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> MAF vs MAP
post May 27, 2009 - 2:14 PM
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jason



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Just curious what everyone's opinions on these are (FI application)

for a street driven car (low throttle driving) that also see's its share pf peppy driving (wot pulls) which is "better" and why?

blow off would be recirculated, and leaks not being considered, why would one choose a map system besides tunning capabilities?


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post May 27, 2009 - 2:33 PM
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Fastbird

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Actually your typical MAF based system is easier to tune than a MAP based system because the fueling for the MAF system is all based off of airflow charts. X airflow = X fuel whereas the MAP system uses volumetric efficiency based on MAP, RPM, and Temp. The MAP system takes longer to get dialed in, adapts somewhat to temp/altitude changes but has it's limitations. It's biggest advantage is that the Fueling is MAP based, and you can extend the tables as far as you need. A MAF only operates in a certain feedback frequency range, so you're limited with how much boost you can run. Once you're out of the MAF frequency range you're essentially in a big guessing game and your tune pretty much ends up out to lunch.

For a mild setup, the MAF setup won't hurt anything. For a wild setup, I'd strongly suggest a switch to a MAP system.


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post May 27, 2009 - 3:53 PM
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lagos



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map


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post May 27, 2009 - 5:09 PM
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presure2



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fastbird pretty much hit the nail on the head.


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post May 28, 2009 - 9:25 AM
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jason



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got this elsewhere. all i know.. is that when i had a maf setup previously the back of my car was clean compared to when i switched to a map setup.

by wild... i presume doubled stock power? (200hp engine now producing 400hp)

QUOTE
It doesn't matter if the vehicle uses MAF or MAP, the ECU still needs to come up with a number representing air mass flow rate. In MAF based systems, this is a direct measurement from a sensor that is compensated for temp, baro, and other conditions. In a MAP based system the ECU must back-calculate the theoretical air mass flow rate based upon reference tables stored in the calibration.

The biggest limitation to a MAF system is the sensor itself. Most OEM MAF sensors are not sized to measure flow rates 100% in excess of stock power levels. With a change to an appropriate meter (and the corresponding ECU reprogramming), one gets the benefits of MAF accuracy with the extended power levels. The MAF sensor itself (and ultimately, the ECU) doesn't care what the boost pressure is. What really matters is actual airflow rate and overall VE.

On the OEM level, going to a strictly MAP based system is usually a cost saving on the hardware. The downside is that any significant change to the engine's hardware will usually require reprogramming of the ECU to properly accommodate the change.


i guess what i take... is if its already map based to keep it such, but what if you take an engine thats maf based? is it "better" worth it to convert to map or as that comment suggests to upgrade the sensor? guess market availability comes into play there


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post May 28, 2009 - 10:26 AM
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Fastbird

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Wild would be LOTS of boost essentially, cams, ect. Enough to take the MAF out of it's operating range. It can only read so much air, and once you've exceeded that, it's a no brainer. The move to MAP usually happens when doing the final tuning and it becomes known that you're exceeding the capabilities of the MAF. Take my TT Corvette for instance. When the kit initially went on, we were planning on sticking with a MAF tune. But while tuning, we found that the MAF tables were just getting blown straight through, so we switched to a Speed Density (MAP) tune, and the car was rock solid after 3 straight days worth of work. With the new setup however, we're moving back to a MAF tube, but using a drop in maf out of a Saturn Sky Redline which has GREATLY extended frequency ranges that will hold up to the boost I'm going to be running.

If it's a MAP system, it doesn't hurt to keep it that way, and it doesn't hurt to add a MAF. Just depends on what your pain tolerance is, or rather where/when you want the pain. Tuning pain with MAP, redoing lots of wiring with adding a MAF.

The catch is finding a MAF that has the extended frequency range needed that can be wired up to work with the application.


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post May 28, 2009 - 10:49 AM
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good stuff

everyone seems to say that going map is a cure all... but ive always thought that maf was "better" for the extent of what i use a car for - going around town with peppy driving.

i guess one of the largest "selling points" to map setups are that cold days arent near the problem they are with maf - but if its not a car that needs to be reliable 100% of the time then seems negligable to me - i can just wait for it to warm up or other pita fixes

anyone know of any descent resources off hand that delve further into this?


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post May 28, 2009 - 1:53 PM
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what car are you talking about?


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post May 28, 2009 - 3:05 PM
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jason



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none specifically - was in discussion

seems like for everyday and normal weekend car use a maf would be better suited ("low" tech maintenance). but for track use and the need for high end accuracy map shines a bit brighter (more high tech maintenance). i presume maf & a piggy back would get you descent times to keep one happy without breaking the bank on more advanced electonics

personally... everything ive ever had with maf has worked well enough for my likings. im just curious why most people scream out map as being faaaar more superior when it seems they are both about equal, just different approaches. maybe because they can have a loud vta bov easier without bogging between gears

another opinion for future reference (from jack)
QUOTE
Well, the MAF has its issues, but I use a blowthrough setup that eliminates two of the complaints most people have about the maf, which is low airflow issues (idle problems) and misreads/disruption of airflow or blowoff valves/whatnot.

A properly tuned speed density system runs great, but the difference is a speed density system is a calculation, a MAF system is an accurate measurement (within reason)

I have been running a blowthrough FORD based MAF for over a year now, good drivability and no major idle issues that can't be resolved with some simple adjustments.

There is only one real downside to using an aftermarket MAF (besides a 90% ignorance of its existance) and that is on some types of hot-wire maf sensors, you can get some condensation on it when its cold, so it takes a bit longer for the wire to warm up and read correctly... THis seems more common on the GM sensor from the complaints I've heard.


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post May 28, 2009 - 3:22 PM
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Fastbird

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VERY easy to circumvent VTA BOV issues on a MAF car. Put the BOV in front of the MAF. Problem solved.

I've watched this discussion go round and round on several forums now, and in the end it really is choice, cost, and what the tuners preference is. Really, IMO, it doesn't matter as long as the car runs right and the owner is happy.


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post May 28, 2009 - 6:34 PM
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theres issues with the MAF sensor on the 3sgte going bad.... but then again MAP sensors go bad too... the one nice thing about MAP.... MAP reads after the turbo... so if you switch turbos (within close reason) or have parts that might be a tad old or leaky... the MAP will read the actual pressure at the intake manifold rather than the assumed pressure before the turbo... the MAF reads air before the turbo and piping.. MAP reads at the manifold... so at WOT, when i switched to front mount intercooler, my A/F is now super rich at WOT because of the amount of air in the entire system, the delay between MAF and actual manifold has changed so now its almost like my MAF is a step behind...

switching to MAP made my car run like a dream... i got it retuned and havent had even close to as many problems as i did with the MAF... now i can also blow off to atmosphere... some people don't like that, i do smile.gif

This post has been edited by pittfirefighter: May 28, 2009 - 6:35 PM


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post May 29, 2009 - 2:17 PM
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jason



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ive read that what you said is contradictory

maf = better acceptance to mods

map = more persnickety to mods

because when you change something on a map setup - you HAVE to get it retuned to update the charts

on a maf system, you can within reason change parts and not have to change since its sensing actual values - instead of predicted values

since you switched to map and got it tuned - i wouldnt count that as a strike against maf. id bet had you simply gotten the re-tune while on the maf your car would still run fine enough - minus the cost of switching

personally i think ill stick to a maf setup and just upgrade accordingly if problems arise that cannot be easily fixed.


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post May 29, 2009 - 2:32 PM
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lagos



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I cant help to think that this is such a silly topic. Without knowing what car we are talking about, or what setup, you cant really say one thing is better then the next.


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post May 29, 2009 - 3:30 PM
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just on my 3sgte - the gate style MAF sensor... whether i was boosting 8lbs or 13 lbs, the MAF was reading the same value at WOT frown.gif


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post May 29, 2009 - 4:41 PM
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lagos



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QUOTE (pittfirefighter @ May 29, 2009 - 4:30 PM) *
just on my 3sgte - the gate style MAF sensor... whether i was boosting 8lbs or 13 lbs, the MAF was reading the same value at WOT frown.gif


No it wasnt.
How did you verify that? do you have a wideband? did you log AFM output voltage?


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post May 29, 2009 - 5:46 PM
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yes i logged it on my AEM EMS but before my AEM UEGO verified it (off the UEGO under full boost, ran super rich, also Apexi AVCR gave same reading for injector %, before EMS swap)... thats why i converted over to MAP, we were having too tough a time tuning with the MAF at WOT... i tried it on two different MAF's also, i doubt they were both bad... the gate read all the way open for both settings at WOT

one tuner, this is complete speculation, thought that it could be the gt2871r, it was pulling a lot more air than the stock turbo, going past the threshold that the MAF was supposed to be operating within

This post has been edited by pittfirefighter: May 29, 2009 - 5:56 PM


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post May 29, 2009 - 6:02 PM
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Art, this is far from a silly topic. This is general tuning stuff that no matter the application has value.

Jason, you're right that when you change a part on an MAP car, you'll most likely need a retune vs. the MAF's capability for adjusting to changes. Absolutely correct.

Pittfirefighter, sounds like with the GT2871R you were maxing out the MAF (AFM) and you saw things become easier after switching to MAP, which is right in line.


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post May 29, 2009 - 11:01 PM
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QUOTE (pittfirefighter @ May 29, 2009 - 6:46 PM) *
one tuner, this is complete speculation, thought that it could be the gt2871r, it was pulling a lot more air than the stock turbo, going past the threshold that the MAF was supposed to be operating within



This is why. the 2871 makes a good 40-50hp more at the same boost level then the ct26. On the ct26, i have personally seen different air flow values and a/f ratios at 7psi and 12psi. after that, it just keeps the same air flow reading.


QUOTE (Fastbird @ May 29, 2009 - 7:02 PM) *
Art, this is far from a silly topic. This is general tuning stuff that no matter the application has value.


Its a silly topic because its too general. You cant say a one is better then the other in a general sense, and that everyone, regardless of what car they are in, should ditch their setup for the clear winner.

Take a look at the evo and sti guys. Their cars come with mafs located preturbo. Now by all accounts this is great, the maf should account for changes in VE and everything should be fine no matter what minor bolt ons you do to the car. However this is not the case. Those guys (expecially subaru guys) run into all kinds of trouble just from installing an intake. Seems simple things like that throw off their highly sensitive hot wire systems giving them all kinds of drivebility problems. So why dont all those guys just convert to map? Because they have fully programmable ecu's and can simple change their tune to account for the difference in air flow reading. in that cause, it actually makes no sense to convert the car to a map system just to fix what is essentially a maf related problem.

point is... work with what you got. the real problem is not so much the sensor, but the ability to retune your stock fuel maps to account for your new mods. Only at very high hp levels will you see some sensors run out of resolution, and at that point, you will be on a stand alone ecu, and will be able to convert to the type of sensor that suits your needs (generally map).

This post has been edited by lagos: May 29, 2009 - 11:17 PM


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post May 30, 2009 - 12:02 AM
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Art, I don't think anyone is saying that it's better to ditch one or the other. I made that pointedly clear that depending on the capabilities of the components being used you can go either way. Admittedly there's going to be different situations on different vehicles, but the overall concept remains the same.

I disagree about the sensor not being the real problem though. The sensor is a VERY big part of the system/problem though because it's only good for a predetermined range, and once that is exceeded then you're essentially screwed for that particular component. This is what drives the switch to a MAP based system the better part of the time. Tuning it is only half the battle. Even with an AEM on the 3S with an AFM like PittFireFighter has with the GT28721R, there's nothing you can do about it because the sensor itself is maxed out. You absolutely need the hardware to support what you're doing in addition to the software capabilities.


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post May 30, 2009 - 6:59 AM
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IMO basicly, the MAF is fine, 1st provided it is in good working order (these 3sgte AFM's are getting OLD...) and 2nd provided you stay within its working range. IE: in the case of a 3s, once you get out of its range, you get what pitt got.
once you hit that threshold, your pretty much done.
with the map, you dont really have that "threshold" only the limit of what the map will read. (which in most aftermarket cases never gets seen with a 3 or 5 bar map that some of the guys are using.)
as long as your staying within the factory "margin of adjustment" with a MAF, IMO there is no downside to it, untill you go out of that range.


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