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Power Fc Oddities...

carl h

By carl h,
in Engines & Forced Induction

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carl h Proficient

carl h

Posted
Posted

ok heres the problem, rb25pfc on a rb20 using rb20 base maps...

greddy/denso 720cc injectors with dropping resistors to suit.

doing the injector correction math for the power fc 370 / 720 = .515 or so so 51.5% correction on the power fc.

inputting the said 51% change into the power fc causes the car to run EXTREMELY lean and can only be compensated at that setting by changing the lagtimes for the injectors to +70 or so.

not sure what the deal is here or why its running so lean, anyone have any ideas?

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paulr33 Grand Master

paulr33

Posted
Posted

why are u using resistors (sorry if its something obvious) but i dont see why?

are they the wrong impedance or type? there should be no reason it will run mega rich or lean with different injectors, providing the right values are dialed in

rob82 Mentor

rob82

Posted
Posted
ok heres the problem, rb25pfc on a rb20 using rb20 base maps...

greddy/denso 720cc injectors with dropping resistors to suit.

doing the injector correction math for the power fc 370 / 720 = .515 or so so 51.5% correction on the power fc.

inputting the said 51% change into the power fc causes the car to run EXTREMELY lean and can only be compensated at that setting by changing the lagtimes for the injectors to +70 or so.

not sure what the deal is here or why its running so lean, anyone have any ideas?

For that ratio to work both injectors must be statically flowed at the same pressure. Which is how most injectors can be compared. However the flow rate of 1 injector at x ms could be alot different to another injector at the same millisecond -this is where comparing injectors at a signgle duty cycle is useless. What I am trying to say is that the ratio used by PFC is not exact.

Sydneykid Grand Master

Sydneykid

Posted
Posted (edited)
ok heres the problem, rb25pfc on a rb20 using rb20 base maps...

greddy/denso 720cc injectors with dropping resistors to suit.

doing the injector correction math for the power fc 370 / 720 = .515 or so so 51.5% correction on the power fc.

inputting the said 51% change into the power fc causes the car to run EXTREMELY lean and can only be compensated at that setting by changing the lagtimes for the injectors to +70 or so.

not sure what the deal is here or why its running so lean, anyone have any ideas?

I would have input 48.5% to reduce 720 cc down to 370 cc's equivalent.

:) cheers ;)

Edited by Sydneykid
carl h Proficient

carl h

Posted
  • Author
Posted (edited)

paul - resistor pack is on there from when i was running the std rb20 ecu, as it used for running low impedence injectors on a high impedence system...

greddy injectors are 3ohms give or take, so that would neccsistate running the resistor pack to keep the car (ecu) from farking its self up no?

Edited by carl h
Color_Of_Green Enthusiast

Color_Of_Green

Posted
Posted
ok heres the problem, rb25pfc on a rb20 using rb20 base maps...

greddy/denso 720cc injectors with dropping resistors to suit.

doing the injector correction math for the power fc 370 / 720 = .515 or so so 51.5% correction on the power fc.

inputting the said 51% change into the power fc causes the car to run EXTREMELY lean and can only be compensated at that setting by changing the lagtimes for the injectors to +70 or so.

not sure what the deal is here or why its running so lean, anyone have any ideas?

That function is there only to offer a basic starting point for your next tune. Back to the dyno my friend.

carl h Proficient

carl h

Posted
  • Author
Posted

with swapping 2 wires round and clipping one it plugs right in and runs fine, will even run on the rb25 base maps but runs poorly due to the lack of ignition in the map.

ive realized that the compensation bit isnt as apex described and gonna go back to what i was doing before with changing correction till i get the afr at idle thats ideal (14.5) and going from there...seems to work better that way.

AzzurrA Grand Master

AzzurrA

Posted
Posted
with swapping 2 wires round and clipping one it plugs right in and runs fine, will even run on the rb25 base maps but runs poorly due to the lack of ignition in the map.

Wow! Do you have a link to any information on how to do this? As i don't really see the value in paying $1500 for a AP Engineering Unit when you can buy an RB25 one for $900ish, when its pretty much the same!?

carl h Proficient

carl h

Posted
  • Author
Posted
pardon my ignorance…

but of you are running rb20 base maps, then shouldn’t your formula be using the rb20 standard injectors?

As in 270cc…

I was under the impression rb20 was 270cc and rb25 was 370cc

no even tho im running the base maps for the rb20 it still is a rb25 power fc and there for expects 370cc injectors as stock...

and as far as base maps are concerned, yes they are basemaps but they are also VERY good starting points no one said they would be perfect.

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