550CC injectors

[Newbie99]

If I manage to get a set of 550 CC injectors from a UK supra, am I guaranteed they will fit my jap spec, as I just talked to Toyota and the chap came back with 8 different types of injectors!?!?!?!!?

 

Also is the fuel rail different, from a jap spec to a UK spec?

 

And finally if I upgraded to something bigger than 550's would I still require a resistor pack?

 

Thanks.

[Guest Terry S]

Yes UK injectors will fit the JDM rail.

 

You will only need a resistor pack if you buy LOW Impedance injectors ( such as the UK's). There are aftermarket bigger injectors such as Blitz which are High Impedance, and will therefore work without a resistor pack. If you want to reuse the existing rail you will need to buy side feed injectors.

 

FYI the JDM injectors are 13.8 ohms whilst the UK's are around 2.8 ohms. Using LOW impedance injectors WITHOUT a resistor will cause injector/engine failure, as the injector/s will run dry eventually.

[dude]

Originally posted by Terry S

Yes UK injectors will fit the JDM rail.

 

You will only need a resistor pack if you buy LOW Impedance injectors ( such as the UK's). There are aftermarket bigger injectors such as Blitz which are High Impedance, and will therefore work without a resistor pack. If you want to reuse the existing rail you will need to buy side feed injectors.

 

FYI the JDM injectors are 13.8 ohms whilst the UK's are around 2.8 ohms. Using LOW impedance injectors WITHOUT a resistor will cause injector/engine failure, as the injector/s will run dry eventually.

 

Has anyone done this terry , surely everyone knows about fitting the resistor pack

 

John:flame Dev

[Guest Terry S]

Originally posted by dude

Has anyone done this terry , surely everyone knows about fitting the resistor pack

 

John:flame Dev

 

You'd hope so, but there is always one.

[dude]

 

John:flame Dev

[THOR Racing]

WITHOUT a resistor will cause injector/engine failure, as the injector/s will run dry eventually.

 

That is the effect rather than the cause.

 

Sorry to be pedantic but the resistance is required to set the drive current for the injector coils. The ECU has a low impedance (resistance) drive output which is current regulated by the external resistance.

 

You need the same resistance for the ECU regardless of JDM or UK so you either make this up with 100% JDM Injectors at 13.8ohms or have 2.8ohm injectors and a 11ohm external resistor pack for UK.

 

If you overdrive the coils (too much current caused by too low resistance) they will undoubtedly work for a while but on high load (WOT) they will get hotter and hotter as the coils heat up and eventually will fail.

 

Look at the maths.

 

12V voltage feed to the injectors. (ground switched)

Current = Voltage / Resistance

So 12V / 13.8R = 0.87A

 

But use 2.8R UK spec injectors and you get....

 

12V / 2.8R = 4.29A

 

4.29A is far larger than the original 0.87A

 

Either the injector coil will burn out or the output drive from the ECU would fail. (Modern ECU's are limited to a maximum current output which is probably why the injectors would last longer than you would first expect in this condition)

 

Similarly you wouldn't fit high impedance injectors on the UK spec car without removing the resistor pack as this time you'd get too little current flow and the injectors would take longer to turn on and hence effect the fuel delivery.

 

Regards

Pete