Ok, this is in response to a thread on nissan forums. Somebody asked if they could run both a larger MAF and larger Injectors and get them to cancel each other out. Is this theoretically possible, if you could find the right combination of Injectors and MAF? Would this be able to workout throughout the entire rpm range? Or would it only be able to equal out at a specific point? I was thinking if you can get the right combo of MAF and Injectors it might work. Of course I could be completly wronge, i dont know. What do you guys think?
This is the thread on nissan forums: http://www.nissanforums.com/showthread.php?s=&threadid=13484&perpage=15&pagenumber=1

i think itd be pretty hard to perfectly match your injectors and maf not to mention your fuel supply (pressure +pumps volume rate)

And for what you would pay someone like RC Engineering or someone like that to do it you couldve bought an s-afc and be done and relatively safe....in other words for optimum performance, not to mention safety you should control those parameters somehow..(ECU/s-afc)

yeah i brought this up a couple of months ago. It is theoretically possible, but in order to use 370cc injectors, you'd have to bore the MAF out to like 59.5mm which is not possible

Even at that, the MAF isn't the restrictor at part-throttle conditions; the throttle body is. The ECU is still working overtime reading from the O2 sensor and fighting to keep your mix at Stoich when you're below 80% TPS voltage.

read (http://www.autospeed.com.au/A_0008/P_1/article.html) This shows a few ways of doing it and without ECU tuning.

So theoretically, you could do this? That is assuming that the proper MAF Injecter combo exists? And fastnx, what about running a new MAF all together, not just a bored one?

yeah, but the electronics inside the MAF sensor itself may not be compatible with the ECU. One thing you could do is bore the MAF and raise the fuel pressure to match the bigger amount of air coming in. what is this for?

someone on that forum wanted to do it. But what if you use a MAF sensor that is compatible?

Guys,

the tread in nissanforums.com is a perfect example of how far the nonsense can go if someone starts shooting questions without investigating. Then another person answers without investigating and pretty soon you have a 4 page thread containing exactly ZERO information.

To the problem:

Is it theoretically possible? If you do not know how a MAF sensor works then Yes it is. If you do, it is NOT.

Is it practically possible? Maybe but it is a 1 in a thousand shot!

So what is the "limiting" factor?

Injectors are basically (not exactly correct but for the technical level of the thread we can make this assumption) linear devices. A 370cc injector measured at 43.5psi fuel pressure flows exactly 42.857% more fuel than a 259cc injector. It does not matter how long the injectors stay open, if they both receive the same signal, the 370 will flow 42.857% more fuel.

MAF sensors are non-linear devices. They all (I know of) output to the ECU a voltage signal 0-5.12 Volts. The ECU has in it a "translation table" so it knows what each voltage from the MAF means. This output from the MAF is NOT a straight line, it is a curve.

Therein lies the problem. If the response of the MAF was a staight line, then it would be possible (but not prebable) to find a MAF sensor that would be measuring exactly 42.5xx% more air than the stock one and it would consequently output a signal 42.5xx% lower than the stock at ANY LOAD.

Well, the response from the MAF IS NOT a straight line and the whole "possible" theory goes out the window.

Just for demo purposes, here are the response curves for the stock SR20DE MAF and the one from a Z32-VG30DETT.
MAF voltage is on the vertical axis, measured MAF load/flow on the horizontal axis.

SR20DE 0 to 5.12Volts 5.12 Volts indicates a flow good for approximately 280-300hp on an SR20DE
http://www.reporter.gr/images/0test/MAF1.jpg

Z32-VG30DETT 0 to 5.12Volts 5.12 Volts indicates a flow good for approximately 500hp on an VG30
http://www.reporter.gr/images/0test/MAF300ZX.jpg

Note that both MAFs have an unequal initial section before the response curve starts ramping up and that the shape of the curve at the last half is slightly different.

If the ECU does not have the "translation" table in it that is represented by the yellow dots, it will not work properly even if there was a MAF flowing exactly 42.5xx% more than stock.

Chris

Alright, cool. Thanks for explaining that!

Ohhh Noooo!!!
This question again!!!!

Originally posted by hpro123
Just for demo purposes, here are the response curves for the stock SR20DE MAF and the one from a Z32-VG30DETT.
MAF voltage is on the vertical axis, measured MAF load/flow on the horizontal axis.
Dude, that was a sweeeet example.

I'm not even gonna read all this BULL SHIT it can't be done correctly, if you do find the match it was simply pure luck! There is so much more to it than meets the eye. The only way this can be done reliable is with a SAFC or JWT. The SAFC has the calibration of most Nissan MAF programed into it. If I want to run a MAF other than my stock MAF I simply wire that MAF up change my IN or OUT settings accordingly, and presto I have more readable air flow, down side the SAFC has to know the calibration of both MAF sensors to work, so you can't use a COBRA MAF, don't know why you would want to use this MAF anyways. Damn the SAFC is great.

hpro123, thumbs up.

Originally posted by charlie2020
The SAFC has the calibration of most Nissan MAF programed into it. If I want to run a MAF other than my stock MAF I simply wire that MAF up change my IN or OUT settings accordingly, and presto I have more readable air flow, down side the SAFC has to know the calibration of both MAF sensors to work, so you can't use a COBRA MAF, don't know why you would want to use this MAF anyways. Damn the SAFC is great.

So basically I can put a maxima or 300zx MAF on my car and just switch the setting on a SAFC and it will work fine. Or do you need to correct the fuel map?