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ST165 running so rich falling on face.

Sat Oct 25, 2014 12:35 am

I got this car without a engine and have put it all together. When piecing it together I realized i didn't have a Air FLow Meter. So when looking for one I ended up pulling one from a 89 celica.

Now from what I see on a manual is

engine off it is 4-6 volts
at idle it's 2-4 volts
fully open is .02-.5 volts

the meter i pulled had

engine off 4.026 volts
Idling 2.167 volts

my question is could the spring on a NA engine be less restrictive then a turbo charged car? IF I verily push the throttle it will rev to about 5500 as soon as I feel good boost it bogs out. If you do anything over just slight throttle you won't get above 3500.

Even sitting still and idling if i put it to the floor it will rev to about 3500 and sputter if you hold it down it will start blowing black smoke...rich and quickly die out. If I slowly roll the throttle it will run to redline.
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Re: ST165 running so rich falling on face.

Sat Oct 25, 2014 1:30 am

I continued to research and found a page talking about afm calibration and cleaning. So I opened mine up used a marker and made a few factory marks and then made my adjustment.

I moved it 5 spots clockwise which increases spring pressure which leans it out.

5 clicks and then a test and the car rev'd to red line. Came back to a idle and rev ' again. Use to wot would die out around 3500. So using a NA "AFM" you need to adjust the spring load.

NA afm on turbo.

Re: ST165 running so rich falling on face.

Fri Jan 02, 2015 1:17 am

I fiddled with that Idea this summer too because externally they have the same housing and pinout, iat is compatible ,
the spring color is not the same also, the 3s-gte is using a black spring and 3s-ge something gold or silver if memory serves me right.
I was told by some other people it would not work and it cannot work WELL, it works but I would not bet my engine health on it.

The thing is, the spring rate for both AFM is not the same,
you can prove this by placing a mass suspended with a wire on the flap door, afm facing up,
the 3s-ge afm and st165 afm dont wont have the same flap door angle for the same mass attached to the flap door and this means the readings made by the ecu wont be the same for the same conditions.

Yes you could retune your afm to mimick the st165 behavior for a specific engine load only, but again it will never have the same exact curve all the way, it will be right at one condition and wrong everywhere else.

Re: ST165 running so rich falling on face.

Fri Jan 02, 2015 2:22 am

Yeah.... my donor engine i ended up doing a diypnp and when tuning ran into the same issue. Motor ended up having 530cc injectors so that was the problem all along. As far as different pressure ratings you are changing its pressure. After all the playing i did I think it would be just fine at stock boost. Although for me I prefer to always use a afr sensor so yeah.

Re: ST165 running so rich falling on face.

Fri Jan 02, 2015 5:30 am

What you might be able to do is buy a fried AFM off someone and swap the spring into your N/A AFM. I'd also do some datalogging of the AFR's before calling any setup with a different AFM good to go.
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