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Discussion Starter · #1 ·
It's called Volumetric Efficiency and is a measurement in percentage of the actual ability of the engine to move air versus what it could move in a perfect world. To use this test, you need a scan tool capable of recording data and a VE Calculator like this one. The calculator requires the engine size in cubic inch displacement, airflow in grams/second, engine rpm and intake air temperaure when tested. Set your scan tool to record these PIDs (Parameter Identifications) and take the car out for a test drive. If you want to test the accuracy of the MAF sensor, record the fuel trim PIDs (STFT and LTFT) as well.

From a rolling start in first or second gear, perform a wide open throttle run while recording the data. Make 3 or 4 passes in order to compare results. Back at the shop, find the point in your recording where airflow reported by the MAF and engine rpm are at their highest. Enter these values into the calculator. The result is a percentage to "ideal". Ideal would be 100% of the engine's displacement. However, "ideal" is not real world and normal efficiency is generally 80% or more. Turbocharged and supercharged engines will run higher than 100%, naturally, so bear that in mind if testing an engine so equipped.

If VE is low, and fuel trims are correcting positive (for a lean condition), then suspect an inaccurate reading from the MAF sensor. If VE is low, and fuel trims are normal, then look for restrictions to air flow. A "running" compression test can help isolate whether the restriction is on the intake side of the combustion chamber or the exhaust side.

The VE calculator is another diagnostic tool that can provide quick direction in diagnosing various driveability complaints. But just is as the case with other diagnositic tools, it should be followed by more pinpoint tests to verify the results...and the failure.


Now if someone would be kind enough to give me a place to host the file I will make the VE calc available for download
 

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Discussion Starter · #2 ·
Wow six view guess no one needs this info they would rather just replace expensive parts.
 

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Should probably be on the DYI forum, right? What is the scan tool? The peake tool or something else?

Awesome write up jbeurotech..
 

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Discussion Starter · #7 · (Edited)
Any cheap scan tool that can read data will work fine. As far as the VE calculator it is very easy to use if someone can host the file I will upload it for everyone to have.

This tool looks like it would even work for this basic test
http://www.dealextreme.com/details.dx/sku.16546

I think some of the Autozone ones that you rent even do live data.

HERE IS A SCREEN SHOT OF A GOOD MAF
 

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Discussion Starter · #8 ·
Here is a bad maf on a Toyota(I know why was i working on one of those..... Long story!!)
 

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Discussion Starter · #9 ·
Is that better I am still learning what you know and don't and how best to help you. Trust me I am not trying to talk over you guys. I thought this was a simple straight forward test. let me know what gives you troubles about it and we can have a discussion and see if people can get through it
 

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Seth, I will gladly host the file for you (if it's not HUGE). Email me - [email protected].

Regarding the Peake tool's capability of recording the required data, they do not offer that feature. This is why the customers that demand live data tend to opt for a generic tool with that capability. Keep in mind that the generic tools differ from the Peake tools in that they don't read the BMW specific diagnostic codes. The Peake tools are a single-purpose, BMW-specific code reader/reset tool - not a data logger. Two distinct types of products, both have benefits. Most of my customers prefer the functionality and accuracy of the Peake tools (as described in the article linked above and in my sig).

Ken
 

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Discussion Starter · #11 ·
Ok sent it to Ken who should have a link for you guys soon have fun!
 

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Discussion Starter · #13 ·
Autozone code readers do have this thing to record live, just plug it up and scroll through the menu instead of choosing enter to read codes.
Perfect there you go you can do all of this for free!!! Now someone should do this before and after cleaning there maf and record the results to test the effectiveness of this cleaner.
 

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Discussion Starter · #15 · (Edited)

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Thanks to both you guys. Ill be downloading this over the weekend when Im cleaning my MAF and changing plugs, etc.

You guys rock
 

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Discussion Starter · #17 ·
Top for guy with Maf issue
 

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Question. MS43 3.0 - running poorly, misfiring, and accrid white smoke....unplug new MAF since I was no longer using the MS45 DME and wiring harness (swapping the 3.0 / 6spd into a 325 auto wagon)....

anyway - unplug the new MAF and the car runs fine, idles great, no surging of rpm's, no misfires, can rev the engine without it dying...plug the maf back in...all goes to sh1t

I am turning the car off each time before plugging and unplugging. I had thought it was a fuel, spark or vacuum problem(s) up until I figured out the problem with the wagon by accident - I unplugged the MAF and then prepared to tear other things apart...then remembered I wanted to spray starter fluid to check for vacuum leaks and started the car (with the MAF still unplugged) and it ran perfect...no missing, no surging and no rich fuel smoke out the exhaust....turned it off - plugged in the MAF and it ran like crap again...missing, surging, etc....

Unplugged the MAF - ran fine. So tomorrow I am going to test the MAF wiring and the MAF and try to get a replacement or test MAF
 

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Perfect there you go you can do all of this for free!!! Now someone should do this before and after cleaning there maf and record the results to test the effectiveness of this cleaner.
Why do I get the feeling you already know the answer to this? Is it modern day snakeoil? I'de do the test but I don't have a dirty MAF to test. Mine was replaced recently.
 

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Discussion Starter · #20 ·
Why do I get the feeling you already know the answer to this? Is it modern day snakeoil? I'de do the test but I don't have a dirty MAF to test. Mine was replaced recently.
I know the answer in my testing I want to see what other peoples results are before I draw any conclusions


MS43 and MS45.1 us different inputs and Maf sensors are you sure you have the right parts on that car??? Why not use the MS43 harness and DME?
 
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