"The device does not do a 4:1 current limit but rather 4A and 1A independantly because limiting the current is not function of applying inline resistance. Obviously if the injector you are using doesn't draw 4A then it becomes the current limiter and not the driver."

My assumption that resistance was added to the circuit by the driver was incorrect. He states they don't publish details about the inner workings and I respect that. So, current is limited to 4 amps for the peak stage, so there is no minimum impedance injector we can run. In cases where 4 amps cannot flow in the circuit, the injector is the limiting factor for the peak stage. 1 amp is always used to hold the injector open.


"Unlike other drivers or some ECU's, the KID0404 has a very sophisticated method of determining when to transition from Peak to Hold. The design also takes into consideration that you are switching a coil on and off and not just a resistive load. They are different and this is where the KID0404 can really make a difference when tuning low duty cycles. This applies to low and high impedance injectors. The box was designed for racing applications that require high flow injectors, yet still offer tunability at very low load conditions."

Sounds to me like they've done a lot of testing as to timing of this and when the pintle is actually pulled back in the injector. What does this mean to us? Basically that FJO provides some very precise control of the injector. Is the peak and hold feature being used at idle/low load? Only an oscilloscope can tell us, but the driver is designed to do this.


"Because the KID0404 can drive 4 injectors independantly it is possible to mix injector types (low/high impedance)."

Earlier in this thread people were asking if the driver can drive primary OEM high impedance injectors as well as secondary low impedance injectors. Yes. As long as the impedance of the injector is below 14 ohms. I say 14 ohms because I'm factoring a 14 V operating system. If above 14 ohms of resistance, the resistance of the injector will become the limiting factor of the circuit for both peak and hold functions so they will be run saturated, and really won't change anything. Any injector under 14 ohms of resistance though, will have peak function, and will be held open with 1 amp.

 

Why not just run the high impedance primaries off th ecu... and the low impedance off the p&h injector driver? That would mean each injector is operating in optimal conditions.

 

That will work just as well as with the injector driver, not any difference really. People were asking about it earlier in the thread.

 

I was just thinking run my primaries saturated off the ecu and then run the 4 secondaries (4 in the gz lim) off of the fjo injector driver.

 

I found an article that dumbs it down for people that got a little lost in this thread (like me). Great stuff as always Howard.

 

Earlier in thread someone was concerned with the mode-of-failure if one of these failed. I'm running 850 primaries off a PFC, and 2x 1680 secondaries with 2x S-HSV's from Coolingmist through one of these boxes and had a failure (using all 4 channels).

The way it failed was that I lost 2 channels while not under load, channel 1 and 3, the other two remained functional. The way I have things wired, that meant I lost water/alch injection to the rear and secondary fuel injection to the front.

It didn't damage anything, engine is fine, just noticed a super lean condition and stuttering when tipping on throttle. There wasn't really a partial fault that I saw.

Also, probably the reason for the failure was that I mounted on the firewall near the DP. I'm running a coated and wrapped downpipe so I was thinking it would be okay, but it was above that area on the firewall. I'm going to get another and mount in a different location.

 

So if I run a high impedance injectors with the FJO box will I see improved on off times for the injectors?

Also you state that as long as the injector is below 14ohms there will still be a peak funtion with a hold function of 1 amp.

Would this allow for the PFC have less chance of burning up? Like what we face with adding resistors in line on the driver curcuit on the PFC?

I ask these question for the fact that I have this box new in box and I am looking for my injectors and was told about dynamics ID2000s witch I am being told are better then the bosch 1680. With the fuel issues of a FD I would think the fastreaction time of an injector would be better for us.

If I am way off on this let me know.

 

No more input on this?

 

So this is still dead topic?

 

There is no need to run a FJO driver with high impedance injectors as it will not gain you anything and adds another coponet that could fail.

With the newer ID 750/2000 (Bosch rebadged) injectors, no need for an FJO.

 

What is the failure rate of the FJO driver? Anyone have it fail on them yet? Also It seems that people were implying that running the driver gave better control of the injector no matter if it is a high or low impedance injector. This goes back to my question. If we have fueling concerns on this cars wouldn't we want as much control as possible?

I also understand having another component that could fail being a concern as well. This brings me to AI. Heat is the devil to these engines and running a water injection or some type of water/meth mix helps cool the combustion temps downs. Would this help in saving an engine if you had an injector concern?

 

a little late to that discussion, check the auxilary injection section, all your questions will be answered there. And yes, it's a great idea.

 

Reviewed some of the AI stuff. Found that it does wonders for our engines if it is set up correctly.

Still on the fence if I should sell the FJO and go with the ID injectors or keep the FJO and go with something else or stay with the ID's.

Anyone running FJO with high impedance injectors?

 

why would they?

 

As I stated in the question a few past back. with the box allow for improved on/off times? Will the box allow for more control of the injectors?

 

I wouldn't think so, but I honestly can't back that up with anything. I think the ability to control the injectors quickly and accurately would depend more on the ecu you chose to use with the PFC being possibly the hardest to control accurately, but otherwise the most widely used, best known, and least expensive.

 

I don't know the failure rate, but mine did within a year.
It was a Biatch to diagnose and find the problem.
It took about 4 hours for Chris from Rotary Performance to find the issue, because the misfiring would come and go so quickly.
He said he never seen one fail before.
His impression was, that the failure was caused by the engine bay heat.
The unit was installed by me, high on the fire wall, near the OEM ground cable on the exhaust side of the engine.
Anyways, we put a new unit now inside the car near the ECU.
We'll see what happens.

 

What style injectors are you using? And do you have more control with the injectors?

 

Howard Silly question but i have to ask it. I am running an aem ems do i need an injector driver or will the ecu be enough.

 

Not needed with AEM EMS...

 

Sorry to necro this thread but I just found some new information that might prove useful

I'm currently using the FJO P&H box to run both my 550/1680's with a PFC on the stock twins and I was having difficulty leaning out my idle and high vacuum areas.

Then I tried using negative lag values to lean out my idle with some success.

After a bit of searching I found this:

According to their data Peak and Hold Drivers do have an affect on the injector lag time, looks to be nearly half as much as without, and this is the only thing that makes sense as to why my idle was so rich even though I was using the stock primary injectors.

Here's where I found the info:
Fuel Injector Lag Time

 

Apologies for reviving such an old thread, but I had some questions on the FJO driver and stock 550 lag times as I origionally intended to install my FJO on all 4 injectors

The comment quoted below which references the injector rehab site quotes lower lag times for denso 550cc injectors when running them through the FJO box. Which is interesting as I thought the FJO would simply run in "pass through" mode for stock injectors. But then I noticed in the table of data the 'ohm' rating for a denso 550 is 2 ohm - I thought our injectors were higher than this, could this table be for a different injetor?

Thanks in advance for any help

Daniel

 

There are both high and low impedance versions of the denso 550 injectors. Mazda used the 14 ohm (high impedance) units for the REW. (note peak & hold has no benefit for the high impedance units since the injector itself limits the current)