FC3Sdrift

iTrader: (5)

yes I know.... i'm stubborn! you guys can say i told you so


I found out today that i definately am running on one rotor

i pulled the sparkplug wires off the rear rotor and it runs the same...

i triple checked the compression...I get 3 even bounces to around 75-80psi and when i leave it closed the overall compression is about 100psi or alittle more
so theres good compression....cranking it over with all the plugs out it sounds equal

i checked to make sure there is spark

but the plugs will be bone dry, maybe a spec of moisture on the trailing

so i pulled the UIM off gave the injector some taps to see if i could unstick it and i tested it with 12V and it clicks

but why is it not shooting fuel in the motor?.....could it be clogged or maybe a wiring problem?

evildeadbadguy

I would ohm them out for peice of mind, but i was having the same problem but my front rotor was not firing and it ended up bein the injector clip itself.

HAILERS

If that injectors plug has 12vdc on one wire, all that is needed to make it work is the ECU sending a ground signal to it on the other wire.

So, ohm out the other wire to the ECU's small plug (series four) and see if it ohms out. If it does, then I'd guess the driver in the ECU is kaput. The driver for that primary injector.

FC3Sdrift

iTrader: (5)

i've been doin some searching theres been a few people with the same problem with the n374 ecu

can i check at the ecu for 12v's or do i have to do it at the injector clip?

the ecu was always questionable ...when i got it it had a reistor or something rattling around i soldered back in and a burnt circuit i recoonected with solder lol

it started it and i figured it worked but its gotta be an ecu problem

where is and what does the #2 primary injector driver look like....and can you replace them?

i'm thinking about getting a N370 ecu and just putting the tom's eprom chip in it so i can keep the tune thats on it

HAILERS

Yes. Connect all the injectors up to their plugs. Turn the key to ON. Go to the ECU and pull the plug off that has the injector wires. Put a meter on each wire. They, all four, should have 12v on them. If they do, then the problem probably is the ECU.

If I remember this is the series four car with a series five engine/ECU/modified harness. So that would be pins 3W, 3X, 3Y and 3Z. Rear primary is 3Y, a light green/black wire.

fc3s91

iTrader: (23)

If you are running the n374, it will not fire the secoundary injectors.

HAILERS

We might heed what fc3s91 just wrote.

I did a search for N374 and came up with the following threads: https://www.rx7club.com/forum/search...archid=4567268

There's a few of those threads that mention your problem of problems with the injectors not firing or the spark not being there.

I don't think it's anything I could figure out online. Your problem is almost like the ECU is doing fuel cut on the rear rotor. Like it thinks it's overboosting and cutting fuel to the rear rotor. Got me. You might try disconnecting the output of the boost/pressure sensor to the ECU and see if things change, but like I said, I don't think I could figure it out from here.

Buy a series five turbo ECU seems like a winner if you read those threads in the url I posted. Some of those guys just plugged in their old non turbo ECu and then they had spark and fuel to both rotors. I know you can't do that because of the swap you did.

RotaryResurrection

iTrader: (8)

Ah, the continuing saga of electrical gremlins with cross series swaps. Gotta love it. Especially since no one suggested that this might happen beforehand. But hey, what do we know, right?

I have heard of people having this issue and an n370 curing it. I have never had the opportunity to explore why. In the past I have run n374's on running US spec s5 NA--->turbo conversions, and on running US spec s5 turbo II's. I did encounter one car that refused to run on the n374, but due to time limitations I was not able to investigate why that was the case.

FC3Sdrift

iTrader: (5)

I've got a S5 ecu lined up i just have to go pick up

the ecu was banged around enough to knock a resistor inside it loose

i'm just goin to swap the eprom from the tuned ecu into us ecu so i can keep the tune

Thanks hailers, i was reading through some of those threads before i'll try that out with the boost sensor this weekend i should have the ecu by then so i'll let you know how i made out

HAILERS

Ah, heck. I guess some of my responses didn't get posted. I found one that showed a place that sold the devices/drivers for the injectors. It was something like 25bucks to buy.

If I had a N374, I'd ring out the wiring from point to point before applying power to the car. There must be some wiring that isn't kosher and it's wiping out the rear driver. Done.

HAILERS

https://www.rx7club.com/forum/showth...highlight=N374

This thread. There's a thread in this thread. Gone.

kustomizingkid

iTrader: (2)

I replaced my buddies motor and it was only running on one rotor. The metal contacts for the injector plug actually got pushed up in the injector plug not making contact. Sounds stupid simple, but some times that is all that is wrong.

HAILERS

I think this thing could be figured out just by getting a meter out and going to the ECU and the four wires for the injectors. Then disconnect all four injector plugs on the engine. Ohm out each injector wire from ECU to the given injector.

I think you'll find that the injector that is not firing, will have its wire b/t the ECU and the injector OPEN. In other words that injector signal from the ECU is going to another place.

I remember a thread where the fella figured this N374 deal out. In the back of my head it was connected with the boost sensors wire also. So if you find the *bad*injectors wire open b/t the ECU and the injector, go see if it's actually going to one of the wires on the Boost sensor.

I found three threads related to this N374 and they're worth reading. I'll attach them later.

https://www.rx7club.com/forum/showth...highlight=N374

The guy called HUNG LO is the one worth reading. It's towards the bottom.

https://www.rx7club.com/forum/showth...highlight=N374

Thrasher is the one to read on this one....above.

http://www.dilbert.com/comics/dilber...-20080111.html

Heck, I lost track of the third one. So read Dilbert for humor.

FC3Sdrift

iTrader: (5)

I hooked up an N351 i got from Joe at RPM.....and it works perfect.....both rotors are working, he gave me another N374 ecu but it ran the same as mine......

so i'll toss my eprom in the n351 ecu and hope it still works

i'll post the video of it running with the n351....its gotta have some kind of port work to the motor it sounds like it

it pulls 16-18 for vacuum now but i didn't get a chance to get it fully warmed up so the idle drops

HAILERS

Glad you got it running.

RotaryResurrection

iTrader: (8)

This is the common failure mode of trying to use the n374 ecu with a turbo swap, that no one has been able to figure out. I would like the opportunity to inspect a car with this issue for a long period of time to resolve the problem.

The only solution is to find an n370 ecu, or to go standalone. The n351 is unsuited to even a stock turbo application.

FC3Sdrift

iTrader: (5)

http://www.youtube.com/watch?v=SWDfva41scQ

http://www.youtube.com/watch?v=3QqTdm5MXtQ

this one is on a video camera and my dad copied it with the sound down so you have to crank the speakers up to hear it

http://www.youtube.com/watch?v=Q0O4z1vC8Os


what kind of port job do you guys think this has


i want to get a n370 ecu and put the eprom in it from the original ecu
i tried putting it in the n351 ecu but it didn't work.....it must have different I/O functions

FC3Sdrift

iTrader: (5)

i think it might have something to do with the little black box attached to the n374 ecu's ...someone said it was a knock sensor module or something????...but maybe the n374's need that hooked up or they keep the rev limiter on all the time....and thats why the knightsport chips work because they have the revlimter removed?
i wanna try just disconnecting the knock sensor and see what happens?

or hopefully i can put my eprom in a n370 so i can keep that tune.....if not i'll get a standalone cuz i don't wanna try running this engine on a stock computer

Chris Boots

Well here's some news... N374 computers are pretty much crap. I have never heard of one working in a US car. I have even tried 8 different N374 computers in a 1990 TII and they all didn't work. not one. Get a N370 and all you're problems will be gone. Oh and the N351 ECU may start your car and run it but that is poison. The NA's had different injector cc's than the TII. The N351 will supply the wrong amount of fuel and will seriously hurt your engine in the long run. Its great for quick diagnostic but not for running the car, get your self a N370 and everything will be all good.

RotaryResurrection

iTrader: (8)

Actually the n351 is okay to start and drive on as long as you stay out of boost. The injector cc difference is not that big a deal. In fact, the n351 supplies roughly the same amount of fuel to the engine when off boost, but since it uses smaller injectors than the turbo, it uses a wider pulsewidth. So you put turbo injectors under that computer and it actually runs richer than it would with the turbo computer, UP TO A CERTAIN POINT which is somewhere in the boost threshold.

The bigger problem is timing map and advance with the NA ecu versus the turbo ecu. NA ecu's continue to advance timing more aggressively at higher rpms/loads than do turbo ecu's which pull some extra timing out for boost.

FC3Sdrift

iTrader: (5)

the cars not on the road yet so idling it on a n351 won't hurt....the only way i would run a ecu on this motor is if i can keep the original tune..i wouldn't risk running this engine on a stock n370 or 351 (other than idling it in my driveway)
electrically speaking this set up would work perfectly with a n370 ecu.....but my motor isn't stock, and i don't wanna blow it up on the first drive

The problem with the N374 is not that they are junk....they have some extra knock module or something...that attaches to the ecu and connects through the chassis harness i think....but when you run them its as if the fuel cut to the rear rotor is constanly on
thats why the knightsport chip in an n374 ecu will work because it has the rev limiter removed
i'm goin to look through the chunks of S5 chassis harness i have and either figure out how to hook up or try to find a way to disable the stock rev limiter

a standalone is starting to look more tempting

Aaron Cake

iTrader: (1)

A standalone is your only option, as was mentioned months ago in your original thread.

Upgraded turbo and porting always means a standalone.

Could it be run on a stock ECU with piggybacks? Sure. Will it run well or last long? No way.

RotaryResurrection

iTrader: (8)

just run the power fc, there was an AP PFC kit for sale in the classifieds for 800 bucks a few days ago. I gave well over that for mine. Or you can run Banzai racing's adaptor kit for the FD power FC.

rx713bt

iTrader: (4)

We did a S5 NA to turbo conversion and had problems with the N374 ECU.

It had the same symptoms with the rear rotor not getting any fuel. It turned out to be fuel cut. Did you check to see if the NA dash cluster is outputting 12V from the volt gauge to the boost sensor? That's will overload the boost sensor and tell the ECU to hit fuel cut.

FC3Sdrift

iTrader: (5)

did you guys solve that problem and get the n374 ecu to work?

I have a S4 TII chassis with a S5 TII engine ....I have the stock boost gauge hooked up and working..could that maybe interfere with it?
maybe i'll see if disconnecting the stock boost gauge helps?