Larger MAF body

[silverton]

Sounds like a lot of work and money to not get gains that would make it worthwhile.

[ejin4499]

Sounds like a lot of work and money to not get gains that would make it worthwhile.

 

As stated before it depends on if you have made other mods to your engine. stock engine absolutely not worth it larger engine with better exhaust maybe.

Edited December 21, 2013 by ejin4499

[MY1PATH]

The the MAF and Injectors are 2 essential variables that make up an equation to define your AFR. The nissan ECU uses a number within this equation (called K Constant by NisTune) to balance how one effects the other. When you change one or the other you change your K constant to balance the equation. If you do not have NisTune, you have to balance both sides yourself because you cannot change the K constant....

A MAF sensor tells the engine how much air is going to the engine. If you bore it out or go to a larger one it tells the engine there is less air going to the engine and leans out your fuel.

Why? Because the opening is larger so more of the air is NOT going to the sensor. This is considered to be a 'higher resolution MAF' it takes greater changes of airflow to make the same voltage changes to the sensor output.

 

You can balance this equation by going to larger injectors or higher fuel pressure a the same time because even though they flow more the modified MAF is telling the ECU to restrict them more.

Beware, your target fuel pressure should stay between 30-60 psi above this and you get poor metering from the injector cycle and below this you get poor atomization coming out of the injector.

 

You should be monitoring all these results with a wide-band AFR gauge to help you track how well you are balancing the equation.

 

If you have an N60 MAF and 180cc injectors (typical stock Nissan scenario) upgrading in balanced pairs would look like this.
N62 and 270cc
Cobra MAF and 500cc

In theroy, and I have not tested this, for a pathfinder it would look like this

stock and 180cc (true)
n60 and 270cc (theoretical)
n62 and 320cc (theoretical)

Now to simplify things even more, the ecu can compensate for small changes and small changes is really all you need for running an N/A 3.3 (180-210 HP depending on how its built) or N/A VG34 (190-220 HP depending on how its built)

The stock 180cc is just a hair lean up top when you make 200hp out of a VG. You can get away with this and leave the fuel pressure alone if you don't have your foot in it all the time but if you like to step on the gas and like to rev high then the duty cycle of the injectors will be about maxed (over 80% duty cycle and they start to fail). A small dent in the top of a stock FPR can raise the fuel pressure by 10psi making your effective flow rate more like 196 or 200 or 210 (47 or 50 or 53psi vs stock 43.5) AND your o2 sensor will see this enrichening and the ECU will be able to partially compensate for it when your are off the throttle while still giving you more fuel where you need it.

This is really all you need for 200hp, yes the stock MAF is a major restriction but unless you are really trying to make more than 200 HP I would not mess with it. And yes your vacuum gauge may never reach 0 at WOT with your 3.3/3.4 swap while using the stock MAF but 1-3 hg vacuum isn't that bad.

 

I have 2 pathfinders, one is running an N60 MAF (It came with the M30 ECU I'm running so the tune is already correct for it) but honestly at 200hp (which it is right now) I think it would be fine with a stock pathy MAF if it was running a stock pathy ECU.

Eventually my 2nd pathfinder will be getting the 3.3 and it will be running a stock pathy MAF and Stock flow rate injectors and it will be fine. I May or may not bump the fuel pressure (put a dent in the top of the regulator until it reads 47 psi) but that's about it.

Edited December 21, 2013 by MY1PATH

[Nefarious]

Exactly, good post. Thats why I'm going to use n60 maf, 260cc ka24 injectors and an ecu tune to dial it in perfectly. It will definitely be worth the effort if you want to make your vg as efficient as possible.

[MY1PATH]

Exactly, good post. Thats why I'm going to use n60 maf, 260cc ka24 injectors and an ecu tune to dial it in perfectly. It will definitely be worth the effort if you want to make your vg as efficient as possible.

Be aware, ka24 injectors are fine but stay away from ka24de if you can (or any 4 valve engine for that matter) because the DE engines use a split spray pattern to spray 2 valves at once. When mounted in a 2 valve engine they wind up spraying the port walls and puddling the fuel.

 

 

[Nefarious]

Hmm I wasnt aware of the spray pattern differences in the injectors, that's good info. I'm not sure ka24 injectors would be ideal either then since it's a 12 valve engine. It utilizes 2 intake valves just like the ka24de. The difference is the ka24e has 1 exhaust valve and the ka24de has 2 exhaust valves per cylinder.

 

One would think if both engines have 2 intake valves, they would both have a split spray pattern? I'll have to do some research into this now.