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View Full Version : Bigger injectors + Modified MAF, part 2...



orion
01-29-2003, 07:10 PM
OK - This idea really intrigues me...

I think I understand it, I think it will work...in theory and based on AceInHole's experience, and I think it may be a cheap way to run 370cc injectors on a stock ECU. I like it...

But what confused me was this from d240t2:
</font><blockquote><font class="small[/img]In reply to:</font><hr />
The MAF really does read Mass Air, not just airspeed. It is true, like you said, that flow = Area X Velocity, but that is just volume air flow. The mass airflow is also a function of density, which is a function of pressure and temperature.
And yes, the MAF does read mass air...

[/QUOTE]

But then AceInHole came back with:
</font><blockquote><font class="small[/img]In reply to:</font><hr />
Wouldnt the mass air reading then just be a percent of the sample tube in comparison to the overall area of the MAF cross section?? In this case, changing the MAF size would still work...

[/QUOTE]

Makes sense...seems to work. Here's the review:
</font><blockquote><font class="small[/img]In reply to:</font><hr />
The MAF is bypassed by inserting the entire body (ends cut off) into 3" PVC. I had to block part of the bypass (actually bolcked a lot of it) to get the system to run a bit richer for the turbo setup (adjusting the bypass for now with the A/F gauge... not precise I know, but the best I can do untill I can get the setup on a wideband O2). The reason I might have had to block a lot of the bypass is because 3" pvc has a 3" ID (I think....). The theoretical bypass calls for a 2.9" ID (makes a big difference area-wise)...

[/QUOTE]

So if the pipe size were a better fit, this could be perfect, or close enought for a low buck KA turbo.

I think the way the "perfect" 2.9" tube was derived was from the area stock (~2.6" MAF I.D. area = 5.3093 square inches), and the injector size difference of 27% ( 1-(270/370) = .27).

Take that size difference and increase the old area by it (1.27 X 5.3093 = 6.743)...then figure out the new diameter of the pipe that would give you that area, which comes out to 2.93", or 74.42mm.

I figured a piece of 3" O.D. exhaust tubing would be right at 2.9" I.D., and starting measuring from there...

My piece of tubing is a leftover piece from making my short-ram intake, a straight section of a Dynomax mandrel bend. 3" O.D. with 1/16 walls is 2.875 (73.025mm)...pretty damn close, and just a tad smaller, which should richen up the mix just right.

So I think I'm gonna try the 370cc injectors with a hacked MAF...i.e.:

Cut off the ends of the MAF, and then cut off the bottom half of the circle, leaving only the top portion with the hot wire and some plastic which should *almost* wrap around the outside of the 3" tube...then just drill a hole for the 'probe', and then attach the apparatus to the tubing with the probe in the center as it was stock.

So, anyone see any issues here?

AceInHole...maybe try some tubing like I have and see the results - It already makes great I/C piping and turbo inlet piping...and a mandrel bent peice is $20 or so from Jegs. The reason I volunteer you is b/c you already have the hacked up MAF...

If you don't get to it, I will try as soon as my injectors get here...on N/A first, but should be boosted ASAP.

I will report 02 sensor voltage if I can...

Again, I fell like I have wrapped my mind around this concept, and the #s look good to me...but as always, feedback is appreciated.

Thanks - Brian

Kookz
01-29-2003, 07:20 PM
Well, the injectors are 37% larger, 370/270. You are getting 37% more fuel than 270s, so (if you calculated the area) it will need to be a little bigger than you have it.

orion
01-29-2003, 08:01 PM
You know...that was the on part where I wasn't sure if the math was correct, but in thinking back, it makes sense:

270cc X 1.27 = 343cc...obviously not correct.

270cc X 1.37 = 370cc = That's dead on.

I did it backwards...

So that makes the theoretical ideal pipe size:

5.3093 X 1.37 = 7.274 for the new area needed. Which is a diameter of 3.04" I.D...a little bigger.

Oops...

So AceInHole shouldn't have had to block any airflow for his to be dead on, no? That doesnt make sense, unless I did other bad math.

Thanks

asad
01-29-2003, 08:10 PM
AceInHole didn't want it to be dead-on. He wanted it to run richer than stock to provide a margin of safety for forced induction.

Asad

AceInHole
01-29-2003, 08:14 PM
When I measured the MAF I came up with an ID of 2.5", so that's the number all my calculations were based on.

A peice of Sched-40 3" PVC piping has just about a 3.05" ID, and leaving it like that had the A/F so lean my autometer gauge wouldn't even read anything at WOT, so I'm pretty sure my measurement of the S14 MAFS is pretty close. In addition to that, you'll want to obtain a slightly richer than stock A/F (12:1 or even slightly less on boost). The thing is... it seems that the A/F gets richer as you get on boost with the draw through setup. The way it works is simply how boost works: you're drawing more air through the compressor inlet than is going into the engine (if you weren't doing so, you wouldn't be building boost). The MAF reading more air, obviously tells the ECU to inject more fuel.

But, back to the math:
2.5" /2 = 1.25" radius.
pi*r^2 = 3.14*1.25^2 = 4.9 in^2
4.9in^2 * 1.37 = 6.725 in^2
sqrt( 6.725 in^2 / 3.14) = r-mod = 1.46"
r-mod * 2 = ID-mod = 2.92"

That should be correct assuming my MAFS measurement was any more accurate than yours.

orion
01-29-2003, 10:18 PM
Asad:

I knew that...as I said that it should "richen up the mix just right..."

My point about AceInHoles measurement (although badly worded) was that based on my MAF ID calculations, and the correct 37% size difference, 3" ID should have been dead on, though it wasn't. Made me question the validity of the whole idea...

But my measurements were crude at best, so it makes sense the the ID of the MAF is more like 2.5", which actually works better, as my mistake in size difference put it too small, but the true ID of the MAF puts the 3" OD pipe right back on target at 2.875" or so...

AceInHole:

Thanks for the better MAF #s...looks good now.

I'll try mine out ASAP and report back.

Later - Brian

d240t2
01-29-2003, 10:21 PM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
The way it works is simply how boost works: you're drawing more air through the compressor inlet than is going into the engine (if you weren't doing so, you wouldn't be building boost).

[/QUOTE]

That works while you are building boost, but not really once you have reached full boost (assuming the lag time between engine breathing and MAF reading air is negligible, which is a pretty good assumption).

It makes it sound like you are trying to say that the car is going to run rich just because it is under boost now...which isn't the case. All the air that the MAFS reads still goes into the engine (assuming no leaks, no vented BOV).

But maybe the part that confused you, Orion, is the one thing I left out in the statement that you quoted. I believe I left it out because it didn't pertain to what I was talking about at the time.

Yes, the MAFS does measure Mass Air, not velocity, or anything else. However, it doesn't measure all the air, it measures a sample of the air, and it calculates the total amount of the air, based on the ratios of amounts of air that go through the sampling tube and how much goes around. What we are doing here is increasing the amount that goes around...so the ECU sees less air.

Dennis

orion
02-06-2003, 01:50 AM
The Review!!! -

So I hacked up my MAF, installed some 370cc injectors, and took it out for a test drive...noticed it was a *little* more rich (the goal anyway), but not too bad. Seems to be a success!!!

What I did was exactly what I described above: Used a piece of 3" exhaust tubing, 2.875 I.D., and hacked all of the MAF except the top square part and the round edges that follow it down. It mates almost perfectly with the tubing, but need a little more sanding. I used a GENEROUS amount of electrical tape all around to seal it for now, as it's seeing no boost...

Why do I say it's more rich? ...Well, it's an assumption based on the fact that for the last 2 weeks my A/F gauge has read right at the "I" in 'RICH', with a little fluctuation towards lean at WOT. Now it reads solidly at the C, with some flutuation both ways. Not bad...

So AceInHole...Good thinking, good for having the balls to test it...seems the old DSM trick will work for us Nissan guys. Maybe try the exhaust tubing and see if your A/Fs are more in spec with the proper I.D...

Anyway, I think this is a good option to the JWT ECU for turbo KAs with plans of 10psi or less. Back the timing to 18-19, watch your A/Fs, and get the damn thing on a dyno with a wideband soon after installation to be sure it's all good...but I am pretty confident it will serve me well.

I will sand it down, epoxy it in place, and boost it within 2 weeks, then report back...

Later - Brian

IKu
02-06-2003, 02:25 AM
say you wanted to use 550's... i calculated a 3.5 in ID (about). is that right? could 550's be used the same way?

Kookz
02-06-2003, 02:29 AM
3.5 is ~ right. That's going to be quite rich though. 3.5 with an S-AFC would be great.

philipwight
02-06-2003, 02:49 AM
Just wondering what the mafs you are hacking up looks like. I looked at my 93 240sx mafs and it is all alluminum. Just wondering if this is the mafs you are hacking up or is it the plastic one(on s14s i think) that looks similar to the z32 mafs.

AceInHole
02-06-2003, 06:12 AM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
So AceInHole...Good thinking, good for having the balls to test it...seems the old DSM trick will work for us Nissan guys. Maybe try the exhaust tubing and see if your A/Fs are more in spec with the proper I.D...

Anyway, I think this is a good option to the JWT ECU for turbo KAs with plans of 10psi or less. Back the timing to 18-19, watch your A/Fs, and get the damn thing on a dyno with a wideband soon after installation to be sure it's all good...but I am pretty confident it will serve me well.

I will sand it down, epoxy it in place, and boost it within 2 weeks, then report back...


[/QUOTE]
Thanks for the props and advice, but I think my setup is pretty much as good as it can be (for the type of setup that it is at least).
My new MAF looks like this: http://www.engr.uconn.edu/~corrales/240/new_MAF.jpg

I'm using 3" PVC, which is actually around 3.05" ID. The setup has obviously since been reconnected to the turbo setup.

I'm getting my new headgasket soon (assuming nismoparts.com isn't bs'ing me about it shipping out today) so I'll be able to test it beyond the 6psi its already gone up to. I'll tell you one thing though.... my timing is over 20 degrees and it was running fine, and I can pretty much get the Autometer A/F gauge to read however rich I want it to using baffles in the bypass since I didn't completely hack the thing.
It looks something like this (since replaced with PVC of course):
http://www.engr.uconn.edu/~corrales/240/seethruMAF.jpg

As for 10psi? Why stop there?? As soon as I have a turbo capable of going over 10psi the plan is to run 4 bar fuel pressure and remove the baffles from my bypass. Gonna bring this sucker to the limit, hopefully.

Also.... a side project like this will help with more accurate tuning without having to pay for dyno sessions: www.diy-wb.org (http://www.diy-wb.org)

EDIT:
I also forgot to mention that I got a MAF Voltage vs ECM air in #/min. Apparently at 0 airflow the MAF reads 1v, so I don't think there's a lower limit that would be crossed in the case that a MAF was too big (and the airflow at idle would be to slow for the MAF to read). In theory the setup should work for any injector size as long as the MAF is correctly sized. A 4" MAF wouldn't be unheard of, 256% larger... (691.2cc equivolent).

orion
02-06-2003, 09:43 AM
ALso, I forgot to note...I am still using the JWT N/A upgrade...can't wait to see where the A/F is when I put my stock ECU back in. Ought to be good - Nice and rich, more conservative timing, etc...

I'll have pics later today probably (Once home from work - 40hr/week sucks...college is more fun - Hehehe...)

But as for how mine looks - Just like the stock S14 MAF, just in a bigger body. S14 MAF is plastic, so cutting away the body is easy. S13 MAF would be harder to do, but could be done for sure...

Later - Brian

orion
02-06-2003, 10:44 AM
Iku -

I forgot to note - The stock MAF runs out of voltage somewhere, hence the need for a Cobra MAF. I don't know where exactly, but I wouldn't want to push more than 260-280 on a modified stock MAF - I would limit the use of this to 370cc injectors. But maybe that's just me being safe...?

How much have you guys seen on a stock KA MAF? I think the highest is under 300rwhp without Cobra MAF and 50lb/hr injectors...

Later

IKu
02-06-2003, 11:07 AM
i see... what size is the cobra maf? does the sensor work the same way as the ka maf?

Kookz
02-06-2003, 01:08 PM
Brian...

I'm curious why you are going this route when you already have a JWT ecu. Selling it to recoup some of the turbo cost?

AceInHole
02-06-2003, 02:50 PM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
i see... what size is the cobra maf? does the sensor work the same way as the ka maf?


[/QUOTE]
From what I've heard, the stock Cobra MAF starts at 3.5" and tapers down to 3".

They both work the same way: airflow past a resistor cools the resistor changing the voltage output of the MAF. One could assume that not all companies use the same resistor (or even the same company), so MAFs most likely differ from more than just body size.

orion
02-06-2003, 03:01 PM
Curiousity mainly...

I will *most likely* get another MAF and get the JWT upgrade at some point in the future, and maybe swap at the dyno to see what (if any) gains there are for either. And this way there is no hold-up in my turbo install due to JWT slowness...

I'm takin' one for the team here! I figure for the cost of a new MAF (~$50 shipped) I can get the Nissan community some good info, and maybe make some power in the process.

"More power? How?...":
Less restriction on the inlet side (2.5" to 3"...neglible under boost)
Better timing maps with hopefully similar A/F richness
Cheap, reliable options...'ufkook' could have done his whole turbo for sub-$1000 if it were not for the JWT ECU.

That, and I like unique and custom...

Later - Brian

IKu
02-06-2003, 07:00 PM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
Iku -

I forgot to note - The stock MAF runs out of voltage somewhere, hence the need for a Cobra MAF. I don't know where exactly, but I wouldn't want to push more than 260-280 on a modified stock MAF - I would limit the use of this to 370cc injectors. But maybe that's just me being safe...?

How much have you guys seen on a stock KA MAF? I think the highest is under 300rwhp without Cobra MAF and 50lb/hr injectors...

Later

[/QUOTE]

wait, the limit isn't the injector size, right? it's the mass of air flowing. but 370's would probably be enough for the amount of air that would max out the maf, right?
so if i wanted to use cobra or z32 sensor, the maf size couldn't be calculated, it would have to be guessed?

silvia7
02-06-2003, 11:04 PM
Theoreticly can't you just keep increasing the bypass piping diameter and injector size at the same rate without changing your MAF? For example you have 2.9 ID pipe and 370cc injectors, then you can upgrade to 3.5 ID pipe (made up number) and 555cc injectors? I don't have this mod, but does it make sense? if someone did this mod please tell me. Thanks.

Kookz
02-06-2003, 11:09 PM
Theoretically, yes. That's what everyone here is talking about doing, and AceInHole has done it successfully. The problem is that when you start wanting to run 550s, you're looking at quite a bit of power, and you should probably be going with something that you can easily tune or that is tuned properly.

NOSTALGIC_HERO
02-06-2003, 11:26 PM
dont worry, brian really does suck at KA turbos. http://forums.freshalloy.com/ubbthreads/images/icons/smile.gif

orion
02-07-2003, 01:25 AM
Yeah, that Brian guy...WAIT! Screw you, man! http://forums.freshalloy.com/ubbthreads/images/icons/grin.gif

I hate you guys...

Later - Brian

joemumz
02-11-2003, 11:44 PM
couple questions on this setup iw ant to run it on my 95 s14 do i cut the mafs insert the stick part in the oversized tubing after that then what do i just seal it up or do i put the round tube from the mafs inside the the oversized piping something like this ( &lt;&gt; ) ?? also what should i take the 370 injectors out of i have access to a junk yard thanks for the info im really intrested in doing this thanks- Joe

orion
02-12-2003, 12:00 AM
Proceed at you own risk, and know it will be too rich.

I don't wanna be responsible for someone blowing their KA due to an un-tested design. Give me 2 months and I'll report back if it works perfect...

But here's a pic:

http://www.cautioncreativity.com/briand/images/hacked_MAF.jpg

And 370cc injectors from SR20 or Z32 Turbo 300ZX...

I sealed it with 'The Welder' glue and some tape just to be sure. I'll figure out a better seal later...

Good Luck - Brian

philipwight
02-12-2003, 12:28 AM
has anyone tried this with a s13 mafs, or will be the first one to try that.

joemumz
02-12-2003, 01:30 AM
what are the problems that you got so far from it im runing 6- 6.5 pounds of boost now on the stock ecu blow through setup with walbro high pressure fuel pump and fmu thats it i was planning to get a afc shortly alls i want for now is to turn up the boost to 8 psi until i can save some more money to drop in my fully built ka what do you think??

AceInHole
02-12-2003, 02:38 AM
AFAIK orion and I are the only 2 240sx's that have gone this route for boost, and both are using S14 MAF's. IIRC, the S13 MAF body is made of metal, although I have no idea whether or not you can take the MAF sensor and plug off of the MAF body on it in order to insert it into a larger pipe, as well as if the 2.5" cross sectional area used as a basis for the S14 MAF body could be used in determining the new pipe size for the S13 MAF.

philipwight
02-12-2003, 03:12 AM
what about using the s14 mafs on an s13?

orion
02-12-2003, 10:12 AM
what about using the s14 mafs on an s13?



Don't think they are interchangable at all...Doesn't the S13 MAF shrink down to 1.5 or so in the center?

So a 3" pipe would be WAY too big...

And as for running this as a blow-thru...it's hard to seal up the MAF completely...4.35psi is easy, but 6-8psi may start to leak. Mine is taped heavily until I find a better way to affix it.

And I think is a better solution than and FMU, as at least it's reading airflow and determining the amount of fuel, not just forcing more throught the injectors. You're just sneaking 37% more by the element...

Anyway, proceed at your own risk...hehe.

Later - Brian

IKu
02-12-2003, 10:17 AM
Don't think they are interchangable at all...Doesn't the S13 MAF shrink down to 1.5 or so in the center?

So a 3" pipe would be WAY too big...




does it matter how big the s13 is? it can just be remeasured and recalculated, right? the thing i would be concerned with is if the s14 and s13 sensors are the same.

asad
02-12-2003, 10:25 AM
Don't think they are interchangable at all...Doesn't the S13 MAF shrink down to 1.5 or so in the center?

So a 3" pipe would be WAY too big...




Overall size doesn't matter -- what matters is a) whether the sensor element itself has the same output curve, and b) the relative areas of the MAF sample tube vs. the rest of the MAF.

FWIW, the Apexi S-AFC uses the SAME MAF setting for both the S13 and S14 MAF.

Asad

philipwight
02-12-2003, 10:40 AM
i am going to get a extra s13 and s14 maf and see what i can do with them, i will see if the s14 will work on the s13, or is that a bad idea with s14 mafs being much larger? I dont have an A/F guage.

AceInHole
02-12-2003, 11:06 AM
And as for running this as a blow-thru...it's hard to seal up the MAF completely...4.35psi is easy, but 6-8psi may start to leak. Mine is taped heavily until I find a better way to affix it.



Try RTV sealant or JB Weld....



i am going to get a extra s13 and s14 maf and see what i can do with them, i will see if the s14 will work on the s13


I thought the S13 MAF had a 4-pin setup and the S14 MAF had a 3-pin setup, or is this like how later Sentra SE's can use Maxima MAFS but only use 4 of the 5 pins?

asad
02-12-2003, 11:26 AM
I thought the S13 MAF had a 4-pin setup and the S14 MAF had a 3-pin setup, or is this like how later Sentra SE's can use Maxima MAFS but only use 4 of the 5 pins?



The S13 MAF is also only 3 pins. Cobra MAF is 4 pins, but 2 are ground. Z32 MAF is 6 pins, but only 4 are used, and 2 are ground.

MAF only needs power, ground, and signal out wires.

Asad

asad
02-12-2003, 11:28 AM
And as for running this as a blow-thru...it's hard to seal up the MAF completely...4.35psi is easy, but 6-8psi may start to leak. Mine is taped heavily until I find a better way to affix it.




Or...just run it as a draw-through and you don't have to worry about pressure.

Asad

orion
02-12-2003, 12:55 PM
Or...just run it as a draw-through and you don't have to worry about pressure. - Asad



Mine run as a draw-through had horrible idle due (I believe)to turbulence...but the MAF was placed at the turbo inlet.

And the wires were not long enough to run it just behind the filter. I will extend them at some point an try to see how that does...and I'll need to re-circ the BOV as well - Next time I rent a welder.

philipwight
02-12-2003, 03:49 PM
89-90 mafs are 3 pin i think and 91-94 are 4 pin. So I can use a s14 mafs if i can figure the wiring. Will the ecu know how much air is going through? The size of the s13 vs. the s14 is alot different. I will give it a try. I got an extra mafs from both to see what can be done. I still want to know if using the s14 mafs will lean out the mixture because it is so much bigger.

asad
02-12-2003, 03:54 PM
89-90 mafs are 3 pin i think and 91-94 are 4 pin



My '92 MAF is 3-pin.



. Will the ecu know how much air is going through? The size of the s13 vs. the s14 is alot different.



Like I mentioned earlier, the overall size doesn't matter. It's the fraction of sampled air that matters.

Asad

philipwight
02-12-2003, 04:07 PM
i am sorry that i said 91-94 were 4 pin...the one that i got today is a 4 pin so i though that all 91-94 were.

mafs are at the very bottom of the page (http://www.funtigo.com/my240sx)

AceInHole
02-12-2003, 04:55 PM
I wonder if that S13 MAF can just be honed out?? I mean... it looks like the sensor area can be considered negligible, and if the bypass area has a .75" radius, you'd only need to take out .65 in^2 or so.

philipwight
02-12-2003, 06:44 PM
without a caliper i cannot measure it correctly but i think it is close to 60mm without counting the little hole for the actual sensor. so that means the you would have to bore it out to 76.2mm???? right???? If so i dont think it can be done.

jimc-s13
02-12-2003, 11:19 PM
Here's a picture (http://www.the-crates.net/cars/images/jimc/mods/MAF_adaptor_02.jpg) of a DOHC S13 MAF (which has a 3-pin connector, BTW).

I'd be more interested in seeing if an S14 MAF will work on the S13, rather than try to adapt the size of the S13 MAF.

Jim

AceInHole
02-13-2003, 12:43 AM
without a caliper i cannot measure it correctly but i think it is close to 60mm without counting the little hole for the actual sensor. so that means the you would have to bore it out to 76.2mm???? right???? If so i dont think it can be done.


Who says you need to bore it out in a perfect circle? Looks like there's a lot of room on the sides of the MAF to take material out.

philipwight
02-13-2003, 01:40 AM
the thickness of the walls of the s13 maf is fairly thin, not enought to get the proper amount of compensation. I will try to get a s14 mafs on my car. Does anyone know how to tacle this task. I have somewhat of an idea but not enough to do it without some advice. I do have the harness for it.

AceInHole
02-14-2003, 01:38 AM
heh... feels like no one understands what I'm saying.... but here's another shot at it:
On the S13 MAF you have two smaller circles within a larger circle. Between those circles and that larger circle (which is the MAF's overall body) you have some material. On a quick glance, you easily have at least 50% of the inner circle in area with that extra material filling in the larger circle.

philipwight
02-14-2003, 02:08 AM
there is nothing behind the larger circle, here is a pic (http://www.funtigo.com/my240sx?b=15672&amp;p=2.0&amp;nav=next) of the side view. I may not be understanding what you are saying.

IKu
02-14-2003, 03:19 AM
look at your pic again and read what ace is saying... carefully

Kookz
02-14-2003, 03:24 AM
No, I think Philip is right according to the pic. The MAF would have to be bored out to a point where there is no material left. It's like trying to enlarge a hole in a 2" pipe out to 3" when the outside diameter is only 2.5". However, I'm not sure if Philip's MAF is actually for an S13, since he did say it had a diff. number of wires. I'll take a look at mine tmr.

philipwight
02-14-2003, 03:44 AM
i went and looked at mine, they look the same and i am 99.9% sure that this came off of a 93 240sx. Here is a comparison pic (http://www.funtigo.com/my240sx?b=15672&amp;p=start) of mine and the one from the junk yard.

philipwight
02-14-2003, 03:46 AM
the pic is at the bottom of the page...it looks bigger but it is just the angle that i took the picture from.

Kookz
02-14-2003, 03:53 AM
S13 MAF will be so easy to do this bypass to!

I had never seen an S13 MAF inside before, but you can see that it uses a small tube for sampling, and the larger opening has nothing to do with the hot-wire at all. All you would have to do is run another tube that is 37% the size of that (large tube + sample tube) area into the intake after the MAF. Cake I tell you.

philipwight
02-14-2003, 04:04 AM
the hot wire does have something to do with the opening, the air returns to the opening through some vents (http://www.funtigo.com/my240sx?b=15672&amp;p=start) but that could somehow be manipulated to work with a larger piece.

Kookz
02-14-2003, 04:22 AM
Yeah...but that's ok. In fact, the MAF would really matter, you could simply run another say...1.5" Diam(whatever gives 37% of the total area) tube into your intake after the MAFS. Not too hard.

AceInHole
02-14-2003, 04:54 AM
aiight... since it's apparently hard for some to understand what I'm saying:

remove the red areas:
http://www.engr.uconn.edu/~corrales/240/S13MAFS.jpg

I haven't looked at an S13 MAFS closely in a long time though.... but I'm fairly sure those areas are not vital to the MAFS.

EDIT: it looks as though doing so would end up with a larger MAFS than the stock S14 MAFS.... without having to use an unnecessarily large bypass MAFS body.

Kookz
02-14-2003, 04:58 AM
The problem is, if you check out those pictures above, behind those red areas is air. It's not solid metal.

AceInHole
02-14-2003, 05:06 AM
The problem is, if you check out those pictures above, behind those red areas is air. It's not solid metal.


Even if it's only a plate, it's blocking off part of the cross sectional area of the MAFS. As described in my thread about the larger injectors + custom MAFS idea:
mass airflow = density*velocity*cross sectional area
The point of the bypass is to increase the cross sectional area, thus flowing more air per some constant velocity.

Kookz
02-14-2003, 05:11 AM
Yeah, but it's got nothing behind it...you could drill a hole right through it, it's only ~1/8" thick. That part isn't a pipe inside a pipe, it's just a constriction in a pipe.
Are you saying just open the whole MAF up to open air?

AceInHole
02-14-2003, 05:23 AM
blah... forgot the MAF itself narrows down. Thought you were saying the MAFS was just a hollow wall. Although, splitting a peice of PVC pipe in half you could probably make your own outer walls and come out with a better MAF than the S14 version.... sorry about the mix up, but i still say it's possible to modify the S13 MAFS.

Kookz
02-14-2003, 05:32 AM
Actually, you could cut out that wall part, bend that inner part out to be flush with the outer, and then just have to fill in the gap at the top. However, that seems like a LOT of work compared to just running a small intake with its own filter (where have I seen this before? I can't remember).

philipwight
02-15-2003, 05:15 AM
how would you know that the added on filter is flowing correctly(adding the 37% more air). Seems like the best thing to do on a s13 is upgrade to s14 mafs which i am in the process of doing but i do not know how to hook up the wires. (i am not a good electrical person)

AlligatorMan
04-10-2003, 10:29 AM
Ok, the black wire is a ground wire (always). The white wire is signal wire. The striped is power wire. The question is: which pins do what on the S14 MAFS?

http://www.sr20development.com/Instructions/Z32-MAF.pdf
I wouldn't doubt that a Z32 MAF and 370cc injectors wouldnt work perfect together on a 240sx with minor tuning for off-boost throttle with an S-AFC (-37% maybe?).

insndrvr
04-10-2003, 10:46 AM
The problem I see with the S13 MAF is that you don't really know the cross sectional area. Yes you can measure the area of the reduced pipe inside the MAF, but the sensor is not in the pipe. You have to figure out what % of the air is going through the read hole to be able to estimate the cross sectional area if it were one open pipe. Then you could add a second pipe of the % increase you want to bypass the MAF. I would rather try and get a S14 MAF to work, because either way, it's going to be try and error, and you are probably going to need an AFC or something to tune it correctly. Or just keep trying different size pipes until you get it right.

duncan351
04-10-2003, 02:46 PM
Acutually the Z32 Maf doesn't work well at all on the KA-T.
I'm dealing with Jim Wolf right now on this. The car is insaine lean with 50lbs injectors. I changed to the stock MAF and now the car idles great with a .63v O2 voltage. Jim Wolf is working on calibrating it now.

Greaser_
04-10-2003, 11:27 PM
what about using the s14 mafs on an s13?



Don't think they are interchangable at all...Doesn't the S13 MAF shrink down to 1.5 or so in the center?

So a 3" pipe would be WAY too big...

And as for running this as a blow-thru...it's hard to seal up the MAF completely...4.35psi is easy, but 6-8psi may start to leak. Mine is taped heavily until I find a better way to affix it.

And I think is a better solution than and FMU, as at least it's reading airflow and determining the amount of fuel, not just forcing more throught the injectors. You're just sneaking 37% more by the element...

Anyway, proceed at your own risk...hehe.

Later - Brian






Fiberglass resin by itself will work wonders....or 24 hour epoxy. Those two have withstood coolant system fixes on my rally car in the middle of no where. sold the car after using it like that for 8 months....get rid of the duct tape.

orion
04-11-2003, 10:02 AM
I swapped it to draw through just to see, and I like it better - Much better throttle response.

No more stumbling when I get on the gas, and seemingly no reduction in power...

I think it would be fine with an intercooler to smooth out the flow a little, but without, and with the BOV right before the MAF, it didn't like quick stabs or shifts.

But fiberglass is the next solution...

Later - Brian

Fred_Allen_Burge
04-11-2003, 10:23 AM
Hey,
I like the idea of putting in a small tube directly behind the mafs with a small filter - to bypass air. Maybe you could rig up an adjustable bypass to get the a/fs just right? Even better would be some sort of electronically adjustable "pipe" or valve that would be open more at low rpm (for a leaner mix) then close some at higher rpm for a richer mix. Maybe it could be adjusted automatically according to boost? Anybody have a guess as to what size tube would be close for and s13 (93) with 370cc injectors?

thanks,
allen

orion
04-11-2003, 12:03 PM
I think there are too many variables to be considered...

What if the filter on the extra tube got dirty and flowed 15% less before you cleaned it?

What if the path of least ressistance changed enough that at high RPMs it pulled more from the small tube and leaned out the mixture?

Etcetera, etc...

IMO you need all the air from one source to insure consistancy and reliability, so a bigger tube housing the element is the only way.

Or possibly a Y pipe with a MAF on one end and a tube on the other, both fed from the same filter - Weird adapter, eh?

Later - Brian

AlligatorMan
04-12-2003, 03:13 AM
Brian could you please explain the difference between 'blow-through' and 'draw-through'?

Thanks

Kookz
04-12-2003, 05:14 AM
Draw through: The air is drawn through (doh!) the MAF before the turbo. The air goes through the compressor, then through solid piping/intercooler to the throttle body/intake mani.

Blow through, the MAF is between the turbo and throttle body.

Jonny_290
04-12-2003, 02:40 PM
Does the heating of the air by the turbo (in a blow-thru setup) affect the MAF signal at all? I would think it would considerably, since it's a hotwire and all that.

Kookz
04-12-2003, 04:27 PM
Does the MAF work differently at 20 below zero and at 120 degrees? Nope.

Jonny_290
04-12-2003, 06:01 PM
Good point.

I neglected to take into account the fact that it heats it up a certain fixed amount above its current temp, which is gonna be pretty close to ambient, and then factor in the cooling effect of the air. something like that.

ftrceo
05-08-2004, 02:05 PM
has anyone had any new news on the hacked maf for the S13? As soon as i can get a yay or nay on this I am gonna start buying my turbo parts, or scrap the plan altogether.

1. Can the S13 maf be hacked?
2. Can you run a S14 maf on a S13 ?
3. If I put a S14 maf and Ecu on my S13 could i hack it then? Are the ECU hookups even the same?


thanx,
Ftrceo
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