Blow through MAF users check in

[480sx]

Im thinking of running a blow through setup on my Ka-T and am wondering what kind of results you guys have had with that setup. I would be most interested in the Z32 Maf, but i guess all nissan mafs would have similar results. From what i gather the best place to put the maf is on the cold pipe near the throttle body, or next to the IC.

Heres a few questions i have for the blow through guys..

1 - Are you running a FMIC?

2 - What boost levels do you usually see?

3 - How long are your MAFs lasting?

4 - How long have you run Blow through? (kind of the same question as 3..)

[neverlift]

its the best imho, I mean the maf cant measure boost ,no matter what it only reads the amount of air flowing inside it. Soem think that means draw thru is better but in fact draw thru doest even take into account for the heat made by compressing air so its giving a colder reading than the actual intake air. Wont go into the ota venting and stall issues associated with suck thru setups...

starion mod'd fmic,10psi daily(was 7~8), have not blown my sohc or z32 maf(been z32 for about 3000 miles) yet, my z32 has been blow thru before I had a fmic, I was using it with the sr smic too... its been monthscold pipe with a few inches of straight pipe just before it and you should be fine.

[srblacks131]

I have a front mount 24x12x4 and I have my Z32 MAF on the cold pipe right before the throttle body. I run 25 psi on it. Always been good to me. I didnt buy one of those adapter flanges tho, I cut off the flange side of the MAF and left a little lip so I could put the silicone coupler over it with a clamp. I dont know, I think it works just fine

[neverlift]

same here with the cut off the flange thing...

[yoshi_hito]

can i get some pics

[srblacks131]

My car is in storage and thats the best pic I have

[spooled240]

1) Yep, running a huge fmic 24x11x3 (I believe it's recommended so you don't cook your mafs)

2) 9~10 psi, not a really high boost level like 20 psi yet

3) Z32 mafs, working great so far no problems/maintainence

4) Probably coming up on 7 months now.

here's a pic of my blow-through mafs: it's on the lower left-hand side

[boznuttz]

Has anyone had experience with the MAF on the cold pipe and the BOV on the hotpipe while running an FMU setup?

[480sx]

Just for the record, i have yet to find a single person from ka-t forums and here who has had a bad experience with blow through on a Z32 maf. Infact, everyone who runs that setup loves it, and has had no problems.

[boznuttz]

Ugh, I'm going to have a few fitment issues with a pull through setup, so if anyone can chime in.... Is it possible to run a blow through setup with the stock MAF before the TB if I route the bov on the hotpipe? I know that I woudln't have to worry about unmetered air escaping if I ran an open atmospheric setup for the BOV.

[scheffler]

should be fine. You would will still have to worry about maxing out the stock maf. but you could run it as a blow through.

[480sx]

So far, the only bad stories iv heard about blow through setups are with stock mafs. Like, really bad, as in they dont last more than a week or so. Just food for thought

[yoshi_hito]

can i get anyone's AIM screen name so they can help me out with fmic tubing and maf solution? lolz.. i got everything else planned except this and tuning for the car.

[eazye2000]

All of the KA-T AIM Screen NAmes are in the sticky up at the top of the page......

[yoshi_hito]

yea, id rather no go threw each one bugging people... if someone wants to help then they will give me their s/n and not to tell me to bug the other hundred people on here

[spooled240]

yoshi, my advice: ebay fmic kit (some custom work involved if you have custome turbo mani) then either a stock>sr20>or z32 mafs depending on your hp goals. Or if you have the cash money go and get the ka greddy fmic piping but that's 400 w/ the ic.

boznuttz, you'll be fine-idk about the stock mafs but I think it should last, the z32's last for awhile so i think it SHOULD...

[yoshi_hito]

yea, been hearing people about the stock mafs don't last with a blow threw... but i'm willing to give it a shot! What type of fabrications stuff you talking about? I don't have access to a welder thats the only thing i am really worried about

and my set up that i have in mind is

obx manifoldt25370c injectorscalum ecu (need to learn how to tune it)safc iistock maf w/ blow threwssqv(maybe) bovand my friend has a wide band that i can borrow while tunning

[spooled240]

i couldn't weld aluminum either but i had a ton of couplers laying around to make it a temporary solution, but somehow it ended up staying that way permanently lol

you could go to atpturbo.com and order custom fabrication pieces for your ic piping also.

[yoshi_hito]

ill probably do the same thing as you and just get a **** load of couplers!

[GTR PrYdE]

Do you have to do anything special to run blow-thru? Or just move it over and go? Thanks

[Florida240sx]

Extend wires, hacksaw to cut pipes. File for the edges, couplers and screwdriver for the clamps, and have it in the correct direction for flow. And send me a 6pack of Beer or bottle of jack daniels otherwise it won't work. Most important step right there.

[GTR PrYdE]

Thanks. No tuning changes for this to work either?

[yoshi_hito]

something about it runs a little lean due to it can not read pressurized air... something like i just read it but ask the pros =]

Thanks. No tuning changes for this to work either?

[480sx]

I posted the same thread on Ka-T.org and got a response from a guy who appeared to know his stuff. He told me that he ran dangerously lean just by switching to blow through. Havnt been able to confirm or deny this however.

[srblacks131]

I ran more rich when I switched over...

[C-Kwik]

something about it runs a little lean due to it can not read pressurized air... something like i just read it but ask the pros =]

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.

[jebova2301]

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.

well...i think you mean BEFORE the intercooler, since thats where the air is hottest.(after turbo, before IC. But i could be wrong, and if i am, please tell me so. I can accept the fact that i may be wrong

Thanks for all the great info though.