Larger MAF body

[ejin4499]

Our maf works by putting out x volts through the hot wire and measures what it gets back. Depending on how hot that wire is allowed to get will dictate the resistance and thus the mass of air moving through a known diameter pipe. If I want the computer to think less air is going through the housing I would add a resistor to the line making the computer think the hot wire is hotter than it is. And if I wanted the computer to think more air is getting into the engine I would reduce the amount of resistance.

 

So if my above statement is true then if we want to use a larger MAF housing(boring VG33 etc) then we need a way to reduce the resistance of the hot wire circuit by an amount proportional to how much larger our new housing is.

 

I think the ways to reduce resistance is to cool the conductor (not likely) shorten the circuit (also not so likely) or increase the size of the conductor. Since the copper wire that goes to and from the maf doesn't really bring a lot of resistance we would have to look at changing the hot wire in the maf in order to change its resistance.

 

So assuming everything I have just typed is correct what is that thing made out of and can we get a slightly larger one proportional to the size of our new maf housing.

 

I am sure after the crack wears off this will make absolutely no sense but right now it sounds good.

Edited December 5, 2013 by ejin4499

[Nefarious]

You can buy individual maf elements but they won't work properly with an factory ecu. It's not so much the amplitude of the 0-5 v signal, its the analog steps between those voltages called the "maf curve". Each style of maf has different voltage steps based on temp than another maf.

For example one maf may put out 1.1v at temp1, 2.3v at temp2 and 4v at temp3

Where's another maf may put out .8v at temp1, .2.5v at temp2 and 3.8v at temp3.

 

There are far more than 3 steps since the analog signal is converted to digital for use in the ecu. There are usually 40-100 analog levels that convert over to digital so just plugging and playing with a new maf element (although u may get it to work) is really not ideal because even if it runs fine under some rpm/load conditions, it most likely will not run all values correctly.

 

Even the difference between an n60 maf and n62 maf is enormous, value wise, and they share identical maf housing even with just different elements.

 

I am currently working on setting up a stock ecu with a programmable tune to utilize a larger maf and more aggressive afr and timing curves. I'm finishing up my second year of industrial electronics/automation diploma so time is tight but I will definitely have a setup going in the new year.

 

My plan is to run an n60 maf and some slightly larger injectors (possibly 260cc from a ka24de) to keep the duty cycle and pulse width low. This uses the same housing as a n62 (around 3" diameter air passage, much bigger than the 1.75" stock maf air passage) and doesn't get near 5v output until over 300 HP. They can be had quite cheaply as well.

[Nefarious]

With my setup plugged into virtual dyno, I'm expecting 210-220 HP and 230-240 lb ft once the tune is complete with some dyno time to dial it all in.

This is my exact setup, just have to do the electronics still.

 

Vg33e engine

Vg30e cams

Obx headers (2" exits)

Full header back exhaust 2.5" from the y pipe back(magnaflow hi flo cat and flowmaster 40).

Cone air filter

N60 maf (maxima)

260cc injectors (240sx/frontier)

Custom ecu tune

 

This is what I have so far, I am currently trying to find a way to convert to a vg33 upper plenum and throttle body as well to match, I have a couple 3.3 intake manifolds outside to play with to get it to work.

I have everything figured out except for the idle solenoid, may need to do some machining to make it work.

Edited December 7, 2013 by Nefarious

[Precise1]

 

(around 3" diameter air passage, much bigger than the 1.75" stock maf air passage)

That sounded off, so I measured a 1995 MAF at 1.97", call it 2" diamter with what the element channel allows by.

So you are going from 3.141592653589793" area (interestingly enough, PI) to 7.0685834705770345" area, basically 2X? Is this really necessary? What about the flow rate? Have you considered the effect of reducing the velocity as well? Seems a bit extreme, especially since your exhaust is only 4.908738521234052" area.

Breathing and farting well matters, but all too often velocities, back pressure, scavenging, etc are overlooked or negated. I'm not a car tuner, but I also know that wide open on both ends is pretty much only desirable when you are wide open throttle.

 

B

 

[Nefarious]

The intake should be larger than the exhaust to make maximum volumetric efficiency. The Nissan maxima with the vg30e does use an n60 maf and they also make more horsepower. Less restriction will not = less power. There's a reason all Nissan after that point use large free flowing mafs. With the use of early vg30e cams this engine will need the extra breathing room. This is all based off my success with the ka24de engine in my 240sx. It uses a similar setup with a n60 maf and its a 2.4l. Not only did my power increase but so did my gas mileage. The trick is dialing it all in with the tune after all is said and done. thats where you get the major gains in efficiency. These engines run rich, and they dont push very much true timing. There is a serious amount of performance that could be unlocked with the right forumla!! I can only speak on it for so long but the proof will be in the numbers.

[Nefarious]

Pardon my guess on the stock maf BTW, I didn't have one to compare handy it was just an approximation.

[ejin4499]

You can buy individual maf elements but they won't work properly with an factory ecu. It's not so much the amplitude of the 0-5 v signal, its the analog steps between those voltages called the "maf curve". Each style of maf has different voltage steps based on temp than another maf.

For example one maf may put out 1.1v at temp1, 2.3v at temp2 and 4v at temp3

Where's another maf may put out .8v at temp1, .2.5v at temp2 and 3.8v at temp3.

 

There are far more than 3 steps since the analog signal is converted to digital for use in the ecu. There are usually 40-100 analog levels that convert over to digital so just plugging and playing with a new maf element (although u may get it to work) is really not ideal because even if it runs fine under some rpm/load conditions, it most likely will not run all values correctly.

 

Even the difference between an n60 maf and n62 maf is enormous, value wise, and they share identical maf housing even with just different elements.

 

I am currently working on setting up a stock ecu with a programmable tune to utilize a larger maf and more aggressive afr and timing curves. I'm finishing up my second year of industrial electronics/automation diploma so time is tight but I will definitely have a setup going in the new year.

 

My plan is to run an n60 maf and some slightly larger injectors (possibly 260cc from a ka24de) to keep the duty cycle and pulse width low. This uses the same housing as a n62 (around 3" diameter air passage, much bigger than the 1.75" stock maf air passage) and doesn't get near 5v output until over 300 HP. They can be had quite cheaply as well.

 

I get what your saying about not being able to use a different maf, but what about replacing those two wires (pictured below) on our stock maf (what are those by the way) with a slightly larger diameter wires? That would lower the resistance inside the maf itself. That way I'm not messing with the output I'm messing with the input the sensor is useing. Everything else that the maf does says the same. It just now thinks that more air is getting in. Which is correct because we would use a larger diameter maf housing. Either bore out a stock one or build one.

• 

Credit goes to Precise for the picture

Edited December 8, 2013 by ejin4499

[silverton]

4 cylinder engines use big MAFs to make them more drivable. Going too large just makes anything undrivable, that's why the Q45 throttle body is not linear.

It is interesting that the maxima uses a larger MAF than the other VG equipped vehicles. But it's also interesting that they use the n60 MAF in both the VG30E and the VE30DE.

 

Can't say you'll actually see any improvement in the real world as the restriction in the VG**E is that intake manifold was designed with forced induction in mind.

[ejin4499]

4 cylinder engines use big MAFs to make them more drivable. Going too large just makes anything undrivable, that's why the Q45 throttle body is not linear.

 

It is interesting that the maxima uses a larger MAF than the other VG equipped vehicles. But it's also interesting that they use the n60 MAF in both the VG30E and the VE30DE.

 

Can't say you'll actually see any improvement in the real world as the restriction in the VG**E is that intake manifold was designed with forced induction in mind.

 

Could you go into what you mean by un-driveable? I always figured more air means more power and on naturally aspirated engines more air means less restriction.

[Inyourface1650]

Yeah I'm not sure I understand that either. Your restriction point in the end should be the throttle body and nothing else. I guess I can see large diameters MAF setups having problems reading the much smaller amount of air passing through them that our VG's use.....

 

[silverton]

If the throttle opens too fast, you're just going to burn out. Maybe I explained it weird. It's all about throttle response right? Say your car comes with a 60mm throttle body, that's pretty big. But, an NA engine is only going to suck as much air as it physically can. So lets say you upgrade to a 75mm or whatever and the motor is optimal with a 70mm. The engine is going to be at WOT before the pedal is all the way to the floor. What's the point? Now, people get crazy and bigger is better right? Let's put the 90mm throttle body from a Q45 on this thing and still N/A. The engine is going to be wide open before you even reach 50% of the pedal travel.

 

Read this thread from hybridZ, lots of good info: http://forums.hybridz.org/topic/54034-big-throttle-bodies-why/

Edited December 9, 2013 by silverton

[ejin4499]

If the throttle opens too fast, you're just going to burn out. Maybe I explained it weird. It's all about throttle response right? Say your car comes with a 60mm throttle body, that's pretty big. But, an NA engine is only going to suck as much air as it physically can. So lets say you upgrade to a 75mm or whatever and the motor is optimal with a 70mm. The engine is going to be at WOT before the pedal is all the way to the floor. What's the point? Now, people get crazy and bigger is better right? Let's put the 90mm throttle body from a Q45 on this thing and still N/A. The engine is going to be wide open before you even reach 50% of the pedal travel.

 

Read this thread from hybridZ, lots of good info: http://forums.hybridz.org/topic/54034-big-throttle-bodies-why/

 

Ok I totaly understand that, but where I'm lost is we are talking about making the MAF bore larger not the throttle body.

The other part of this discussion wich is unstated is that some of us are using a VG33 block on VG30 equipment. How can we uncork the intake so we can make the most of that bigger block?

To me the throttle is the easy part to figure out. Bore it out and put a bigger plate in there. The tricky part is the maf. How can we open that up without having to reprogram the ecu for a new sensor? Thus my question what is the hot wire in the existing maf and can we replace it with a bigger lower resistance one to recalibrate the sensor for a larger bore/maf body?

Edited December 9, 2013 by ejin4499

[Nefarious]

This ^!!

I know my maf is a major restriction now. Cams, 3.3 swap, headers, exhaust, cone filter....etc. the stock maf is a major bottleneck and its not a very good design either.

There's a reason even the vg33 in pathfinder, etc uses a maf similar to the n60.

[silverton]

LOL. I couldn't hit the broad side of a barn with a brick apparently.

 

Modifying the device that tells the ECU how much air is moving through it seems quite difficult. Most of the newer turbo charged Subaru's are MAF based and don't have any problems making power, so I doubt it's much of a restriction.

[Nefarious]

It's not the fact there's a maf, its the size of the maf inner diameter and flow path. The stock pathy maf restricts down to under 2" diameter and the element is seperate from the flow path in a second chamber.

The maxima (n60) maf is closer to 3" diameter and the element is inside the flow path so it measures more accurately. With a modified 3.3 engine, increasing the size of the maf will definitely improve performance as long as its tuned for.

 

I'm curious if ejin can get it working without a tune but it would be quite tricky to get it right with a custom built maf and no tune. I know some of the 240sx guys go from 260cc to 370cc injectors and switch from stock 240sx maf to n60 maf and since the maf reads the same amount lean as the injectors run rich. The setup actually balances out and runs the car okay but its not ideal. Worth looking into using slightly larger injectors to balance out the increased lean read of the maf from being over sized. This is the only way I can see it working without a tune.

[ejin4499]

Does anyone know where I can find any specific documentation about our maf. The only thing I am able to find is generic to MAFs in general. I'm hoping for a break down of what its output vs input is and what the darn thing is made out of. I am reasonably sure that it is a platinum resistor similar to what is used in thermometers but I would love some manufacturer specs on it.

[Precise1]

All I have been able to dig up from the FSM is that the input voltage is 11-14, and the output voltage is "Less than 1 volt with ignition on, engine off, and aproximately 1.5-2.0 volts, engine warm, idling, no load".

 

B

 

 

[silverton]

I can't remember, is our MAF flapper door or no? In the Escort GT world we could swap the MAF from an RX7, but we had to open it up and adjust the clock spring that was inside so that the ECU was still seeing the proper signal while no longer having a restriction.

 

Go digging through FSM's and see if the larger MAF's match the voltage output of the factory unit.

[ejin4499]

Ours is a hot wire element not a vane type MAF. The fsm only posts 1 temp vs voltage output at idle no load. The fsm for the 97 posts 2 idle and 2500 rpm. As Nefarious pointed out there is some where around 100 different steps. I need enough points to estimate the current maf curve and then see if I can match that curve with a different hot wire. My hope is that I can make the same shape maf curve with the new element but make the MAF report that the air has more mass than it really does. If the computer thinks the air has more mass it will richen up the mixture. Once I know how much then I can tune the bore to the right size for the new element.

[silverton]

Sounds like it's going to be more work than the gains you could expect. N/A SOHC VG's just don't breathe well enough and the restriction is not in the air flow meter.

[Nefarious]

when you look at maf values in tuning software, its a non-linear curve for just about every Nissan maf that I have looked at, which makes it difficult to duplicate but not impossible.

 

when I get home I can open up nismotronic and check what the maf values are for the n60 or n62 maf but it doesn't have a pathfinder maf pre-programmed. just the main ones tuner/turbo setups will use.

any other vg30e equipped vehicle uses the n60 maf aside from the pathfinder. maxima and m30 are both n60 mafs with the vg30e stock.

[Slartibartfast]

The M30 ecu swap is a thing, right? Why not swap in the M30 ECU with the N60 MAF it's built for?

[Nefarious]

A 1.97" (thanks precise1) diameter restriction in your intake pipe on a 3.3l engine with cams, and supporting breather mods(intake/exhaust) is NOT adequate. On a stock vg30e maybe it was beneficial but not on a modified vg33e. I am confident I will see gains by upgrading to a larger maf with my setup. Proof will be the numbers on the dyno before and after.

 

I am interested in ejins idea too, would be easier the just swap a maf but tuning after is what ties all the mods together so swapping to the n60 would be a lot less time consuming and would cut the headache factor down getting it dialed in.

 

If you get it working without tuning i will be seriously impressed!

[Nefarious]

You can do that too! Just repin the ecu plug (may need the m30 pigtail) to match the m30 ecu to the pathfinder harness. Then you just need the maf and ecu from an m30 or a maxima . They are very similar but even better ecus than the pathfinder ecu. If you use the latest ostrich it doesn't matter though as it bypasses the differences between the three ecus (consult equivalent and data logging) and makes them all equal. It is easier to get started though since your maf curves and VQ tables will already be there. It's easy enough to snag the maf data from one vehicle to the next so its not a big issue.

Edited December 10, 2013 by Nefarious

[ejin4499]

Update

Found a patrol website (foreign cousin of the pathfinder right?)

 

http://www.patrol4x4.com/forum/general-patrol-discussion-17/donator-maf-sensor-booster-65671/

 

Where they discuss a voltage modifier. Tell me this doesn't sound like exactly what I was trying to do but better because its programmable.

 

also found this

http://3rdstrikeperformance.com/index.php?main_page=product_info&cPath=23_73_192_1260_3289&products_id=1660&zenid=38b1aadd7f1a041fce16ea05b470c371

Edited December 20, 2013 by ejin4499