenths or .00000000 ? This may give you better control also.



P&P Tuning
420.5whp / 359.8wtq

Re: injector constant - issues and a theory
Saturday, June 28, 2014 3:03 PM
QWK LN2 (P&P Tuning) wrote:

DaFlyinSkwirl (Pj) wrote:

right now I'm no longer using the IPW, but if I do I want to keep the numbers low.

if I need to bump my fuel a lot, I'm going to use a skewed injector constant in order to get a lot more injector then use the VE tables to bring it down and keep my VE offset to a minimum as well.


tricking the PCM to fueling boost
tricking the PCM to run 1000cc injectors

I wonder how many more tricks are gonna be needed
Do you have your table scaling to nearest tenths or .00000000 ? This may give you better control also.


i didn't really word my previous post correctly/ fully state what I'm doing now


I'm using the constant as a way to get more fuel now instead of using the IPW.

If I do use the IPW, I'm going to use it globally... that is, for ALL kPa values.

so my coarse adjustment (now) is the injector constant.
I'll then tune using the VE tables as usual

and MAYBE throw a little bit of multiplier on the 0kPa cell just to be sure the car gets excess fuel in boost.

I can rev match again!
I can start the car easily!
I can clutch in and not stall!

the wonders of a good tune.
just took me a while to get the hang of HPT, the P11 and tuning for boost.





Re: injector constant - issues and a theory
Saturday, June 28, 2014 3:08 PM
DaFlyinSkwirl (Pj) wrote:


I can rev match again!
I can start the car easily!

Lucky you...



"In Oldskool we trust"
Re: injector constant - issues and a theory
Saturday, June 28, 2014 4:16 PM
pretty much lucky you x10



Re: injector constant - issues and a theory
Saturday, June 28, 2014 4:21 PM
BuiltNBoosted wrote:

pretty much lucky you x10





"In Oldskool we trust"
Re: injector constant - issues and a theory
Saturday, June 28, 2014 4:31 PM
I apologize for the slight misinformation. As I've been working w primarily ford lately and the newest gm's have all been lnf. Made an assumption and was mistaken.

The only setting I've ever had in the ipw has been 1.0. I use offset and constant to get things in a workable range. On the plus side PJ, shouldn't run into too many more issues. I always stretched my ve out 3 decimal points. Like Ryan said...makes for better control. I've got a 3 bar os ls1 that I've got out 2 but I've got matt's @ 3.


---------------------------------------------------
4 Cams...32 Valves...5 Liters...This Could Get Fun!


Re: injector constant - issues and a theory
Saturday, June 28, 2014 4:50 PM
Skunk wrote:

I apologize for the slight misinformation. As I've been working w primarily ford lately and the newest gm's have all been lnf. Made an assumption and was mistaken.

The only setting I've ever had in the ipw has been 1.0. I use offset and constant to get things in a workable range. On the plus side PJ, shouldn't run into too many more issues. I always stretched my ve out 3 decimal points. Like Ryan said...makes for better control. I've got a 3 bar os ls1 that I've got out 2 but I've got matt's @ 3.


this is basically what I will now be doing.

the IPW is going to be for slight changes in boost only.

now that I have the constant in a workable setting, I'll use the VE tables the way they're supposed to be used, which makes much more sense to me.

yay =)





Re: injector constant - issues and a theory
Sunday, June 29, 2014 1:31 PM
I dunno what curt has my car doing; but it runs quite well despite being incomplete because we ran out of time.

Tuning wise I have nothing to contribute though. lol.





"A car just isn't a car without a little blood, sweat, and beers." -- Shadowfire

Re: injector constant - issues and a theory
Monday, June 30, 2014 12:56 AM
Here's a thought that I'm just throwing out there that you might be trying to tune around a mechanical issue.

Maybe an issue with injector dead time???? Or possibly issues with injector spray patterns at idle/low duty cycle operations?

From what I've found, the larger the injector, the more grumpy they tend to act at lower operation cycles.




Currently #4 in Ecotec Forced Induction horsepower ratings. 505.8 WHP 414WTQ!!!
Currently 6th quickest Ecotec on the .org -12.453 @ 116.45 MPH!!!

Re: injector constant - issues and a theory
Saturday, July 05, 2014 10:47 PM
I've swapped out the 1000cc injectors for 80# because the 80# at least clip to the rail.

the 1000cc with a stock rail or the out-of-the-box mounting spacers are dangerous.


but my issues persist.

when I get the constant ok and the IPW at 1.0 across the board, the car starts and idles and drives pretty good.

in boost, I'm seeing mid 12s to low 13s AFR.

when I try to add more fuel (either by upping the VE offset, increasing the IPW or changing the constant) the car runs like complete CRAP.


nothing I do works.

I'm going to try a fake tune to see if that's any better, if not I'm going megasquirt.





Re: injector constant - issues and a theory
Sunday, July 06, 2014 3:56 AM
DaFlyinSkwirl (Pj) wrote:


if not I'm going megasquirt.


Thats pretty much the point I am at........ Sell my HPT to counter the cost of the megasquirt and wire the car up... I hate wiring, so you know its going to be a pain in the ass for me!



Re: injector constant - issues and a theory
Sunday, July 06, 2014 4:46 AM
I really like MS3. I used it on a Miata and it was bad ass.



FU Tuning



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