Correct MAF Setup?
#1
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Correct MAF Setup?
A few months ago I tuned a turbo RX-8 with the Interceptor-X. During that time I had an interesting discussion on the forums about MAF vs MAP and I admit I was a little close-minded at the time. Since then I bought my own RX-8 for a winter car and a project car as I don't like the turbo kits available on the market atm. I'm going to be doing things my own way and see how it turns out.
Anyway, I decided to give the stock PCM+MAF a shot before going full standalone+MAP since Mazdamaniac seems so adept at convincing people the stock PCM+MAF is the greatest :P. So I'm testing this for myself and going into this with a complete open mind/attitude. If I don't like how it turns out, I'll go to standalone+MAP, if I do then there would be no point of course. Either way, it will be a good learning experience in something I haven't worked with before.
Now getting the question. Is this the correct way to setup a blow-through MAF system with an open BOV? Would there be any problems in doing it this way? (I remember reading something about turbulence) Could the stock MAF sensor be used and if I use a pipe with the same dimensions as stock, would the MAF calibration still need to be calibrated? Has anyone done this before?
![](https://www.rx8club.com/attachments/series-i-aftermarket-performance-modifications-23/150178d1263042181-correct-maf-setup-maf.jpg)
thewird
Anyway, I decided to give the stock PCM+MAF a shot before going full standalone+MAP since Mazdamaniac seems so adept at convincing people the stock PCM+MAF is the greatest :P. So I'm testing this for myself and going into this with a complete open mind/attitude. If I don't like how it turns out, I'll go to standalone+MAP, if I do then there would be no point of course. Either way, it will be a good learning experience in something I haven't worked with before.
Now getting the question. Is this the correct way to setup a blow-through MAF system with an open BOV? Would there be any problems in doing it this way? (I remember reading something about turbulence) Could the stock MAF sensor be used and if I use a pipe with the same dimensions as stock, would the MAF calibration still need to be calibrated? Has anyone done this before?
![](https://www.rx8club.com/attachments/series-i-aftermarket-performance-modifications-23/150178d1263042181-correct-maf-setup-maf.jpg)
thewird
#2
You're missing the intake on the turbo. The MAF goes in the intake tract before the turbo. The only problem when running a MAF with an atmospheric blow off valve, is that it will be counting on air that isn't there when the BOV actuates. This is because since the air is metered before it enters the turbo, and the the BOV is obviously placed after, when it opens, the MAF won't know that air is being released. One way to fix this is to recirculate your BOV back into the intake tract (after the turbo)
#4
Baro Rex
iTrader: (1)
Note that there is an admissible temperature range for the MAF as well. I don't remember what it is and as a pull through, it's a temp you can't hit. However, it is something you might want to check out on paper. A well designed turbo system probably doesn't have to worry about it. A greddy trying to do 300 whp might. So as a custom setup, you'd at least want that number written down.
Second, say you go to full boost, WOT and then close the throttle. When the BOV opens, could the MAF see a reverse in flow? Does the maf read in both flow directions? Would it output garbage if it saw flow reverse?
Second, say you go to full boost, WOT and then close the throttle. When the BOV opens, could the MAF see a reverse in flow? Does the maf read in both flow directions? Would it output garbage if it saw flow reverse?
#5
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I've been contemplating trying a blow through setup myself so interested to see how you fare, or if I get to it first I'll post up my results as it should be within the next few months. Don't know what you're thinking about turbo wise, but I'm probably heading towards a 60-1.
#6
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Note that there is an admissible temperature range for the MAF as well. I don't remember what it is and as a pull through, it's a temp you can't hit. However, it is something you might want to check out on paper. A well designed turbo system probably doesn't have to worry about it. A greddy trying to do 300 whp might. So as a custom setup, you'd at least want that number written down.
Second, say you go to full boost, WOT and then close the throttle. When the BOV opens, could the MAF see a reverse in flow? Does the maf read in both flow directions? Would it output garbage if it saw flow reverse?
Second, say you go to full boost, WOT and then close the throttle. When the BOV opens, could the MAF see a reverse in flow? Does the maf read in both flow directions? Would it output garbage if it saw flow reverse?
Also, I'm assuming since the MAF works in all weather conditions, it has its temperature sensor built in to correct the reading? If not, that means its relying on the AIT correction from the PCM which would mean I might have to play with that as well to get it to work right if I do blow-through?
I'm considering running something in the range of a GT35R - GT40R. If Garrett releases the new GTX-R's in that size by the time I get working on this, I will probably get it in the 35R size. Everything will be custom made and done properly (in my eyes at least).
The only thing I'm unsure about is this MAF stuff since every time I think about it, it just seems like it adds more and more challenges to get it to run mint hehe. But I'll give it a shot nevertheless.
thewird
#7
Boosted Kiwi
iTrader: (2)
What is the main reason you want to run blow through maf ? Is it just so that you can run a vent to atmos BOV ?
No-one on here has done it yet but I don't think anyone has tried that hard either .
FWIW - I run suck through maf with the IAT sensor seperated and an alternate one just before the throttle plate .
No-one on here has done it yet but I don't think anyone has tried that hard either .
FWIW - I run suck through maf with the IAT sensor seperated and an alternate one just before the throttle plate .
#8
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Want to keep the setup as simple as possible for easier placement of things. If I put it in front of the turbo, I will need to make the MAF section and make sure its straight, have the screens, long enough etc. Also, I want to make a V-mount so I want as much flexibility with where things go. Something similar to what I did on the RX-7...
*This picture was before the ducting was done so you can better see how its designed
![](http://thewirdsdomain.com/rx7/parts/vmount12s.jpg)
This is with the ducting...
![](http://thewirdsdomain.com/rx7/parts/vmount14s.jpg)
thewird
*This picture was before the ducting was done so you can better see how its designed
![](http://thewirdsdomain.com/rx7/parts/vmount12s.jpg)
This is with the ducting...
![](http://thewirdsdomain.com/rx7/parts/vmount14s.jpg)
thewird
#9
Considering the concerns that are "forcing" you to design a blow through set-up and the kind of turbo you're looking at maybe you should at least try if there's enough straight intake lenght before the turbo to install a draw-through (sp?) setup.
You would probably be close to the max scaling of our MAF in that way with a gt35, i don't know how it would work in a blow-through setup
You would probably be close to the max scaling of our MAF in that way with a gt35, i don't know how it would work in a blow-through setup
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
#11
Yes, you will also have to study what kind of diameters you're going to need to better calibrate the MAF for your goals in that position.
I'm not able to properly scale a MAF sensor beyond the "standard" limits but MazdaManiac could chime in setting us straight![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
Some people are using a split set-up with a draw-through maf and a barometer placed after the turbo in order to better adjust the maf's readings with some data after the turbo.
Playing around with a Maf based system gives a lot of opportunities tuning wise, especially when air pressure is used as a correction factor
I'm not able to properly scale a MAF sensor beyond the "standard" limits but MazdaManiac could chime in setting us straight
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
Some people are using a split set-up with a draw-through maf and a barometer placed after the turbo in order to better adjust the maf's readings with some data after the turbo.
Playing around with a Maf based system gives a lot of opportunities tuning wise, especially when air pressure is used as a correction factor
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
#13
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#15
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First of all, that is a sweet drawing.
You can do a blow-through with our MAF, but I bet the plumbing restrictions are gong to be so much more difficult that it simply isn't worth the effort.
If you are going to have to make a whole bunch of fabrication puzzles, you would be better off doing them on the suck-side.
You can do a blow-through with our MAF, but I bet the plumbing restrictions are gong to be so much more difficult that it simply isn't worth the effort.
If you are going to have to make a whole bunch of fabrication puzzles, you would be better off doing them on the suck-side.
#16
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I was originally going to do my setup blow through. Even started fabbing up a tube for it. But once I got to looking at turbo positions and realized I'd have more than enough room for a draw through..I just stuck with what was proven. ![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
I had trouble getting the Maf close enough to the TB for my taste anyway. The way our TB is angled aimed "across" the front of the engine bay was the problem. Had my turbo and Maf fighting over the same spot![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
My thought was that the closer the Maf is to the TB the more reactive it would be. Being farther away kind of puts it in the middle of a pressurized tank so it wouldnt react right away when the TB starts pulling air.
Prefering this:
|||||||||||||||||||||||MAF>-TB
To this:
||||||||MAF||||||||||>>>>-TB
Decided it was too much work to fab up for something that may not even work properly![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
If someone else gets a blow through setup working I may give it a go on my "rebuild" when I fab up the final version of my setup though.
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
I had trouble getting the Maf close enough to the TB for my taste anyway. The way our TB is angled aimed "across" the front of the engine bay was the problem. Had my turbo and Maf fighting over the same spot
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
My thought was that the closer the Maf is to the TB the more reactive it would be. Being farther away kind of puts it in the middle of a pressurized tank so it wouldnt react right away when the TB starts pulling air.
Prefering this:
|||||||||||||||||||||||MAF>-TB
To this:
||||||||MAF||||||||||>>>>-TB
Decided it was too much work to fab up for something that may not even work properly
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
If someone else gets a blow through setup working I may give it a go on my "rebuild" when I fab up the final version of my setup though.
#17
Banned
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The pressurized air in the system is all moving at the same speed where the pipe diameter is the same (allowing for changes in temperature and, therefore, density).
Its not a tank - its a column.
As a matter of fact, the air is moving at the same speed from the filter to the TB, only speeding up for the restrictions like the volute of the turbo and perhaps the IC piping, which is usually only 2 - 2.5 inches or so.
If your filter pipe is 3.375" and your TB pipe are 3.375", the velocity is identical, regardless of how far away it is from the TB.
Additionally, since the TB is a restriction, there will be an "eddy" just in front of it that will screw with the MAF.
That is why you don't want diameter changes near the MAF.
Last edited by MazdaManiac; 01-13-2010 at 08:08 PM.
#18
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Ahhh thanks for the input MM ![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
But if my intercooler pipes are all 2.5" and I wanted my Maf tube to be 3.5" wouldnt that create issues trying to keep the air smooth within all those size transitions and curves? I know on my suck through setup I used 3.5" and 3" transitions and it takes up alot of space. More transitions would take up even more space.
I know I could put the sensor on a smaller tube, but I was of the understanding that the smaller tubes become less accurate and max out the sensor faster? Any truth to this?
![Smilie](https://www.rx8club.com/images/smilies/smile.gif)
But if my intercooler pipes are all 2.5" and I wanted my Maf tube to be 3.5" wouldnt that create issues trying to keep the air smooth within all those size transitions and curves? I know on my suck through setup I used 3.5" and 3" transitions and it takes up alot of space. More transitions would take up even more space.
I know I could put the sensor on a smaller tube, but I was of the understanding that the smaller tubes become less accurate and max out the sensor faster? Any truth to this?
Last edited by Mawnee; 01-13-2010 at 08:26 PM.
#21
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thewird
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