2002 Silverado 5.3l IFR

[ippielb]

So, i am a complete newbie at tuning, and i have just been fiddling around with little things at my own leisure for the past little while just to get kind of familiar with the program. I have tuned my transmission perfectly in my eyes, nice smooth crisp shifts, and i have taken off the cat protection and the rear o2 sensors. I was reading the topic, > > > General Tuning Information < < <, and What To Tune First, and the first thing i did was the IFR Table. I used the IFR Spreadsheet that RedHardSupra provided on his website, and the values already put in on the spreadsheet where for my 5.3l Engine already. So i went ahead and used the numbers for the flow rate on the g/sec, put the tune on my truck just to test the IFR table, and boy did i make a huge mistake. It sounded like my truck had a cam if was running so rich. Stock tune on my truck has a value of 3.179688 from 0 all the way to 80 in the table.

Anyone have any pointers where i went wrong?

[joecar]

Your truck has a MAP-referenced FPR, i.e. it has a vacuum hose connecting FPR to the intake manifold...

the FPR regulates pressure to base pressure plus MAP (manifold absolute pressure)... i.e MAP is added to base pressure, this is the pressure the FPR regulates to.

At WOT (MAP equals BARO, 100 kPa near sea level) the FPR regulates higher pressure then at closed throttle (MAP equals say 33 kPa for stock cam);

MAP-referenced FPR keeps the pressure difference across any one injector constant:
i.e. pressure at top of injector is base pressure + MAP; pressure at bottom of injector is MAP; difference is base pressure (i.e constant)(i.e. MAP subtracts out).

IFR is proportional to the squareroot of the pressure difference across an injector... so for MAP-referenced FPR (constant pressure difference across injector) the IFR is flat same value all across.

------

For non-referenced FPR ("returnless"), the pressure difference across injector varies with MAP, so the IFR has to be sloped, i.e. the IFR table takes variable pressure difference into account (i.e. slope is squareroot of pressure difference).

[joecar]

This thread shows how the FPR influences IFR (it's a technical read): Calculating-Injector-Flow-rate (http://forum.efilive.com/showthread.php?4821-Calculating-Injector-Flow-rate)

[ippielb]

I'm a total newbie here, all the abbreviation lingo doesn't mean much to me except 3 capital letters. I can give a guess at what they are though. My guess is FPR is Fuel Pressure Regulator, WOT is wide open throttle?

Anyways what i understand from what you said is that the manifold pressure is used by the fuel pressure regulator. The fuel pressure regulator keeps the fuel pressure to the manifold pressure. At wide open throttle there is a different pressure in the manifold, so the fuel pressure regulator changes the pressure of the fuel to match the pressure in the manifold. So, at higher throttles the manifold pressure is added to the base injector pressure. Is my figuring correct?

So my IFR table should be straight across instead of on an increase like it has?

http://i53.photobucket.com/albums/g79/halfsoldier/ifrtable.jpg

There's the IFR Table i have.

[joecar]

Oh, sorry about the acronym soup...

MAP = manifold absolute pressure
FPR = fuel pressure regulator
IFR = injector flow rate
WOT = wide open throttle

BARO = barometric pressure (what MAP equals with key on engine off)

[joecar]

...

Anyways what i understand from what you said is that the manifold pressure is used by the fuel pressure regulator. The fuel pressure regulator keeps the fuel pressure to the manifold pressure. At wide open throttle there is a different pressure in the manifold, so the fuel pressure regulator changes the pressure of the fuel to match the pressure in the manifold. So, at higher throttles the manifold pressure is added to the base injector pressure. Is my figuring correct?

So my IFR table should be straight across instead of on an increase like it has?

...Yes, this is correct for manifold-referenced FPR (trucks have this type of FPR)...

does your truck have the FPR located at the fuel rail(s)...?

if it does, it will also have a vacuum/reference hose going to the intake manifold...

if it has the reference hose attached, then your IFR table should be flat across same value in all cells.

[ippielb]

You are correct, it appears my truck has a fuel pressure regulator at the drivers side fuel rail, i'm assuming it regulates both rails. There is a few hoses attached that go to the manifold, well under the beauty cover, i was too lazy to take it off, but i've double checked on the internet here and my truck does have the rail FPR, and the reference hose.

Now that my truck needs to have the same value all the way across, how would one determine the value needed? Just use the number at closed throttle?

[Taz]

Are your current injectors an upgrade or a non-stock replacement ? Or was this exercise a tuning misunderstanding ?

The Injector Flow Rate (B4001) value for stock injectors in 2002 Sierra / Silverado Gen III trucks is 3.1797 g/s. This value is entered in all B4001 cells from 0 kPa to 80 kPa.

Hope that answers your question .......


Regards,
Taz

[joecar]

The rails are connected together they have the same pressure.

The value to use for all cells is the value calculated in the spreadsheet for MANVAC = 0...

but see what Taz said.

[ippielb]

I guess this was a tuning misunderstanding. I blindly just followed the "what to tune first" thread. Thanks for clearing that up. 3.1797 is the stock number, and was changed back right after screwing it up.

[Taz]

Confirming accurate injector data is where any tune should begin - so the advice was sound. Your injectors hadn't been changed / upgraded, so the original data remained accurate - in other words you should have skipped to the next step in the "what to tune exercise".

If it makes you feel any better, this is often how I learn "how things work" - by making changes to a calibration, observing the outcome, and revisiting the original changes. I have a "shop truck" that is lucky to be alive - its been a Guinea Pig for many tuning experiments.


Regards,
Taz

[ippielb]

Thanks for the reply. I used this thread. http://forum.efilive.com/showthread.php?7866-What-to-Tune-First

I am waiting on my LC-1 Controllers to come in the mail, so i cannot do my VE tables or use the tutorial. But i will be doing that once i get my controllers.