Nissan 200SX Club - South Africa

Ok so I installed my new Zeitronix wideband, its super cool and so easy to install. Now I have found that my AFR's are SOOOOO far out that its not even funny.

On light throttle freeway cruising its about 18:1 which is a bit on the lean side but the car is not jerking or anything so thats not to bad but EGT is about 670degrees which is good.

When I accelerate slowly and boost is about 0Kpa (no vacuum no boost) its about 15.5:1 which is too lean, good for fuel consuption but not for torque.

If I floor it AFR would drop to about about 12.2-13.0 which is again to lean, althought that was with the water/meth on. I noticed sometimes that its even as low as 10:1 at about 0.6Bar boost but then leans out as boost goes up, it just makes no sence. EGT reaches about 850-880degrees on a 10 or so second run.

Also when cruising, straight after I tap off it richens up to about 11:1 and then leans out. Why does it richen up straight after I tap off when I have set the fuel cut active??

I did all of this using the datalogger which is a real cool function but shows your everything little problem in the map . All of these results were done with all compensations off, air and engine temps, (I wanted to see the problems in the main fuel map).

Now I have found the problems what should I do?? Should I go to the map and adjust it accordingly or do a few more runs and see if there is a pattern and then adjust it??

Also this datalogger is very very sensitive should I concider ever little blipper in it or just the big ones?? It is reading at something like 75 samples/second .

SO let me guess, no one here besides Duane knows anything about AFR's?? Damn just my luck.

Oh while on my way to site I floored it in 3rd and the max AFR was 13.3:1-13.7:1, which means its too lean.

so turn down the boost dude!

Its boost at 0.6bar at 3000rpm . I am going to take it back to the guy that tuned it.

The thing is even at those AFR the motor is not pinging.

Gary, I just feel you miss something about water/meth and AFR. From normal 12.5:1 it should only drop a point to 11.5;1. Then add boost, up the timing, add boost up the timing and keep on going until dead sure no detenation of course. I think I did inform you in the past about this one?

Yeah Freddie you did mention that to me. But right now I am now really worried about the max power torque it is making but rather the part throttle and lower rpm power and torque.

I mean the car goes great, but it can go better.

Doesnt water/meth move the AFR towards stoich, so you should set the AFR to 11.5:-12:1 and the add the water/meth which should "lean" it out to 12:1-12.5:1.

You tune the car without w/m = 12.5:1. Like normal. Then add w/m. You should notice the AFR drops one point to 11.5:1. Then add boost, timing etc. And that is it. Nothing like bottom, middle top etc. Tune once and off you go.

Then like my unichip will take away and add timing during the feul map as is needed. Nothing more to it. This is how it is done with mine.

I would hate to be cruising the freeway at slight throttle and vacuum and have a AFR of 12.5:1.

The car idles smooth at around 14.7:1 give and take 0.3:1 depending on the conditions. So I would say the motor should richen up almost linear to 11.5:1 at WOT when the boost is more than 0.5Bar. On the cruise and light throttle, it should be around 16.6:1 - 17.0:1.

Now how would I go about tuning these AFR via datalogging and road driving. I would say the best way would be live tuning, me in the passenger seat tuning while someone else drives?!

Gary what fuel pump and FPR are you using if i may ask

Walbro 255lt/h and stock fuel pressure. At 1 bar boost the fuel pressure is 3.8Bar.

Ok well this morning I found the problem of running so lean. I had loaded an older map on the weekend while stuffing around and by mistake loaded the wrong one, anyway the AFR is now about 12.7:1 - 13.0:1 at WOT and max boost. Now the car pulls like it should, I thought the power was down but just thought I was getting used to it. Oh well now all my datalogging on the weekend was a waste.