Hacked MAF???

[tony/ka24de]

has anyone tried to use a resistor to change the voltage going back to the ecu?

[huguetpj]

If u use a resistor you would mess with the MAFs resistor bridge used to determine air flow. It would be best to use a high impedance amplifier to alter the signal.

[daniel240]

im currently running a hacked mafs w/ a 2.6'' ID pipe and its running great. i went with a little bit smaller one to make sure i dont run lean becuase i dont have any way of getting the AF right now. but it runs great.

[Xren17]

If u use a resistor you would mess with the MAFs resistor bridge used to determine air flow. It would be best to use a high impedance amplifier to alter the signal.

Correct me if I'm wrong but why can't you just use a voltage divider circuit for the line that's going into the ECU? Won't this stop the ECU from seeing the max voltage and hence have the same effect as doing a hack maf? or is it more similiar to using a Z32 MAF? I'm confused about something but I can't seem to put my finger on it.

[huguetpj]

Yes you can. But the divider needs to be high impedance so you won't mess with the sensor's wein (sp?) bridge - need to catch up on some theory. Hence you can't just use a resistor bridge. You need a high impedance voltage divider/amplifier.

[aleph1]

No the S13 maf is not the same as S14 maf. I think you can hack the SOHC maf, but not the S13 DOHC maf...which sucks, cuz thats what I wanted to do, but I think Ill experiment with WDs idea, cept just have an extra pipe that runs from RIGHT after the filter, but before the maf to after the maf....hope it works cuz I dont feel like spending 300 on an AFC...

[junk240sx]

I hav a question. It seems like this 'hack' would be slightly unreliable being that you have to get the right size (which i'm sure most can get close to based on the instructions here) but there is still the possibility of it being 'slightly' off.

Wouldn't it be better in the long run to just get an air fuel controller and adjust the % throughout the rpm ranges? This way you can fine tune it?

(that was my understanding so I got my 370cc injectors but bought a HKS AFR along with it..obviously i haven't finished the project yet so i can't say how it runs though)

[:: orion ::]

If you stock injectors give a great fuel curve...and then you change them to 370cc and hack the maf to compensate, why do you need the tune-ability???

My A/F's are close to perfect with a hacked MAF, tuned a little with higher fuel pressure. 14-15:1 under idle and cruising, then drops to 12s under boost, and ~11.7:1 under WOT...

No need to tune, no need to spend $$$ on fuel controllers.

Later - Brian

[SloS13]

Im currently running a Z32 on my KAT. I dont know what the hell is up, maybe the Z32 is messed up, but my A/F seems irradic at times and Im having a hard time leaning it out under WOT.

Im gonna hack the S14 MAFS with a ~2.9"ID exhaust pipe and see what happens.

I got a question that might be a dumb question. Does the computer read the s14MAFS the same as the s13, i.e. I should be able to 'zero out' all the info on my SAFC and not do any MAFS converstions. As far as the SAFC knows, its reading from an S13 MAFS, right?

thanks for any info

Edit: BTW, i have a wideband, so I'll let you guys know how the hacked MAF works

[daniel240]

2.9" ID might be a little big. most people are using about a 2.7'' ID pipe. im running a 2.6'' right now without any problems at all.

[junk240sx]

ok, well if you never have inconsistencies then I can see the point. cheaper is always better if you can get the same thing done. But I got my HKS AFR for $120 and I just thought it seemed like a better solution than hacking.

How hard (as in time wise) is it to hack an s14? 5 min deal?

[Redline240]

2.9" ID might be a little big. most people are using about a 2.7'' ID pipe. im running a 2.6'' right now without any problems at all.

He mentioned he had a SAFC, so he should be able to compensate for the larger size...

Redline

[SloS13]

He mentioned he had a SAFC, so he should be able to compensate for the larger size...

Redline

Yeah, but in the interest of experimentation, I want to keep the SAFC out of the loop, at least at first

[Redline240]

Yeah, but in the interest of experimentation, I want to keep the SAFC out of the loop, at least at first

Alright then, in that case what can be done to compensate for even larger injectors other than a AFC? I suppose you could just use a bigger pipe to match up the larger percentage...how big would it have to be for 555 injectors?

Redline

[SloS13]

i suck at math

[Redline240]

The pics from the first page don't work...could someone post another pic of a hacked MAF? Or can someone just e-mail a pic to me, [email protected]

Redline

[justjuiceit]

What does a hacked MAF and bigger injectors do to your gas mileage when you are not using boost? I imagine it decreases?

[C-Kwik]

Assuming the hack is done well, there should be no appreciable difference in gas mileage over any other type of fuel management.

[TurboKA37]

Alright then, in that case what can be done to compensate for even larger injectors other than a AFC? I suppose you could just use a bigger pipe to match up the larger percentage...how big would it have to be for 555 injectors?

Redline

if my calculations are correct it should be about 3.58" ID. which is some pretty huge intercooler piping. i think the hacked MAF is best suited for smaller injector upgrades such as 370 and maybe 440 injectors. and i made my calculations assuming stock piping for the maf is 2.5"ID and stock injectors are 270cc

[Redline240]

I have a safc, so i figure when i go larger than the 370cc i'll be able to compensate for it...but it was worth asking...

Redline

[racin-type]

Can S13's with dohc engines use the S14 mafs?

[:: orion ::]

NO.

Not a direct swap. Voltage curve is different, as expected...

Later - Brian

[racin-type]

damn hehe

[justjuiceit]

Would the HKS AFR allow enough adjustment to work with 370cc injectors in a non-turbo motor? It claims to allow +/- one point on the air/fuel ratio, would that be enough to compensate for the 37% increased fuel flow? How hard would it be to replace the stock fuel pressure regulator and attach a adjustable FPR and turn down the pressure? Would this work too?

[spitz7985]

Brian-I e-mailed you on this but I'm still a little confused. Maybe you can clarify. I believe your math over mine, but I can't figure out where i went wrong.

270 = x 370 100

370x=27000 x=72.973

Which concludes that 270cc injectors are capable of injecting ~73% of the fuel that 370cc injectors are able to, or ~27% less.SO, wouldn't you need to increase the MAF size by 27% instead of 37% like it says on your site?

stock MAF area (using your ID measurment) = 4.731 inches squared, using only significant figures

127% of 4.731" = 6.008" (the MAF area required for 370cc injectors)

6.008/pi square root = 1.383 * 2 = 2.766" ID

Please show me my error.

Thanks.-Brandon

[TurboKA37]

your error is the first step you made. 270 = x 370 100 Is wrong

you are correct that this equation will find that the 270cc injectors will flow 73% as much as the 370s will but you need to find the difference in injector size. 100% - 73% does nto work.you have to set up an equation like this:370 = X270 100which will come out to a 37% increase. plug 37% in for your 27% and you will have the same results as orion.

the reason you got 27% is because you found the % difference of the 370 injectors. in other words you found that if you subtract 27% of 370cc from 370cc you will come up with 270cc (370-(370x.27)=270). then you tried to turn it around and say that 127% of 270cc is 370cc which is incorrect.

[spitz7985]

:thumbup

[:: orion ::]

Brian-I e-mailed you on this but I'm still a little confused. Maybe you can clarify. I believe your math over mine, but I can't figure out where i went wrong...

Did you get my reply?

I sent:

Quote »You're doing the math backwards...the calculations need to be based off the original injector size, not the reduction from the new (larger) size.

27% larger is like multiplying by 1.27 - (270 X 1.27) = 342.9

37% larger is: (270 X 1.37) = 369.9

It's true that [ 370 - (370 X .27) ]= 270.1, but the ECU is tuned for 270 as the original injector size, and the calculations need to be based off the increase, as I said before...

And for the record, the 2.75" ID MAF gave me A/F's in the 13's under boost - It was still too large In my case.[/quote]And that's been posted already here...

Later - Brian

[spitz7985]

Did you get my reply?

yep, thanks, but i didn't completely understand.

And that's been posted already here...

sorry

[:: orion ::]

Didn't mean to be rude or insulting, just giving credit to "TurboKA37" for posting the same info...

Later