Hi. I have a question of AFR mixture on a Mazda rx7 fc turbo2. Im running with a OEM ecu, OEM injectors, fuel cut defender, OEM fuel pump, OEM turbo, boost controller and fuel pressure regulator at 3bar.These are the numbers that the car is doing:

Target for Iddle: 14.5-14

Target for Light throttle and Cruise 11.9-12

Full throtle under boost 0-6psi: 10.5

Target for Boost 6-8psi: 12.5 - 12

I buy a 4 720injectors and rtek1.8. Why is my AFR mixture too rich when I cruising? Thanks in advance friends

 

is that what it is doing? or what you would like it to do?

 

These are the numbers that the car is doing. I think when Im cruising at 2-3k rpm and the turbo isnt work it should be at 13-14.Thanks

 

I think you should get rid of the FCD, get a stand-alone with proper tuning.

The FCD is altering actual values so I wouldn't be surprised if you get odd results.

 

IMO the stock TII should run around AFR 13 in idle and light acceleration.
Only at constant cruising it switches to 14,7 via lambda control
Full throttle around 11s
But this is with the stock idle timing etc. and the rtek wont change that

 

So I am guessing you replaced the stock narrow band O2 with a wideband. You will need the wideband to output a narrowband signal to the stock ecu so that when you are cruising, it goes into close-loop mode, and it can only do it if the ecu gets the narrowband signal from the O2

 

Do you still have the factory smog pump and air control valve? If so your readings will be wrong on the wideband.

 

I am running a full Megasquirt 3 standalone. I started with Arroncakes writeup, which had the AFR table look like this:



My table is a modification of this, with idle leaned out slightly, with timing changes and fueling to get as much vacuum as possible.
My cruse cells were richened up as well, I found that being richer made more power, allowing me to use less throttle, meaning a fuel savings ( sounds odd but remember we are talking about ratios ) I can get 32 mpg on a 40 min trip in southern MN with hills and such, 34 if I try to hypermill. The ECU cuts off fuel if in overrun for 2 seconds, so more fuel savings there too. It was a little less when I lived in Utah with the larger vertical changes (highway miles of course)

I also found a old post that someone had a timing table 3rd generation section that were able to pull the S4 Turbo II timing map from the stock computer converted into a KpA x RPM map that I am using https://www.rx7club.com/3rd-generati.../#post10475634

It was several more degrees aggressive then Arroncakes writeup, and designed to run on 87 octane




Reason I am bringing all of this up:

The stock O2 Sensor bung is able to be accessed in the engine bay, on the passenger side. The stock NA RX7 manifold then has its first flange a few inches from this. Initially, I was having much lower fuel mileage, and discovered that the gasket there had burned out one side, so what was happening was that with each exhaust pulse, it was pulling fresh air into there, and was enough to throw off the readings on the O2 Sensor. It is less of an issue at high RPM with large amounts of flow, but at idle, and cruising, there was a lot of suction in there (verified with a smoke machine, you can also use a propane source and watch the reading get richer if you get it down there too) I have seen several drag racers with very short exhaust tubes with the O2 bung a few inches from the end have incorrect readings as well because of this.

The stock config also uses an airpump, so it is going to change the readings with it as well.