SD and EFILive Auto VE tune with Returnless fuel system?
11-06-2005, 02:24 PM
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SD and EFILive Auto VE tune with Returnless fuel system? Preface:
the regulator will also pull fuel presure when under a vacume. at idle it will pull a little fuel presure and under decel it will pull even more(more vacume=pulls more presure). the whole idea is to keep the presure across the injector constant so if there is a vacume on the intake side of the injector you have to pull fuel presure to keep it around a 58psi and if there is boost it will need to add fuel presure to keep it at a 58psi diference.
from:
http://www.performancetrucks.net/forums/showthread.php?t=351255&page=2&pp=10&highlight=fue l+system As the FPR is not boost referenced, the only way that the returnless fuel systems have to compensate for decreased injector flow under boost is to keep the injectors open more. Hence those of us with this setup should see higher duty cycles and max out the injectors sooner if properly tuned.
If 1 psi of boost equates to a loss of 1 psi of FP and my actual FP also drops 5 psi under boost, that is like losing 13 psi of FP at 8 psi of boost! From my calculations that works out to at least +13% duty cycle at the corrected flow rate of 37 lb/hr(Radix 42LB injectors).
Now, I don't see anything in the tune where I can correct the IFR for boost or the line pressure drop. Magnuson has the IFR set to 5g/s for all MAPs pre boost but there is no table for boost. So as there is no feedback in Open Loop, I assume that there is no compensation for the decreased IFR other than programming a richer "PE modifier based on RPM" or “Boost VE” table of EFILive's custom OS than what you actually want to achieve if you go MAFless. Does this mean AutoTune is not an option?
Originally Posted by parish8
most of this was said above but it is worth saying again. if you have a return line then the fuel presure is refrenced off of the intake presure. the BASE presure is around 58psi. if you pull the vacume line going to the regulator you should see around 58psi. the regulator seems to add about 1psi of fuel presure per 1psi of boost. when i am over 20psi i see about 80psi of fuel presure.
Originally Posted by parish8
the regulator will also pull fuel presure when under a vacume. at idle it will pull a little fuel presure and under decel it will pull even more(more vacume=pulls more presure). the whole idea is to keep the presure across the injector constant so if there is a vacume on the intake side of the injector you have to pull fuel presure to keep it around a 58psi and if there is boost it will need to add fuel presure to keep it at a 58psi diference.
from:
http://www.performancetrucks.net/forums/showthread.php?t=351255&page=2&pp=10&highlight=fue l+system
If 1 psi of boost equates to a loss of 1 psi of FP and my actual FP also drops 5 psi under boost, that is like losing 13 psi of FP at 8 psi of boost! From my calculations that works out to at least +13% duty cycle at the corrected flow rate of 37 lb/hr(Radix 42LB injectors).
Now, I don't see anything in the tune where I can correct the IFR for boost or the line pressure drop. Magnuson has the IFR set to 5g/s for all MAPs pre boost but there is no table for boost. So as there is no feedback in Open Loop, I assume that there is no compensation for the decreased IFR other than programming a richer "PE modifier based on RPM" or “Boost VE” table of EFILive's custom OS than what you actually want to achieve if you go MAFless. Does this mean AutoTune is not an option?
