Smitter

last year my car started having ignition break-up issues, car would just bog while driving and trying to increase engine speed over 3000-4000rpm. even when just reving the engine you could here it sputtering, just did not sound crisp and responsive. the car would idle beautifully however, and compression was good.
so i had some extra parts to try out to try and pinpoint the problem, they included
ignitor
leading coil
map sensor
tps
and power fc ecu.

i changed out each of these items one at a time, trying to pin point the problem.
the last one i tried was also the one i least expected to be faulty, it turned out to be the power fc unit. when the new ecu was installed, the car ran perfectly, throttle response was clean and crisp. all was well other then the fact i had to buy a new power fc.

But again today, the car started acting up showing the exact same symtoms as listed above. Could another power fc have crapped out on me? Naturally i am thinking it is the culprit again.

Anyone had any problems with the power fc going bad, a faulty connection in the unit or something, Can this be repaired somewhere?

cewrx7r1

iTrader: (2)

Why do you say ignition?
Maybe it is fuel.
Which secondary injectors are you running and how are they installed?

Smitter

well i cant say its ignition for sure, i am running 1600 secondarys (unsure of the brand), 550 primary,
the secondarys are installed with resistors in one of the wires off the harness (not sure what u mean by how are they installed). i have constant fuel pressure @ idle and am not losing fuel pressure while driving or trying to accelerate.

the reason why i am pointing the finger at the power fc is because last fall i changed mine out with a new unit and it fixed the problem immediately. had no issues with the car again until yesterday, and they are the exact same symtoms. i am not ruling out coincidence, but my first line of action is gonna be to borrow a pfc (that will be the 3rd one) and see if it fixes the issue once again.

R-R-Rx7

iTrader: (24)

if the stock ecu got screwed and then the power fc, im pretty sure it has to do with the secondaries wiring.. or any other wiring that shorts somewhere and burns ur ecu.

Before you try that power fc ( Dont burn another one for Gods sake) try to find any shorts on the wiring..

Smitter

^^it wasnt a stock ecu, both were power fc
the first power fc was burnt before the upgraded secondarys were installed. i was using it on my twin setup with stock fuel system, but it wasnt until i did my Single turbo setup that i figured out the power fc was faulty. when i installed the 2nd power fc the car ran perfectly for 3000kms so i am confident that i wont burn out a 3rd one just by trying it for 5 minutes.


maybe i should change the engine harness aswell then if something is shorting out the power fc.?

R-R-Rx7

iTrader: (24)

hey you never know...since you have an idea what it could be, check the wiring first.
my opinion

Dudemaaanownsanrx7

iTrader: (23)

the odds of 2 power fc's failing for no reason is slim. If it is the PFC then most likely something is causing them to burn out. I i have heard of people sending them off to get repaired for like 150 or so. If you can find out what is being damaged inside the PFC then it will be easier to fix it.

I know some people have burned out the injector firing circuits by not running the resistors.

Smitter

thx for the opinions, i will try another pfc tomorrow and c if that fixes the problem and report back and let u guys know, if it does i will try to figure out why the car is damaging them, if nothing else replace the engine harness. I have cut alot of the clips that i no longer need off of it so maybe that is the problem.

Regardless of what is causing this i do need to send both units away for repair, do they have to go right to Apex or does someone else possibly repair them?

cewrx7r1

iTrader: (2)

You did not completey finish how your 1600s are set up. What size resitors?
Too small and the PFC secondary injector drivers can be overdriven and fail or go bad.

They always said use 10 ohm resitors withe the 1600s.

From Howard Coleman "That’s why most of us have 10 ohm resistors in our secondary (Low Resistance) fuel injector circuits.
14.4 V / 12 ohms = 1.2 Amps. 1.2 Amps is OK as to protecting the Power FC circuits."

But some later 1600s were higher impedance (5 ohms) and people were using 3 ohm resistors with them.
14.4 / 8 = 1.8.

Smitter

^^ i will double check my resistor size aswell

Smitter

the secondary injector drivers failing sounds like it could be it, the car acts up while trying to accelerate only, not when idling and under extremely light throttle, sounds like a secondary injector issue to me. Does it make sense to you that it would take approx. 3000kms of overdriving the secondary injector drivers before they fail?

Smitter

OK, tried another pfc today, didnt fix the problem, so i guess i can start looking at some other ignition issues.

i talked to my builder today also, he is the one that supplied me with the injectors and resistors, they are both bought through Ari at Rx7.com so the chances they are the problem is slim. they can be view here:
http://www.rx7.com/store/rx7/fdfuel.html

kinda stumped about the whole pfc thing and am not totally ruling it out as an issue either, remember i did have success merely changing out my first pfc last fall with a new one?????????????
any help, comments or advise is appreciated

cewrx7r1

iTrader: (2)

It does not say what size.

Smitter

i emailed rx7.com to confirm that the resistors are 10 ohm, i will check for sizes marked on them aswell.

Smitter

finally got around pulling the Uim today to check on the resistors and i believe what i have found are 3 ohm.
heres what stamped on them: HEI TMC-25 3(ohm symbol) 1%
i will try and fing out the impedance of the injectors.

on side note i changed out the leading coil and tried some different plugs while i was under there. didnt help

Smitter

i found this thread that seems to support the idea of using the 3 ohm resistors
https://www.rx7club.com/showthread.p...osch+injectors

Smitter

ok, so i found this video on youtube to figure out my injectors impedance:

http://www.youtube.com/watch?v=xoh-_6tVjsw


by following these instructions i found my injectors to be 4.4ohms(a high resistance injector?), my resistors are 3 ohm as stated before. Am i overdriving my power fc circuits? i need help pluging my numbers into the formula, but i think it goes like this
14,4v/7.4ohms= 1.87amps
which should be safe? did i do this right?
i'm trying really hard to learn this ****

Smitter

damn just checked my numbers
it should be 14.4v/7.4ohms =1.95 amps

Smitter

with the drivers seeing 1.95 amps i should be safe, but is there anyway way to test the power fc circuits to ensure they arent burnt up?

Smitter

Got my new power fc today, plugged it in and just as i suspected the Car ripped like it should. So this solidifies that my 2 power fcs both have fried secondary drivers. Running with 7.4 ohms of resistance.

I emailed Steve Kan to get his recomendations and he said that the power fc circuits can only with stand 1.5 amps of continuous load, Not 2.0 amps that many have told me. That explains it. That being said, he recommended a minimum resistance of 8.7 ohms.

Rx72Heaven

iTrader: (2)

COOL MAN! awesome, we need to go for a rip today!

Dudemaaanownsanrx7

iTrader: (23)

in post #12 you said you had already tried another PFC does that mean the other one you tried was fried also?

Also you said you got the resistors from rx7.com or something, did they also provide you with the PFC? seems like if they are selling resistors that are supposed to work with the PFC but instead burn it up that they should be held accountable and replace or repair the PFC for you.

Smitter

^ i didnt actually try driving the car with the power fc i initially tried in post 12. i just reved the car and it still seemed to b breaking up, i think i might have screwed up while trying to load my map????

as for the liability issues, i am waiting for comfirmation from apexi that it is indeed the injector drivers that are fried in both units. in all likely hood rx7.com will cover the cost of repairs, when i find out i will let u guys know.

FC3S Murray

iTrader: (7)

Any update from Apexi?

I am awaiting word from them on mine that possibly fried. My symptoms where my 4 10ohm resistors were heating up progressivly when the ignition was on. I was an idiot and while testing my fuel system for leaks(have a hot pump) my UIM slid down onto my alternator 12V wire and caused a big boom. Unfortunately the other end of the UIM was laying right on top of my 2 injector ground wires bolyed to the housing.

Anyway you said your injectors tested at 4.4 ohms right? Those are low impedence injectors and you will need 10 ohm resistors wired into your fuel injection wires.

High impedence injectors usually measure somewhere around 12-14 ohms I believe.

That sucks that they are both fried BUT from what I can tell from old threads it doesn't cost too much to repair but may take a while to get back to you from the repair shop in Japan.