Maf Sensor

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Maf Sensor

Post  Thrilla559 on Wed Feb 23, 2011 12:34 am

Is it possible to put a bigger maf sensor in place of the stock one? thanx
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Re: Maf Sensor

Post  Thrilla559 on Tue Mar 01, 2011 2:21 pm

Maybe I should speak up a lil louder.... ANY SUGGESTIONS? lol
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Re: Maf Sensor

Post  S13 on Tue Mar 01, 2011 9:51 pm

Z32 Maf but need to rewire it i think. study
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Re: Maf Sensor

Post  StryfeS13 on Tue Mar 01, 2011 11:52 pm

You can replace the stock maf with a Q45,Z32,Cobra,Lightning,N60,etc. But there is absolutely no point if your motor is stock. Upgrading the maf won't give you any power advantages at all. Just leave it all stock. If it's not broken don't screw with it Smile
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Re: Maf Sensor

Post  Thrilla559 on Thu Mar 03, 2011 11:03 am

Yeah but the stock one looks pretty restrictive and small. More airflow is better right?
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Re: Maf Sensor

Post  StryfeS13 on Thu Mar 03, 2011 2:17 pm

It's not restrictive, the motor is naturally aspirated and will never make more power than that MAF can handle anyway. The stock MAF is supportive of ~250HP
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Re: Maf Sensor

Post  Thrilla559 on Thu Mar 03, 2011 8:43 pm

Have you done that mod before?
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Re: Maf Sensor

Post  StryfeS13 on Thu Mar 03, 2011 11:36 pm

Nah I haven't. It'd have no effects on performance so I have never done it or even thought about it.

People with boosted cars don't change out the MAF to go faster, they change out the MAF cause their current MAF is maxed out. For example if you have a 350WHP SR20, you need to upgrade to a Z32 MAF, cause it's able to read that much flow. A stock SR20/KA24 MAF wouldn't be able to read that much flow, which is why people swap them out.
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Re: Maf Sensor

Post  onevia drift on Fri Mar 04, 2011 11:32 pm

If your not boosting your car at all or you dont have any form of forced induction, then the stock sizing of your MAF is perfectly fine. IF you decide to "boost" your car then basically, the bigger the better. To my knowledge the largest MAF made by Nissan and is a SUPER SINCH to wire up is a Q45. The Q45 MAF is 90mm ( Same as GTRs) .. I think. The MAF measures the actual mass of air going through it. To do this, it uses a hot wire that is maintained at a specific temperature. The voltage required to maintain this temp (Or at least some representation of it) is what is read by the ECU to determine how much air has passed through it.

If you've taken a chem class, you'll know that the voltage needed to maintain the wire temperature will be directly related to the number of atoms/molecules that pass in close enough proximity to the wire to absorb heat from it. Pressurized air is denser so it will provide more atoms/molecules in close enough proximity to the wire to absorb the heat from the wire. This will be in direct proportion to the mass of the air. So the MAF should have no trouble compensating.

Now there are other variables that can affect a MAF reading. While unlikely, especially if the MAF is placed after the intercooler, is the heat. The hot wire can only work effectively if there is enough of a difference in the heat between the wire and the air going through it. For example, if the temperature of the air going through was the same as the wire, it would not carry away any heat from the wire as heat only transfers from hot objects to cool ones. Since no more voltage would be necessary to maintain the hot wire temp, it wouldn't read any air you put through it.

It should be noted that the MAF automatically accounts for temperature too. At lease up until the situation I described above. Perhaps even to some temperature below the hot wire temp. This is because heat is directly related to the density of the air. Since it is essentially reading density over a known volume (or cross-section), it makes little difference what the temperature is.

The other major factor thatc an affect a MAF reading and the most likely one in most cases is turbulence. MAF readings are highly dependent on how well the pressure of air is spread out within the MAF. Typically, in a draw through set-up, an MAF receives smooth flowing air from the air box with no obstructions to flow behind it ensureing the flow is reletively smooth. If you look at the factory air box for any 240sx, you'll see a small venturi in the inside where the air exits the airbox into the MAF(The S13's is bigger than the S14's). This is there to help smooth the air going into the MAF. However, if you put the MAF next to or within a sharp bend, the air can easily become turbulent creating high pressure or low pressure areas within the MAF. If the hot wire sits in a low pressure area or high pressure area and the average density through the MAF doesn't equal the local density near the hot wire, then the reading can easily be skewed. Many people have seen evidence of this even with pull-through systems where they've recirculated the BOV directly behind the MAF. When the BOV recirculation is too close and/or at an entry angle that is too steep in relation tot he airflow direction in the main pipe, it can cause turbulance ahead of this point. It can be enough to affect the airflow reading causing stall outs and stuttering everytime the BOV operates.


WOW.... I believe i went off subject just a tid bit there....... lol
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Re: Maf Sensor

Post  Thrilla559 on Sat Mar 05, 2011 5:33 pm

Holy Underwear Batman!! That was a very informative response. Hmmm so the venturi effect of air traveling through piping has an major effect of the maf's hotwire temperature readings? So that's why pretty much everyone I saw in the drift event had there front bumpers off. That's another subject I want to learn more about is how a turbo set-up functions in every aspect of it!!
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Re: Maf Sensor

Post  onevia drift on Sun Mar 06, 2011 3:42 pm

yea kinda sorta. Venturi mainly focuses on air flow from a larger diameter through something of smaller diameter to increase air pressure (i think)

The main reason ppl have theiur bumpers off while drifting is airflow through the intercooler. Most people have a fmic. BUT if you think about it, how many of them have one that is partially covered by the bumper? How many of those ppl have a front mount that is actually set in between 6-12 inches behind the very front of the bumper?

Whe you drive normally, the air passes through the bumper (straight through) which allows the intercoolerto cool the air passing through the fins.

When you drift, you are sideways and normally yor motor has a lot more "load" on it and it is at higher RPMs than normal driving, right?
The thing about driving sideways is that the ammount of air flowing through the intercooler is far less than if you were normally driving in a straight line, which leads to higher intake air temperatures and/or less dense air entering the throttle body.
IF you are running a "blow through" MAF (on the intercooler piping) setup VS. a "draw through" (on turbo inlet) then the air passing through the MAF will be at a higher temp.

People take off their bumpers to allow the most air possible to flow through the intercooler. So, without the bumper restricting the air it can cool more efficiently.
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Re: Maf Sensor

Post  Thrilla559 on Sun Mar 06, 2011 11:14 pm

that's one thing I did learn about IOT taking HVAC classes. When air is traveling through any piping you have to take in consideration of any factors that may obstruct the air flow, for example the stock maf goes from a 3" opening to what looks like a 2" where the maf sensor is and back to a 3" exit. I just don't like how it bottle necks pretty much. It's the point where it reduces itself that I kind of what initially started this thread I was hoping to change out and sounds like the q45 maf's will work. Eventually later on down the line I want to go turbo so if I managed to change it out now I won't have to worry about it later!!
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