s13 mafs hacking

[ca240]

alright...it's all startin to make sense...thanks guys

[aleph1]

As Slo said, it does nothing to alter the signal of the injectors, but it CAN read stats from the injectors and more...Throttle position, rpms, *injector duty cycle*, etc...it can show, I believe 5 stats at the same time...This applies to the AFC2, dunno too much about the AFC1.

[andrave]

how does it know injector duty cycle without monitoring the injector leads?

[aleph1]

Id imagine it can tap into them, I suppose it was not programmed to change them though...Also can monitor knock =)

EDIT: Upon further research, I dont think it can display Injector duty...Its hard to find direct, concise info for the SAFC2 (lots for AFC1). Many sites just cut and paste apexis SAFC1 description. I now believe it CANT, but I am still looking for a more reliable source...

[andrave]

there is some apexi computer that can, some dude was trying to sell me his honda civic and he had some apexi device (looked like safc2) that would show you injector duty cycle, throttle position, and some other neat stuff...

[aleph1]

AH! Apexi Multi Checker...or the newer "version" which is called the Rev/Speed Meter, which is the one that looks like an AFC, Yes these CAN monitor injector duty cycle. I got confused as well.

[andrave]

sorry if I spread misinformation. I'm just a dumbass sometimes.

[AceInhole]

I think that would be too big, if you want that much horsepower then you should probably go for some form of piggyback fuel computer.

considering that the hacked MAF of 3" is too large for 370's, it would be a good guess that a 3" hacked MAF would work with the 424's created by using a 4bar fuel pressure system, or maybe even 440's.

[TopStreet240]

it is a 3 inch pipe that we cut a hole into and then welded a flat part that holded the afm on it... then welded it on the inside and out side. Its pretty hard to explain... when i have it off the car I will post pictures.

[node]

I have just taken a look at a S13 AFM I have sitting around. How about this idea. It should be easier than hacking the S14 MAF and it will take less time.

Use a restrictor plate, NO im not talking about NASCAR, but it is the same idea. Basically cut out a little plate with a smaller hole in it to block off some of the air flow through the hotwire channel. Here take a look, the second image has the ristrictor plate installed with a smaller hole for less flow.

Sorry for my poor rendition of the AFM but you get what you pay for

[node]

And now with a baffle installed. You could use metal tape cardboard, whatever you want to do this and it should allow you to run larger injectors without buying anything.

Im not sure how to calculate the correct size of the hole since this is a venturi flow meter but at least you guys will have somthing to go on now.

Cheers

[ftrs13]

Im not sure about this???

wouldnt the best solution be to take out the afm unit and then put it into an open pipe that would actalyy flow more air??

[node]

Why do that when you can do this. Think about it, rather than mess around with a huge surrounding assembly or specific sized bypass pipe, all you need to do is make a little block off plate. Way eaisier than building some sort of flow around caseing.

Thinking of it now the same principals for aria flow should work even with a venturi type system. The hotwire hole only flows a % of what the main pipe is flowing due to the venturi affect so if you block off some air flow then you will affectivly lower the percentage that the hotwire sees.

ftrs13 I know you have the will to try this. If you want an extra s13 AFM to play with Ill be happy to send you an extra one.

[node]

Here look maybe this will be a little more clear.

for example here is the S13 MAF in stock form. The hole at the top is where the hotwire is.

[node]

Now the pice of paper represents a restrictor plate with a smaller hole in it than the hole the sensor was originally mounted in.

The only probem I can forsee with this setup is if the hole is right in front of the hot wire the velocity of the air may be increased causing improper readings. To remedy this I would recomend some sort of extension to get the restrictor plate further from the wire. That way the air will get a chance to even out and the flow past the wire wont be turbulent.

This is the basic ideaNow all you S13 guys go upgrade your injectors, try this out then raise the BOOST!

[ftrs13]

my only problem with this is the restriction of the MAF itself. the idea of increasing the diameter of the MAF is to increase the possible flow. I think this would work for small numbers which are what Im going for. but other than that, the MAF would cause too much of a restriction.

I dont think that velocity would be too much of a problem, because with a turbo somewhere in the system, you will either be pulling the air through or pushing it through. and also as long as the path into the "hacking hole" is smooth and there is no turbulence in the hotwire path. the huge change in diameter from the inlet to the path may cause a little, but Im not sure if it will be enough to disturb the functionality of the AFM.

does the dohc MAF have the same hole type setup? I havent seen an s13 dohc MAF.

[node]

The pics here are of a DOHC S13 MAF I just pulled from a car. I think it was a 1990 not sure though. Is yours different? If it is what does it look like?

Yes the ID of the large hole is a little small for super high horsepower applications. I see no reason why it couldent flow say 300HP though. Why not, I have seen some hondas running VERY small intakes and still make good power.

My concern with the setup was, since the hole in the restrictor would be sooo close to the hot wire the velocity of the air passing over the wire could be increased due to the higher pressure difference within the metering hole. I think if the restrictor was made kind of thick and had a taper twoard the hotwire it would work perfectly.

Perhaps we should start a thread about just this idea so we can get it figured out and save you S13 guys some serious cash.

[aleph1]

Thats cool man! I would have never thought of that! Finally, there maybe some hope for DOHC S13 maf hacking...But is there a way we could test this without possibly ruining the motor? =P Taper towards the hotwire as in...the opening gets smaller or bigger? BTW- 1990 still had the SOHC engine....DE was in 91-94.

[node]

Ok ok thanks aleph1. Then it was a 91 since I have the KA24DE engine from it sitting in my driveway.

Anyway the taper would start at a small hole and gradually get bigger as it approched the hotwire hole.

Ok I have a final plan for you guys now. There is this blue foam board that home depot sells called STYROFOAM. It cuts niceley with a razor and it has enough thickness that it would hold up well with lots of air going past it. You could cut it out and make a kind of insert that would stay in place without using any adhesives. The best part is that the material is only like $5 for a huge sheet that you could make lots of baffels out of.

Im rendering some pics of the insert now. I should have them ready in a couple min.

[node]

Ok here you go

Top left air flow follows arrowThe restrictor ring is inserted into the AFM and stays inplace because it is exatly the right size. the smaller hole is facing the direction the air is coming from. The larger end of the hole meets up with the inlet for the hotwire

That should do it. I would be willing to figure out the sizes of the restrictor if someone wanted to bring a S13 to my house.

[ca240]

nice pics...is that a cad program or somethin? you do that for a living or what?

[aleph1]

Looks like 3Dstudio max or Maya.

[aleph1]

I would be willing to try this out on my car, as long as it wouldnt damage my engine. I suppose if its working, the car will stubble/stall due to too much fuel being dumped? Note my engine is completely stock.

[node]

The program is called True Space. It’s a solid modeling/animation program. I took some cad in school but rarely use it since im now an electrical engineer.

As for testing this idea. It would just be tested at idle, that should be enough to be sure that the calculations we formulate are correct. I don’t think there is much risk involved even if the mixture were to go lean since there will be little load on the engine. I would prefer to use a wide band though just to be sure.

Ok now I need some help with the math:

The calculation for the flow reduction on this type of meter are a little different. The hole is only a percent of the total air flow. Would making a hole that has half the cross sectional aria of the current one half the injector pulse? If so we can use the same calculation but instead of increasing by the cross sectional aria by the amount we need, we will reduce it. OK here goes

Original injector size eg. 270cc

Sensor hole roughly 1.1906cm in diameter (this is an average since the hole is oval shaped.)Main air passage is roughly 5.395cm in diameter. (For any of you who may know how to do this math better than I.)

Taking the aria calculation just as we can for the S14 http://www.ka24development.com/hacked_MAF.html

we get

Pi(1.1906/2)^2 = 1.1133cm Cross sectional aria

If we want to double the injector size for example we would have to roughly half the aria of the sensor hole. I say roughly because changing the size of the sensor hole changes the size of the total AFM and that requires some calculus I don’t want to deal with. This calculation should be more than close enough.

New injector size 540cc for example

1.1133cm / 2 = 0.5566 New cross sectional aria for sensor.(0.5566/Pi)^0.5 *2 = 0.8418cm New sensor hole diameter

I hope these calculations are clear enough for everybody here. I suppose I could make up an java applet to calculate injector sizes but, I cant do everything for you guys

Now everyone can run bigger injectors without a fuel computer.

Happy motoringJim

[node]

ca240 Send me an email I have some parts you need.

[email protected]

[aleph1]

I understand it. So in my case, using 370cc SR20DET injectors, witch is roughly 1.37 times the greater than 270cc-I just replace this number in your calculations and come up with a new diameter of ~1.0179cm.

But I dont think its that simple....what I still dont understand is exactly how shrinking the inlet of the sensor hole will do much. From what I understand the sensor is a hotwire that detects (along with other sensors, 02 etc) the amount of fuel to use based on the volts needed to keep the wire at a certain tempurature...so the amount of air in this hole is irrelivant, I would think the velocity of the air (along with tempurature) is how the wire is cooled, hence needing a HIGHER than normal velocity to raise the amount of fuel being used-wait-I think I just figured it out on my own...lol of course i could be way off. SO having a smaller hole and forcing a similar amount through it, which would raise its velocity would in turn raise the amount of needed fuel...hmmm...but wouldnt this be more effective if the taper was the opposite way? Starting out larger then getting smaller towards the sensor?

If my above understanding is on track, what I STILL dont understand is if I make the hole roughly .2cm smaller, it doesnt seem like it will do much, let alone run 100cc more fuel...I think we are missing a key part of this formula. We are not taking velocity into account here, only area, which I believe is not what needs to be modified in this type of maf hacking. I would need to find a way to increase velocity at any one time to 1.37 times normal, right? Once again, I could be entirely on a different plane of thought, filled with visions of idioicy.

[node]

You seem to have it backwards. We want to ECU to dump less fuel so that it opens less time with bigger injectors. That way you get the correct amout of fuel even though the injectors are bigger and dimping more fuel.

The idea behinnd the wire is that it mesures the volume of the air going pased it in a fixed space. Although my calculations may be off the principal IS correct. If the aria of the hole is smaller the sensor will see a smaller % of the air flowing through it. This in turn will tell the ECU to shorten the injector pulse. That will lean out the mix back to where it should be.

Think about it this way. If you do nothng else but double the size of your injectors then the ECU will see X amout of air and open the injector the ammount of time it takes to put in enough fuel with the stock injectors. If the size of the injectors is larger however you will have WAY too much fuel. What you need to do is fool the ECU into thinking you are useing less air than you actually are. That way the ammount of fuel dumped gets corected taking into account the larger injectors.

This thread may help you http://www.nissaninfiniticlub....g+MAF

The reason you need to make the tiny hot wire hole smaller is because you need more of the air to go through the big hole (see my above pics) That way the ECU will think there is less flow and compensate by dumping less fuel. You will however have installed larger injectors so it will all even out and you will be closer to stock.

I doubt that this will be as acurate as hacking the S14 MAF but, it will save you a lot of cash $200 to $300 for an AFC vs JWT-ECU for above $600 plus reflashing each time you make a change.

[aleph1]

AH! I see how it works now! Thank you for explaining. But like I said, I dont think ~.2cm difference will do much...but Id be willing to try this out. If you give me the measurements (dont feel like taking my MAF out), I go down and get some foam. Also, if you made the hole for lets say the 370cc injectors (but on 270cc) will this be enough to detect that its doing something different, without any A/F gauge?

[huguetpj]

If we want to double the injector size for example we would have to roughly half the aria of the sensor hole. I say roughly because changing the size of the sensor hole changes the size of the total AFM and that requires some calculus I don’t want to deal with. This calculation should be more than close enough.

I'm pretty sure you will need more trial and error than calculus sessions, since for one thing you aren't taking into account the venturi effect of the MAF design (the outlet of the small hole). This could very well try and force more air into the small hole, so you'll need to go even smaller, or it could be the other way round.

But halfing the hole is a start.

[WDRacing]

I'm not one to stamp out creativity by any means. But here is a far easier way to go about this. If you simply want to run a slightly larger injector like the 370. If your going to use the original hacked MAF idea, which also increases airflow.

On the back side of the MAF, simply cut a whole and have a filtered tube attached. It will suck in unmeasered air. If you want it to come from the same source, then route the tube to start just prior to the MAF and end after it.

So troubleshooting would be easy, simply install your injector, cut a drill/cut a whole in the intake. Start with a small whole and gradually increase the size of the whole until your idle stabilizes and your at a good AF ratio. The whole process would take me 15 mins after the injector install.

WD