I touched on this real quick on another thread, but didn't wanna hijack.

OK, so from what I understand, offset has to do with the speed in which an injector opens, stays open, and then closes (mechanically) compared to another injector of a different brand or style. More less. Of course I could be wrong, but I would certainly understand how being different, without compensating via tuning could potentially cause issues with how the car ran.

First question: Is that accurate?

2nd question: At what level of tuning does this become necessary? I went from stock 22#'s to SVO 24#'s on the old L98 and while I did have it tuned, I gave no info other than 24 pound injectors and honestly, and ran fine on the hypertech tune and the custom tune. From what I've read, these SHOULD have had different offsets. How many people swap injectors? LOTS! how many people ask questions and ultimately need to have the offset tuned? Judging from a search, some, -but not many. This IS something I could do now, while I'm putting together the motor. I'm in the process of setting up the base tune. Really more reading at this point, but ya know what I mean. ...or....is this more for fine tuning to the "nth" degree, later, once I've got the tune pretty well put together, and the car running well?

...and finally, with EBL Flash I'm looking at all the INJ tables, and I've got the attached calibration summary. Honestly.....it's above my head. Whether you guys think it necessary or not, honestly I have no idea how to USE this information. I think I get the concept at the theoretical level, but....that's about it.

Thoughts?

 

I'm with you, I'm not sure how much it helps...

Though I do know that playing around with the injector offset vs battery voltage table does have an affect on the driveability of the car. I was swinging it around like crazy trying to get those FIC Connection modified injectors to work and the car would go from bad hestitaion to snappy throttle response (but with VE's and lean/rich condtions all over the place).

I'm not sure at this point how much of that was due to bad injectors or not...

My guess is you can probably tune around slightly incorrect injector offsets (i.e., the VE and AE tables). Maybe it'll make tuning a little more difficult than if you started out with the right offsets...

 

Abubaca, read the pdf I linked to in ULTM8Z's thread. It explains a lot about how injectors work regarding the offsets.

https://www.thirdgen.org/forums/diy-...ml#post5981255

This thread explains more about the compensation data along with how to use the data sheet you posted:

https://www.thirdgen.org/forums/diy-...gn-iii-pw.html

Note that I posted the 'BB302 data @ 44 psi fuel pressure in that thread. As far as I am concerned, having the proper injector compensation data goes a long way toward getting a stable tune.

RBob.

 

Yep, I did. While I may have trouble properly explaining it to someone else, I do think I understand the mechanics of it. Thanks.

Yeah, I read that, and it looks like in that thread, The Punisher is using the SAUJP4 def, and references two tables. ...and then you mention zeroing the values in the PW Low offset/Base PW table (makes sense) and ask him about fuel pressure in the Offset/Voltage table. Again, I feel like that makes sense how it would relate to the file I posted. BUT.....I dont see those two table in the EBL def file. And I'll be honest, they may be there and I just missed 'em. I've answered so many of my own questions as I've been able to have TGO up on one monitor and TunerPro open on the other, but other times some of this stuff goes over my head.

...and yes, I see your values at 44, and see that file I posted is at 39.15. Thanks. I DO understand that !!!

 

This is proving to be a very correct statement.

 

As usual RBob is absolutely correct regarding use of the correct offset values.
Accel does not provide the IB for their "21lb" injectors so I finally ended up paying someone to get them empirically. In particular, the idle and low speed(rpm) cruise is so much smoother. Throttle response is crisper, more immediate. Spent mucho time and burned quite a bit of fuel re-doing the fuel map and timing to adapt to new values but it was worth it. As typical, you start out trying to optimize one thing and it branches out into several other areas.
I ended up addressing the IAT Comp tables(relocated to air bridge inlet) also giving me more consistent fueling at varying ambient air temps.

 

These two:

. INJ - Injector Correction Offset
. INJ - Small PW Correction - PORT Only

The high slope, low slope, break point and minimum PW for them is at 39.15 psi (upper left table of data). The table below that is used for battery voltage compensation, while the remaining tables adjust the main values for different fuel pressures.

RBob.

 

OK, with every question anwered....more questions.

...and thank you btw.

First, I see those tables....thank you. ...the volts/offset tables that I see seem to go to 15 or 16 volts, but the EBL table goes all the way to 25.5. How do I tackle that? Continue the curve?
...AND, you mentioned that you posted the BB302 data at 44 psi. So if I run at 44 psi, I can plug those in right? ...it seams those are the same numbers on my sheet, which I thought was 39.15. I'm going to assume you're right, and that I do NOT in fact understanding how the pressure relates to that table.

Second, with regard to zeroing out the Small PW table. ...what exactly does that table show? In terms of milli vs. micro? I mean what does zeroing it out do?

...and to further illustrate my misunderstanding, isn't the WHOLE exercise, the whole point of the calibration sheet and the reason for having the tables in the def file, so that you can tell the ECM the difference between one type of 30# injector and another? Wouldn't changing the volts/offset table calibrate the ECM to the type III's flowing more at lower PWs?

Anyhow, I appreciate all the help. Not sure I could put up with all the "me"s out there, lol. I can plug in numbers, but I like understanding why.

 

Alrighty....so I've been reading. Lots. ...especially from here. Read every article a few times.
http://injectordynamics.com/the-library/

So from what I can see...the different voltage offsets are simply for varying states of the electrical system, not some sort of purposely regulated ECM variance, right? The EBL table just goes lower and higher than most published offset tables, correct?

Second, the offset is time in milliseconds (Micro on the EBL table) that is being ADDED to the PW to account for opening/closing mechanics, right?

Third, the Low PW table is just a closer, more specific table handing the same principle. The larger flow capability means shorter PWs, were flow becomes non-linear, and harder to calculate. If I'm not mistaken, the regular offset value is added everywhere...and the low PW offset is added the regular offset below 3.9 mSec...which is the largest PW handled in the "low" table.

Do I understand this????? Am i right? I hope so. Eyes are bleeding.

 

It's tough getting past the librarian, although once in there is lots of good reading material.

Yes, the vehicle voltage varies quite a bit. As it does the time it takes for the injector to open also varies.

Yes.

The offset table is always used. While the short PW table is only used if the PW is under 3.9 ms. And the injector PW is used as the look up into the short PW table. So it compensates the low slope of the injector flow curve.

Although, what we run into is that Ford and GM used opposite methods of specifying the low PW compensation. Which is why we end up zeroing out the short PW compensation table. There should be a way of extracting this information from the Ford data sheets.

RBob.

 

https://www.thirdgen.org/forums/diy-...es-needed.html

Mine above are 24 lbs at 43 lbs FP. Gearhead forum has those posted. Also supplier of injectors has the data. I also received from "fuel injector connection".

 

Is this a non issue? The tables go to where the ECU will never see actual running time. My experience is that my car only sees low voltage when the alternator fails. I never have had a reg fail with any car.

 

As far as I can tell, the curve goes well below and above where the car would function properly. ...so I just imagine I/you/we don't need to change those values.

 

Set the 0 volt entry the same as the 12.8 volt entry. Extrapolate the 15 volts data value out from there to the higher voltage entries. Use the graph feature to maintain the basic curve of the data.

As for the values from 1.6 to 4.8 volts, just use the 6.4 volt value in them.

The reason for the 12.8 volt value in the 0 volt entry is in case of a loss of input. The value at the 0 volt entry may not exactly match the proper offset, but it will be better then having 0 usec or a high offset.

RBob.

 

After reading some of that I can't understand why my car even runs without using correct values.
1.) mechanical offset values (to correct theoretical to actual output)
2.) voltage corrections (to keep the mechanical relationship correct at all power levels)
** 1 & 2 are combined item in voltage table **
3.) low offsets for the "non-Linear area (to make small PW linear to the ECM request)

Makes perfect sense, just need the actual data on your injectors.

If your current values were incorrect by a bit, your tune WILL change and need to be redone when warmed up and at the current environmental conditions.
Then redo the cold start, altitude and temp changes.
Oh well, there goes next summer... (Car is in hibernation)
Jp

 

Awesome chart. I am new at tuning using an ALD1 tuner with Tuner Pro RT v5
I can use this info( I think ) to compare with the same info for my injectors to guess how much " offset" to make on my chips chart while tuning. I think !! Thanks

 

The offset is whatever the offset is, and hopefully you get that from the manufacturer of the injectors. I had to get mine flow tested by someone that m assured the offset empirically.

 

After putting the SFI-6 on my TB, and installing the 50lb/hr injectors, getting the (I think) correct injector offset really helped the tune. It is hard to get the offsets for a lot of these injectors it seams.