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The mkiv Supra Owners Club

Emanage - pressure sensor and 'off scale' mapping


SimonR

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I posted this one on the Yahoo Group but no luck. Anyone?

 

"The Greddy pressure sensor is described as a 3-bar sensor but I've just been looking at the voltage/psi table that was posted in the Files section {
of the Emanage Yahoo Group
} and it shows from .54v (-14psi) to 4.46v (+43psi).

 

This means that the sensor covers a 4 bar range - that's 4 bar absolute or 3 bar relative. If it's a 4 bar sensor then it means that I can map up to 3 bar (gauge) rather than two bar.

 

Does anyone know the correct situation? Thanks."

 

 

Also, does anyone know what happens to airflow/injector adjustment if you go 'off the scale'. For example, if I mapped additional injection against the Greddy sensor up to 3.5v and for any reason I exceeded that voltage in operation, what would happen? Would the injectors revert to the stock map? Would they continue with the last adjustment?

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Simon heres the full voltage Vs pressure specs

 

http://www.mohdparts.com/emanage/pressure_sensor/index.html

 

As for the additional injection map, I would assume the Emanage would use the last correction factor entered at highest you had in the map as some sort of safety faeture. I.e if you had a correction factor of +4% @ 3.5v (29psi??) then 30psi 31psi 32psi would also use this correction factor. Ian may know the definitive answer to this though, im just hazzarding a guess.

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Thanks, that the voltage scale that I was referring to. So, it looks as though it's actually the Greddy 4 bar MAP sensor. Don't know why I was convinced it was 3 bar.

 

I'm hoping that the mapping bahaves as you have suggested. I just want to confirm it before I do something horrible to the engine.

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What i would do is set up a simulated pressure. either by applying pressure to the sensor or for instance using a variable 0-5V output to mimic the pressure signal...I.E the TPS output voltage as a pressure sensor voltage, maybe tap the TPS to the Pressure sensor signal wire. With the ignition on you could apply throttle and watch the Cell location being highlighted, when you apply more pressure than the table is set for, will it auto add more cells or just stay on the highest one you have set in the map?

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Interesting. Add more cells 'on the fly'? I wasn't expecting that. I was assuming that it might just 'peg' the additional injection to the last known value that was mapped for. Thinking about it a bit more, I would be able to see what was going on from the Emanage logs anyway. They would tell me the sensor voltage and the amount of additional injection being used (if any). So as you say it's just a question of getting the voltage high enough on the sensor to test it. Thanks.

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...surely your not going to boost over 43psi:(
Not intentionally anyway! :) It was two separate threads of thought really.

 

However, Ian’s confirmation has given me more food for thought. I’m finding that the 16x16 mapping on the Emanage may be something of a limitation. For example, the default scale (on my kit anyway) for the Greddy pressure sensor is .5 to 3.5v. Sounds fine but the cell labelled 1.7v will, as far as I am aware, cover the range 1.6v to 1.8v (the cells above and below being 1.6v and 1.9v respectively). This covers the range from roughly 1.5psi to 4.25psi. Similarly, the next cell will cover the range from roughly 4.25psi to 7.5psi. These seem quite wide ranges to cover in one cell.

 

To illustrate that point, I’m currently getting AFRs between 14.3 and 12.6 in the 1.6v-1.8v/2750-3250 rpm range, all controlled by one cell (values in adjacent cells notwithstanding).

 

Now that I know that the additional injection values from the last cell are used when the boost goes ‘off the map’ so to speak, I’m thinking that I may be able to introduce some more resolution in those areas that may require it at the expense of those that may not (if I can find any).

 

Hopefully I’m not talking complete bolleaux here. Please tell me if I am.

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First off its not worth trying to map anything below 4,000 RPM as the std lambda feedback will just keep trying to pull AFRs back to stoic,i suspect that is the reason you are getting the big variation in these areas as your fighting the ECU! so why not just expand the scale above that point and get some extra resolution? what are you logging AFRs on?

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Hmmm, I thought that you could see when it was in closed loop due to the fluctuation in AFRs as it bounces either side of stoich. It stops doing that a lot lower than 4,000rpm on my car. Maybe it's over 4,000rpm on the 2JZ ECU?

 

I'm using the AEM wideband plugged into the 2nd airflow input.

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First off is you car an Aristo? you didn't say, and is the emanage blue or ultimate? can't see why the ECU would be much different as it still runs the sequential system, i am not familiar with the AEM obviously can output a simulated narrow band from its wide band signal, is this calabratable? i have innovate LM-1 and can configure the narrow band signal, i have the ultimate and this has an input that can take the narrow band input and that is also configurable, but i have yet to see a resulting AFR log map that will match my LM-1 logs, so i am not to inclined to take it to seriously.

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Sounds fine but the cell labelled 1.7v will, as far as I am aware, cover the range 1.6v to 1.8v (the cells above and below being 1.6v and 1.9v respectively). This covers the range from roughly 1.5psi to 4.25psi. Similarly, the next cell will cover the range from roughly 4.25psi to 7.5psi. These seem quite wide ranges to cover in one cell.

 

To illustrate that point, I’m currently getting AFRs between 14.3 and 12.6 in the 1.6v-1.8v/2750-3250 rpm range, all controlled by one cell (values in adjacent cells notwithstanding).

 

Doesn't it interpolate between the cells? So if you have an input of, say, 1.8V it will use the settings from the 1.7V and 1.9V cells. (and the same for the revs axis).

 

Dunno what you do about the 'off the scale' boost levels, but I guess that mappers put in a row or few of estimated values that would run rich.

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Doesn't it interpolate between the cells?
Yes I believe it does, but if the range between each cell equates to 3 psi then it's interpolating across that entire range. The 'start' and 'end' points of the interpolation are the values that you put into the cells so everything between that is just an extrapolation of the values that you have set. My point was that an extrapolation across a 3psi range lacks resolution.
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Dunno what you do about the 'off the scale' boost levels, but I guess that mappers put in a row or few of estimated values that would run rich.
I know, I'm not explaining myself very clearly. I was trying to refer to pressure sensor voltages greater than the highest value that you may have set in the map.
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I know, I'm not explaining myself very clearly. I was trying to refer to pressure sensor voltages greater than the highest value that you may have set in the map.

 

That's what I thought you meant, I just borrowed your description because I was too lazy to describe it more accurately :)

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OK now i know a little more about what we are dealing with, i would be inclined to do this, first determine where the std ECU goes open loop, expand the map scale before this point, ie make it much coarser, you should be be able to close up the scaling to obtain more resolution in the open loop area,which should allow you to include the higher load points you want, this applies to both RPM and boost, i guess if you want to make timing adjustments while the ECU is still in closed loop but off or low boost the fact that it will be a coarse adjustment shouldn't cause problems, does this sound like it might work for you?

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Sounds good to me. I was going to look at chopping some scale off the top of the map but I don't see any reason not to chop it off the bottom as well. If they both work then I'll be able to spread things out nicely, particularly in the peak torque area. Nice.

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