750cc injectors on stock ecu Options

[Neon90424]

I am curious if 7500cc injectors if i put them on and hook them to the stock st205 ecu will it work or will the car run pig rich?

[3WayStunna]

7500!!! Holy balls you would get horrible gas mileage, lol...but serioulsy i see you meant 750cc injectors. Honestly man, you shouldnt run injectors on the stock ECU that are 15-20% larger than the stock ones...If you do, you WILL have horrible idle issues, amongst many other things. If it were 550's, or even 600's it would be possible but it would be better to control them with some sort of Fuel Managment Unit...

Btw, not saying you dont know what you are doing but.....make sure you have the proper injectors and fuel setup for what you are looking to do...just saying..if you dont already know, you can use this website as a tool..

http://www.rceng.com/technical.aspx?UserID...rtodKzHIQgRGSAc

And also..check out this thread...
http://www.alltrac.net/phpBB2/viewtopic.php?f=9&t=12333


Honestly man, id stick with a proper ECU of some sort. You could be asking for trouble being too cheap or creating too man y shortcuts....

[Cuts_the_Pilot]

dont do it, while it will just run, it will over fuel terribly, probably enough to wash the bores and cause damage.

ive started mine on the stock ecu once (sard 800cc) (i put it back in to get an abs error code and started the car before i remembered to put the pfc pro back in) it only ran long enough to hear it was running sh!t and remind me what was going on.

This post has been edited by Cuts_the_Pilot: Jul 6, 2011 - 8:56 AM

[Neon90424]

Thanks for the advice guys Im havin a hard time finding a cheap power fc lol! a friend found one for 450$ from Iquique (thats chile where all the jap cars are unloaded)

according to that page...and to some stuff I read

I have 4 750CC Injectors matched flow rates low impedance yada yada yada

255 Walbro LPH with the right numbers for the st205 tank

I read somewhere the st205 FPR is a 1:1 ratio ( whatever the hell that means) and that with the walbro 255 will reach somewhere around 63 psi ?

so I calculated and at 63 psi with 80% injector duty at .60 brake whatever that is and it shows 450bhp I am gonna give my friend with the st185 that has the power fc in his car I wonder, will his car work with the 3rd gen ECU since it has been all wired up to work with the power fc it should be plug and play right?

all that plus water and alky injection should be good

[Cuts_the_Pilot]

1:1 means for every psi of boost the fuel pressure goes up 1 psi, im not sure what the base fuel pressure is for a 205.

One way (a dodgy way mind you) to do a band aid fix is to get an adjustable fuel pressure regulator and drop your fuel pressure right down so the correct ammount of fuel is injected, i wouldnt do it this way though, ide stick with stock injectors till you can get a pfc.

Yes your mates one will work

[Neon90424]

I know his PFC will work, my question is will my ECU work on his 185 which is wired up for a pfc?

[Smaay]

you have no idea what you are talking about. the PFC will not work because one car runs on a MAF and the other car runs on a MAP.

[Neon90424]

I do know what I am talking about, this ST185 has been modified in japan to work with the SW20 PFC, It has no MAF.






So again, If this car works with a PFC,

If i trade my injectors fuel pump and stock ecu will HIS car work?

This post has been edited by Neon90424: Jul 7, 2011 - 11:52 AM

[stephen_lee]

if u want to use larger injectors with the stock ecu, match a new map with it.

it will run closest to right



say the 205 has a stock 2.5 bar map and 450cc injectors

get a 4 bar map and 720cc injectors.

(new map value in bars \ stock map value in bars) * stock injector size = new injector size

yay math

[Neon90424]

stock ecu cant be modified, it has 540cc injectors and I thought the ECU fuel map has to be changed

This post has been edited by Neon90424: Jul 7, 2011 - 3:22 PM

[stephen_lee]

fuel map cant be changed. this isnt modifying the ecu at all. its changing the way it reads pressure.


say u have one bar map. (reads vac to 0 psi)
you add a 2 bar map.

guess what? full throttle (0psi) reads as 50% load on engine where the stock map would say 100% load

now lets see what happns at the injectors.. the ecu sees a 50% load, so it fires the injectors at 50%

well the stock 300cc injectors doesnt supply the 280 or so cc the engine needs to run at full throttle cause thyre only firing at 50%... so to correct this you double the injector size(since you doubled the map)

with 600cc injectors running at ~50% you get the correct fueling.

[Neon90424]

I feel this wouldnt really work specially at idle seems like a cheap fix...Im seeing how cheap I can get a power fc from chile since my friend is too scared to give me his.

[czwalga]

edit.

This post has been edited by czwalga: Jul 7, 2011 - 10:05 PM

[Cuts_the_Pilot]

getting a pfc (or another programmable ecu) is really your only option unless you put some stock injectors back in.

[stephen_lee]

its what some 7a turbo guys do. seems to work ok for them. then of course later u can get some piggy back to help even things out