Still got issues tuning in my 60lb injectors

[Dixit]

Well not sure how many have followed my thread on LS1tech.com but I thought Id see if the masters at HPtuners can help me out on this.

I basically installed 60lb mototron injectors and then adjusted my IFR table to the values below.

69.26006	69.69410	70.12814	70.56218	70.99621	71.43025	71.86429	72.23632	72.67036	73.10440	73.47643	73.91047	74.28250	74.71654	75.08857	75.52261	75.89464

Now when I started the car, it idled fine and never has had a problem there. The problem is CLEARLY during the decel where Im say under 2000rpm, during that time I see my STFT (when I had LTFT disabled) go to in the -20 range and sometimes -30. If I would get back on the gas just a little bit during the time its in the -20 range, the car would jerk a few times, like a quick jerk in about less than 1sec like it bogged for a split second and then runs normal again, but everyime i decel I see this happen. Heres an example of what I see on my chart



Now you can see once the MAP drops in the 25kpa range, the STFTs go straight south. I also noticed the O2s go flatline during that time. I dont have my wideband in at the moment (sorry still working on getting that back in) but it seems to show its running really rich on the decels. More proof that I have that it is running rich is that on the decels you can see the Injector pulse width is about 1.3msec and before the injector change (from my stock 02z06 injectors) the decel showed the injector pulse around 1.6msec (when DFCO doesnt kick in) and Im still doing 1.3msec on a 60lb mototron which is definetely throwing double fuel on the decel. Now Ive halved my minimum pulse width, default pulse width, short pulse adder tables and just cannot get it to command less than 1.3msec.

Ive tried to drop the VE table on 25kpa and below almost 30% and still dont do the trick.

I then setup a custom map against battery voltage and 0 through 80kpa (like the injector offset table) using my fuel trims and then modified the injector offset table almost 3 times (each time either adding or subtracting 10-20% in columns based on what I needed to do) and that still dont help. Ive run around this in circles trying to figure out something to get this slight hesitation/bog on the overly rich decel solved but cannot figure it out. Ive ran this in SD mode most of the time and the problem is still there, I then turned LTFTs back on and the MAF back on and saw the problems still happen but not as bad, the hesitation/bog during the decel/accel transition is not as harsh as in SD mode.

I talked to a few people and they said they've been able to just drop in the 60lbs and just change the IFR table and call it a night with no problems, that definetely has not been the case for me. I remember reading a thread awhile back on LS1tech.com that Chris from HPtuners I believe actually dropped in 60lbs on his car before going boosted and still maintained stock driving. Thats all Im trying to do before I get the STS twin turbo kit on. I just want all these small injector tuning issues out of the way.

What am I doing wrong? Like Ive said, Ive probably flashed the VCM about 50times trying to try different thins and still no go. If I cant get this resolved Im going to be forced to remove these injectors and go to some SVO30lbs in the meantime cause I drive this Z06 daily and these 60lbs are not giving me a good feeling.

Dixit

[WS6FirebirdTA00]

the injectors are prob too big for your mods, i have the same problem right nw with my 42's, on decel i go to about a 12:1 AFR, only thing i can think of is they cant hit a lot enough pulse width to lean out

[chrisj6]

Isnt there a minimum pulsewidth you can change to try and get that value lower?

Chris

[WS6FirebirdTA00]

no this didnt work for me, it is just what the injectors are capable of doing i think

[WS6FirebirdTA00]

actually your lucky, my damn injectors dont go below 1.8 ms and yours go to 1.3, what the hell is up with that? can you post up your tune on here or email it to me so i can compair to mine and see if it could be something in my tune?

[Dixit]

Heres my latest tune.

So you got the same problems with your SVO 42s? This is not right. I mean even if the injector is too big for these mods/engine setup that shouldnt keep it from working.

I mean I know plenty of people who are 346 displacement and run blowers or twin turbos and got 60lbs injectors. Technically they got to be having the same problem since the blower or turbo wont affect the decel much. Im worried cause if this cant be fixed putting on the twin turbos is going to really piss me off that Im still going to get the same problem.

Dixit

[Casey]

So you got the same problems with your SVO 42s? This is not right. I mean even if the injector is too big for these mods/engine setup that shouldnt keep it from working.

Dixit

Not exactly true. The injectors have a minimum pulse width time. Getting too close or going past this will cause them to misfire and not fuel the engine.

You will most likely need to add a vacuum referenced fuel pressure regulator or size the injectors to what the engine actually uses.

Also make sure the Injector Offset vs. Battery Voltage vs. KPA Vac table matches the Injector MFGR specs on how fast it can work.


-Ken

[Dixit]

Ken, How do I get those Offset specs? The only specs on that injector that they show are as follows:

Static flow 10.8g/sec @ 600kpa
Gain=0.110ms/mg
Offset=0.055ms
Turn on Time=1.14ms @ 14VDC
Turn off time=0.85ms @ 600KPa

I dont know how to set that offset to the table with just those values above.

Also if I use this vacuum referenced fuel pressure regulator I assume its going to bring the FP down from 58 to a preset value so essentially it doesnt throw the same amount of fuel as without it on the decels.

How large can I go on a 346 injector wise with this vacuum references fpr? Just wondering as I preparing to drop a 402 TT setup and been thinking about forging this 346 and pushing the limits. Well lets say I want 800whp, I got a feeling Im going to have to run a return line and then a boost referenced fpr, but if I run that can I still run the vacuum referenced one or do I buy a single unit that does both. I mean Im assuming Im going to need about 75-90lb injectors to support that power.

Dixit

[WS6FirebirdTA00]

yeah the problem is finding injector offset data for injecotrs.

like Dixit said, you need large injectors for proper WOT fueling but down low you will not need it. i have seen scans from similar people who dont think they have a rich decel issue and i have seen it on every car i have done with large injectors like the 42's

[Dixit]

At this point my option is to remove the injectors and drop in a pair of SVO30s. And then when I get the TT kit on there put a vacuum referenced fpr, another option is to just use a normal FPR and just drop the base FPR to 43psi and then just recalc the IFR, that could fix the decel issues.

Dixit

[NTIMID8]

I wouldnt give up on either injector.

The SVO 42s are easy to tune and have done them numerous times with stock drivability on very basic cars with customers planning to do more.

The motoron 60s will also work well and I suspect you decel fuel is not enabling. I see way to much "overtuning" and not tweaking the right knobs for the job. In general the stock injectors offset will work fine except for 1 spot that ken pointed out. They will usually lean missfire due to the slow reaction of the injector. This is the notorious "decel or light load" buck. Its created at high map/light load. Adding injectors pulse time in the offset at high map will cure that issue.

Phil

[Dixit]

Well I have played with the DFCO but that is not the answer, right now it kicks in right around 2100rpm, if I drop it to say 1500, then it starts hampering driveability.

You mention the stock offset values will work except one spot, which spot is that? Im still trying to get answers on how one sets the offset table, the manufacturer only provides the info above on the injector, nothing more.

Im not getting a lean situation on the decel, getting extreme rich situation, adding pulse to the offset there is not going to help, cause its just going to drop more fuel in there. Or am I completely off there?

Dixit

[WS6FirebirdTA00]

i have no driving issues with my injectors, it just goes rich on me on decel. even with dfco off the car shouldnt run 11.5-12.0:1 AFR on decel

[WorkingManPerf.]

Ken, How do I get those Offset specs? The only specs on that injector that they show are as follows:

Static flow 10.8g/sec @ 600kpa
Gain=0.110ms/mg
Offset=0.055ms
Turn on Time=1.14ms @ 14VDC
Turn off time=0.85ms @ 600KPa
Dixit

Same deal that I am in I tuning my first set of 60lbers

So do I set 14vac line to .055 across the table and blend it out??

[WS6FirebirdTA00]

on the cars I have done, lowering the table by 30% generally put it close. Now I have some more tweaking in there, but that got the car to where it needed to be.

[sikhabib]

ive got this same problem with my 42s. you can lean it further out by turning off transient fuel on decel or by reducing the min fuel milligrams but his will cause lean conditions during throttle changes
i have set min rpm to 3000, tps to 0.5, left milligrmas stock and only have lean problems when i first come out of decel but i think this is because im too lean on decel now (afrs 17-19). i think i have min pulse with set too low so hopefully when i get it close everything should be ok

[WS6FirebirdTA00]

just lower the mg, leave the rest stock. 0.032 will work. It will go a little lean on throttle changes, but it shouldnt go way lean.