Why aftermarket MAF's don't work

[Redog]

I have to replace mine. That is why I'm getting the bucking I was telling everybody about.

Also, it's not a good idea to remove the screen

GM parts direct has MAF's for $132 for the Alero 3.4

http://forums.corvetteforum.com/showthread.php?t=854920

http://www.silveradoss.com/forums/in...showtopic=3333

http://www.gm-trucks.com/forums/inde...howtopic=70752

[Redog]

And this is a detailed reasons why from the Corvette forum

I was looking over some old tuning posts struggling with KR on Aftermarket MAFs.. So I decided to put together a document to cover the facts and dispell some myths as to why they do not work.

Why Aftermarket MAFS and MAF ENDS introduce Knock Retard on the LS1 Engine


Aftermarket MAF’s and MAF Ends are a big cause of Tuning Problems and Knock Retard. The ones with recalibrated electronics are bad and the plain MAF ends are worse. It seems that GM really did know how to make a stock MAF work properly and keep the Velocity up.
First let’s understand how the MAF Works.

MAFS measure air volume by determining how fast it can cool down the “Hot Wires” inside it. The stock MAF is fixed in diameter and is calibrated at the factory to respond a certain way as the measured air moves through it. The faster the air moves across the wires the more volume is being interpreted by the PCM. It then adds fuel accordingly and determines the Timing needed. If you change the ends of the MAF to be bigger, you in effect increase the “ability” of the MAF to flow more air. But. The reality is that you have just slowed the velocity down and have not increased the volume at all. To demonstrate this I will use this example..
Lets use an engine spinning at a steady 3000 rpms. It will require a “fixed” amount of air volume (CFM) to continue to pump at that rpm. Lets say you had a Stock MAF that was 3” in diameter. If you measured the velocity and the CFM you would get some value for each. Then swap the MAF with a 6” one and then take the same measurements. You would see the velocity of the 6” MAF drop significantly and the CFM stay exactly the same.

This problem of KR is well known and misunderstood. Most everyone believes that the KR is caused because the MAF is Bigger and therefore it is Flowing more air. Since it is flowing more air then it is leaning us out. This is wrong. KR shows up in 2 places for different reasons.

Part Throttle KR - The KR that shows up during part throttle driving shows up because the Air is traveling though the MAF at a much slower VELOCITY due to the fact the opening is bigger. Now the PCM sees that slower velocity as low engine load and in turn jacks you up to a higher timing point. All we have successfully done with this bigger MAF is fool the PCM into doing something we don’t want.

WOT KR - The KR you see at WOT is most definitely due to the lack of Fuel. But again, the lean condition is not caused by the fact that MORE air is flowing. Actually, it is still flowing EXACTLY the same as the stock MAF. The problem is caused by the fact that the Velocity is slower than the stock MAF. Therefore the PCM now thinks it does not need as much fuel and starves the motor.

Velocity is King.

[Jferg2223]

But descreening never was an issue actually two out of the three sites said it was fine.

[BlackJack]

these guys have truly lost their minds....I hope he doesn't speak for their whole group. I'd be so embarassed.

"MAF measures Air Volume...blah blah...fuel...blah...retard...etc...."

I'm sorry, but most people that know something about tuning also know that with a larger MAF, comes different MAF tables in the PCM. You don't just slap on a bigger MAF and go. KR comes because they aren't changing the TUNE to go with the different MAF.

I'm running a damned LS6 MAF on a little 3400 V6 without a problem.

[jabartram]

i've been running a screenless maf for 3 yrs with no problems, i removed mine because i damaged the honeycomb while doing other modifications, but it has caused no problems at all.

[sorrowfulkiller]

wow..what retard would change out the maf without tuning >_>

[BlackJack]

Originally Posted by jabartram

i've been running a screenless maf for 3 yrs with no problems, i removed mine because i damaged the honeycomb while doing other modifications, but it has caused no problems at all.

and you're right, there SHOULDN'T be a problem in running without a screen. Although it does serve two functions, one being that it keeps larger pieces of debris from entering the intake, the other being that the "fins" are supposed to "straighten" the air flow before entering the metering wires in the MAF...the truth is, the air flow should be reasonably stable within a couple of inches of the MAF as it is. Might be beneficial if your MAF is located right after (inch or two) an elbow. Otherwise, it won't make that much difference. As far as people believing that removing it reduces flow restriction, that is a myth as well, unless it is damaged or fins are bent, as in your case, then removing it would be beneficial to flow.

[redrider07]

So basically just keep the stock maf on our aleros. I have a CAI and I wanted to add a high flow maf like off summit racing to complement the intake. But, from what you guys are saying it will be pointless. Also, what about a high flow cat?

I am about to install the DHP PCM 1.0 and I wanted to add a high flow cat as well?

I guess I will just stick with the CAI, 180 t-stat, and cat back exhaust with the stock cat then?

[BlackJack]

basically, unless you're installing a MAF for a much higher air flow rate than factory, yes. It would be pointless.

My LS6 MAF is because it will accomodate a much higher resolution at the flow rate that pumps through that massive turbo.

"High-flow" maf's would only benefit you if you were pushing a serious N/A build or a boosted setup.

CAT's - My recommendation would be a CATCO with stainless core, not ceramic. Make sure you order one at the same diameter as your cat-back, not stock size. Cats already restrict flow as it is, and if you go 2.5" catback system with a 2.5 high flow, then you'll be ready for it when you upgrade to headers.

[Redog]

I thnk You can do an downstream O2 delete with a the DHP PCM 1.0. I know I couldn't do it when I bought mine, but that was a while ago.

The aftermarket MAF's help you if you have serious mods like a cam, turbo, s/c, and so on. Even with everything I have done to my motor, it still doesn't benfit me to go with the aftermarket one

[jabartram]

you have to have a programmer, either DHP or HPT to remove the downstream o2.

[BlackJack]

Originally Posted by Redog

Even with everything I have done to my motor, it still doesn't benfit me to go with the aftermarket one

You did stuff to your motor?

[Redog]

^^ Yes I did, but a stcok MAF still is best for my set-up.

After I get my stage 2 set-up, I'll need the aftermarket

[CiscoPath]

Think it's time to replace my MAF. I'd rather have a brand new one and this is the only one I can find. Anyone have a link to anywhere cheaper?

http://www.drivewire.com/products/ol...w-sensor/4381/

[01silveralero]

http://www2.partstrain.com/store/?N=...low%20s ensor

slightly cheaper and extremely fast shipping