tbm
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« Reply #15 on: April 11, 2013, 02:21:56 PM »
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The ME7's that have MAF don't have a MAP sensor, very simple.
Only a charge pressure sensor before the throttle plate, which is completely useless for air charge calculation except for WOT.
Suddenly... I thought that ME7.5 has both MAF and MAP sensor. |
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ddillenger
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« Reply #16 on: April 11, 2013, 02:27:52 PM »
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Map would indicate it's measuring manifold pressure, as in vacuum as well. Not the case here.
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prj
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« Reply #17 on: April 11, 2013, 02:43:44 PM »
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Suddenly... I thought that ME7.5 has both MAF and MAP sensor.
It does not. I suggest looking at the hardware you are trying to tune and realizing that the sensor is before throttle plate, so completely useless for calculating air charge unless throttle is fully open. MAP means manifold absolute pressure. ME7.5 with MAF has no pressure sensor in the manifold. |
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tbm
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« Reply #18 on: April 11, 2013, 02:52:11 PM »
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Map would indicate it's measuring manifold pressure, as in vacuum as well. Not the case here.
But if we know intake pressure and intake temperature we can calculate mass air consumption with the formula something like below: MAC = FE * Vcyl * P * 293 / (273 + TA) * K FE – percent of effecient Vcyl – volume of cyl P – intake manifold pressure ТA – intake air temperature K – conversion factor of dencity |
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tbm
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« Reply #19 on: April 11, 2013, 02:57:11 PM »
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It does not. I suggest looking at the hardware you are trying to tune and realizing that the sensor is before throttle plate, so completely useless for calculating air charge unless throttle is fully open. MAP means manifold absolute pressure. ME7.5 with MAF has no pressure sensor in the manifold.
Do you mean ME7.5 hasn't MAP in stock at all? How people using MAFless connect MAP to ME7.5? |
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ddillenger
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« Reply #20 on: April 11, 2013, 02:58:06 PM »
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It does not. I suggest looking at the hardware you are trying to tune and realizing that the sensor is before throttle plate, so completely useless for calculating air charge unless throttle is fully open. MAP means manifold absolute pressure. ME7.5 with MAF has no pressure sensor in the manifold.
Just ask britishturbo what happens when you try to use the charge pressure sensor to read manifold pressure  Do you mean ME7.5 hasn't MAP in stock at all?
That is correct. There is no sensor measuring MANIFOLD pressure. Charge pressure, yes. Manifold pressure, no. It'll never read lower than barometric given the sensor location. |
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« Last Edit: April 11, 2013, 03:01:50 PM by ddillenger »
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Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience!
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catbed
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« Reply #21 on: April 11, 2013, 03:04:05 PM »
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Do you mean ME7.5 hasn't MAP in stock at all? How people using MAFless connect MAP to ME7.5?
MAFless on ME7.5 has nothing to do with the MAP. Its because the primary o2 is wideband. MAFless is still not ideal though. Like others have said, it's a true MAP ie. not measuring manifold pressure. |
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tbm
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« Reply #22 on: April 11, 2013, 03:10:20 PM »
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That is correct. There is no sensor measuring MANIFOLD pressure. Charge pressure, yes. Manifold pressure, no. It'll never read lower than barometric given the sensor location.
MAFless on ME7.5 has nothing to do with the MAP. Its because the primary o2 is wideband. MAFless is still not ideal though.
Like others have said, it's a true MAP ie. not measuring manifold pressure.
Thanks guys! It's absolutely clear now. |
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tbm
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« Reply #23 on: April 12, 2013, 01:26:03 AM »
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MAFless on ME7.5 has nothing to do with the MAP. Its because the primary o2 is wideband. MAFless is still not ideal though.
Like others have said, it's a true MAP ie. not measuring manifold pressure.
Which is load factor with MAFless, throttle? |
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prj
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« Reply #24 on: April 12, 2013, 01:43:23 AM »
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Which is load factor with MAFless, throttle?
Yes, RPM x Throttle (Alpha N). The charge sensor is also considered, but only at high throttle opening. So with all normal driving you are only driving from alpha-n which is not very good on a turbo engine. Even if you have wideband to correct the mixture, your ignition timing is still all over the place... |
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tbm
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« Reply #25 on: April 12, 2013, 02:02:51 AM »
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Yes, RPM x Throttle (Alpha N).
The charge sensor is also considered, but only at high throttle opening. So with all normal driving you are only driving from alpha-n which is not very good on a turbo engine.
Even if you have wideband to correct the mixture, your ignition timing is still all over the place...
I see. But I thought that throttle is load factor for ignition timing as well. |
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prj
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« Reply #26 on: April 12, 2013, 02:58:58 AM »
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I see. But I thought that throttle is load factor for ignition timing as well.
Yes, but it is impossible to accurately determine load using RPM and Throttle on a turbocharged application. The only way it even runs somehow in vacuum area is because of wideband O2 correcting mixture. But because it does not know load correctly, the ignition timing is impossible to calculate precisely. |
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tbm
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« Reply #27 on: April 12, 2013, 03:07:02 AM »
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Yes, but it is impossible to accurately determine load using RPM and Throttle on a turbocharged application.
The only way it even runs somehow in vacuum area is because of wideband O2 correcting mixture.
But because it does not know load correctly, the ignition timing is impossible to calculate precisely.
I agree with you. Just to clarify, in order to use MAFless need to use some customs binary flash file or can change load factor in stock file? |
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adeyspec
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« Reply #28 on: April 12, 2013, 04:21:26 AM »
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Does the stock sensor read vacuum? If so move it to behind the throttle body so it sees both positive and negative pressure
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prj
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« Reply #29 on: April 12, 2013, 05:24:06 AM »
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I agree with you. Just to clarify, in order to use MAFless need to use some customs binary flash file or can change load factor in stock file?
Just disconnect MAF, and you are in limp mode. MAFless = limp mode. If you want to do speed-density, then you need custom code. Does the stock sensor read vacuum? If so move it to behind the throttle body so it sees both positive and negative pressure
And then what? ME7 does not know what to do with that. This moving assumes making a hole in the manifold somewhere also... |
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