Sticky Request - Miata Airflow Spreadsheet
07-19-2012, 12:20 AM
#41
I'm so sick of arguing with you, but I can't let myself leave misinformation in an otherwise very helpful thread full of correct design and theory.
A calibration curve is just that, a sensor calibration, in our case a MAF. The calibration curve is not going to change no matter where that sensor is, given a few constants. Here, I'm going to assume temperature and pressure are constant across all scenarios. Did you catch that assumption? (I know you missed the one where I assumed his calibration curve was accurate) The mass of air moving through the sensor correlated to a voltage output from the sensor (actually a resistance change across the sensor body) is not going to change whether that same MAF is on a laboratory bench, in a miata, a corvette, or on an airplane. It doesn't matter whether the air goes through ten miles of pipe first or nothing at all. The sensor will still output a given voltage for a given amount of air flow. I'm assuming this calibration is known. I know how to measure and generate my own calibration for whatever MAF, but I haven't done enough research to know whether a GM MAF calibration equation is accurate for a miata MAF or not. So, if you know that calibration, and can plot the raw voltage reading, you will know with some degree of accuracy how much air goes through the motor. From there, calculating the VE is simply a math problem. Are you all caught up now?
A calibration curve is just that, a sensor calibration, in our case a MAF. The calibration curve is not going to change no matter where that sensor is, given a few constants. Here, I'm going to assume temperature and pressure are constant across all scenarios. Did you catch that assumption? (I know you missed the one where I assumed his calibration curve was accurate) The mass of air moving through the sensor correlated to a voltage output from the sensor (actually a resistance change across the sensor body) is not going to change whether that same MAF is on a laboratory bench, in a miata, a corvette, or on an airplane. It doesn't matter whether the air goes through ten miles of pipe first or nothing at all. The sensor will still output a given voltage for a given amount of air flow. I'm assuming this calibration is known. I know how to measure and generate my own calibration for whatever MAF, but I haven't done enough research to know whether a GM MAF calibration equation is accurate for a miata MAF or not. So, if you know that calibration, and can plot the raw voltage reading, you will know with some degree of accuracy how much air goes through the motor. From there, calculating the VE is simply a math problem. Are you all caught up now?
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07-19-2012, 12:25 AM
#42
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I'm so sick of arguing with you, but I can't let myself leave misinformation in an otherwise very helpful thread full of correct design and theory.
A calibration curve is just that, a sensor calibration, in our case a MAF. The calibration curve is not going to change no matter where that sensor is, given a few constants. Here, I'm going to assume temperature and pressure are constant across all scenarios. Did you catch that assumption? (I know you missed the one where I assumed his calibration curve was accurate) The mass of air moving through the sensor correlated to a voltage output from the sensor (actually a resistance change across the sensor body) is not going to change whether that same MAF is on a laboratory bench, in a miata, a corvette, or on an airplane. It doesn't matter whether the air goes through ten miles of pipe first or nothing at all. The sensor will still output a given voltage for a given amount of air flow. I'm assuming this calibration is known. I know how to measure and generate my own calibration for whatever MAF, but I haven't done enough research to know whether a GM MAF calibration equation is accurate for a miata MAF or not. So, if you know that calibration, and can plot the raw voltage reading, you will know with some degree of accuracy how much air goes through the motor. From there, calculating the VE is simply a math problem. Are you all caught up now?
A calibration curve is just that, a sensor calibration, in our case a MAF. The calibration curve is not going to change no matter where that sensor is, given a few constants. Here, I'm going to assume temperature and pressure are constant across all scenarios. Did you catch that assumption? (I know you missed the one where I assumed his calibration curve was accurate) The mass of air moving through the sensor correlated to a voltage output from the sensor (actually a resistance change across the sensor body) is not going to change whether that same MAF is on a laboratory bench, in a miata, a corvette, or on an airplane. It doesn't matter whether the air goes through ten miles of pipe first or nothing at all. The sensor will still output a given voltage for a given amount of air flow. I'm assuming this calibration is known. I know how to measure and generate my own calibration for whatever MAF, but I haven't done enough research to know whether a GM MAF calibration equation is accurate for a miata MAF or not. So, if you know that calibration, and can plot the raw voltage reading, you will know with some degree of accuracy how much air goes through the motor. From there, calculating the VE is simply a math problem. Are you all caught up now?
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07-19-2012, 04:06 AM
#44
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I'm done reading you. I wish there was a way to block your posts.
You don't learn, you don't want to learn.
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07-19-2012, 06:00 AM
#45
I'm so sick of arguing with you, but I can't let myself leave misinformation in an otherwise very helpful thread full of correct design and theory.
A calibration curve is just that, a sensor calibration, in our case a MAF. The calibration curve is not going to change no matter where that sensor is, given a few constants. Here, I'm going to assume temperature and pressure are constant across all scenarios. Did you catch that assumption? (I know you missed the one where I assumed his calibration curve was accurate) The mass of air moving through the sensor correlated to a voltage output from the sensor (actually a resistance change across the sensor body) is not going to change whether that same MAF is on a laboratory bench, in a miata, a corvette, or on an airplane. It doesn't matter whether the air goes through ten miles of pipe first or nothing at all. The sensor will still output a given voltage for a given amount of air flow. I'm assuming this calibration is known. I know how to measure and generate my own calibration for whatever MAF, but I haven't done enough research to know whether a GM MAF calibration equation is accurate for a miata MAF or not. So, if you know that calibration, and can plot the raw voltage reading, you will know with some degree of accuracy how much air goes through the motor. From there, calculating the VE is simply a math problem. Are you all caught up now?
A calibration curve is just that, a sensor calibration, in our case a MAF. The calibration curve is not going to change no matter where that sensor is, given a few constants. Here, I'm going to assume temperature and pressure are constant across all scenarios. Did you catch that assumption? (I know you missed the one where I assumed his calibration curve was accurate) The mass of air moving through the sensor correlated to a voltage output from the sensor (actually a resistance change across the sensor body) is not going to change whether that same MAF is on a laboratory bench, in a miata, a corvette, or on an airplane. It doesn't matter whether the air goes through ten miles of pipe first or nothing at all. The sensor will still output a given voltage for a given amount of air flow. I'm assuming this calibration is known. I know how to measure and generate my own calibration for whatever MAF, but I haven't done enough research to know whether a GM MAF calibration equation is accurate for a miata MAF or not. So, if you know that calibration, and can plot the raw voltage reading, you will know with some degree of accuracy how much air goes through the motor. From there, calculating the VE is simply a math problem. Are you all caught up now?
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07-19-2012, 10:03 AM
#46
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the point of screens in front of and behind the maf housing is to keep flow laminar. Well if you put say a bend infront of the maf it can easily move the majority of the mass flow away from the middle of sensor as it flows past. Anyone with tuning experince deadling with maf tuning will know this. They will also know by changing out to a bigger housing a maf sensor can be made to read higher airflow. The best way to know what its output to airflow is in a setup is to actually use it for fuel control. Get it down so you know what the airflow numbers are. And yes it does matter if the maf has straight piping before vs no piping before the maf. It will affect sensor readings.
Last edited by Techsalvager; 07-19-2012 at 12:35 PM.
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07-19-2012, 01:05 PM
#47
Tech is correct. The Maf is calibrated for the tube dia it is mounted within. It only samples a small fraction of the airflow so the cal is velocity sensitive. If you use the same dia as what the Maf originally used, and can ensure laminar flow (straight sections up and downstream of the Maf) then the original cal curve will remain valid. Use a larger dia and you will need to recharacterize the Maf if you want an accurate cal curve.
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07-19-2012, 05:46 PM
#48
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Tech is correct. The Maf is calibrated for the tube dia it is mounted within. It only samples a small fraction of the airflow so the cal is velocity sensitive. If you use the same dia as what the Maf originally used, and can ensure laminar flow (straight sections up and downstream of the Maf) then the original cal curve will remain valid. Use a larger dia and you will need to recharacterize the Maf if you want an accurate cal curve.
The MAF as a sensor works within the parameters of a given tube, and if you deliberately set out to sabotage the flow through that tube, you could affect the calibration.
But if you use it as intended, it doesn't matter what else that MAF/tube combination is connected to. It measures the flow through the tube and the flow through the rest of the system MUST be the same.
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07-20-2012, 09:01 AM
#49
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Yes... ...obviously.
The MAF as a sensor works within the parameters of a given tube, and if you deliberately set out to sabotage the flow through that tube, you could affect the calibration.
But if you use it as intended, it doesn't matter what else that MAF/tube combination is connected to. It measures the flow through the tube and the flow through the rest of the system MUST be the same.
The MAF as a sensor works within the parameters of a given tube, and if you deliberately set out to sabotage the flow through that tube, you could affect the calibration.
But if you use it as intended, it doesn't matter what else that MAF/tube combination is connected to. It measures the flow through the tube and the flow through the rest of the system MUST be the same.
actual flow though the tube maybe the same but airflow vs output has changed
where with a bend infront it maybe 1v at idle
and without a bend infront it maybe .7v at idle.
Last edited by Techsalvager; 07-20-2012 at 09:14 AM.
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07-20-2012, 01:03 PM
#50
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And how you gonna use as intended on a completely different car\engine with different size piping? And yes it always matters what maf\tube combination it is if its anything different then a stock it will change.
actual flow though the tube maybe the same but airflow vs output has changed
where with a bend infront it maybe 1v at idle
and without a bend infront it maybe .7v at idle.
actual flow though the tube maybe the same but airflow vs output has changed
where with a bend infront it maybe 1v at idle
and without a bend infront it maybe .7v at idle.
Go away.
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07-20-2012, 04:35 PM
#51
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Do you have first hand experince tuning maf based systems?
Could one do it deliberately? Probably. Is it going to happen because you have a different bend in the pipe flowing into it? Almost certainly not.
Yes it will happen.
It happens so easily as well
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07-20-2012, 05:49 PM
#52
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lol
Yes it will happen.
It happens so easily as well
Yes it will happen.
It happens so easily as well
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07-23-2012, 05:15 PM
#54
I'll cross post this, because I at the very least seriously doubt the VE numbers in the actual tune on a hydra, VE number and HP numbers really arent correlating to something that makes sense. This person does not want me discussing the tune, but I will say based on the VE numbers in that tune and the HP its making stock 1.8 would be in the low 70's for peak VE if the numbers in the hydra are to be believed. So rather than basing it off the fuel table we will just have to do the math ourselves. https://dl.dropbox.com/u/18163809/Ho...ityWorks16.doc
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07-23-2012, 05:21 PM
#55
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I know nothing about Hydra, but VE is rarely really VE. For example in MS1, it is not at all. In MS2 B&G, it's not either. In MS2Extra it CAN be, but ONLY if you enable a non-default option, and have multiply MAP turned on (this shouldn't even BE an option). Even then, I'd be weary of the numbers as you'd need to set up ReqFuel perfectly and that's rarely done correctly, if ever. In fact, it's often beneficial to not do it "correctly". Thus, with a closed source EMS like Hydra, your only option is to do the math yourself.
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07-23-2012, 05:58 PM
#56
I'm used to mostly dealing with GM car, and GM has their own VE which does things a bit different, so seeing a tune that hits 198% VE is nothing abnormal to me. But the work I've done with haltech suggests that at least they use real VE and the numbers seem to make sense. But I guess everything just has to be different.
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08-09-2012, 09:41 AM
#58
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Hey leafy, are you suggesting that the actual VE for the 1.8 motor is closer to 70%? Sorry, I have had a lot of family issues lately (deaths in the family) and haven't been on to keep track of everyones posts on my thread :P
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