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Looking for some help adjusting my injector timing. I'm using hp tuners. The car is a twin turbo 1999 C5 with a forged 347 / LS1. (2bar OS / SD tune)
I swapped the cam out for a rear mount turbo cam and am waiting to play with the EOIT tables.
The car for the most part runs great with the exception of a slightly rich decell and a bit of a lean tip in.
I've worked the VE back and forth a few times now and am down to either adjusting this or trainsient fueling to fix the issues. I'd rather start here and only mess with the trainsient stuff if absolutely necessary.
I've also heard there is some mpg to be gained as well as some low end torque when adjusting the injection timing which would both be nice as well.
Under injection timing, which tables do you adjust? I have 3, (Boundry, normal and makeup table)
I know there is a way that involves alot of math where you can figure out exactly where your SOI and EOIT is.
Anyone know that formula or have another method for adjusting this?
The good news is you probably don't have eoit issues. The bad news is you probably do need to adjust transient tables. The worse news is that both are a bit of a guessing game with anything other than the exact factory hardware, in which case you would need no adjusting. These are tables that would require OEM resources to properly math out, so you are going to have to experiment.
I did a good bit of searching last night and it looks like GM wanted almost all the fuel to hit a hot, closed intake valve and evaporate a bit to give a more efficient burn.
I found that a .01 change in the EOIT table = 9 degrees of motion out of a possible 720 for the 4 strokes. Doing some comparing, it looks like my new cam opens the intake valve about 23 degrees sooner than the stock one. So I think I'm going to try moving my EOIT back from 5.55 to 5.52 to get the SOIT back closer to where it was when all the trainsient fueling calibrations were factored in by GM.. I know since my cam actualy has over lap (3degrees) where as the stock one had none whatsoever, I'll probably loose some fuel out the exhaust at idle and low rpms especially with the turbos.
Hopefully that change cleans things up a bit though. If not I guess I could try and move the EOIT the other way until I start seeing fuel trims go positive, letting me know that more fuel is getting burned instead of blown out the tailpipe.
Either way, VE is going to have to be re-tuned. Again.
Your right about the trainsients, there really is no way of knowing which area to adjust, atleast not that I've found.
I'm assuming for my lean tip in / rich decell it would be the impact factor gain vs airflow table, it's in lbs per hour. So far I have been unsuccessful in trying to log air flow in lbs per hour though. I messed with the user maths to try and log airflow in lbs per hour a few different ways but I haven't found one that works yet.
Yeah min fuel milligrams has not been changed from stock. (.032) everything under the trainsient tab is stock.
I feal like a jack ***, I looked over just about every table In the VCM editor and compared what I'm working with to an older tune and found that when I went to a 1:1 fuel pressure regulator I screwed up my injector flow rate vs KPA values.. I accidentally used the 100kpa data instead of the 0kpa data to flatline my table.
I'm in the process of slowly re tuning my VE on the street now as it is wayyy off. It seams a bit less jumpy on tip in and tip out already though.
You should drop your min fuel mg too with larger injectors. I use .010 for 60s, or as a starting point if I am unsure. You will have random persistent rich conditions if you do not.
You should drop your min fuel mg too with larger injectors. I use .010 for 60s, or as a starting point if I am unsure. You will have random persistent rich conditions if you do not.
Good to know. I'll give it a shot. I'm assuming like everything else, VE has to be re tuned when making that change?
What exactly is the min fuel milligrams? Is that just part of the formula used by the ECM when doing trainsient fuel calcs?
Good to know. I'll give it a shot. I'm assuming like everything else, VE has to be re tuned when making that change?
What exactly is the min fuel milligrams? Is that just part of the formula used by the ECM when doing trainsient fuel calcs?
It should only affect your low pulse width areas. Will not affect midrange or full power much at all. It is the least amount of fuel the ecm will use. But there is a weird calculation error in the scalar for that field, so it is hard to directly correlate.
I will say that when I see larger injectors and this field untouched, it wants to idle rich. So I adjust it on anything I work on.
Look at it this way. Its a pattern that is consistent enough that I asked the question without knowing anything about your car or tune...
That sounds like min injector pulsewidth for EFI Live. Based on injector data I've gotten I always set 60#ers to .8.
I believe there is a separate minimum injector pulse width table. Dont have my laptop with to check but Ill look tonight and give the .8 a try if there is.
I believe there is a separate minimum injector pulse width table. Dont have my laptop with to check but Ill look tonight and give the .8 a try if there is.
Cool. I'm an EFI Live guy so sometimes hard to match tables. There are 2 in EFI Live, 1 called min injector pulse width and 1 called default min pulse width. Both of those go to .8 with 60lbers and have worked well. Curious to see if it makes any difference for you.
Cool. I'm an EFI Live guy so sometimes hard to match tables. There are 2 in EFI Live, 1 called min injector pulse width and 1 called default min pulse width. Both of those go to .8 with 60lbers and have worked well. Curious to see if it makes any difference for you.
Those are in the fuel section. The field I am describing is under transient fueling. And I have found it is necessary when you do bigger injectors right modify those field. With 60s, start with .010
Those are in the fuel section. The field I am describing is under transient fueling. And I have found it is necessary when you do bigger injectors right modify those field. With 60s, start with .010
You said it would idle rich without the change. Why would a transient table impact idle? Transient tables are for on/off/on throttle transitions.
Min injector pulse width all looks good. Car was tuned in the past. I have since re-tuned it off of a stock file but i transfered all the injector data when i started fresh on it. One question I have though is about the default pulse width table. It says when pulse width is less than the minimum, it defaults to the default injector pulse with table wich is all stock injector data. Should I just copy my minimum table into the default table?
You said it would idle rich without the change. Why would a transient table impact idle? Transient tables are for on/off/on throttle transitions.
I do not know the why of it but I know it is true. It is one of the first things to check in the - I have big injectors car will not idle for **** but idled fine on old injectors please help me - posts. 100% correlation.
But if the OP problem is fixed that is all that matters.
01-25-2020, 12:15 PM
Injector timing changes after cam swap / EOIT 
