...between Saturated and Low Impedance Injectors. I know we run Saturated and that 4g63 guys use the low impedance injectors.

I am going to use the MegaSquirt and I just need to know what would be best to use or easier to manage, etc. Looking for 700+cc injectors depending on the info I get here. Thanks

Peak and Hold = Low impedence = low resistance, about 1.5 to 2 Ohms per injector

Saturated = High impedence = high resistance, about 12 to 14 Ohms per injector.

If your only running 4 injetcors, like we do, then the Megasquirt can control either type.

Only difference is a software setting.

And it's very hard to find nay injectors that are "saturated" type over 500cc...

Originally posted by MrSlick
it's very hard to find nay injectors that are "saturated" type over 500cc...

...and they get expensive QUICK.

i thought you don't really need super big injectors if you're running the megasquirt? doesn't it use an adjusted pulse width to supply more fuel rather than higher fuel pressures with the stock pulse width? :shrug

you still need larger injetors.

Originally posted by MCubed45
i thought you don't really need super big injectors if you're running the megasquirt? doesn't it use an adjusted pulse width to supply more fuel rather than higher fuel pressures with the stock pulse width? :shrug

...why wouldn't you? Larger injectors can inject more fuel (duh). You just don't need 8 of them, or ridiculously high fuel pressures behind them.

Indeed. I guess my main question was regarding flow and pros and cons between the both of them. Are there any drawbacks from using either of them? I misunderstood also, I thought impedance concerned fuel flow rather then electricity. So I was wondering if they flowed better or something. I guess I need to do my homework on that department a bit more. To be safe and to save money for the future, I decided to go with 1000cc injectors. I just need to figure out if saturated of low impedance.

I used RC's website to calculate how much fuel I need and it came out 699cc even. THis is with 4 injectors of the same size, .65 BSFC, 80% max duty cycle and an estimated 400HP (350 WHP +-) at the crank, and 65psi of fuel preassure at the fuel rail (considering I would use a 1:1 FPR at 20psi of boost, 45 psi idle FP plus 20 psi FP = 65psi, correct?).

Now, I will most likely be using 91 octane to tune for 20 psi and I will will also install some anti-detonation device like methanol or water injection. Later I will include nitrous, but not now. WHat do you think guys? Am I heading the right way?

Thanks for any help. With luck and good work, I will finally make the car run as it was meant to do.

Supporting mods are:

Crane 16 cams
1mm Oversize ferrea valves
P&P head
55mm bored TB
Ti springs and retainers
PT lasher/adjusters

JE pistons, standard bore
Crower Rods
stock crank

MSD DIS-2 ignition (going out cause the MS can now control ignition)
MSD coil
MSD wires

S20G turbo
HRC FMIC
HRC tubing

I tell you, this car has a lot of potential and good parts in it. ANyway, thanks for any advice.

i don't think it even makes a difference as long as it flows right. but man 1000cc's that's overkill unless you're going all drag and aiming for 650-700WHP. i would just work your way up, start with 720cc's which are at a decent price and enough to handle 500whp. i've seen good prices with them lately on ebay for like $200 for 4.

Well, according to my calculations, and correct me if I am wrong, I would need 700cc at 80% duty cycle. All this considering and aiming at around 350-350 WHP which I doubt I could do on just 20psi of boost. I am still trying to learn and yes, I'll get the 800 or so injectors for now.

Any more info is greatly appreciated.

ok here's what i go with:
let's do 500HP and 720cc injectors
500 x 10.5 x .57BSFC / 4 = 748.125cc
fuel volume at 85%DC(screw 80%): 748.125/.85 = 880.229cc
now the injector fuel pressure: 880.229cc/720cc = 1.2225(^2)= 1.4945 x 43.5psi= 65.011 + let's say around 30psi of boost depends on the turbo you have. 95.011psi.
you're barely maxing out your injectors even at 500HP with 30psi of boost. whp it varies at around 450-470whp depends on your mods. also if you get good injectors like RC engineering type, they can handle a higher duty cycle than most brands. i've talked to one of the guys there, and these injectors are meant to handle higher pressures.

I am using 780CC injectors.

These will be good for 500HP+
I know it can be tempting to think that the bigger the injector the better, but the larger you go, the less control you have a idle...

I can idle fine on my 780CC injectors, but I don't know bout injectors bigger than that...

If you are planning for 300HP or there abouts I'd say go with 680CC or there abouts. That will still give you plenty of headroom.

Originally posted by MrSlick
I am using 780CC injectors. These will be good for 500HP+ I know it can be tempting to think that the bigger the injector the better, but the larger you go, the less control you have a idle... I can idle fine on my 780CC injectors, but I don't know bout injectors bigger than that... If you are planning for 300HP or there abouts I'd say go with 680CC or there abouts. That will still give you plenty of headroom.

Soon we will see how well these 880's idle. :7

if you put in low impedance injectors your computer will not be able to use them right and your car will run like a dog it's very bad. i bought some from a guy and was told there were fine to use. i installed them with my turbo kit. it took me months of trying to figure out what whas wrong b4 i replaced them with the stock ones and found the problem.

Originally posted by ryansiefring
if you put in low impedance injectors your computer will not be able to use them right and your car will run like a dog it's very bad. i bought some from a guy and was told there were fine to use. i installed them with my turbo kit. it took me months of trying to figure out what whas wrong b4 i replaced them with the stock ones and found the problem.

First of all, we're all talking about running low impedence injectors with the Megasquirt...

Secondly, you can run low impedence injectors with the stock pcm if you use a resistor pack. I know, I ran mine like it for a year.

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