Jump to content
SAU Community

Power Fc Oddities...

carl h

By carl h,
in Engines & Forced Induction

 Share

Recommended Posts

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?

Link to comment
https://www.sau.com.au/forums/topic/131130-power-fc-oddities/
Share on other sites
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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • GTSBoy
      new 1.5 LSD issues/concerns

      By GTSBoy · Posted

      A 1.5 way is a 2 way. It is just a 2 way with a less aggressive ramp on overrun.
    • GTSBoy
      Boost cut after swap(RB25DET NEO) R34

      By GTSBoy · Posted

      The ABS and/or TCS being missing/broken will not cause the engine to misbehave. It just casues CEL to come on and annoy you. The CEL is useless if it is always on, so you have to do the things you have to do to get rid of it, so it can be useful. Being a Stag ECU, then yes, it will not expect TCS to be present. But it will expect ABS to be present and working. You will need to either make the ABS CU talk to the ECU (don't ask me what that will take on an NA R34), and make sure the hardware is working....or, you just need to blank it out in Nistune. Do not persist with the stock ECU. You will just have problems. Gte it Nistuned. Start from there. DO YOU HAVE A BOOST SENSOR? The ECU's boost sensor that it. It is connected to the loom at the rear of the coil cover. Usually rides on the firewall on an R34, but is usually bolted down to a bracket along with all the other crap at the back of the coil cover when a Neo is dropped into another car. If you do not have it, the ECU will shit the bed. So, do you have one?
    • Kapr
      Boost cut after swap(RB25DET NEO) R34

      By Kapr · Posted

      So sadly the fuel pump etc was not it. The pump and filter is new and it is still cutting around 4000 rpm. A read something about ABS/TCS (engine is from stagea and ECU too so no TCS) and i dont know for 100% that my car has ABS. It has ABS "cube" in engine bay but i dont think it works(or at least from my braking experience). Can be something like that?  I will be driving the car next week to Nistune tuner to properly see what is wrong...  
    • JC71
      new 1.5 LSD issues/concerns

      By JC71 · Posted

      the Tomei LSD fluid with lsd kit. frustrated that it was shaking the car to crap and affecting everything else negatively, I pulled the diff last night, and removed the lsd carrier, could not find anything wrong, however it seem to be 100 locked up acceleration, and deacceleration, wondering if they sent me a 2 way not a 1.5??  either way I installed the stock open carrier back in place. test drove everything smooth as butter again. no shake, shutter, random, what felt like clutch slip and grab or drive shaft play, etc. something differently wrong in side the lsd. I might bother taking it apart (if possible) to figure out what's going on inside this carrier, as bought too long ago to return.  only draw back is its back to a one wheel wonder.
    • TurboTapin
      Most women will agree that parking is the most taxing part of driving

      By TurboTapin · Posted

      What a time to be alive!!
×
×
  • Create New...