So, Dominick...A verdict???

[Paul Workman]

Kinda wondering how the saga of the fuel cutoff went (I may have missed a post or two of late - I B incredibly bizzy the last couple weeks ) Did it turn out to be a pump issue or ???? Sure would be nice to compare the fix to the data from the scanner; a good learning exercise to be sure!

Keep the shiny side up!

P.

[karterdon]

Paul - Dom posted some pictures of the fuel filter sock that he took out of his car - It was completely plugged and black- He replaced both pumps and the filter sock and he says the cars runs Great !!!!!

Don Yoakem
91 #267 Dark Red Met.

[XfireZ51]

Originally Posted by karterdon

Paul - Dom posted some pictures of the fuel filter sock that he took out of his car - It was completely plugged and black- He replaced both pumps and the filter sock and he says the cars runs Great !!!!!

Don Yoakem
91 #267 Dark Red Met.

Yep. I remembered this happening to my 84. So I pulled the pumps and lo and behold. Ockham's Razor is the principle proposed by William of Ockham in the fourteenth century: ``Pluralitas non est ponenda sine neccesitate'', which translates as ``entities should not be multiplied unnecessarily''.

[Paul Workman]

...the "KISS" principal!

Very glad to hear it is running well! I have a long tube for my fuel pressure gauge. Just for grins, I may want to hook it up and go for a ride.

P.

[XfireZ51]

Originally Posted by Paul Workman

...the "KISS" principal!

Very glad to hear it is running well! I have a long tube for my fuel pressure gauge. Just for grins, I may want to hook it up and go for a ride.

P.

Paul,

I think the key here is WOT. Pumps need to be able to provide much more volume. There may be enough at PT so pressure looks fine but then WOT
basically absorbs any cushion and therefore starves the motor.

[Paul Workman]

Originally Posted by XfireZ51

Paul,

I think the key here is WOT. Pumps need to be able to provide much more volume. There may be enough at PT so pressure looks fine but then WOT
basically absorbs any cushion and therefore starves the motor.

Dom,

You think a long WOT pull in what gear would be best...4th? Or mebby just 3rd, considering the speed one attains at 7000+ in 4th?? The point being, a worst case "stress test" for the fueling system would require WOT at sustained high-end of the rpm band, I would think.

P.

[XfireZ51]

Originally Posted by Paul Workman

Dom,

You think a long WOT pull in what gear would be best...4th? Or mebby just 3rd, considering the speed one attains at 7000+ in 4th?? The point being, a worst case "stress test" for the fueling system would require WOT at sustained high-end of the rpm band, I would think.

P.

The VE tables don't distinguish on the basis of gear ratio. Its strictly RPM x MAP. You need to be judicious if tuning on the street. I've used 3rd gear although now the ZR is at over 10-15mph more than my 84. So I'll use a dyno for 4th gear. I like using the street because it more accurately models the conditions the car is actually run under like any ram-air, load, air resistance etc. Since you're south of 80, you may have better opportunity for open road

[Paul Workman]

Originally Posted by XfireZ51

The VE tables don't distinguish on the basis of gear ratio. Its strictly RPM x MAP. You need to be judicious if tuning on the street. I've used 3rd gear although now the ZR is at over 10-15mph more than my 84. So I'll use a dyno for 4th gear. I like using the street because it more accurately models the conditions the car is actually run under like any ram-air, load, air resistance etc. Since you're south of 80, you may have better opportunity for open road

I guess what I was driving at is your problem (now fixed) brings up a question: What are the actual fuel pressure dynamics under WOT conditions in normal circumstances for these cars? I.e, is pressure relatively constant at the rail under WOT conditions? Obviously, you filters were ultimately determined to be plugged, but what inadvertent affect will the "starving" have on you work w/ the fuel table calibrations, especially in the region where fuel pressure dropped out of regulation?

Which brings up another point...

Fussing with the ECMs for the LSx engines...would be interesting. Given their dynamic fuel pressure control capabilities and dynamic cam timing features along w/ individual cylinder monitoring and fueling/timing capabilities...someone like you (and a several others of us here too) could get lost in the combinations...and love every minute of it! (Marc...If ya ever git bored... )

I don't know where this is going, specifically. So, ya might have to forgive the ramblings of a noobee with a "new" Z and an engineering background. I'm just curious about every aspect of our Zs.

P.

[Aurora40]

I'm not sure the LSx ECMs have individual cylinder monitoring? I imagine they still have one O2 per bank? And I think only the new ZR1 has the dynamic fuel pressure control?

[Paul Workman]

Originally Posted by Aurora40

I'm not sure the LSx ECMs have individual cylinder monitoring? I imagine they still have one O2 per bank? And I think only the new ZR1 has the dynamic fuel pressure control?

Bob, I wuz speaking in more general terms with regard to the exponential increase in tuning variables for today's "ECMs" and those that dabble in tuning them, compared to the OBD-I and the LT5s.

A tuner would know, but I seem to recall reading that the exhaust pulses from the individual cylinders across the respective bank O2 can be (and are in some cases) monitored with respect to the exhaust valve timing. Thus, the mix and even the timing can be or is tweaked on individual cylinders - one of the advances allowed by the faster computers and OBD-II - one of the big advantages of the LSx over previous (OBD-I) ECM limitations. This could make position of the O2 on aftermarket exhausts a bit critical, if correct indexing of the cylinder is to be maintained. (I don't recall the source - been a while back.)

As for variable fuel pressure, I was referring more to the variety of variables facing the tuners of the latest engines (LS9 to be specific - also an "LS" motor). Point being, with the monitoring and sensing capabilities available to today's tuners - to the point of individual cylinders, if needed, certainly raises the bar when it come to tuning (not that every tuner would need or even want to delve to that level).

P.