Fuel Pressure

[LGAFF]

This is really what I am asking.....searched the net, some say thats normal, others its the sign of a defective FPR....

Originally Posted by LGAFF

Free Rev with FPR connected drops to 40lbs


Does the lack of load account for the drop?

[Schrade]

Originally Posted by XfireZ51

AE is a pumpshot in carb terms. DE is not to be confused w DFCO
cuts off fuel not reduces it.

Not sure exactly what you're saying here Dominic...

Is the article wrong? Or it just doesn't apply to LT5?

What does RB say that doesn't apply here? (he DOES say that fuel pressure shuts down on de-celeration)

[XfireZ51]

Originally Posted by Schrade

Not sure exactly what you're saying here Dominic...

Is the article wrong? Or it just doesn't apply to LT5?

What does RB say that doesn't apply here? (he DOES say that fuel pressure shuts down on de-celeration)

What I'm saying is that there really is no mystery to ECM control. It just does the same things we did before, just many more times per second.

[XfireZ51]

Originally Posted by Schrade

Not sure exactly what you're saying here Dominic...

Is the article wrong? Or it just doesn't apply to LT5?

What does RB say that doesn't apply here? (he DOES say that fuel pressure shuts down on de-celeration)

There is a difference between DFCO and DE. That's what I was pointing out. Perhaps RB was generalizing and trying to show the contrast of adding fuel and deleting it.

[Hog]

Originally Posted by XfireZ51

At 51psi, 22.7# injectors will flow as 24.7#, at 60psi, they flow like 27#. So at least 10% richer all around. Your going from a hypothetical 12.8 to an 11.6AFR at WOT.

When setting up your initial IFR(Injector Flow Rate) you use the rail pressure that occurs when the the vaccuum reference is disconnected, correct?

On my setup, the rail pressure is 58psi vaccuum reference detached at idle with vaccuum reference attached the rail pressure drops down to 51-52 psi.

My injectors flow 25 lb/hr at 43.5psi/3BAR, the calculates out to 28.7 lb/ht at 58psi/4BAR.
The IFR I would use in my PCM is 28.7 lb/hr or 3.62 grams/second.

Bottom line, use the unreferenced regulator rail pressure for IFR calcs?

[Hog]

Originally Posted by Schrade

Not sure exactly what you're saying here Dominic...

Is the article wrong? Or it just doesn't apply to LT5?

What does RB say that doesn't apply here? (he DOES say that fuel pressure shuts down on de-celeration)

The part of the article that is circled in purple is wrong, well at least missleading..

The article is describing Acceleration Enruchment which is correct.
Then the article describes DE or Deceleration Enrichment incorrectly. The description given is for DFCO or Decel Fuel Cut Off, not DE.
DFCO actually shuts off injectors during periods of coastdown.

AE is used during short periods of time when the engine takes an extra "gulp" of air, exactly what happens when you stand on the throttle, AE is exactly like the carbs "pumpshot" that will prevent a lean stumble.
AE is a function of necessity, DFCO is purely an economy measure. DFCO is not necessary for proper engine function like AE is.

There is also PE mode where extra fuel is added when engine load is increased and extra power production is required.
There is also a Power Enleanment mode which is the opposite of Power Enrichment mode. Both of these are typically Open loop and do not use narrowband O2 sensor input.

[XfireZ51]

Hog,

The injector flow rate used in the calibration is the one you would have at idle with the FPR attached to a vacuum port. In a stock cal, its set to 22.7#. In older calibrations like the one I had for my 84 Xfire, you would calculate the BPC or Base Pulsewidth Constant. Here, the cal does it for you using the IFR.

[Schrade]

cuts off fuel not reduces it.

That's what the text says.

There is a difference between DFCO and DE.

What is DE? (the author says, "Deceleration EnLEANment, which is injector shutdown. "

...

Then the article describes DE or Deceleration Enrichment incorrectly.

...

I think EVERYone has mis-read the words in the author's text ( all the while, agreeing with the author).

The text describes Deceleration EnLEANment (WHICH HE SAYS IS INJECTOR SHUT-OFF) ... NOT DECELERATION ENRICHMENT.

Circled in purple.

Handheld digital 'smart' devices aren't good for reading comprehension. Seriously......................

[GOLDCYLON]

Originally Posted by LGAFF

This is really what I am asking.....searched the net, some say thats normal, others its the sign of a defective FPR....

Id go with post #5's answer. He's prob forgotten more than most of us could ever know about the LT5

[XfireZ51]

Just to be clear, DE is deceleration enleanment meaning it leans out the AFR as you feather the throttle. Fuel delivery is reduced, not stopped. Lifting off the accelerator will invoke DFCO, Decel Fuel Cut Off, if it is enabled. There are RPM and MAP "windows" where these take place. They don't happen everywhere. Mostly for low end. Both of these are for emissions. For the most part, I have DFCO disabled and I believe Marc does this also in his cals, particularly for those that complain about motor stalling when freewheeling or rolling to a stop.