Aftermarket MAFs: reasons to avoid them

[mikel]

I have been seeing a trend lately of people putting aftermarket MAFs on their LSX powered vehicles. The next thing that happens is that they buy a Predator and want to know why their fuel trims are so far out of whack.
This is because these aftermarket meters are trickery....they simply alter the MAF signal to make the PCM think there is less air moving through them, in order to command less fuel....scary.
This becomes a bigger issue as you add more mods to the engine, since as you increase airflow you generally need more fuel.

Here is a quick list of reasons to avoid these meters:

1. Price. These things aint cheap, and considering they are of little to no use on anything but a bone stock, untuned car, it is not a mod that 'grows' with you.
Plus I hate being the one that has to tell people they should put their stock MAF back on after spending over $300 for one of these things.

2.Tunability. We have seen that in addition to the issues described above, that these meters are not very repeatable, and sometimes have funky curves that are VERY tough to tune around.

3.Airflow. Alot of people seem to think that these meters will flow better than the stocker, but that is not necessarily true. Removing the screen on the stock unit helps alot, and adding aftermarket ported MAF ends to the housing makes it great. The aftermarket units are the same size as stock, and thus flow about the same. Not to mention you would need over 400 cubic inches to really max out the stock 75mm MAF on an F-body or 97-01 Vette, and they will support at least 550rwhp naturally aspirated, and plenty more with boost.

Thanks

[06MonteSS]

The Mass Air Flow (MAF) sensor is a critical sensor used by the engine management system. The job of the MAF sensor is to monitor the Mass of air that is entering across the intake system. This is important because all of the fuel, timing and other critical engine management decisions are based primarily on what the MAF is reading. If this reading is off, then so will the fuel, timing, etc which has the potential to cause poor driving conditions or worse, engine damage.

The MAF sensor only samples a small portion of the air coming into the system. From that sample measurement, the engine management system can calculate how much air is actually entering the system because it knows the inner diameter of the MAF sensor housing it is sampling from.

If the MAF sensor housing inner diameter changes in any way, the calculation performed by the engine management system will be incorrect. This means that the amount of air actually entering the system will be different from what the computer thinks is entering the system. It is being "tricked". This is critical because the computer determines how much fuel and timing to run based on this value of air. When it's wrong, it can cause the engine to run richer, or leaner, than it should.

It is true that some aftermarket intakes show an increase in power when installed on a stock vehicle. This power increase is due to the fact that the aftermarket intakes have a larger inner diameter for the MAF sensor housing to mount into which in turn leans out the Air/Fuel mixture because of this error in calculating how much air is actually entering the system.

Please note this is NOT due to the fact that the aftermarket MAF is so much less restrictive than stock and therefore more air is getting in, but rather that the computer does not know it is now sucking air in from a larger inner diameter tube and therefore more air is getting in.

[jsk06c6]

Please let GM know they should put the screened MAF back in the vette for the 2008 and Z06 models, apparently they are wasting their time because this extra flow makes no improvement to HP and TQ.

Deleting the MAF altogether can add 20rwhp with a speed density tune. The MAF is a restriction and so is its screen.

Any improvement in flow capability requires tuning to take advantage of it properly, I thought this was a computer tuning company??? LOL

[mikel]

Please let GM know they should put the screened MAF back in the vette for the 2008 and Z06 models, apparently they are wasting their time because this extra flow makes no improvement to HP and TQ.

I'm not following...I know theres some sarcasm there somewhere, but I don't get it.
Nobody is saying that the screen is necessary, or beneficial.
Also, the new GM MAF sensor is a slot in type, which just drops right into the intake ducting, and they are pretty nice units themselves.
I promise you will never see a new Z06 with an aftermarket MAF.

[jsk06c6]

Please let GM know they should put the screened MAF back in the vette for the 2008 and Z06 models, apparently they are wasting their time because this extra flow makes no improvement to HP and TQ.

I'm not following...I know theres some sarcasm there somewhere, but I don't get it.
Nobody is saying that the screen is necessary, or beneficial.
Also, the new GM MAF sensor is a slot in type, which just drops right into the intake ducting, and they are pretty nice units themselves.
I promise you will never see a new Z06 with an aftermarket MAF.

Really, the fastest one I know, doesn't even have one, he's running speed density tuning, and runs low 10's.

All I'm saying is your wrong to make this blanket statement that after market MAF's are all bad, they aren't. But all require some tuning to take advantage of its benefits.

[mikel]

Ahhhh...good old SD tunes.
Well, they're great if you live in a climate where the temp and humidity are the same every day, and even then only on 'race' cars.

[jsk06c6]

Ahhhh...good old SD tunes.
Well, they're great if you live in a climate where the temp and humidity are the same every day, and even then only on 'race' cars.

OK, enough then, I know many people running aftermarket MAF's, and have done it mayself in the past, and will do so in the future on this car. I'll just adjust the tune when I do, and if I can't do it properly with this handheld, I get some other software, because I intend on adding many other components along the way as well.

[mikel]

But again, WHY???
It is not flowing any more than the stocker, and then you HAVE to go in and correct the tune, very counter productive if you ask me.....

[jsk06c6]

But again, WHY???
It is not flowing any more than the stocker, and then you HAVE to go in and correct the tune, very counter productive if you ask me.....

The reason you have to adjust is because it IS flowing more, that's why GM changed out the screen on the 08's and 08 Z06. The stock tables don't read the extra air volume, as a result it leans out without any changes to the programming. Not the condition you want, so you adjust to correct the incorrect reading.

The computer thinks your drawing a centain CFM because a certain voltage reading equals a certain value in the tables, but your actually drawing more CFM but producing the same voltage output from the MAF.

The bad MAF's alter the output voltage, but that isn't equal to actual increase in airflow. You can program out this as well actually, but your going to have to fix two things not just one, and most of the voltage changes are not linear, your certainly not going to be able to do it with the limited adjustsments the handheld gives you. Maybe with the CMR software you can, but I haven't seen it, and besides you don't have a single user license for it anyway.

You really need only to look at a stock GM MAF to see how much of a bad piece it is, it is extremely restrictive, and produces a ton of turbulance. On a stock car its who cares, we're only losing a little bit 10hp maybe, but when your thinking performance 10hp is a lot. Your handheld is $400, some would say that's a lot to pay for 15hp too. I'll pay the $300 for the 10hp, and more importantly a unit that will flow up to the 700hp I intend to eventually make.

[supercatxr7]

3.Airflow. Alot of people seem to think that these meters will flow better than the stocker, but that is not necessarily true. Removing the screen on the stock unit helps alot, and adding aftermarket ported MAF ends to the housing makes it great.

Are you telling me it is a good idea to remove the screen then from a stock unit if you have a tuner? I've heard otherwise, many times, but trust your knowledge.

[Orange99z28]

this is sketchy info as best!, don't remove the maf screen if you have an automatic under any circumstances. it WILL mes your car up! i took mine out with no ill effects, but i have a m6. and even then it's risky, i did it before i knew what could happen and i got lucky. if you wanna read up on it go to ls1.com/forums

great site with everything you need to know, and links for what you can't find there

[Orange99z28]

btw releasing the cmr software would put you guys from beggars to gods for soooooooooo many lsx owners!

[mikel]

http://forums.corvetteforum.com/showthr ... ?t=1897246

Some views on aftermarket MAFs from the boys on the Corvette forums....

[RWTD]

First off, I am a professional tuner that does this for a living. What is being stated here by DiabloSport is pretty much right on the money.

Also, I have an '08 Z06. It is one of the fastest N/A Z06s in the world, and is listed in the top 10 of the fastest Z06s. I know what does and doesn't work on this car, as well as many other vehicles.

I have included my well written thread below that one can read to learn more about the power production of my stock C6 Z06 with the factory inlet system, complete with explanation and dynographs. Please click here:

http://forums.corvetteforum.com/showthr ... 1563231039
(post #30)

Please let GM know they should put the screened MAF back in the vette for the 2008 and Z06 models, apparently they are wasting their time because this extra flow makes no improvement to HP and TQ.

When making less than 500 rwhp Actual, the factory inlet system is hardly a restriction on the C6 Z06, and this vehicle's MAF system is NOT a restriction, period. Being that it is a slot-style sensor, it literally can't be (provided the inlet system it is integrated into isn't, and the factory inlet system isn't, as I just stated). This sensor is used in ALL aftermarket MAF housings for the C6 Z06 and '08 Vettes. This slot-style sensor is a much more accurate and less restrictive design than any other GM MAF ever produced (and for what they were designed for, previous GM MAFs were pretty damn accurate, as well).

Deleting the MAF altogether can add 20rwhp with a speed density tune. The MAF is a restriction and so is its screen.

Now THAT is a blanket statement if I have seen one! It definitely is not accurate information in and by itself. It takes additional air molecules and fuel to make more power, period. If there isn't any restriction through the inlet/MAF system, there isn't any gain in power.

Any improvement in flow capability requires tuning to take advantage of it properly, I thought this was a computer tuning company??? LOL

No, that is not necessarily true either. Being that these are MAF based vehicles, provided the MAF transfer is properly calibrated, and the PE table and spark tables are set correctly, you should not necessarily have to retune the vehicle in order to take advantage of any increase in breathing. This is why one can be custom tuned and not have to come back for a different tune as the weather changes (unlike a SD based tune). However, it is true that retuning would be necessary if the airflow improvements made alter the flow pattern across the MAF, as this would then alter the MAF transfer.

Nobody is saying that the screen is necessary, or beneficial.
Also, the new GM MAF sensor is a slot in type, which just drops right into the intake ducting, and they are pretty nice units themselves.
I promise you will never see a new Z06 with an aftermarket MAF.

Really, the fastest one I know, doesn't even have one, he's running speed density tuning, and runs low 10's.

What year is this Z06? If it is a C6 then I seriously doubt he's running a speed density based tune. GM revamped the calibrations on all '06+ C6 Corvettes where they do not have the traditional style VE tables that most are familiar with, such as the LS1 vehicles and early LS2 vehicles had. Basically, the E38/E67 computer systems do not have any VE Table. The VE numbers are calculated instantly from a set of VE coefficients. EFILive (and soon HPTuners will offer) now offers what is called a "Virtual VE Table", thus allowing one to alter VE numbers as though there was a real VE table, which the software then converts the 'Virtual VE Table' into VE coefficients. This is very new, so unless your friend has this capability in his software, or has applied himself towards using it properly, I doubt he's running a VE based tune only.

In certain instances, there isn't anything wrong with VE tuning. However, nothing beats the accuracy of MAF based tuning. In my '08 Z06, it runs a 100% MAF based tune. I completely disabled the VE system in the calibration. It is a much more simple and accurate tune than ANY VE tune could ever be.

All I'm saying is your wrong to make this blanket statement that after market MAF's are all bad, they aren't. But all require some tuning to take advantage of its benefits.

There is only a few aftermarket MAF based options for the GMs. ALL of them are poor in their calibrations, and NONE of them repeat as precisely as factory GM sensors and calibrations do, yes even if these aftermarket MAF based options are tuned for.

But again, WHY???
It is not flowing any more than the stocker, and then you HAVE to go in and correct the tune, very counter productive if you ask me.....

The reason you have to adjust is because it IS flowing more, that's why GM changed out the screen on the 08's and 08 Z06.

First, there isn't any screen on the C6 Z06 (and '08 LS3). Second, GM didn't use a screen in the '02-'04 Z06, but did in all '01s and '02-'04 LS1 and '05-'07 LS2. GM kept the screen on the '05-'07 C6 (non-Z06). They designed the C6 Z06 slot-style MAF sensor specifically not to need any type of air smoothing device (aka screen), plus allow for near maximum possible airflow, and this was especially needed in future more powerful engine designs. Ford did the same thing on their vehicles that use slot-style sensors ('05+ Mustangs, and '04+ F150s, etc.).

You really need only to look at a stock GM MAF to see how much of a bad piece it is, it is extremely restrictive, and produces a ton of turbulance. On a stock car its who cares, we're only losing a little bit 10hp maybe, but when your thinking performance 10hp is a lot. Your handheld is $400, some would say that's a lot to pay for 15hp too. I'll pay the $300 for the 10hp, and more importantly a unit that will flow up to the 700hp I intend to eventually make.

Again, you're giving blanket conjected generalizations without any evidence or proof to back up your statements. ANY GM MAF is a well designed piece, and they do not produce any turbulence in and by themselves. What produces turbulence is aftermarket inlet systems that do not allow the airflow to enter the housing smoothly, or when individuals start modifying the factory sensor (such as aftermarket "ends", or porting the factory housing - neither of these two things are ever suggested).

If one is going to run an aftermarket MAF on their GM it is highly suggested to run the slot-style MAF from the C6 Z06 (and '08 LS3). You can put this sensor in any well designed housing or inlet system and almost always get excellent results (provided it is tuned for properly). There are many aftermarket housings that accept this sensor, as well.

Also, the factory plastic GM 85mm MAF is also a well designed piece that is hardly restrictive up to approx. 550 to 600 rwhp Actual (I have the cfm flow data - I know!). Those who wish to keep MAF based tuning, who have the previous smaller aluminum based GM MAF (such as the LS1 Camaro/Firebird), may want to consider investing in this MAF, or the C6 Z06 (and '08 LS3) slot-style sensor I mentioned just above.

Regards,

James

[mikel]

Good info James, thanks.