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FlexFuel stoich value increasing during acceleration


Hookey
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Hi there my analog flex fuel input is jumping around during acceleration. Sensor is in the feed line and fuel pressure is good. I think it is induced noise on the input. I am an automation engineer and usually for analog's for PLCs at work we use shielded cable. The flex fuel percentage value will move from 0.77 to 0.81. It does affect fueling a little. not enough to deter me though.

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I like this idea and thought about using this. I presume it is auF100035. I thought about making the value about 6 which will hold it when it gets to 2.9psi. or above.

What are others opinions on this? has anyone tried it? Does anyone else have this issue? Thanks Mark

 

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Locking the value is the best idea. The sensors do have an accuracy of +-5% according to the datasheet. Couple this with ground offsets etc it will move around a little. 4% ethanol variance is only going to adjust stoich a tiny bit though. 

If it only moves around during acceleration this is quite odd. Either you are getting temperature/pressure fluctuations or there is a ground/alternator issue. It could also be noise but I'd expect to see this all the time but just during acceleration. 

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1 hour ago, Roland@pcmtec said:

Locking the value is the best idea. The sensors do have an accuracy of +-5% according to the datasheet. Couple this with ground offsets etc it will move around a little. 4% ethanol variance is only going to adjust stoich a tiny bit though. 

If it only moves around during acceleration this is quite odd. Either you are getting temperature/pressure fluctuations or there is a ground/alternator issue. It could also be noise but I'd expect to see this all the time but just during acceleration. 

Thanks, I have a 525 pump, you can see the stoich ratio starts rising up even when boost is building at low RPM when the fuel system wont be stressed at all. I have an extra ground strap from the intake manifold to the neg terminal. The kit is Pirotta so It just uses the standard old 02 plug. I will lock it out at 3 psi. My only concern with this is if it spikes or drops as its locking and then is incorrect for the whole pull. But ill give it a go.

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You could try holding the line high with a voltage divider to say 1v and see if it stays exactly at the same value in the datalogger or not. I believe there is some circuitry around the rear o2 sensor to filter the input as the analog input is non linear (hence the weird curve you get with the pirotta kit).

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