Mounting air fuel ratio in inlet manifold instead of exhaust?

[celicapain]

Hi,
Im tuning an engine for start up and was going to drop an AFR meter into it to get the starting mixture right, Just wondering if anyone has a good reason that the sensor should be mounted in the exhaust instead of the inlet manifold?
The engine is carbureted so whatever is the manifold should be a pretty fair representation of whats going into the motor.
Anybody have any idea why this could cause issues?

[jb_22]

Don't wideband O2 sensors measure exhaust by-product gases (carbon-monoxide)??? My guess is it will read full lean all the time.

[ToyTA22]

That's exactly as I was about to write jb_22.

[jb_22]

Yay! got the hole-shot

Surely you could guestimate a jetting setup for startup? Err on the side of being too rich if anything. What carb/engine setup are you tuning?

[oldcorollas]

dude, you need to look into how an O2 sensor works..

basically, it needs to be hot, like 300degrees..
it'sbasically an oxygen exchange cell, and it measures residual oxygen after combustion.

putting it in the intake makes no sense... you may as well put a spark plug in your inlet manifold to ignite the micture before it gets to the engine....


i realise this may be a troll post but just in case..... DON'T DO IIIIT

[jb_22]

You mean a trolla post

[jondee86]

Don't wideband O2 sensors measure exhaust by-product gases (carbon-monoxide)???

Whaaaaaattt ?? Why do you think it is called an O2 sensor then ??? Wikipedia says it so much better... "The sensor does not actually measure oxygen concentration, but rather the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in air.".

Cheers... jondee86

[dumbass]

Raw fuel Might also fk it
It reads gas not liquid
Which is what the atomised fuel is in the inlet manifold

Mixtures at idle can be done without meter
Turn mixture screw in till it stops
Keep turning it out till motor starts to rev nice keep turning till motor starts running a tiny bit rough
Then turn it back way u came abit
Do it afew times and u will get the hang of it

[Hatta1978]

Whaaaaaattt ?? Why do you think it is called an O2 sensor then ??? Wikipedia says it so much better... "The sensor does not actually measure oxygen concentration, but rather the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in air.".

Cheers... jondee86

If I'm not mistaken the O2 sensor it self does not measure the oxy in the air. Only in the exhaust. And it actually measures the temp of the gas and converts this value to a pre determined display setting(A/F gauge).

[oldcorollas]

this is too painful

hopefully this will settle the confusion
http://www.ngk.com.au/oxygen-sensors...en-sensor-work

Zirconia Sensors: An important property of the Zirconia element is that it can conduct oxygen ions above a temperature of about 350°C. When the sensor is fitted, the outside of the Zirconia element is exposed to the exhaust gas and the inside is in contact with reference air.

Both sides of the element are coated with a thin layer of platinum that act as electrodes and carry the sensors voltage signal from the Zirconia element to the lead wire. At operating temperature, oxygen ions are able to pass through the element and deposit a charge on the platinum electrode thus generating a voltage signal.

If the AFR is rich, a high signal voltage is generated across the electrodes due to the difference in oxygen concentration present across the two sides of the element. Conversely, if the AFR is lean, a low voltage is generated across the electrodes due to the small difference in oxygen content between exhaust gases and the reference air inside the sensor.

[Hatta1978]

Sorry jondee86 your correct. My mistake. Cheers. Nice post.

[dumbass]

Who bloody cares the description of the oxygen sensor
It goes in the exhaust not in the inlet

He is also using a carby
How fking hard can it be to get an engine with one of these started

Get your timing right
Then turn on the fuel tap opps I mean carby and crank her over
Screw mixture screw all the way in the come out two turns
That should be good starting point
Rev it and for start up u might want a tiny bit of smoke when u rev it
This is a same setting to have a tiny bit of black smoke
Then u know your not lean
Or turn out mixture screw bit more to lean it off

[MorGo]

This must be a joke..
But.. the lambda compares the exhaust gas oxygen to the exterior air oxygen.The intake air has all the oxygen(20,9% of athmosphere) so the lambda can't measure anything.
When burning rich mixtures the sensor comes as temperature sensor (because there is no oxygen to sense) and therefore is not too accurate in there.
So,you CAN'T put lambda in the intake!

[Hen]

Don't listen to everyone here, they're just jealous they didn't think of it. But to get best readings you definitely need an oxy sensor with inbuilt heater (3 or 4 wire unit) since it isn't going to be heated by the exhaust. The red hot sensor in the post-carb intake manifold will give very good results.