Injector Offset ?'s vs LS1 edit

[AllCammedUp]

I was just discussing all this with Whitney actually and his car responded just like mine. Very predictable and repeatable with offset changes.

Folks... KISS .... If you have a C5 with an 85mm screenless MAF, use a Z06 MAF table and don't touch it. EFILive provides us with the power of the table editing. Doesn't mean it's benefical to change every table you see.

All I can say is that John is definitely on to something here. I've been testing some offset tables for him, and the trims are getting better and better... I've never been able to get them as close as they are now with 'old school' tuning approaches (endlessly changing the MAF and IFR table).

The car feels very strong through the rev range, and it's immediately noticeable if I switch back to the stock offset table with the SVO IFR table - it's amazing how I couldn't tell the difference before (running the SVO 30#'ers and the stock offset table) and switching to John's calculated offset table with the SVO 30#'er IFR table - it's a huge difference in driveability.

It's helping to get the AFR's more in line in regards to commanded vs. actual, and then I think the hope is that there will be less and less tweaking of the VE necessary for part-throttle tuning and PE transitions. You'll still be tuning PE the same way, naturally.

[bink]

My car ran much truer to Commanded AFR once I was able to get an offset table for my injectors .
I'm running the GTP supercharger/ World Challange injectors.

John Skiba - as you know, I had searched for definitive info on these injectors for quite awhile.
36# at 43# fp and 42# at 58# fp. The ASA (2000 LS1PCM) bin IFR table works out for the 36#s scaled for 58 #.

Anyway, I used the ASA offset table and it cleaned up my AFR considerably.

Recently I realised that the MAF table in the the ASA bin is scaled to 497 g/sec. I then checked the lower values of the ASA MAF table ( around 3250 Hz) and they closely match my MAF table which I rescaled - after almost ten months of trying many different "fixes" for my lean idle!! I then remembered that I had used the Offset table from the ASA tune and compared the ASA IFR table and my randomly scaled IFR table - they are within 0.4 g/sec of each other. I suspect they will be closer when I try the ASA MAF table.
FWIW.

I think the Offset table is critical but I wonder if it needs to be experimentally derived?
The Bosch- GM 36#ers are supposed to be the same as our stockers internally - yet the ASA Offset table (assuming the ASA cars run these injectors) differs significantly from my stock Offset table.

Cheers,
joel

[MN C5]

I ended up calling RC but here is what they gave me for offsets for 72lbers or 750cc @ 4bar or 58psi

16v 1.20ms
15.5 1.23ms
15.0 1.26
14.5 1.30
14.0 1.36
13.5 1.42
13.0 1.46
12.5 1.53
12.0 1.63
11.5 1.7
11.0 1.81

[Dirk Diggler]

Racetronix couldnt give me the information. THey said it was VCM/car specific

Bink

Can you email me the ASA tune so i can see the offsets and the IFR table as my injectors are rated at 36 lbs/hour@58 psi

[wait4me]

I have a bunch of 98 asa files.. they not locked and editable. But you guys cant see them in the editor yet.. Ill post them all when the 98 stuff is released.

[John Skiba]

Bink - Stock 23/24lb bosch injectors and 36lb GTP bosch injectors may look the same but I'm sure the pintle size, springs, etc are different. All which probably contribute to different event timing and thus flow characteristics. This is best answered by an injector engineer.

What kind of intake setup do the ASA cars have? Is it a similar setup to the Fbody cars? Asking because you said your results were close.

Most setups don't vary to far from the factory setup. Example: A C5 intake is still very similar with an aftermarket airbridge and MAF location etc to stock setup. That's why I use the stock ZO6 screenless table with a 85mm screenless maf on a C5 and not a truck 85mm MAF table on a C5.

If we know the flow rate for an injector at a given pressure, then the math should work out. However, we all know that is not the case and most people adjust the MAF table and or tweak the IFR table to compensate. I'm sure Ross can explain all the math calculations, etc involved with a proper MAF reading a lot better than I can. I just prefer to have a sensor read correct (maf, etc.) Just seems like it would make life a lot easier.

Something we didn't discuss yet is the effect of fuel pressure on an injector. Injector timing events are probably going to be quite different at 43.51psi compared to 58.01psi, etc.. etc.. I remember seeing charts of the effects of FP on rochester, bosch, lucas, etc injectors and the rochester would not increase in fuel delivery with any linearity as fuel pressure increased right upto 90psi where it failed. From 65psi to 90psi fuel delivery did'nt increase. (Anyone running a rochestor with FI?? )

BTW, If I recall right, torque is a calculated function. Anyone want to take a guess from what? Again, Ross or someone else can explain the finer details better than I can.

John

PS. If anyone knows anyone from Kinsler Fuel Injection in Troy MI, they can probably shed some light on this topic.

[John Skiba]

Ross/Paul - Thank you for the "Small pulse Adjust" Heh... no wonder...

[QUICKSILVER2002]

I agree that the offset table is the ignored table that needs more attention. People don't want to mess with it, but not getting it right causes all kinds of other problems. There are some injectors that work just like stock, but there are many others that do not.

Here is an old post from ls1tech by a "professional tuner" - who was trying to scare people away from the injector offset table.

People farting with this table are walking on a live bomb.
Guess what happens when someone sets the delay incorrect and the injector is coming on too early or late of sparkplug firing ?

Being that table starts in milliseconds and by PE is microseconds, there is zero reason to play with those values esp since the internal coil ramup time esp on multech II were designed to react faster then older designs did.
The SVO #30 is NOT made by Ford, they are by Bosch, the same vendor who makes the injector for the LSx engines and have the same coil specs.

DOwn the road people cocking with this table may see piston or head damage from out of timing injectors firing at the wrong time.

I've seen countless LSXs using the SVO;s with great performance and all maintained the stock injector offset tables.

Just goes to show you why people have been scared away from it.

Anyway, I was just playing with offsets tonight and would like to clarify my understanding.

The voltage is the same voltage you see on your volt gauge, right? So the values below 10 and above 14 are probably never seen?

It seems that the PCM has a known stopping point for an injector pulse (I'm assuming this is based on crank position). Longer pulse widths mean an earlier start, but it always ends with the same basic timing.

So increasing the injector offset (time to open) actually adds to the overall pulse width.

I really feel this is the key to the tuning problem I have been having with my car. I have 60lb mototron injectors and a vacuum refrenced regulatur (my IFR table is flat)

I get the car running great (during the day) and then I drive it at night and the idle starts to stumble a bit. It also does this during the day when the fans have to kick on full speed.

I feel this is related to the fact that the injectors behavior is being impacted by the cars voltage. The entire idea behind the injector offset table is to make voltage changes have no impact on amount of physical fuel being delivered.

If all this is true, what would be an easy way to dial in voltage. I was trying to think of a way to regulate the voltage and test with the extremes. I can probably just do trial and error with a lot of data, but it sure would be cool to run the car at 10,11,12... v and tweak until the o2s read exactly the same.

Another thing that makes the tuning a pain is the fact that the alternator starts putting out much less power when it gets hot.

[bink]

John - I think the ASA cars are pretty much a straight shot air intake (no bend). Mine is a Vette. wait4me should be able to confirm this.

People farting with this table are walking on a live bomb.
Guess what happens when someone sets the delay incorrect and the injector is coming on too early or late of sparkplug firing ?

Being that table starts in milliseconds and by PE is microseconds, there is zero reason to play with those values esp since the internal coil ramup time esp on multech II were designed to react faster then older designs did.
The SVO #30 is NOT made by Ford, they are by Bosch, the same vendor who makes the injector for the LSx engines and have the same coil specs.

DOwn the road people cocking with this table may see piston or head damage from out of timing injectors firing at the wrong time.

I've seen countless LSXs using the SVO;s with great performance and all maintained the stock injector offset tables.

I believe this is the same Guy that said he uses the GTP/36 lb/hr injectors ( (42# @ 58 psi) and stated on LS1Tech that there was no need to use a diiferent offset table (i.e. use the stock offset table). Well the offset table in the ASA tune is for the GTP/36# injectors (confirmed by wait4me) and it's quite a bit different than the stock table. I guess GM should have consulted with him.

Isn't he also the Guy that claimed 5 gallons of gas would reset the Octane Scalar to 100% High Octane table?


Excellent point Quicksilver 2002 - IMHO.

There was a thread awhile back on pulsewidth.
If you do the Math the injectors are shooting at the backside of the closed intake valve - most, if not all, of the time. This is confirmed in Will Handzel's book " Modifying and Tuning Gen 3 Engines ".

FWIW.

Cheers,
joel

[wait4me]

Hi guys, The Injector offsets are set per injector type and injector size, That is The only thing that effects that table.
They are a strait foward number they should be, and to get the math calculation all you have to do is look at all the ones the gm has set up for you between all the years. But that would only work for a injector type that has been used by gm, Not a ford type or any of the fat shorter injectors..
Intake air or the inlet going into the motor would not effect the offsets. They Do effect fueling and they should be as correct as possible, But if they are already set, you shouldnt mess with them for fine tuning..
Gm's tables are acurate as you can get.. So if you put in the correct tables from a gm stock tune, then that is not something to mess with.
Getting information on how to set up ford or the other injectors is gunna be a pain for anyone. I tried years ago and i was lucky enough to get an accurate maf flow chart...