Originally Posted by adamthedroog

What mod is this? How do you do it?

Originally Posted by snobdds

Lets make this clear from the start, it allows more air, but the ECU still puts the same amount of fuel to the injectors...thus creating the motor to run leaner. It would run richer if the dial was turned to close the air opening.

Originally Posted by MudHippy

That's backwards. It doesn't have an appreciable affect on the amount of air flow. And the ECU does run the injectors to allow for more/less fuel based on how the VAFM is adjusted. Let me explain it from a new point of view...

What you are doing by adjustment of the tension spring in the meter is recalibrating the air flow signal to the ECU.

The initial calibration is done when the AFM is installed at the factory.

That initial calibration setting can be thought of as a "zero" point, and/or "normal" setting.

Any setting "+" or "-" of "zero", or "normal", can be thought of as "richer" or "leaner".

Tightening the spring will result in the air flow signal being "-" it's "normal" value, and the ECU will run the injectors less, making the engine run "leaner".

Loosening the spring will result in the air flow signal being "+" it's "normal" value, and the ECU will run the injectors more, making the engine run "richer".

BTW, with all the 1000's of people who have done this mod, there are no "horror story engine failures" said to have been caused by it. That I'm aware of...and I'm well aware of MUCH...as is quite obvious to see.

Originally Posted by snobdds

This is probably all a mute point in the end, the o2 sensor has a bigger effect on Air/fuel ratios than the AFM has and may counteract the AFM changes...but we'll save that debate for later.

Originally Posted by 94_yota_4x4

is this a mod worth doing or is the supra maf a better alternative?

Originally Posted by Toysrme

So here's my answer to why on a stock 3vz-e, an AFM upgrade is useless. *On the stock/near stock engine*

1) It doesn't help a 2.5L 2vz-fe which makes more power, it won't help a near-stock 3vz-e

2) It does nothing to stock miata engine that consumes almost as much air @ high rpm as a 3vz-e. It DOES help a lot when they have gone FI

3) The math itself says it won't really help very much.

***So here's the math.***

Because of a lack of 3vz-e dyno's, I've never personally even seen one; I will instead use the power curves of a 5vz-fe because it's the only other low rpm Toyota v6 to compare to. Note I said the power CURVE. Not the dyno numbers itself. The curve of 5vz-fe dynos fairly closely matches the published peak figures for a 3vz-e anyways. This will ensure that I OVER estimate 3vz-e numbers. Simply put, the day a 3vz-e power curve is better than an FE head & cams - hell has frozen over.

If someone will provide a 3vz-e dyno, I will be happy to provide the real numbers , but as I just mentioned... It will make the math even more biased that the stock AFM is fine.

Warning: Generalization - SOHC peak volumetric efficiency will be calculated @ 80% peak.



Data:
Bore: 3.44"
Stroke: 3.22
6 cylinders
Ambient air temp: 70*F

@ 3500rpm
Volumetric Efficiency = 80%
145CFM
@ 4000rpm
Volumetric Efficiency = 78%
162CFM
@ 4500rpm
Volumetric Efficiency = 75%
163CFM
@ 5000rpm
Volumetric Efficiency = 66%
171CFM
@ 5500rpm
Volumetric Efficiency = 53%
151CFM

Small Denso AFM housing has been rated 165CFM @ 0.74in.Hg
Large Denso AFM housing has been rated 200CFM @ 0.74in.Hg

As demonstrated, peak flow on a stock engine is @ 5000rpm - 171CFM, while the AFM will measure 165CFM. So now the money question... What *WOULD* happen if you swapped one. Here ya go:
@ 5000rpm you would get a power bump from 126bhp = 165CFM, to 131bhp = 171CFM.
Now remember. The 5vz-fe powercurve is going to fall off less than the 3vz-e power curve. Most likely, it nose dives so fast, it most likely would peak out right around 165CFM - we all can honestly say it surly won't make 171CFM.



Sooooooo. I've said it a hundred times & I can pretty well prove it now. I can prove it 100% if someone provides me a dyno.

The 3vz-e's small denso AFM is NOT TOO SMALL for a stock/near stock engine.!!!





So, you're bummed that an AFM upgrade isn't really gonna do much. No fear. I've said something else multiple times too. We all know stock Toyota tuning sucks.

AFM with the silicon holding the plastic top cut.


Close up of the AFM spring & the cog that holds tension on it.


MARK THE STARTING POSITION.

Tighter spring leans, looser spring richens. ***Most stock & near stock Toyota engines don't need extra fuel, if anyting, lean them slightly.***



Expect a slightly better throttle response, and a few more horsepower @ high rpm. Mid rpm will also pick up a little when the engine is under load. Don't expect a large gas-mileage increase, but several 3s-fe M/T owners have reported less lugging in gear & increased mileage. IDK of any A/T owner of any 3s-fe 2vz-fe 3vz-fe owner that got more mileage.

3vz-e's have a distributor also... If you're not on the brink of detonation, add a few degrees of base timing advance. It won't give any appreciable peak power, but it will improve throttle response, and shift the entire powerband down a couple hundred rpm if you add enough.





There you go. There's the good & the bad. The good news - probably 90% of you that want a new AFM, don't need to waste time & money on one. You can also make more power with what you have already.