Air/fuel ratio confusion

[jakez]

So I've done a bunch of searching but still confused on my specific results. I've just installed my uego wideband on my test pipe closest to the rear of the car, basically I'm sitting right on top of where the sensor is at.

When I am WOT and the turbo first spools up the uego reads 13+ and by the time I'm at around 6000rpm it reads 12.0, so if I actually took it up to 7500rpm it would be like 11.6 or lower? Also I've read that when you have the wideband sensor pretty far down the exhaust like that then your air/fuel ratio will lag behind a bit and the reading you see is actually 500rpm or something behind.. is this true? Maybe if I flipped my test pipe around to make the sensor 1ft or so closer would make a difference.

I've only done these tests up to 6k in 2nd gear so far because it's been raining every day, is there a better gear to be doing this in?

It seems like my car has a nice ratio on it already, which is a bummer because I bought a profec boost controller hoping I could turn it up to about 10psi before having to mess with fuel and such..

Any help is very appreciated!

[Volcom887]

I believe the snsor is supposto b on the dp about a foot after the turbo and make sure u put the maf on top of the tube not the bottom so if I gets any condensation it doesn't just sit in the sensor it actually drip out when its mounted on top of the pipe

[daftphunk]

12 seems a bit high at 6k Rpms but maybe that's me.

[jakez]

Ok I took it to like 6800-7000 in 2nd gear and it hit 11.8, I've never rev to the 7500 redline and don't plan to, but I think it would be like 11.6 at redline, it just scares me how the 5000-6000rpm range is at 12.2-12.0

[EsChassisLove]

12.2-12.0 is actually fine.

Edit-I would move it closer thats for sure. 1-2ft from the turbo max.

[jakez]

Ok I've been reading a lot that having the sensor that far down, like on the test pipe, can make the afrs show very lean, anyone have experience with that or care to take a guess how much the difference is? If it is showing 12.2-12.0 from 5000-6000rpm and 12.0-11.7 from 6000-7200rpm with this sensor location would it be safe to subtract like .3 from those as a more accurate reading?

[EsChassisLove]

Mines about 2 ft away. It read .1 richer than the gauge we had set up on the car when it was being tuned.

The gauge they use for dynos must be advanced as hell since its stuck at the tail pipe and reads great Haha

[jakez]

Yeah I wonder the same thing since some cars have cats or no cats, resonators, more/less bends etc. but they still manage to get an accurate reading from a tailpipe? Wow

My wideband sensor is a little over 3ft from the turbo.

[TheRealSy90]

You need to move it closer. Like right where the downpipe goes horizontal.

[cotbu]

you are lean, idk which turbo or engine so lets say a t25 on an s13 sr.

that turbo spools fast and fall off even faster. So at say 4500rpm you should be 12.0-11.8 est. already! got it? Now at 7000rpm that turbo is out of breath, and boost already fell off. if you running 14psi you're probably at 12psi but you already detonated and are running the knock map, this is getting crazy. me sleep now.

[rcdad123]

i usually mount the a/f sensor about 6-8 inches away from the turbine outlet or exhaust port on an n/a engine. this way it reads the exhaust as soon as possible. also, 2nd gear does not put enough load on the engine to get a good reading. i used to dyno turbo cars on fourth gear starting at about 3,000 rpm so that the data logger can have a longer curve to record and i can go back and see where i need to adjust the a/f and/or ignition timing. the farther the sensor is away from the turbine housing, the later the real reading would be. also, at full boost/load, i always shot for mid to high 11`s a/f. anything lower is too rich and can cause you to loose power, foul spark plugs, bad mpg, or at worst, ring wash. tuners that use exhaust pipe sniffers usually adjust maps 500 rpm`s or earlier than what the graph shows(if it`s showing lean at 4,000 rpm, start richening from 3,500 rpm).

[jakez]

I have a new problem, it's sort of related so I didn't want to start a new thread. And I searched my ass off but can't find anything similar to my problem.

My a/f ratio when idling WAS perfect, around 15.5, but a few days ago it started idling around 17+ and there's a noticeable little "pop" coming from the exhaust every second as if it's running rich. Sometimes it will idle at 11-12. And sometimes it will goto normal again at 15.5 but rarely. I tried wiggling the maf wires and there seems to be a "sweet spot" to hold them at to get it idling normally again but the car died before I could do anything. So I unwrapped the wiring around the plug and cleaned everything, also rewired it cleaner than it was, and cleaned the maf but it's still acting the same way.

It's also changed my idle from 1200rpm at 15.5 a/f to 800-1000rpm when the a/f is 17. Not really sure how to cure this problem besides positioning the maf wires a certain way so that it idles normal again.

[rcdad123]

seems like your maf wire harness plug has loose connectors. check the harness side connector for corrosion or flattened pins/plugs. or just replace the connector with a known good one.

[jakez]

seems like your maf wire harness plug has loose connectors. check the harness side connector for corrosion or flattened pins/plugs. or just replace the connector with a known good one.

I checked em out when I was cleaning everything. All 3 are still square and shiny, doesn't appear to be anything wrong, they move around inside the connector when I move the wires that's about it. And the 3 pins on the maf look mint also. Only thing is it doesn't 'snap' onto the maf, so I either zip tie or tape it from slipping off. Tried wiggling the further down on the wires thinking maybe there's a problem somewhere else but it didn't effect the idle at all. Seems to be something in the connector/maf area. But if all the wires and connectors look fine I don't see why it would be acting up. Should I take the maf apart and inspect that? It wouldn't make sense though if it was an internal problem on the maf. Seems to be something in the wires/connector area.

I just bought a z32 maf setup, but wasn't planning on using it until I install larger injectors/turbo. Can I run the z32 maf on the stock setup without problems?

[chituntang]

Your car isn't suppose to idle at 1200rpm but at around 850rpm, unless you intentionally do so by adjusting the idle screw.

If you wiggle the wire and idle changes, then there is something wrong with the wiring. Use multimeter to ensure you fix the problem you intended to fix.

You cannot use Z32 maf on stock ecu unless you have a piggyback like safc at the minimum.

[WheelTech]

Your car isn't suppose to idle at 1200rpm but at around 850rpm +100 dude.

[jakez]

Your car isn't suppose to idle at 1200rpm but at around 850rpm, unless you intentionally do so by adjusting the idle screw.

If you wiggle the wire and idle changes, then there is something wrong with the wiring. Use multimeter to ensure you fix the problem you intended to fix.

You cannot use Z32 maf on stock ecu unless you have a piggyback like safc at the minimum.

I have a greddy type rs (atmospheric) bov, which according to what I've read it could be the reason for my high idle? I bought a stock sr intake from someone on here earlier today. Going to put that on and buy the recirc adapter for the bov.

I guess I'll just deal with the idle and a/f problem for a week or so until I get around to installing the new turbo setup and enthalpy tune.

Thanks for the info.