"Change" high-impedance injectors to low-impedance without a, want to use different injectors on my L-Jet... Options

[Mueller]

I have a spare set of 19-lb Ford injectors that are ~15 ohms....

The L-Jet uses low-impedance injectors (approx same flow ratings) with the use of ballast resistors to bump up the impedance from 3 ohms to 9 ohms.

Can I knock down the resistance of the 15 ohm injectors to 9
ohms without any ill affects?

If I knock down the impedance, will they
still flow 19-lbs at the same fuel pressure as before??

Hope the question makes some sense...

thanks,

Mike

[bd1308]

Mike, Just use what you have.

If it works why break it

[Mueller]

Mike, Just use what you have.

If it works why break it

okay Mr. I-wanna-do-the-opposite-of-EVERYONE-and-back-date-to-a-tailshifter (IMG:style_emoticons/default/biggrin.gif)

[bd1308]

Ok Mr. I-Used-to-use-LINK-but-I-messed-up-and-now-rely-on-LJET-to-save-the-day-but-stock-injectors-arent-good-enough (IMG:style_emoticons/default/tongue.gif)

[Mueller]

Ok Mr. I-Used-to-use-LINK-but-I-messed-up-and-now-rely-on-LJET-to-save-the-day-but-stock-injectors-arent-good-enough (IMG:style_emoticons/default/tongue.gif)

my stock injectors are toast.......I'm buying some used ones from a fellow clubber, but I'm looking at a backup plan incase these don't work....

the LINK is going to be used on my 1.8T sitting on my workbench (IMG:style_emoticons/default/smash.gif)

[bd1308]

Eventually I want to use MS, but I cant find any cheap kits.

I think I may have one partially complete kit lined up, I really would like some form of adnavced EFI

[bondo]

How are you going to lower the impedance? Raising is easy.. lowering?


Edit: I get it now.. resistor in parallel. Injector wants to see 12v to open... L-jet wants to see a 9 ohm load. I see no problem with a parallel reststor.

[Bartlett 914]

I don't think I would do anything. Adding a parallel resistor may make the impedance the same. The only reason this may be a factor is it the control circuit uses a current controlled logic circuit. I doubt it. I think it is digital and simply an open collector transistor circuit bringing the circuit to ground. I suspect the circuit path is:

+12 volts to the balast resistor to the injector. The other side of the injector to the open collector of the controller output transistor collector with tne emitter at ground. But without seeing a drawing on the control circuit I can't say for sure.

Mark

[Dr Evil]

Parellel resistance formular (for-Mueller (IMG:style_emoticons/default/wink.gif) )

(R1*R2)/(R1+R2) = Rt

Rt = what resistance you want
R1 = injector resistance
R2 = resistor value needed to give you desired Rt

Solve for R2 and you are in bidness.

HTH (IMG:style_emoticons/default/confused24.gif)

Britt, stop being so scatter-brained and by my MS kit already. You have PMed me a few times, but you never seem to finish the tranzaction (IMG:style_emoticons/default/rolleyes.gif) (IMG:style_emoticons/default/wink.gif)

[turboman808]

I could do it with a Apexi AVCR. But if your gonna go and do that you may as well get the megasquirt.

[Dr Evil]

Also

1/R1 + 1/R2 = 1/Rt

if that is easir to solve (IMG:style_emoticons/default/wink.gif)

[Gary]

I don't think I would do anything. Adding a parallel resistor may make the impedance the same. The only reason this may be a factor is it the control circuit uses a current controlled logic circuit. I doubt it. I think it is digital and simply an open collector transistor circuit bringing the circuit to ground. I suspect the circuit path is:

+12 volts to the balast resistor to the injector. The other side of the injector to the open collector of the controller output transistor collector with tne emitter at ground. But without seeing a drawing on the control circuit I can't say for sure.

Mark

(IMG:style_emoticons/default/agree.gif) Quick google showed ths. Check out page 21. Going from 9 to 15 ohm won't likely be a factor. Current draw to the ECU will decrease by 40%. If you're a stickler, substitute a lower dropping resistor in each injector using Evil's formula.

[Gary]

Actually, duh. Dr. Evil's formula is for resistors in parallel. Resistors in series just add. You probably can use no current limiters at all with 15 ohm injectors as the total of the dropping resistor and your stock injector is 9 ohms, as you originally posted.

[Joe Ricard]

DAmn it if I were at work. I could get my genious Co-worker to do this with out any trouble. I'm out for a week sorry man.

The little bit I understand trons is less resistance will allow more current flow. and you will over cycle the lesser injector. the opposite will happen for higher resistance injector.

But..... Aren't injectors really just on/off valves.



Geez reading this it is obvious I am clueless bout dis stuff. (IMG:style_emoticons/default/confused24.gif)

[Dr Evil]

Injectors are actually electromagnetic coils. This is why they go by "impedence" rather than "resistance". The electromagnet is made of a coil of wire and a piece of iron in the center (simplified). Wire on its own shows low resistance, but when coiled in this configuration the electromotive forces at work cause a resistance. That is the value stated on the injector at the given 12V. Adding a resistor in parellel will change it accurately enough to get the load down to wher you want it. As for necessity, I am not sure.

The FI is either on/off, but you need ot make sure you either have enough juice to turn it on, or not too much so that you fry it. That should be the only concern so long as the brain is happy with the change.

Also, note that putting resistors in parellel will change the current.
E = I*R so if Rt goes down, and E stays the same, then I will have to go up. So long as the injectors can handle the increase in current you will also be fine.

[Bartlett 914]

Adding resistors in parallel will have NO effect on the injector. It will only have an effect on the driver (controller circuit). All juice running through a parallel resistor is wasted energy. Sure the resistance in the injector is a coil and has inductance. This inductance may be of concern as to the frequency the circuit driving it must work with. Using resistors will not have any effect on any frequency response! These injectors are digital. That is it is on or off. There is no half way on or any type of volume controll. It is strictly duty cycle. They will work by either a measure of how long it stays open or it may work by controlled pulses per injection cycle.

Mark

[JeffBowlsby]

The injectors only need 2V or 3V as I recall ....12V will fry them.

[Bartlett 914]

The injectors only need 2V or 3V as I recall ....12V will fry them.

My guess is that they are meant to be pulsed. 100% on may mean too much heat buildup.

Out of curiosity, I just scoped my injectors on my 1.8. I measured about a 5ms pulse at the injector. Ay 1000 rpm these were spaced about 30 ms apart. At 2000 rpm 30 ms apart. And at 3000 rpm 20 ms apart. The pulse stayed at 5ms!

I think on D-Jet there are only 2 circuits and 2 injectors fire at the same time. L-Jet is probably the same. We could do the math here but I really need to get back to work for now

Later...

Mark

[jk76.914]

Mike, Just use what you have.

If it works why break it

okay Mr. I-wanna-do-the-opposite-of-EVERYONE-and-back-date-to-a-tailshifter (IMG:style_emoticons/default/biggrin.gif)

I was thinkin' about that. It'd go along with my hydraulic cam and sodium-filled valves. (IMG:style_emoticons/default/smile.gif)

[Katmanken]

Ummm

Might want to do a search on peak and hold injectors....

The VW guys did us a favor by having the peak and holds which are optimum for response, however, read the below....

And, I did have my programmable EFI converted to peak and holds by having the vendor put in a big resistor...

"Injector resistance is an important consideration when matching ECUs to injectors. Injectors are manufactured as low resistance or high resistance. Low resistance injectors typically measure in the 2 to 5 ohm range, high resistance being 12 to 16 ohms. It is important to match injectors with the injector drivers in the ECU being used. Generally speaking, original equipment ECUs are equipped with saturated drivers which drive high resistance injectors. Aftermarket ECUs are equipped with drivers for peak and hold injectors which are low resistance. Some aftermarket ECUs will drive both types of injector: It should be mentioned, however that injectors for saturated drivers do have a slower response time than those for peak and hold. Most peak and hold drivers will drive both high and low resistance injectors but, under no circumstances, should peak and hold injectors be driven with saturated drivers. "

Ken