PDA

View Full Version : Injectors and FPR



AFOUR_PLAY
01-18-2006, 03:48 PM
I have a K04 with GIAC chip and S3 injectors.
Now the chip is for a larger exhaust and fmic (which i'm still in the process of getting)

I noticed that my car is running rich and it has caused the spark plugs to foul up.

Standard I was running 4Bar Fuel pressure regulator and the injector size is about 210cc.

Now I am running the S3 injectors (386cc) still with the 4bar fpr.

Will adding the exhaust (3" dump pipe, 2.5 the rest of the way) lean the car out?
Should I install a 3Bar fpr?

TomRitt18944
01-18-2006, 04:16 PM
nope, u need to get the injectors that the program was written for. Most likely those are way way to big. Do u have the pc-16 file? then u should have 310cc injectors at 2.7 bar, do u have the regular giac k04 chip? then u should use stock injectors with a 5 bar fpr

goldenchild
01-18-2006, 04:19 PM
i used audi tt 386 cc on stock 4 bar and ran great at 20-21 psi.

AFOUR_PLAY
01-18-2006, 05:05 PM
I don't have the regular GIAC chip.

The chip was written for the S3/TT injectors
My car is only hitting 18psi

goldenchild
01-18-2006, 05:09 PM
turn the boost up! that will help lean it out

AFOUR_PLAY
01-18-2006, 05:10 PM
LOL, that's what my mate said!

might install an adjustable fpr

TomRitt18944
01-18-2006, 05:18 PM
Originally posted by goldenchild
turn the boost up! that will help lean it out

Not necessarily, the fuel pressure goes up 1:1 with manifold pressure.

Whats file was written for those injectors?

AFOUR_PLAY
01-18-2006, 05:28 PM
Not sure. I have the AJL engine 180Hp std (from Australia) I

TomRitt18944
01-18-2006, 05:30 PM
hmm id be very surprised if there was a ko4 file for injectors that big..exhaust stuff isnt going to help ur rich problem either

k0mpresd
01-18-2006, 05:44 PM
Originally posted by TomRitt18944
Not necessarily, the fuel pressure goes up 1:1 with manifold pressure.

Whats file was written for those injectors?
im assuming by manifold pressure you mean boost??

TomRitt18944
01-18-2006, 05:51 PM
yep same thing

k0mpresd
01-18-2006, 05:55 PM
so then @ 20psi what fuel pressure are your injectors running @?

since you set them @ no manifold pressure...lets just say 3 bar, 45psi @ zero boost...1:1 ratio....holy fuel pressure batman..youd be running waaay rich

440's flow 440cc @ 3 bar (45psi) which supports around 350hp (give or take)...1:1 ratio would put them @ 65psi w/ 20psi

or did i miss something?

TomRitt18944
01-18-2006, 06:02 PM
nope thats correct, the ecu accounts for this though. I'm currently running my 440's at 4 bar which is about 505's, but im also only running 10psi, so thats about 69 psi

k0mpresd
01-18-2006, 06:16 PM
so my car makes around 330hp @ the crank on 440's

so w/ 20psi whats the ecu do...cut the duty cycle down to like 20%??

what would be the point of running larger injectors? why not just crank the boost up w/ stockers if the fuel pressure/flow rate raises w/ boost...the ecu could just lenthen the injector pulse to compensate and richen it up

TomRitt18944
01-18-2006, 06:38 PM
Just because fuel pressure go's up, doesnt mean you only need that little bit of additional fuel thats added by that rise in fp. Duty cycle also goes up. the motor at 20psi of map needs way way more fuel than the 20psi of fuel pressure is going to add, therefore the ecu increases pulsewidth. Unfortunatly for the dbc folks the ecu maxes out the injector duty cycle at 16.32ms, therefore we need bigger injectors sooner powerwise than the dbw ppl

For your second question, its because the duty cycle on the stock injectors gets maxed out pretty early and u cant keep increasing fuel by adding fuel pressure. Scott at USRT told me you dont want to run more than a 5bar fpr on this motor.

AFOUR_PLAY
01-18-2006, 06:51 PM
So should I be running 3bar injectors?

k0mpresd
01-18-2006, 06:53 PM
good info [up]

TomRitt18944
01-18-2006, 07:18 PM
Originally posted by AFOUR_PLAY
So should I be running 3bar injectors?

well there no such thing as 3 bar injectors, u were prolly thinking 3 bar fpr, but you should be running whatever ur giac file was written for

AFOUR_PLAY
01-18-2006, 07:23 PM
Originally posted by TomRitt18944
well there no such thing as 3 bar injectors, u were prolly thinking 3 bar fpr, but you should be running whatever ur giac file was written for

i meant fpr

mike-2ptzero
01-18-2006, 11:27 PM
Originally posted by k0mpresd
so then @ 20psi what fuel pressure are your injectors running @?

since you set them @ no manifold pressure...lets just say 3 bar, 45psi @ zero boost...1:1 ratio....holy fuel pressure batman..youd be running waaay rich

440's flow 440cc @ 3 bar (45psi) which supports around 350hp (give or take)...1:1 ratio would put them @ 65psi w/ 20psi

or did i miss something?

Cant look at it that way. Most of the added fuel pressure is to help the injectors spray the fuel against that same pressure inside the cylinder. This is exacly why it is a 1:1 fpr.

It is better to start with a lower pressure fpr for a turbo car because the higher the fuel pressure becomes during boost the lower amount of fuel the pump can flow.

AFOUR_PLAY- your stock injectors should have been either 240cc or 270cc.

goldenchild
01-19-2006, 12:33 AM
so how much fuel can a stock fuel pump flow untill u need to upgrade? do u think i need one?

mike-2ptzero
01-19-2006, 01:33 AM
Depends on how much power your making. But the best thing to do is to have a fuel pressure gauge that you can watch or record. This way if you see a drop in pressure at high rpms then you most likely need a higher flow pump or try lowering the fuel pressure and then increase the injector duty cycle with Lemmiwinks.