Injector Resistance

[Bazooka]

Was looking at different injectors today and out of curiosity I am asking these questions.
I have a 100kw 4AGE with the standard 250cc injectors. We have a new injector cleaner at work so I just had to give them a go. Out of curiosity I decided to test them against a set of 4AGZE injectors. Now obvoiusly there was a big increase in flow being 365cc but the figures I found show a different resistance between the two. What does this resistance refer to? Would this make these two types of injectors incompatable? If I were to upgrade to the 4AGZE injectors would I need to do other things to make them work?

[Cuzzo]

There is low impedance and high impedance injectors. Different Stock Toyots ecu's want to see a certain type. However im pretty sure if you know your components you can change them to high/low.

[Crazyracer]

For the most part you can't just exchange high and low impedance injectors. Some after market ECUs can manage either but most likely not on a factory ECU.

The low impedance once are peak and hold which supply a higher current to open the injector and lower the current flow to hold it open. High impedance injectors have a sustained current flow. So the ECUs need to work differently for the different types.

At best the ECU probably won't work with the wrong type. At worst you may damage the ECU or injector.

There may be some aftermarket devices around though, to let you use the other type of injectors, but if you look around you'll probably find something to suit your needs in the correct impedance.

You'll probably need to remap the fuel tables anyway if you change injectors so you might be better of looking at an after market ECU or piggy-back system

[Bazooka]

Thanks Crazy thats pretty much what I needed to know. SO basically you cant just swap them over. Thats fine I dont think I need to put larger injectors in it or anything. Would it really make much difference if nothing else was done/changed/modified?
I was curious more than anything.

[Cuzzo]

No upgrading injectors without doing anything else to the motor will cause nothing but problems. If they even work and start the car, it will deliver to much fuel for the ecu(unless otherwise managed eg. aftermarket/piggy-back) and just run super rich.

[Bazooka]

Just as I thought.
I did find some 7MGTE injectors! Correct resistance and 440cc

[Cuzzo]

EDIT: Misread.

Yeah thats what i have done too.

[Crazyracer]

Going from 250cc/min to 440cc/min, you'll be lucky if the car runs at all. It would be massively rich everywhere.

Even if you could remap the fuel table, it wouldn't be a good idea. Really you want the smallest injector that will supply an adequate amount of fuel. This way the injector open time is maximized and there better chance of the fuel being atomized, rather than it all being dumped in the inlet port in one big burst and just condensing on the walls of the port.

[TheDarkRaver]

Just while on the topic, what is better a high or low impedance injector? Obviously using an aftermarket computer..

Marc,

[thechuckster]

no big difference - larger injectors are usually low-impedance as they need the higher current flow to energize a larger coil (which usually moves a larger clynder of some sort).

fwiw: i use low impedance 4AGZE injectors with a camry resister pack so the ECU thinks its driving high-impedance units.

[Crazyracer]

I gather that the low impedance injectors open a little quicker, so you can reliably push their duty cycle a little higher than you would with a low impedance injector.

I've been told it also results in them having better low duty cycle control, ie gives a more accurate and consistent amount of fuel when opening for only a very short time.