I have been look at injectors to use with my OFAB set up and i have a few questions to see if i am correct in what i am thinking.
They have different OHM`s, CC, Pressure (LB/HR)
(701s) 15.8 OHM`s, 226CC, 22LB

15.8 OHM`s = Power
226cc = Injector Flow Rate, Fuel amount
22LB = Injector Flow Rate, Fuel Pressure

(803s) 4.7OHM`s, 370CC, 35LB
So i would need to use a resistor to lower the OHM`s.
How about fuel pressure? 803 have a higher fuel pressure would i just use a higher pressure fuel pump? What about the fuel pressure regulator?

The above is purely an example as they run at different pressure and require different power, Its just to find out what i would need to do if i chose to use injectors above the 701s i have.
Cheers Stu
PS Hope i made sence

 

they would all run at the same pressure.

the CC of the injector is simply another way of describing the flow rate which is often given in lbs. use one method or the other in order to compare two injectors.

the resistance is not a reflection on power directly but if you're using low resistance injectors then your ecu must be able to run low resistance injectors properly or you will need series resistors which is botch up way of doing it.

 

What engine is this for? The next up from 701's is "Green Weber IW 31"

 

They will be for a full ZT and want bigger injectors than the 701s i have atm, So i was looking at what i could use.

 

a "botch" way? It there another way of using cossie injectors on FRST management?

 

What CC are they?

 

235cc/min – Bosch ‘701’ £63.99 330cc/min – Weber IW 31 £59.99Off Area Six, So its cheaper to have better ones.

 

What sort of BHP are you after?
The IW 31 are good up to 280bh. You will need the IW 58 up to 320bhp. And then bigger for up to 400.

Ollie

PS I will have a set of IW 058 for sale in about 2 weeks time.

 

can you go to big? or as long as there not stupid big it wont matter?

 

There is no "botch" at all about resistors in the earth line to each injector, that'sd complete crap, the only difference is it happens externally instead of internally in the ecu.
tabetha

 

I didnt think it was botch.

 

im useing saab turbo injectors they flow to 358.00 cc/min and they are high ome.

 

tabetha - whenever you post about ecu's or injectors you just talk bollocks.

which ecu that is designed for low ohm injectors has internal resistors then?

if it has resistors then it was NOT designed for low ohm injectors but has been frigged to make them work.

the fact is that low impedance injectors (peak and hold injectors) are designed to be low resistance to allow for higher power at the instant they are commanded to open = "peak" and then the drive power is reduced for the "hold" part.

series resistors prevent the high turn on power making sluggish opening and also prevent the injector closing circuitry operating correctly as well, resulting in sluggish closing too = BOTCH UP.

many people apparently do use series resistors successfully but it would appear that the greater the size of the injector, the greater is the potential problem

 

Agreed 100% and I have designed a few ecu's in my time

 

any more input?

 

Use high impedance injectors (high ohms)

You cant live map OFAB yourself so I would recomend you asking your tuner/chip supplier for proper advice.
Doing this DIY is NOT the way to go unless you change the managment to an after market type

You may save a few quid by getting injectors cheaper but in the long run it will cost you money !

 

Correct. You may as well just use the saturated coils instead,

 

There are quite a few saab high impedance injectors with higher CC than my 701 but how about combatability with a off the shelf chip? Or is proper mapping the only way?

 

damn, everyone else corrected tabetha before i had a chance

 

RS Stu,

If you deviate away from a standard conversion, It will need custom mapping and cost you loads extra !

There are very few who can do this properly on OFAB.

If you intend to keep the standard ECU, you really need to talk to someone like MSD or Collins about what they can do for you.

When I say standard conversions, proper tuners will probably have something near to what your engine spec needs but you will have to use the correct parts for the job in order to be correct.
Bigger is not always better !

Sorry !



PMSL @ jim Galbally

 

What will be best?
engine spec atm
2.0 16v Blacktop
low comp pistons
701s
OFAB ecu
Cossie T3
Adj cam pullys
piper valve springs.
Will a ofab chip run this ok? or will it need custom mapping regardless?

 

When you say OFAB chip do you mean any chip ?

The chip MUST match the injectors and engine spec exactly or it will need a live map.

Looking at you spec, it certainly isnt a standard although the companies I mentioned above may have something near enough but I think to stop it melting and get the best performance, a live map is what you need !
Will be worth it in the long run.

 

It'll need to be mapped really. 701's are way too small for that spec, unless you want to run half a bar of boost (< 200bhp)

 

So, as long as i get high impedance injectors ill be ok, As it going to be live mapped any way. So lets just say i am going down the live map route it OFAB ok? or will it be better and cheaper to change to cossie mangement or an aftermarket unit?

 

Use IAW 048s (IIRC) mate. Otherwise nobody will have a base map and you will be paying far more to have it live mapped, and its expensive enough as it is because its a bit of a pain in the arse.

 

With OFAB?
How about if i use cossie management? Or is it not worth it?

 

when i wants mapping it will be going to MSD anyway so whats best for you to work with. With the part i have?

 

Yes with OFAB or C.
Weber Cossie is fine, far more flexible and iof course sequential too so if your budget stretches to it go for it.