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MAF Placement?

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I'm having a hell of a time of getting my car to stay idling.  I think it's the distance of the MAF.  I've got it about seven inches away without a filter.  She'll idle with the hood open, but the moment I shut the hood, no bueno.  I'm trying to figure out how to relocate the MAF over by the intercooler, but I have no idea on  how I should go about it.

 

I would run it as a blow through style, but I don't have a lot of room, and it seems like I've got a good bit of blow by.

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If you have room and running low boost , i'd install it after the intercooler ( better reading on air temp. ) . Check your PCV system for blow-by problem . Most cars i've worked on don't like to idle when MAF sensor is sitting naked without filter or long intake boot . Too much turbulence at the sensor causes to have irractic reading .

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That's the thing, I don't have anything going to the valve covers right now, but I'm starting to see oil leaking from my intake manifold's vacuum ports underneath of the plenum (even though it passes a boost leak test?).

 

So I'm a little iffy if I should place it in a blow through setup.

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Don't do a blow threw setup. Your going to open a whole new can of worms. You want the air flow meter at least 12 inches away from the turbo so you don't have turbulence problems. The farther away the better.

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Don't do a blow threw setup. Your going to open a whole new can of worms. You want the air flow meter at least 12 inches away from the turbo so you don't have turbulence problems. The farther away the better.

That's why " blow through setup " is better , keeping the MAF sensor farther away from the turbo and the throttle body . It's better to have it after the intercooler for better reading on air temp. . If you have a thin cheap plastic MAF sensor housing and running high boost then this method is not recommended .

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Your going to have tuning issues with a blow though set up. The system wasn't designed for a blow though set up ( ask me how). I learned alot with my rb set up one thing is the K.I.S.S rule... Keep it simple stupid. Just place the MAF 1 foot or more away from the turbo and your done. Drive it and enjoy!

 

When I had my rb20 I had the same problem. I had the MAF placed in front of the intercooler. Nice and cool air. I ran tubing from the MAF to the turbo. Easy as pie. Problem fixed and fixed fast.

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Your going to have tuning issues with a blow though set up. The system wasn't designed for a blow though set up ( ask me how). I learned alot with my rb set up one thing is the K.I.S.S rule... Keep it simple stupid. Just place the MAF 1 foot or more away from the turbo and your done. Drive it and enjoy!

 

When I had my rb20 I had the same problem. I had the MAF placed in front of the intercooler. Nice and cool air. I ran tubing from the MAF to the turbo. Easy as pie. Problem fixed and fixed fast.

Was your MAF sensor on the intake or discharge side of the turbo ?

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I cut a hole in the core support for another pipe to pass through. Then I had to put a 90 degree coupler in. I made a flange out of sheet metal and exhaust tubing for a flange to mount up to the MAF. I think I posed pics on hybridz years ago.

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Nissan MAF runs off a heated wire and it uses that wire to measure the amount of air that passes that wire. The ecu measures the air by how much power it take to keep that wire a certain temp. So when you run a blow threw set up that air intake changes because of the heat generated by compressing air by the turbo. That intake charge temp is a lot higher than it would be if it was stock even when it passes through the intercooler. On a nice and hot day with heat soak your looking at 200f + degrees higher than the intake charge before the turbo . So with that said it will have to be tuned for that blow through set up. And I wouldn't think the stock MAF would stand up to that temp for very long.

 

K.I.S.S keep it simple stupid. Sometimes we try to redesign the wheel when the original wheel works perfect to start with.

Edited by pat1

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Nissan MAF runs off a heated wire and it uses that wire to measure the amount of air that passes that wire. The ecu measures the air by how much power it take to keep that wire a certain temp. So when you run a blow threw set up that air intake changes because of the heat generated by compressing air by the turbo. That intake charge temp is a lot higher than it would be if it was stock even when it passes through the intercooler. On a nice and hot day with heat soak your looking at 200f + degrees higher than the intake charge before the turbo . So with that said it will have to be tuned for that blow through set up. And I wouldn't think the stock MAF would stand up to that temp for very long.

 

K.I.S.S keep it simple stupid. Sometimes we try to redesign the wheel when the original wheel works perfect to start with.

Would it be better to have actual air temp reading after intercooler then before , so ECM can calculate for actual temp before intering the throttle body ? I have read and seen setups where MAFs mount after intercooler , work better and fix idle problem . HKS sells a hardware that fixes ( helps ) idle problem with MAF that mounts too close to the intake side of the turbo . I agree that you need to keep MAF sensor away from turbulence air . If you get 200F + higher than intake side after the intercooler then you need a larger and more efficient intercooler . Blow htrough is just an alternative if you don't have space and try to fix idle problem .

Edited by Domzs

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Sorry to revive an old thread, but those who ran the blow-through maf, did you have to retune after this or was this on a stock ecu?

 

I'm running a z31 ecu on my L28ET, and I just don't have room to route my intake with my A/C Compressor in the way. I'm debating going blow-through, but I'm holding off on Nistune for a little bit longer. I wanted to be sure I could run blow-through on a stock ECU.

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Can some one explain what the turbulence from the turbo do to the maf signal in detail? I currently have mine about 7-8" from the turbo but mine idles fine. My problem is that the ECU starts to freak out as the car warms up and retards the timing as if it is getting a lot more air than it is really getting. When I first start the motor from cold state everything looks normal. The timing is at 15 degrees like it should be but as the motor warms up the timing starts to pull back until it is below zero. There is a Red/Green indicator at the bottom of my consult that tells you if it is running lean or rich and once the motor has warmed up it stays Red/Lean and the motor wont make any power unless the CAS is fully advanced. I have been frustrating my self with this problem for about a year so if anyone has some insight please let me know.

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The turbulence causes extra air flow around the MAF which cools the hot wire faster. This makes the engine think it is getting more air than it is. Moving the MAF farther from the recirc and/or turbo decreases the turbulence and gives a more accurate air reading. Putting a 90 degree bend in the intake piping between the MAF and turbo should also help this problem.

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I know this is super late, but I finally have been able to get back on HZ :)

 

Anyway, I ended up redoing the intercooler piping on the left side.  Flipping some pipes around, rewelding, and cutting the hole a little bigger was I was able to put the MAF in front of the grill.  It runs a lot better, but sometimes still stalls, but at least it's actually idling now, versus never idling at all.

 

Speaking of idle, sometimes she idles really really high....oh well, one step at a time :)

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IMHO, if you have the money for an RB you aught to be using a standalone. Blowthrough works but only if you have enough control of the ECU. A factory car likely has an airtemp sensor in the manifold or it has a carefully calibrated adjustment for hotter air temps based on boost pressure, etc. This is all highly dependent on the factory intercooler, turbo, etc.

 

MAF-wise, I will explain a bit of the MAF dynamics so ppl can understand how to place the MAF. When fluid (liquid or gas) flows through a pipe, it starts out very disorganized. As it continues to flow through the same pipe, it starts to take on a velocity profile with respect to distance from the wall of the piping. In other words, the air flowing through the very center of the pipe flows a lot faster than the air flowing along the wall of the pipe. This is the velocity profile. When you have a factory setup, the MAF and ECU are carefully calibrated for the velocity profile that the intake system experiences. It is all made to stay consistent and predictable. The piping BEFORE the MAF is crucial. Especially the airbox design, how many bends there are, etc. Bends will cause the air to crash to the outside edge of the bend after the bend and it will take a while to reestablish the same profile, so having a MAF after a bend is bad. Right before the bend will also do it a bit. Having a MAF not at the center of the piping is bad. Having the MAF somewhere that the center of the pipe reads hardly anything is bad (such as RIGHT after the start of the pipe; the air will flow into the pipe like a toilet flushing and won't read much at the center or it will be chaotic).

 

For idle, you should have pretty solid control of your idle solenoid, stepper, whatever it is. In addition to that, you can use an authorized range of about 10 degree timing plus or minus to also step in after the idle circuit is adjusted to about half of it's authority. If you want it to idle smooth, run it just a tad rich. If you want it to idle efficient, you will need more IAC to do it and authorize and bit larger rpm range to wander around in. If you want it to sound cool and lopey, narrow the rpm range, use timing and leave it leaner so you also don't foul the plugs. Colder plugs and bigger injectors will require the timing unless you want to raise idle rpm (which i would not do too much). If it retards too much while idling, you will cook your engine bay.

Edited by WizardBlack

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I've read theses air straighteners can really clean up the maf signal....

 

http://www.ebay.com/itm/3-5-88-9mm-OD-x-5-Air-Straightener-Screen-25-6-35mm-open-cell-/251337605931?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a84e3832b&vxp=mtr

 

I don't know that this is the exact one to get, but if you read up a bit, it organizes the air and stabalizes the maf signal.

 

As an alternative to a standalone, if you are ok at soldering Nistune is a pretty good option. The RB25 Ecu isn't readily compatible, but there is a writeup on converting a Z32 ECU to work (cutting a few board traces, soldering a few resistors, etc). After that you have the option of buying the full nistune board, burning chips a few times to get a decent tune started, or like I am doing is to get an ostrich eprom emulator. Picked up the emulator for about $150, Z32 ecu for $40 (you can find them cheap if you look hard enough), $200 for the nistune software, and $40 for a consult cable adapter to USB. About $400 and a little work, but certainly cheaper than a $1000+ standalone.

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Wizard,

 

I'm a little confused.  On my setup I have the MAF in the grille, So it goes; Cone filter, MAF, coupler, 90 degree aluminum pipe, straight pipe, turbo.

 

On the past few nissan engines I used, I've put the filter directly on the MAF with no problems.

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Good post wizard, mtnickel. I am ready to use standalone if stock system cannot work. One question? Do the honeycomb air straighteners that mtnickel suggests work? My system has long runs of piping from front of intercooler to MAFs. The MAFs are 18 and 12 inches from turbos with a bend or two. Seems to work okay, but I want better. Have a good radiator and fan system, everything runs cool.

The problem my build has is inconsistency, Idles great, runs great. Next time high idle, miss at high rpm. Haven't found anything loose yet or air leaks. Perhaps air temperature differences as my intake slightly blocks my FMIC. The air entering MAFs should be cool. When car is behaving badly it seems to be a lean condition though not positive. Anyone else having these issues?

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Wizard,

 

I'm a little confused.  On my setup I have the MAF in the grille, So it goes; Cone filter, MAF, coupler, 90 degree aluminum pipe, straight pipe, turbo.

 

On the past few nissan engines I used, I've put the filter directly on the MAF with no problems.

Not ideal, but I guess it depends. Some cars have different factory setups and therefore the stock ecu is built differently. The best thing you can do is replicate the length, bends and placement of the stock setup.

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