BOV + MAF

[XxantwawnxX]

Yup just what i wrote above you : P

[Jacbs2007]

Had to fix the photo, it kept comming up too small to read...

[Bochek]

Well if you think of it like this.

You don't want any of the air's quality's to change between the MAF and yout TB...otherwise the calculations it makes for the fuel/air will be incorrect. If you have the Turbo, BOV, and wastegate after the MAF...then the calculations will be incorrect and you will either run Lean or rich because the air's quality's have changed since they were measured by the MAF.


Hope that helps you grasp the concept that I see in my head.

-Curt-

theres a problem with this, only a VAF will read properly under boost conditions, a MAF will not work be able to tell the difference when boost is applied making your engine run way ritch, i believe that a MAF only reads air speed hense, mass air FLOW.

i will ask my auto teacher tomorow morning.

Bochek

[fieromx3]

u can still use a maf after the turbo and still tune it!!!
u can use a maf BEFORE the turbo and tune it to have an atmosfere BOV or recircualte it and still use a maf befor the turbo. its best to have the maf after the turbo after the BOV. if u have the BOV before the turbo and dont got it tunes for an atmosfere you will run rich when the bov goes off...
also i wouldnt beleive everything an auto teacher says unless u know for a fact hes smart..some of the auto teachers i had didnt know s--- lol

[Jacbs2007]

theres a problem with this, only a VAF will read properly under boost conditions, a MAF will not work be able to tell the difference when boost is applied making your engine run way ritch, i believe that a MAF only reads air speed hense, mass air FLOW.

Bochek

Don't you mean it will make you run extremely lean? The MAF will only read the amount of air going in and not the density of it...meaning there's more air molecules than what the MAF measured, thus you'll have more air then fuel causing a lean mixture.

only a VAF will read properly under boost conditions, a MAF will not work be able to tell the difference when boost is applied

Yeah see that's what I thought as well, But apparently some people with 4cyl have done it without a piggy back or Megasquirt according to prior posts? But yes us v6 MX-3's and the mx-6's are lucky because we're virtually plug and play with a Turbo as far as Air/Fuel goes...Unless you're planning on running extremely high boost, then you'll need new fuel pressure regulators and injectors and a few pennies worth of internals. If you find that anything I've said is incorrect, please correct me.

-Curt-

[Bochek]

theres a problem with this, only a VAF will read properly under boost conditions, a MAF will not work be able to tell the difference when boost is applied making your engine run way ritch, i believe that a MAF only reads air speed hense, mass air FLOW.

Bochek

Don't you mean it will make you run extremely lean? The MAF will only read the amount of air going in and not the density of it...meaning there's more air molecules than what the MAF measured, thus you'll have more air then fuel causing a lean mixture.

only a VAF will read properly under boost conditions, a MAF will not work be able to tell the difference when boost is applied

Yeah see that's what I thought as well, But apparently some people with 4cyl have done it without a piggy back or Megasquirt according to prior posts? But yes us v6 MX-3's and the mx-6's are lucky because we're virtually plug and play with a Turbo as far as Air/Fuel goes...Unless you're planning on running extremely high boost, then you'll need new fuel pressure regulators and injectors and a few pennies worth of internals. If you find that anything I've said is incorrect, please correct me.

-Curt-

YOU... are correct. i did mean lean and yes. that is the problem how i see it, im going to get a few expert oppionion on this in a few days, and if need be, im going to tear apart a old maf i have to see how it actually works, i believe mazda maf's are different then any other ones,

a normal maf uses wires that heatup and the air flowing over them cools them and that can tell the computer how much air is going though the maf by using the restance of the maf.

but as i beleive a mazda maf uses a flapper type device that gets moved by the air flowing,

actually il have a answer to this on monday.. il take alook inside my maf when im installing my new cai.

Bochek

[BuGS]

ahahahahahaha that picture is extremely funny. Wastegate is for EXHAUST gasses, not measured intake HAHAHAH

But yes, if you do not have a Flapper type MAF or VAF, then you want to run it before the TB and after the BOV but that is only for atmosphere venting. If you have recirculation do whatever, just make sure it hooks back in after the MAF/VAF (non-flapper type).

If you have a flapper type, no Recirculation is needed, and you can have it placed wherever you want.

[Joey's mx]

ok so SOHC can put anywhere and DOHC has to be after the turbo!!

[Bochek]

ahahahahahaha that picture is extremely funny. Wastegate is for EXHAUST gasses, not measured intake HAHAHAH

But yes, if you do not have a Flapper type MAF or VAF, then you want to run it before the TB and after the BOV but that is only for atmosphere venting. If you have recirculation do whatever, just make sure it hooks back in after the MAF/VAF (non-flapper type).

If you have a flapper type, no Recirculation is needed, and you can have it placed wherever you want.

so your saying that a flapper type maf can go after the turbo? if i remember right, a flaper meter is caled a VAF.... Vain Air Flow.

read this

http://72.14.207.104/search?q=cache:itP ... =firefox-a

Bochek

[ariesdude]

This is my limited understanding about airflow sensors - i could be totally wrong about this and if i am please correct me.

I think the SOHC/BP engines use flapper type sensor (but is called MAF for some reason) and the K-Series engines uses VAF. They are both VAFs technically speaking.

The DOHC engines use heated wire type MAF. This type has a heated wire sensor and an air temparature sensor. The air flowing over the heated wire will take heat away from the wire and it needs current flowing thru the wire to maintain the temparature. Thus the ecu will know - more current -> more air. The values will be offset by the intake air temparature - hot intake air wont take away as much heat as cold air. At WOT the engine sucks in more air faster which reduces the heat at a much faster rate. At closed throttle very little air is going in and hence takes very little heat away. This provides a fairly accurate reading about the amount of air going in - irrespective of the pressure.

At higher pressure, the air flow will be much faster (if you dont believe that put your hand infront of a vaccum cleaner in blow mode or compressed air out of a compressor). So boosted air (at high speed) will take away much more heat from the heated wire and hence the MAF would correctly register more air.

I think the VAFs work by having a spring loaded trap door that is moved by the the amount of air going in. The springs are usually calibrated for normal atmospheric pressure and when the engine sucks more air the door opens more and vice versa. There is a sensor attached to the door which tells the ecu about the movement of the door. So the ecu knows the size of the opening (by the position of the door) and calculates the volume of air that can flow through that opening (hence VOLUME air flow sensor). It is also known as Vane Airflow Sensor because vane is another name for the trapdoor.
The trouble i see with this design is - if you apply boost pressure without modifying the springs - the door will be held open by the boost pressure alone and not by the amount of air that is going in. The ecu will think that more air is going in and start dumping in fuel to compensate for that.

So for SOHC/BP/K-Series it is best to put the trapdoor type sensor(they come with) before the turbo and have some other fuel management system to compensate for the vented BOV. The hotwire MAF sensor (for the DOHC) can go on either side - but to me it would make more sense to have it as the last element before TB (for vented BOV). But the caveat is that the factory MAFs pressure range is limited because of their plastic housing and the delicate heater element which could break at higher air velocities.

[Bochek]

i have one thing to argue with, your correct it will flow more air under pressure, but only when there is no restriction.

the air will actually be moving slower or at the same speed across the wires, the air will just be compressed. if boost presure is maintaied at a stedy presure, then the air inside the cylinders on the intake stroke is the same presure, meaning the air is moving at the same speed across the wires.

Bochek

[XxantwawnxX]

A mass airflow sensor does the job of a volum airflow sensor and an air temperature sensor. It measures air MASS. The mass of a given amount of air is calculated by multtiplying its volume by its desnsity.

the mass airflow sensor converts air flowing past a heated sensing element into an electrical sensor. The strength of its signal is determined by the enregy needed to keep the element at a constant temperature above the incming ambiant air. As the volum and density (mass) of airflow across the heated element changes, the temp of the elemnt is affected and the current flow to the element is adjusted to maintain the desired temp of the heating element. The varying curent flow paralles the particular characteristics of the air (hot,dry,cold,humid,high/low pressure)

[ariesdude]

At intake stroke - the cylinder volume increases (because the piston is moving down) which creates a low pressure inside the cylinder. For N/A this temporary vaccum/low pressure sucks in more air through the air intake. (Air always flows from high pressure to low pressure - like when you move the plunger in a syringe - the volume increases and it creates a low pressure according to the heat equation Pressure * Volume = Gas Constant * Temperature - if volume increases without temp change the pressure has to decrease to maintain constant product). For boosted apps - the intake pressure is much higher than the atmospheric conditions and so it will flow even faster to go fill in the temporary vaccum/low pressure inside the cylinder (at intake stroke). Only at/near the end of the intake stroke the air inside the cylinder and the air in the intake would reach the same pressure (because the cylinder is filling up with air). By then the piston is ready to start the compression stroke - so the valves are closed and there is no more airflow anyway.

[ariesdude]

Dont forget that compressed air is hotter, maybe the change in temp on the wire (then the change in volts that the cmop reads) wil not be as drastic with the hotter compressed air.

Dont know if thats true i just threw it in there cause i feel like it : P

Thats why MAfs have IAT(Intake Air Temperature) sensor to compensate for changes in intake air temps.

[XxantwawnxX]

Look above i changed it, and thats hwo it works. so disregared my first statement.

A mass airflow sensor does the job of a volum airflow sensor and an air temperature sensor. It measures air MASS. The mass of a given amount of air is calculated by multtiplying its volume by its desnsity.

the mass airflow sensor converts air flowing past a heated sensing element into an electrical sensor. The strength of its signal is determined by the enregy needed to keep the element at a constant temperature above the incming ambiant air. As the volum and density (mass) of airflow across the heated element changes, the temp of the elemnt is affected and the current flow to the element is adjusted to maintain the desired temp of the heating element. The varying curent flow paralles the particular characteristics of the air (hot,dry,cold,humid,high/low pressure)