Ainis

Hello to everyone.
I have and isue with my fd. It is reshelled USDM car runing JDM ecu (i ran usdm ecu before pluging jdm, but there was no feelable difference). Car has cat back exhaust, some kind of aftermarket catalyst converter (came with it from USA) and running stock seq turbo. Primary cat has been removed. It has disabled secondary throttle plates (they are always open) air pump, air control valve, AWS system, EGR valve has been removed too. All these systems are "resistored" so no fault codes. It also has new spark plugs, new fuel filter, new o2 sensor, ultrasonic cleaned injectors. Engine loom refurbished (new wires/connectors).

The problem about the car is, that engine runs very rich on idle or low load at low rpm. Here is the datalog:


I failled at comverting MAP voltage to PSI, so if remember corectly, 6 represends vacuum at idle, 14-15 is atmospheric pressure, and 19-20 10PSI of boost

AFR at idle when cold is around 11.5, when fully warmed 11.8.
I have read, that this might be due to the removed air pump, that O2 sensor senses "wrong" mixture, so tried to feed 0-1.2v via a potentiometer to the ECU thru a O2 connector. No matter what voltage I fed at idle, there was no change in AFR.

So Iam interested in what could cause such AFR?

Tem120

iTrader: (5)

looks normal .. if you have a stock ECU it will always run rich as the stock ECU uses fuel to cool the cat and keep it from dying to soon .

rotaries run rich at idle your light load cruising range is mostly blacked out so i cant see but the parts i do see seem ok as well

Ainis

Yes, running stock ECU. If it is tuned to run rich at idle, then what is mazda lean best idle control system described in manual?

I mostly shift at 2-2.5k rpm, so my cruise zone is all visible.

Tem120

iTrader: (5)

LoL cruise is usually at 3-4k , remember rotaries make their power up top , if you short shift like that it essentially bogs the car into the low torque area . and you go into higher loads in order to maintain and gain speed. try running the gears a bit longer


and like stated 12.9-13.1 is normal idle afrs for a rotary. with the AIR pump . the air dumped by the air pump leaned the air comming out of the exhaust to a stoic level . But hte car will still be using the same ammount of fuel . as it would with the air pump leaning it out for Emissions.

if you want to lean your mixtures even more you need an aftermarket ECU liek a Power FC , learn to tune . or pay someone to tune drivability not just top end .

I'm not sure how to translate your log , but basically anything over 10 inches of vacume is light load , so over 10inches , and betweeen 2500-3800 is your cruising range .

Ainis

If I remember corectly, mazda user manual sugest for normal driving shift at around 2500 and cruise at 2200-2300, which is what I do. In my country speed limt in city is 50km/h - 30mph, so I cruise in 4th gear. Out of town we are alowed to run 90km/h - 56mph, so I drive in 5th gear, and at 2200-2300 I am going at 60mph. Also from the log we can see, that 2200 has perfect AFR for cruising.

I agree that 12.9-13.1 would be normal AFR, but i get sub 12:1, which is the problem for me. Exhaust has smell of gasoline, and engine sometimes missfires (runs perfectly while driving, so definately not the engine fault on it's own)

Also, we have metric system over here, so it is little bit hard to understand those PSI and in Hg things.