Please Read --> MAF Sensors with the EMS - Great Thread!

[anoldsman]

I talked to the AEM technical advisor on how to view or log the airflow from my MAF on my 1990 GSX.  I was told that since they do not know the flow of the MAF they can not determine the airflow.  So I advise everyone that is using their MAF sensor to convert over to the MAP.
  I believe that this would be true for ALL of the MAF systems.  This is based on the fact that the MAF calibration is for voltage vs. load %.  It is possible to have two MAF's that have the exact same voltage to load % graph but have very different airflow at those load points.  
  I am not trying to bad mouth the EMS.  I believe that the Automap and the data logging abilities alone warrant the purchase of the EMS.  I just want people to know that the AEM EMS IS NOT MAF CAPATIBLE.  That is why I believe that all of the users that have converted over to MAP have performed better.  Do not knock the system, just know its limits.  I will now be converting to MAP.  I would prefer to run MAF but any other system that claims to be MAF compatible cost too much for the time being.

Chris

[WadZii]

im just curious.. why would you prefer to run a maf?  going to speed density you take a huge restriction out of the intake, thats why they get more power w/speed density than maf

[anoldsman]

WadZii,

  I want to run a MAF for several reasons.  One is that a MAF is way more forgiving when making changes.  Say, I change the lobe separation of the cams.  This would change the manifold vacuum.  A MAP system would need to be retuned to compensate for this change.  Another is weather changes.  A MAP system usually has to be tweaked for varying patterns where as the MAF compensates for these patterns.  A MAF can work around this because the airflow would change.  Now it would not be perfect but, it is much better than the MAP way.  Remember that a MAP interprets the load on a motor based on vacuum or boost and that a MAF actually measures the airflow requirements and therefore the load.
  MAP is excellent for many applications but I believe that with a properly sized MAF you will obtain better power, drivability and tuneability.  I firmly believe that the main reason people are gaining hp from converting to speed density is that the EMS is not actually reading airflow.  The EMS is using the stock MAF as nothing more than a frequency based MAP.  The reason that other systems use MAP is because it is easier to program and there are more types of MAF sensors used in the automotive field than MAP sensors.  This reduces the amount of R&D to test sensors.  The gain in hp over stock MAF systems is more a result of the ability to tune than the type of system.
  I bought the system based on many factors.  One requirement was that it used MAF data to determine the fuel requirement.  I will still use the system but I wish that AEM would have told me this up front so that I could have evaluated it differently.  

Chris

[Erich Moraga]

im just curious.. why would [Chris] prefer to run a maf?

1) less money
2) less labor
3) less thinking

  Some people like to take the path of least resistance.

-Erich

[WadZii]

i dunno... i think that once setup properly map is better than maf.  you dont have any limits on the power.  i have done some work with nissans and toyotas w/mafs and imo the mafs is just a pain, specially on the stock mafs.  spend a few bux on a gm iat and a 3bar map and your set to 30psi, and however much power you wana make.  with a mafs with big power you can run into the problem of loosing the ability to measure small ammounts of air flow. yeah it takes a little more thinking to make a MAP based system running good.. but whats that, tuning a AIT correction table? and depending on the setup the baro correct table? its not that big a deal imo.  and you get rid of a huge restriction in the intake flow.

[BLKMGK]

Okay, so you need to know what the aqirflow vs voltage reading of the MAF is then right? Has anyone considered sending their MAF sensor someplace to have it MEASURED? Just because AEM doesn't know this value doesn't mean that you cannot tune using MAF, you simply won't be able to use math to figure out your theoretical fueling is all. Try tuning it!

MAP systems do have to be tuned for additional airflow, it's a PITA. However for MAF to have the flexability you want there are still some tradeoffs. Loss of resolution at higher airflows for one. Needing clean airflow for another. MAF sensors DO represent a restriction, you can probably measure it using a sensitive vac sensor sourced between the TB and turbo inlet. If you see ANY vac then you have witnessed a restriction!

The only other system I'm aware of that runs MAF and isn't a modified OEM ECU is the Electromotive system. Folks I've talked to who have used it and someone I met who used to work there (they're local to me) have told me that it's less than perfect. I believe it operates much like the AEM does in fact - they treat the MAF sensor as a load reading device just like a MAP sensor. That said I've never used an Electromotive system so I cannot comment firsthand. Having watch someone ROM tune an EEC-V it does appear to be easier but they run into issues at idle and with having too much airflow (max the sensor).

Anyway, if you truly want to run MAF contact Pro-M for a MAF sensor that's compatible with the AEM. I'm not sure which one would work best (Ford probably) and get one that can flow as much air as you need. Pro-M supplies a calibration chart with each of their meters that I believe shows the calibration curve of that meter which is what I believe you need. I'd actually be pretty interested in hearing how you fare with this. Might be interesting to slap a Ford MAF on the end of my turbo inlet and see how much air I'M moving actually. Maybe AEM and Pro-M could work together to figure out what would work best in the way of a MAF sensor. <shrug> Car to car in the same line the various MAF sensors should measure nearly EXACTLY the same if you were to get your OEM sensor measured BTW. They would have ot in order for the OEMs to be able to use them...

P.S. Less money to run a MAF? Not if you want a calibrated one!

[fusionsport]

IMO MAF are a waste of time. BLKMGK is spot on and I can only add that a properly tuned MAP sensor with IAT corections wil be just as drivable and efficient, easier to tune, and have no limitations on power. If you dont want to use MAP as load then use TPS as load with a boost comp table. MAF is far to imprecise for the power levels most people wish to run.

[anoldsman]

I am not trying to make any one mad.  Of all the people here I believe that you, BLKMGK, are the most knowledgeable person regarding the AEM EMS.  You have certainly helped me in the past.   I am just pointing out the fact that the AEM EMS is not setup to read airflow.
 
The loss of resolution can be over come with the correct type of MAF (edge orifice vs. hot wire for one).  As far as a restriction goes, has anyone actually measured the restriction?  I believe that with the correct MAF you can achieve excellent resolution as well as zero (relative) restriction.  Remember, most of us are still using an air cleaner.  Even the use of a K&N filter can result in a larger restriction than the proper MAF.
 
Also, even if I used a calibrated Pro-M MAF the EMS only looks at voltage vs. load % and not at voltage vs air mass.  I have the calibrations for some GM MAF's that have different air mass specifications but similar load %.  So, it still would be a fudge factor to make it work.

Why doesn't AEM just tell everyone to convert to MAP?  Instead, AEM just “recommends” it.  I am just trying to give AEM’s customers more knowledge about the system to show that they should ALWAYS convert to MAP with the EMS.

By the way, I am converting to MAP.  Tunning is not an issue as I have experience with many other MAP based systems.  Like I stated in another topic, I believe that the AEM is a very good MAP base system and probably the best “bang for the buck”.  That is why I am keeping the system.  I just wanted to try a MAF based system.  Does everyone try to convert the Ford Mustang owners to a GM product?  I do not think so.  So why is everyone trying to convert me from MAF to MAP?

Chris

[fusionsport]

I never cared much for any MAF, and having seen your other thread regarding the MAF translator, am just trying to save you some headache. I certainly mean no offense, and am not the ultimate authority on much of anything.

[SA]

I am just pointing out the fact that the AEM EMS is not setup to read airflow.

Wrong.
 

Also, even if I used a calibrated Pro-M MAF the EMS only looks at voltage vs. load % and not at voltage vs air mass.

Wrong again.

I am just trying to give AEM’s customers more knowledge about the system to show that they should ALWAYS convert to MAP with the EMS.

There's a lot of Ford guys still using the MAF sensor with the EMS and everything is just fine.  There's nothing wrong with the function used on the DSM's either to calculate engine load based on the frequency output of the KV MAF sensor.  

PM me.  I'll give you my direct phone extension.  Call me and I'd be happy to explain the calculations to you.

SA

[BLKMGK]

I am not trying to make any one mad.  Of all the people here I believe that you, BLKMGK, are the most knowledgeable person regarding the AEM EMS.  You have certainly helped me in the past.   I am just pointing out the fact that the AEM EMS is not setup to read airflow.
 <snip>
Chris

Anoldsman, no heat here man - you're not making me angry. I understand that you wish to measure directly rather than infer air mass. I've come to understand that even MAF sensors do some inferance though so no matter what there's going to be some sort of compromise. I also understand your being curious about setting it up this way and I'd be interested in any progress you make on this after speaking to Scott. I admit to being curious too after having watched this guy tune a Mustang locally. I do however believe that the MAF would create a measurable restriction - and yes so does the air cleaner. If I were to try this I'd be using a pretty big MAF and certainly NOT the one that was stock on my car 8O Big Pro-M meters all but fall out of trees around here so that's probably what I'd choose <shrug> If you've got GM meters and calibrations then that's probably easiest....

[Sleepr DSM]

Strong reactions.  

I really want to talk to a 1G DSM EMS user who is running a stock MAF sensor successfully, on a car that is daily driven and pushed on the track/and or dyno.  If anyone knows someone who has been successful, please let me know.  
All the DSM owners I know experienced frustration trying to use their MAF setup and switched over to speed density.  

Correct my faulty thinking on the following points.  Given, the stock MAF on a 1G DSM is simply not up to par for making massive power.  The 2G MAF (the use of which is a common mod for 1G's) flows 30% more air and puts cars into the low 11's.  One can go larger with a Pro-M set up.  But, as with other bugs and problems, AEM should work harder to publish the fact that the EMS as it stands, is not going to work effectively with the stock MAF system even on a car making very modest power in a daily driven capacity.  All will defend that it is "CAPABLE" of doing so.  "Someone, somewhere" with a great amount of  time and money MAY be able to make the stock MAF work "well", but for the average person who purchased the EMS it will not work properly and they will be dissapointed if they expect their car to run well with a stock MAF.    I expect to be told I am Wrong.  Please allow me to talk to the person who is driving that car.  (1G DSM, EMS, stock MAF, track capable)

But all of the above may be pointless anyway.  Why?  If it is reasonable to conclude that the stock 1G MAF meter is insufficient to make an extraordanry amount of power because of the deterioration of the air flow measurement at higher volumes, then why would AEM do anything other than provide a very rough.."Get your car started and around the block" guideline for the EMS to apply to the stock 1G air meter?  They would conclude that most people (upon learning of the 1G maf limitations) would upgrade to a speed density system, or a larger MAF unit anyway.  Why put a great deal of R&D into it anyway then?  AEM's recommendations, at least any of them I have seen so far.. are in reality the only door that will take you where you want to go.   Choose the recommendation, or choose frustration.      
But, If that is the case, it should be made explicitly clear to potential EMS buyers.  Upgrades and modifications to the cars existing system of operation that MAKE SENSE because of how the EMS is designed, should not be recommended, they should be described as "mandatory upgrade, or suffer the consequences".

In addition, I agree 100% with Anoldsman on the merits of MAF.  Please examine carefully his responses to the listed weaknesses of MAF.  The independent research I have done is in harmony with the responses he has made, regarding the level of restriction, and the advantages vs. disadvantages.  Anoldsman I would like talk with you about the information you learn from investigating this further, perhaps after you talk with Scott a.k.a. SA?

[Mello]

Dear Anyone who wants my opinion.  

I use the MAF system and my car runs better every single day than anyone else's car that I know of.  I tune several cars using the AEM (and other) EMS.  Everyone at the moment is asking me to set their cars up with speed density which is fine because it is an easier system to get drivable.  None of the switched over cars has made any more power from the switch.  You guys are just plain clueless as to what is going on here.  A sensor is a sensor, end of story.  If it’s a flow sensor, it’s a flow sensor.  A flow sensor put out a signal base on flow characteristics through it; a pressure sensor’s output is based on pressure.  All the EMS does is take this sensor’s output signal (the EMS input) and makes calculations with it to determine a calculated response (EMS output) for control.  Neither one of these setups has to output any real world values to control a vehicle.  As long as it is properly sized to cover the operating range of the motor it is being used on it can be tuned (hence percentage values).  The actual flow or pressure is just for us people, not the EMS.  I read almost every post in this forum but find that trying to respond and convince people of what is really going on with EFI tuning would probably be a fruggle effort so I usually just remain silent and laugh.  I will probably not post much more on this subject either.  But there is a reason why the multi million dollar automobile industry is evolving to MAS systems, they are much better at determining the final air volume requirements for engine management.  Also speed dendity is cheap to setup.  MAF systems are more expensive.  A MAF sensors is more than both the IAT and MAP sensors together, even the good ones.  In summary:

Speed density is CHEAPER not more expensive.
Speed density is easier to get running not harder.
Speed density will not make more power than a MAS system, but it will not make less power either.  Matter of fact, last I look the sensor weren't make the power at all.  The power comes from the other thing, the motor setup.  But it does have to be controlled.  Which bring all of us to the one common fact, we all purchased an AEM EMS.

[supra87t3/t4]

Thank you Mello, I am in 100% agrement Please post your insights more often, I understand how easy it is for the knowledgeable people to be overwhelmend by how fast misinformation spreads when it has a "believable" explanation.

[BLKMGK]

Well, yeah. Mello is right <shrug>. It would be easiest if you know the voltage vs flow curve of the sensor IMO since, at least the charts I've seen, haven't been completely linear. That said - if you tune the engine for a specific A/F vs flow (psst, just like MAP) then it'll be repeatable even if you don't know what the actual amount of air moving through it is.


All that said - you guys must have some awesome flowing MAFs not to be seeing any restrictions. The Supra picks up power for sure and if you ever looked at the MAF you would understand why! 8O Same thing on a Mustang - stock they have a small MAF and you can max out it's flow on a good motor. In general they are a restriction but perhaps not in every single case...