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GA16DE
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606 Posts
Discussion Starter #1
Hi
I installed my old o2 sensor (from my e assisted carb) and got readings between 0.46 to 0.50 ac volts at idle (my personal multimeter is not a cheap one), and under acceleration in 2nd or 3rd gears got 0.50 at 3000 rpm to 0.56 at 5000 rpm (stock cams and dual mikuni 40 carbs)
Acording to this
http://www.datsuns.com/Tech/oxygen_sensors.htm
I am at the proper jetting for an economy setting (have to admit gas lasts a lot ;))
Question is, what is a proper air fuel ratio for a performance engine? A race engine?
I found 13:1 to be a recomended setting
http://www.carcraft.com/techarticles/116_0402_tune/
Thanks in advance
 

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Ex-mod/nissan guru
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2,136 Posts
turbo engine engine goes as low as 12.5~11.8 to 1 ... on a perf engine !.
N/a engine will get around 12.5~14.5 wich is still richer than sthoic.
 

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GA16DE
Joined
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606 Posts
Discussion Starter #3
One thing I noticed is that when I decelerate abruptly in my dual carbed car the AF voltage climbs to 1.1 - 1.2 volts...
No wonder the EFI can save more fuel by controlling this situation
I'll play with my carbs and post my findings
 

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Viva el iPod
Joined
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1,232 Posts
is it a narrow band or wide band O2? Narrow band sensors are very slow and inaccurate on carburated applications, especially an old sensor. You should get a wideband sensor, which are still kind of expensive, but if you're race tuning it is a very justified expensive. At the very least you should get a new O2 sensor.
 

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GA16DE
Joined
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606 Posts
Discussion Starter #5
In fact I was surprised to see the voltage correlate so quickly with the acceleration and deceleration, not exactly slow
I took a copilot for dmm reading, and he told me the numbers as quick as he could and we both were surprised
But you are right, I should try using a newer sensor...
 

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Ex-mod/nissan guru
Joined
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2,136 Posts
the reading is quite fast but slow enough that you get to read it like a few millisecond after the facts. im pleased to have one and know my car doesnt fuel after 5300rpm... this way at least, i wont blow my engine trying to push it too much... i can put my hand on wide band, but that will only be when ill change ecu and retune it completely... it is only needed for such an application. you dont need an exact reading all week long ;) tune it once, its good for a long time afterwards... unless you boost more :D
 
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