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Stock Maf Limits

Well then I guess I have to revisit what i'm doing with the MAFs. Maybe Ill try cleaning mine and see how that goes. Can anyone check the voltage that

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Old 08-18-2014, 07:23 PM   #16 (permalink)
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Well then I guess I have to revisit what i'm doing with the MAFs. Maybe Ill try cleaning mine and see how that goes.

Can anyone check the voltage that they are seeing? Ill do some more testing on my end and post up a log.
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Old 08-19-2014, 08:35 PM   #17 (permalink)
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I did some logging today and here are both runs. You can watch the MAF go all the way up to 5 Volts. I guess with Sasha's kit its just moving that much air at 12-13PSI? There is nothing in the tune that would lower the MAF voltage.





You can see it maxes out at 4500rpm (which is crazy low). I pulled both MAFs and they had some oil on them but I cleaned them and reinstalled them. I have no idea how you guys are running higher boost on a stock maf with 2.75" boost tubes.
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Old 08-19-2014, 08:39 PM   #18 (permalink)
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MAF Settings for reference



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Old 08-20-2014, 12:39 AM   #19 (permalink)
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Now you have me worried I wont hit my goals with the stock mafs. Is anyone running 14+ with the bp kit?
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Old 08-20-2014, 09:49 AM   #20 (permalink)
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Unless my MAFs are different than other stock MAFs I dont see how anyone could run more air through these 2.75" boost tubes with them in their stock location.

BBRSpeedworks put me onto these which takes advantage of the laminar flow in the boost tube and the fact that the friction along the sides of the tube actually slow down the incoming air and thus allow you to read higher flow values with the stock MAF by moving it out closer to the edge of the boost tube.

Hitachi Slot Style MAF Mass Air Flow Adapter Flange, FORD and GM- TREADSTONE PERFORMANCE
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Old 08-20-2014, 10:36 AM   #21 (permalink)
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Nice! Simple cost effective solution, if it works. Did you order these up Mitco?
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Old 08-20-2014, 11:04 AM   #22 (permalink)
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Originally Posted by TopgunZ View Post
Nice! Simple cost effective solution, if it works. Did you order these up Mitco?
I think I might try them just to see if they work, I think ultimately I will just end up running 3" boost tubes though as that seems like a more permanent solution.


Edit... On second thought they are not just spacers but it looks like the maf adaptors will have to be torn off the current boost tubes and these installed. Too much hassle for me, I thought they were just spacers at first.
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Old 08-20-2014, 12:51 PM   #23 (permalink)
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U could get them cut of and grinder down then weld on the new ones..
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Old 08-20-2014, 12:57 PM   #24 (permalink)
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For reference, with my Greddy kit that uses 2.75" MAF tubes, my MAF voltages are ALMOST maxed out in the 9psi area. I hit 4.9's in voltage. But boost pressure is not exactly an indication of airflow.
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Old 08-20-2014, 01:07 PM   #25 (permalink)
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Originally Posted by phunk View Post
For reference, with my Greddy kit that uses 2.75" MAF tubes, my MAF voltages are ALMOST maxed out in the 9psi area. I hit 4.9's in voltage. But boost pressure is not exactly an indication of airflow.

While I agree with you where the MAF is being measured the restriction to airflow past the maf should be consistent engine to engine unless you have extensive throttle body or plenum mods. Or if you figured out how to increase flow via VVEL. This is measuring the boost right after the MAF on Sasha's kit. But your right, where you measure boost can have a very large effect on what your seeing vs how much your flowing when compared to the next guy.

What is interesting to me is how it is not common knowledge that these stock MAFs are not suitable for what I would call over 475-500hp on stock sized MAF tubes. It can get very dangerous very quick when you get into the upper ranges of the MAF.
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Old 08-20-2014, 01:51 PM   #26 (permalink)
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Airflow and pressure are not directly relative anywhere you take reading or measure. Different turbo systems on the same engine will achieve different airflow mass at the same pressures. Which is why I have my MAF voltage nearly maxed out and I am not even at 10psi boost.
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Old 08-20-2014, 02:00 PM   #27 (permalink)
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Quote:
Originally Posted by phunk View Post
Airflow and pressure are not directly relative anywhere you take reading or measure.
Care to elaborate?

If you have the same restriction downstream of a flow and it is in steady state conditions you will have a very similar flow as long as the device reading the flow has the same cross sectional area. Albeit if you are not in a steady state condition when dealing with air you will have density changes as the pressure changes as it approaches a particular restriction. If pressure was not relative to flow you couldn't have MAP tuning on engines at all as you would never know the mass of air being ingested by the engine.

While I agree with what you are saying I reason that if you have some constant variables then the system becomes measurable and if you wanted to even tunable based on pressures instead of flow rates.
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Old 08-20-2014, 02:05 PM   #28 (permalink)
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I see you did a ninja edit there.

I agree with you up until you measure after all the modifications. If your measuring at the turbo outlet then yes, you will have restrictions that cause pressure and reduce flow. But if you measure right at the TBs then it doesnt matter what is pushing the air before it, all that matters is that air is getting to the engine at some flow rate. This is assuming your IATs are very similar to another platform you are measuring against.

Its like having a large industrial fan pushing air through a very long cylinderical pipe, while at the same time using a small fan through a short pipe. If you cut both pipes such that you want the outlet flow to be the same it no longer matters what was before the pipes. All the losses incurred through the system happen before the point of measurement, not after it.


Again I could be wrong, but its how what I was taught sat with me. I will have to go find my fluids text.
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Old 08-20-2014, 02:28 PM   #29 (permalink)
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The discrepancy I believe you are missing is that a MAF sensor is not "boost-smart". Once you are using the MAF sensor in a blow-through application, while you will maintain repeat-ability in the installed application (hence still allowing for a consistent and safe tune), there is no longer any direct correlation between MAF voltage and PPM of air. You are now tuning based on literally just MAF voltage VS RPM, rather than a known quantity of air vs RPM. Without outside data collection such as boost gauges and logging, while tuning the UpRev, we would be entirely blind as to have any idea how much air mass is entering the engine.
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Old 08-20-2014, 02:31 PM   #30 (permalink)
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The dependency I believe you are missing is that a MAF sensor is not "boost-smart". Once you are using the MAF sensor in a blow-through application, while you will maintain repeat-ability in the installed application (hence still allowing for a consistent and safe tune), there is no longer any direct correlation between MAF voltage and PPM of air.
I agree with that 100%. I would suspect with higher pressures your going to have more air available to cool the sensor and "fool" it under pressure. That explains how on a NA car you can still see ~4.6 volts yet it still works under boost which much larger flow rates.
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