Hi guys, been riding my car with a weird symptom for 200km now...I need to explain for you to understand:

-At highway cruising speed, while keeping my foot on the pedal steady, 3500rpm (4.3:1 ratio), 110kmh, my car hunts between the two maps I think.

The AF ratio goes between 11.3 and 18:0+ ratio. Reads 6hg/in on the boost gauge, no boost whatsoever. It studders very very lightly when going 18:0+ AFR then It changes by itself to 11.x:1. I feel a small burst of power when the 11:1 tune gets going. It does it every 3-4 seconds.

I have a 1993 JDM greddy turbo kit with the OE MAF sensor, narrowband OE sensor still on the car (if you guys happen to know how to get rid of those flintstone pieces of hardware, let me know...I'm aware of the maf voltage simulation on the AEM site but didn't had a chance to do it while the car was still NA...) The car has been roughly d on a dyno to get started with the 440 RC's and FIC6 250km ago. I have a boost gauge and AEM wideband for keeping an eye on things if it gets ugly.

When going full throttle, it just goes in the 11.3 range and pull evenly, no hiccups. When keeping the throttle at the same position, it hunts between the two tunes I suppose. Im scheduled to go to my dyno guy in the next two weeks. If any advices comes to your minds, let me know so I can direct my dyno guy to look for something.

Does clamping the two parts or reclocking the interns of the MAF can help me through this???

Thanks guys, I greatly appreciate picking through your geniuses minds.
Almost-

 

Datalogs, and do you have an actual wideband installed? Hopefully you don't only have the stock narrowband.

 

I have a AEM wideband kit in there since the FIC6 and greddy kit install. That's how I found out how much it fluctuates.

Precisions: As soon as I stay steady throttle cruising on the highway, it happens (vacuum, oem ecu tune???). As long as I keep my car in acceleration, even with the lowest pedal effort, it goes on the FIC tune. I will find some time to get on the road and datalog for you guys to see what happen in there.

 

I experience the same issue at times although never in areas of higher boost. It normally happens in very low load situations where application of slight to moderate throttle gets me the lean afr for a few seconds. It is in situations where the boost is rising though. It never occurs when a strong application of throttle is involved. There is no knock, but it is like the engine is not producing power. Spark blown out? Plugs look good. I keep all my previous plugs when they are changed so I can do comparisons to the last set.

I am wondering if it is possible I am actually getting too much fuel and getting a false lean condition on my AEM UEGO. Could be that the stock ECM is trimming what it sees as a lean condition in this section of the map and eventually it trims this section until it gets to this point? This happens when I am in the portions of my maps where things are set to all zeros, so the FIC should not be involved.

I have reset my ECM by pulling the battery a couple of times. I cannot tell for sure this has any significant effect. This time I am going to log with my OBDII scan software at the same time I am logging my FIC to see if I can tell any mis-fires or other anomalies.

The other thing that may be of note is that I normally set up my maps to have 1 psia increments from 13.7 and above. Below that they are set up as a calculated value. I have considered that the FIC uses a fixed calculation of the distance between rows and I am confusing these calculations with my varying spacing on the rows. I've tried to contact AEM to ask how the unit would handle this setup for two days but can never get through.

If I find something out I'll make sure to pass that info on.

 

I have to tell you that after having a 60miles ride tonight. You seem to be right. It feels like a too rich condition if you forget to look at the AF gauge. Getting sluggish throttle response if I want to accelerate slowly on the highway, even had studerring/hesitations. If I beat the ish out of it, it goes to 11.x:1 and pulls evenly for a 8psi kit. Thanks fwman1, its a variable I wasn't thinking possible, getting those kind of lectures in THAT situation.


Gotta have to buy the newest AEM wideband failsafe gauge and my dyno guy to remede the situation.
Waiting for a price quote on it. My laptop will be in the car shortly for datalogging then sending my maps over here for you guys have a look at it...

My 120 miles used AEM WB kit is for sale btw.

 

If I forgot to install the resistance (1000u 1/4w IIRC...) on the MAF wire??? Is it really necessary?? I just thought about it...

 

Any thoughts about the solution guys??

 

I'm not clear on or familiar with your application but it sounds to me like the ecu is in closed loop and trimming the fuel across stoich but the ego signal is very slow. My Miata has an unheated ego sensor at the end of long tube headers and when the sensor is not hot enough it will do the same thing.

Maybe check to see that your ego sensor's heater is hooked up and getting power. If you're using a synthetic narrow band signal from the uego signal check to make sure it is toggling from 0.2 to 0.8 volts right at lambda 1.00/14.6 AFR.

 

the narrowband sensor is brand new. Its a NTK sensor. Im using the oe narrowband for ecu signal and the AEM wideband for monitoring.

 

It it heated? I put a heated (NTK I think) sensor in my car and after several hours on the highway it failed. It put out a valid but incorrect rich signal. The engine control trimmed the fuel and went super lean (18 or 20:1) until it reached the end of its authority and gave up. Then it went open loop for a time until it would try to trim again and go super lean again.

I would disconnect the sensor and see if the fueling at least becomes stable. If the ecu sees no sensor it should throw a light eventually but not to trim the fuel lean. It will trim rich though. On mine periodically the CEL would go out and the fueling rich for a short period. Then the ecu re-throws the code it sits in open loop for a while again. Your base map may not be so accurate so be careful there. I had my base map pretty good so I was able to drive home no problem when it happened to me.

I put an unheated sensor back in and have been putting up with the slow response. I may try a heated one again at some point but I'll make sure the heater is turned off above maybe 2000 rpm.

It may also be that the heater failed and now it is very slow. If it's unheated it may still have failed or just be cold and very slow. In any case I suggest disconnecting it to see whether the closed loop function is the source of your fueling issue. It sure seems like a good possibility to me.

When my car first goes into closed loop mode if the sensor is cold it will trim as lean as maybe 17:1 and back to 12:1 until the sensor heats up more. I have long tube headers and use the wide band gauge mounted in the glove box for monitoring.

 

the narrowband is not heated for sure its a one wire sensor, but I have to tell you its positioned 8 inches away from the turbine outlet so it is heated by the turbo for sure. I will try to disconnect it then post results.

 

After trying to disconnect the narrowband sensor, the car stumbles a lot more when applying throttle to take off. One of my hypothesis : the narrowband sensor is seeing too much fuel and try to take it off to get back within his own AF parameters. My injector size is 440 and I believe the fuel map has a lot of workout to do the get the right amount removed to eliminate a too rich situation. I try to connect my laptop to the FIC but It doesn't recognize it... I have to go back to the dyno. I believe he has to clamp the o2 and MAF signals before going into boost!?! Am I right.

I checked AEM videos on how to clamp. Then there's a mention about short term fuel trims and long term fuel trims and monitoring them with a obd-2 scanner. My car is a 1993, so I'm trying to figure a strategy to get better fuel trims without having to wonder if the ECU will try to change for his own fuel tables...anybody follow where I'm trying to go?? Is it plausible?

I know someone who suggested me to change for 330cc so the FIC wont have to be too much corrected to be on the right fuel strategy, having enough volume with a 255lph HP to run 13psi of boost with my td04h greddy kit...

 

Found that after installing an olderguy o2 clamp, the car runs better. the hunting is gone. I think the two ecu's dont fight each other anymore. The car doesn't stumble anymore and the AF ratio while cruising and vacuuming is 14.5 up to 15.0:1. Problem solved. I just need to find how to take the voltage signal to calibrate the voltage clamping. It says to take reading between the white and black wires while the car is running.
I might need some more clarification on how to get it ''really'' done...thanks.