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09-14-2013
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#11 | |
 
Join Date: Mar 2007
Location: Crystal Lake, IL
Posts: 7,180
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Re: Fuel Pressure
This is really what I am asking.....searched the net, some say thats normal, others its the sign of a defective FPR....
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LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 |
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09-14-2013
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#12 | |
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Join Date: Dec 2012
Location: NC
Posts: 1,783
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Re: Fuel Pressure
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 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) |
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09-15-2013
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#13 | |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,686
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Re: Fuel Pressure
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09-15-2013
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#14 | |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,686
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Re: Fuel Pressure
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09-16-2013
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#15 | |
 Join Date: Jul 2010
Location: Woodstock, Ontario, Canada
Posts: 1,271
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Re: Fuel Pressure
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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? |
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09-16-2013
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#16 | |
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Join Date: Jul 2010
Location: Woodstock, Ontario, Canada
Posts: 1,271
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Re: Fuel Pressure
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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. |
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09-16-2013
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#17 |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,686
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Re: Fuel Pressure
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. |
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09-17-2013
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#18 | |||
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Join Date: Dec 2012
Location: NC
Posts: 1,783
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Re: Fuel Pressure
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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...................... Last edited by Schrade; 09-17-2013 at 01:43 AM. |
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09-17-2013
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#19 | |
 
Join Date: May 2007
Location: Peoria, AZ
Posts: 9,117
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Re: Fuel Pressure
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Id go with post #5's answer. He's prob forgotten more than most of us could ever know about the LT5
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GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director  91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V |
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09-17-2013
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#20 |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,686
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Re: Fuel Pressure
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.
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Linear Mode
