MAF Relocation to post turbo?

[eg6siR]

i am working on a few things getting ready to install my kit in a few weeks, i am completely building it from the ground up myself, the only things i am buying and not building myself are the turbo, wastegate, and FMIC core. i am building my tubular manifold, downpipe, 3in exhaust, and i dont see the maf fitting infront of my turbo. and since it just meters air it shouldnt matter if its before or after the turbo right? i would think if i mounted it about a foot from the throttle body it would work great, and i could run a tune where it still uses a MAF and i could run a full BOV because it would be located pre-maf and none of the air it blows off would be metered yet so in turn i wouldnt run rich because i am only dumping unmetered air...?

anyone know how this will work? i obviously know i need to add a few feet of wire going to the maf to relocate it to the drivers side, but other than that i dont see any problems...

please shoot this idea down if you know something i dont!

[traf818]

no

[eg6siR]

no

haha, be more specific, why wouldnt it work?

[F16HTON]

haha, be more specific, why wouldnt it work?

Because it wont!

[eg6siR]

Because it wont!

have you tried it greg? i know this isnt a normal thing to do but there is no reason i can see that it wont work...

[F16HTON]

The air is compressed and does not represent the volume that has entered into the intake track...

[audi808a4]

nicely put

[eg6siR]

i understand that part of it, but its not like extra air sneaks in post turbo, the same amount of air is still going to go thru the maf whether it is compressed by the turbo or not.
its not like our cars run a Vane style maf, we run a hot wire maf.

incase you dont know the differences here they are:

Vane type sensor:
The VAF (Vane air Flow) sensor measures the amount of air flow into the engine with a spring-loaded air flap/door attached to a variable resistor (potentiometer). VAF sensors measure air volume and not mass. The incoming air strikes or pushes against the internal air flap on the VAF sensor, which also moves the variable resistor’s sensing arm (wiper arm). As air flows into the engine the mechanical air flap rotates further, causing the wiper arm to contact a series of resistors, changing the voltage signal output.

and what Bosch uses on our car:
The HOT WIRE MAF sensor is a fully electronic unit. It senses the amount of air flow into the engine by measuring the amount of current needed to maintain a constant temperature through a very thin (70 micrometers) platinum hot wire. Hence the name hot wire MAF sensor. It also measures air by weight, since it takes into consideration the air temperature as well.

This sensor works as follows. As the air enters the intake manifold through the hot wire MAF sensor it cools down the platinum wire, which is heated at a very precise temperature. When the MAF circuitry senses the platinum wire cooling down it increases the amount of current flow through the hot wire trying to maintain a specific temperature. This varying current flow is then converted to a voltage output signal by the MAF electronic circuitry and is used as an air flow indicator by the ECM. Hot wire MAF sensors have a signal that is directly proportional to air flow. So as air flow increases so does its voltage signal output.



there is no reason why our MAF sensor cannot be relocated as it measures the weight and density of the air entering the engine, its not just a potentiometer which would stay pegged the entire time during operation.

i am not saying you i know it will work, i just dont see why it wont work in theory

[Ill 3.0]

The air is compressed and does not represent the volume that has entered into the intake track...

wouldn't that basically be equivalent to a vac leak? If all the air isn't coming in through the intake, then it's not being measured by the MAF. Or am i missing something? Seems to me heat would be the biggest problem with putting the MAF post turbo, but I'm just speculating.

[eg6siR]

wouldn't that basically be equivalent to a vac leak? If all the air isn't coming in through the intake, then it's not being measured by the MAF. Or am i missing something? Seems to me heat would be the biggest problem with putting the MAF post turbo, but I'm just speculating.

see, atleast someone else is thinking like me. i dont think heat will be an issue though, as i plan to locate the maf post FMIC but before the throttle body.

[F16HTON]

The air that is compressed is heated and the volume changes because of this. The MAF measures the amount of air that enters the intake tract through the airbox and IS NOT a representation of the total volume in the intake.

For some goofy reason you guys seem to think that once the MAF reads the airflow that it has the ability to follow each molecule of air until it catalyzes the fuel in the combustion chamber...not true.

All the MAF does is smooth out the idle and provide fuel map switching in part throttle situations.

[eg6siR]

All the MAF does is smooth out the idle and provide fuel map switching in part throttle situations.

well if thats all it does then i should have no problem installing it anywhere in the intake plumbing i wish....




regardless of where i locate it the same amount of air is going to go thru it correct? and like i said before an older style vane type sensor would not be able to accomplish this transition to the compressed side of the turbo, however a hot wire maf which can measure the weight and density of air coming into the engine should have no problem being relocated to the compressed side of the turbo..

i am not saying you are wrong greg but until i try it i am gonna have it in my head that the theory is possible, and if it dosnt work like i want i will just run maf-less.

[dirtybrd]

I'd be worried about the temp. of the compressed air going thru it. It's not made to handle that kind of heat.

[eg6siR]

I'd be worried about the temp. of the compressed air going thru it. It's not made to handle that kind of heat.

its going to be installed after the front mount so the air should be cold and dense.

[dirtybrd]

The worst that can happen is it won't work.

[F16HTON]

Build something, then get back to me...

[eg6siR]

Build something, then get back to me...

oh dont worry, i am gonna try this greg. if it dosnt work oh well, and if it does work, then great...

[AudiA4_20T]

i dont know why you care about running a maf man

[eg6siR]

i dont care, my question is can i relocate it?

[F16HTON]

No, here is a thread regarding it from a Scion build, they may or may not have it working as a blow through MAF setup, feel free to read.

Scions do not use ME7, it may not be possible to rescale the MAF properly with .

http://www.scionlife.com/forums/view...3fba436ea77186

[eg6siR]

thanks greg.. lol

[JustinCase]

Another reason I think it wont work is if the air is hotter than ambient air, the MAF wont read it correctly because as it said in the article you posted, The wire measures air volume by the amount of current it takes to make a fine wire a certain temperature. So if that air is too hot the reading might be off. Either way it really isnt worth it. If you are going BT then just dont run a MAF.

[F16HTON]

Like I had said...

This is what a blow through MAF would have going against it

1.) Compressed air is hot and the density has been changed.

2.) When the throttle body closes, the air will go backwards into the BOV, the readings will get goofy

3.) The element will get oil from the intake tract on it

4.) The element will get destroyed by the air pressure

5.) It is not likely you can rescale ME7 to make it work

6.) To make it work, you may need SEM, in that case who needs a MAF?

7.) If you properly design an exhaust manifold for the turbo, you should be able to fit a MAF

[Don Supreme]

It was attempted on me38x by a well known tuner... He didn't like it for some reason and switched back to pre-turbo.

I ran a blow through maf setup on a previous boosted car.... worked fine.... It was a Nissan though.

[eg6siR]

It was attempted on me38x by a well known tuner... He didn't like it for some reason and switched back to pre-turbo.

I ran a blow through maf setup on a previous boosted car.... worked fine.... It was a Nissan though.

i have also seen this done on a nissan with an RB motor, that is why i brought it up in the first place... i have a spare MAF so i think i am going to try it, if it destroys the maf then oh well. but maybe just maybe it will work... we will see how the me7 reacts soon, i will try it this week when i have some time to take some things apart.

[eg6siR]

7.) If you properly design an exhaust manifold for the turbo, you should be able to fit a MAF

i can fit the maf, i just dont like the way its setup, and i was just curious to see if anyone tried this setup on one of our cars.....

[eg6siR]

oh and i wont need to rescale anything for the MAF calibrations as i plan to run the sensor in the stock tubing diameter, MAF scaling only becomes an issue when you try and run a sensor designed for 2 1/2" piping in a 4" tube. the other reason i was thinking about the maf location being moved to post turbo is so i can run a 4inch intake down to my headlight for track purposes as well as not restrict the air going into my turbo, once its compressed it will go into my IC piping which is the same diameter as the stock maf housing so i dont see any issues coming out of this, but we will know in a week or so as i plan to try it this week. and i will be logging while testing this

[diagnosticator]

Like Greg and others have said, it won't work blow thru. The calibration will be so far off it won't perform the intended function, there is nothing to be gained doing this setup.

[Molotov]

and listen to this guy ^ he knows almost, if not, everything

[JustinCase]

Seriously, if you listen to anyone, let it be him.

[dougyfresh]

Like Greg and others have said, it won't work blow thru. The calibration will be so far off it won't perform the intended function, there is nothing to be gained doing this setup.

That is what I was thinking for reasons Greg has mentioned. ME7 is only calibrated for uncompressed in-coming air. The density changes after compressing and I doubt ME7 has enough 'wiggle room' for your tuner to actually make adjustments.

[Capt. Obvious]

If you're going BT, why are you even running a MAF? Most people with BTs don't even run a MAF anymore (Shawn, Greg, B6Lovin, etc.).

[eg6siR]

it was just an idea i had as i have seen it used on some high horsepower nissans. just thought it may work on our cars as well... more than likely i wont be using a MAF, but since i knew this had not been tried on our cars i thought it may be a possibility.

[AudiA4_20T]

it was just an idea i had as i have seen it used on some high horsepower nissans. just thought it may work on our cars as well... more than likely i wont be using a MAF, but since i knew this had not been tried on our cars i thought it may be a possibility.

yo, u ready for this weekend? im picking up my 35R tomorrow

[Papachristou]

i dont understand how it will hold up to the temps or what the purpose of doing this is... get REVO where you can run mafless or just run the stupid thing where it was intended to be run... show me the benefit to be gained by moving it

[dirtybrd]

yo, u ready for this weekend? im picking up my 35R tomorrow

What happened to the Bullseye?

[dubenvy]

put it on the downpipe.

[DenverNoob]

lets also not forget that there is a bit of post-MAF air that is added/subtracted throughout the intake system. Not the least of these is DV recirc...which is air already accounted for via the MAF at intake. a post TIP MAF location of any kind will not read properly for those simple reasons (i.e. TIP connections that add/subtract metered air) unless those connections, too, are relocated post MAF in its new location.

also, adding to the above postings, temps are NOT nice and "cool" entering the intake post IC typically...40 deg c is still 105 deg F....not exactly "cool dense" air in the least. Those are pretty good IATs for a boosting BT setup...and it only gets hotter from there.

Just too many issues at hand for this to be practical.

Also, nothing wrong with running MAFs on BT setups...just takes a bit more work to dial in (stock location). There are some benefits to keeping them in the car. I'm still running one!

[MacDaddy]

The air is compressed and does not represent the volume that has entered into the intake track...

thats why there is a pressure sensor in the intake manifold

[Das General]

What happens when you exceed the map sensor limits. Lets say your sensor is for 22.5psi and you plan to run more boooooost. Is it going to withhold you from running more boost.