Injectors & AutoVe kicking my BUTT!!!

[GAMEOVER]

Working on a 2003 1500 Silverado Stock 4.8ltr mods: Longtubes, CAI, Victor JR EFI Intake w/Edelbrock Elbow & owner says redtop 29lb injectors from a 2001 5.9 Grand Cherokee. The stock fuel rail had a vacuum referenced regulator and owner changed it to returnless fuel system because of new fuel rails...He's using a Corvette filter/regulator
I put new injector values into spreadsheet then copy/pasted new values into tune.(Values were sloped) I tried to do AutoVE but as soon as I turn truck on Wideband goes crazy lean 23-26 AFR for about a minute...After initial minute, AFR settles down to a normal 14.5 AFR....What would be causing this? Only happens on initial start up every time...Almost have VE table dialed in...
I'll post up tune file in a little bit...

[swingtan]

Long Term Fuel Trims? If in doubt, reset!

[GAMEOVER]

No matter what I do to VE table, AutoVe isn't doing what it's supposed to....I get good data, copy paste & multiply seems like nothing is happening...I don't think the injectors are 29lb's at 58psi....My injector flow rate must be totally wrong...:confused::confused::confused:

[GAMEOVER]

After a flash, my AFR is real rich or real lean...AFR 10-18...:shock:
Thru out entire VE table

[swingtan]

Post tune + log......

Oh, and if the IFR is off, the VE should still be able to be tuned, as the IFR and the VE are basically MAP referenced. It's just that the VE will look pretty bad and it will impact other areas of the tune.

If the AFR's keep randomly changing, then I'd guess the fuel supply pressure is bad and either changing pressure or there is air in the feed. Of maybe the injectors don't work correctly with the PCM drivers????

Simon

[joecar]

Simon made some very good points.

[GAMEOVER]

Good call Simon....Fuel pressure was averaged at about 47.5 psi...:bad:
While I was checking fuel pressure I could see the needle fluctuate pretty bad!!!(42-52)
This the second time I assumed fuel pressure was good on a vehicle I was gonna work on...:shock:
Man all that time wasted...

[swingtan]

Hmmmm.... Excellent! My usual bill plus 20% is in the mail http://i280.photobucket.com/albums/kk167/lenchooie/animated%20stuffs/thevil-rubbing-hands.gif

[GAMEOVER]

Hmmmm.... Excellent! My usual bill plus 20% is in the mail http://i280.photobucket.com/albums/kk167/lenchooie/animated%20stuffs/thevil-rubbing-hands.gif

Hahaha...Overlooked little things always make a BIG difference...:grin:
New fuel pump going in this week!

[eficalibrator]

...My injector flow rate must be totally wrong...:confused::confused::confused:

...or the injector offset ...or the short pulse adjust. Only correcting one out of three of the primary characteristics of the injectors is a recipe for frustration when it comes time to calculate airflow. If you started with a set of injectors that have known parameters, you likely wouldn't be having half the issues.

[joecar]

Do those injectors have data available somewhere...?

Or, how would one go about measuring the offset and SPA using some tools...?

[GAMEOVER]

I looked for data but so far nothing...

[swingtan]

Do those injectors have data available somewhere...?

Or, how would one go about measuring the offset and SPA using some tools...?


It would be very hard to work out SPA etc without some tricky gear. The SPA is a setting to help make the injector flow more linear when very short pulses are commanded.


The PCM / ECM can command very sort pulses, as it's an electrical signal.
The injector needs to convert that signal into a mechanical opening and closing of the needle valve.
The needle valve takes time to fully open and close, while moving, the flow rate is changing as the total orifice size is changing.
On very small pulses, it's possible for the PCM / ECM to close the injector before it's completely opened.


To help make the flow appear more linear, the SPA is added to correct the amount of fuel that can flow when the open and close time of an injector becomes a significant component of the total open time.

If you really wanted to try and work it out, you could try this....


Set up a test bench to measure flow.
Measure a base reading by holding the injector wide open at a fixed pressure for a fixed time, maybe 10 seconds.
Measure the flow of the injector when it is pulsed at differing pulse widths, for the same 10 seconds.


If the injector was perfect and linear, you would see a linear graph of total flow reducing as the pulse widths get shorter. However because of the open / close times, at some point the flow rate will drop off until the pulse is so fast that the injector will not even open.

The theory would be to work out how much additional time you need to apply to the pulse, to bring the total flow back into a linear result.

Simon.