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:rolleyes: ) 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 !!!!!:thumbsup:

Don Yoakem
91 #267 Dark Red Met.

[XfireZ51]

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 !!!!!:thumbsup:

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! :thumbsup:

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]

...the "KISS" principal! :thumbsup:

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]

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?? :jawdrop: 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]

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?? :jawdrop: 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]

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...:dancing )

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]

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.

[Aurora40]

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.)
They certainly seem to be able to infer things like misfiring on an individual cylinder. I didn't know they also made fueling decisions on a per-cylinder basis, though.

Using a more modern controller would certainly be interesting, and perhaps could eliminate some of the difficult to find electronics. Though I wonder if it would be hard to get these newer ECMs to work with the 9-slot crank ring?

[Paul Workman]

They certainly seem to be able to infer things like misfiring on an individual cylinder. I didn't know they also made fueling decisions on a per-cylinder basis, though.

Using a more modern controller would certainly be interesting, and perhaps could eliminate some of the difficult to find electronics. Though I wonder if it would be hard to get these newer ECMs to work with the 9-slot crank ring?

I dabbled in machine language programming once. But, in a nick of time, I saw my own insanity looming ahead and veered away from "the dark side"!:jawdrop: But, maybe some prison inmate (with that kind of time on his/her hands) can re-write the code so a currently available ECM would be able to be substituted for the (now up to 18 year old) ECMs in our cars. :icon_scra

Anywayz...I find engine design and the attendant control thereof to be a fascinating topic. (Maybe that afore mentioned insanity got me anyway, and I just am not sane enough to realize it!:D )

P.

[XfireZ51]

I dabbled in machine language programming once. But, in a nick of time, I saw my own insanity looming ahead and veered away from "the dark side"!:jawdrop: But, maybe some prison inmate (with that kind of time on his/her hands) can re-write the code so a currently available ECM would be able to be substituted for the (now up to 18 year old) ECMs in our cars. :icon_scra

Anywayz...I find engine design and the attendant control thereof to be a fascinating topic. (Maybe that afore mentioned insanity got me anyway, and I just am not sane enough to realize it!:D )

P.

You'd be surprised what some people are doing with older ECMs and their own source code. This is the ECM (www.dynamicefi.com (http://www.dynamicefi.com)) I was using on my 84 with a VAFPR for Dynamic Pressure Control.
In the case of TBI, it allowed me to increase FP and therefore fuel flow across the rpm range while maintaining an optimum PW for each area of operation like idle, part throttle, WOT. FP would range from 10-20psi using an Aeromotive 13301 regulator. There was a 2D table for BPC x VAC. In the case of the PFI motors, the VAFPR is used to maintain a constant FP across the engine operating ranges at the injector since they operate in manifold vacuum.
I WISH I could use the EBL for the ZR-1. The tuning tools and flexibility in the parameters were awesome for an ~ $300 package.

As for the LS stuff, I haven't seen anything to suggest that there is an individual VE table for each cylinder. In some definitions for LT motors for example, there exists a way of addressing the "split blm" issue we see in our motors allowing you to "trim" each bank.

[Paul Workman]

Well, now my curiosity is piqued. I remember reading about individual cylinder management about 3 years back, in an article on the LSx. I specifically remember the discussion on how the single O2 is used to monitor the individual oxygen levels of each cylinder on it's respective bank.

I'll see if I didn't save it somewhere. But, in the mean time, I'll drop a line in the CF C5/C6 forums and see what comes back. Stay tuned.

P.