Blow through AFM *now with dyno sheets, 14.4kb users beware*

[slighty_sykotic]

Hey,

Ive seen a post about this on a 3sgte, but it was a fair while ago and it didnt really come up with a solid answer.

Can someone tell me for sure wether or not having the turbo blow through my afm on my aw11 gze motor is going to have bad effects. Talking low boost (8-10max).

Who's done it before and didnt have any problems?

Thanks,

--Sykotic

[KE20]

it designed to go first and be sucked thu, why you wan to blow thru it?

[fivebob]

It may work, it is a mass flow sensor, but IIRC the temperature sensor component of the AFM may be limited to <50degC and even then the stock ECU (if that's what you're using) won't have the necessary temperature compensations to cope, unless it also has a manifold temp sensor in the system.

[vvega]

yeah i thnk the earlier ones did have both like the 165 gt4
but just have a check for a sensor in the intake someware
it will be 2 wire and quite liky have a yellow plug on it

just for intrest the afm sender has the same static output as the manifold mounted one
i just poped outside and tested the resistance on them both

v

[slighty_sykotic]

Main reason is that it becomes a shit load easier to route the piping etc.

And yeah, its got two temp sensors, another one in the manifold.

But, hasn't answered my question yet

--Sykotic

[slighty_sykotic]

It may work, it is a mass flow sensor, but IIRC the temperature sensor component of the AFM may be limited to <50degC and even then the stock ECU (if that's what you're using) won't have the necessary temperature compensations to cope, unless it also has a manifold temp sensor in the system.

And are you sure its a mass flow sensor? Not a volume one?

--Sykotic

[fivebob]

And are you sure its a mass flow sensor? Not a volume one?

Of course it's a mass flow sensor. Each molecule of air (well not exactly as air is a mixture) at a known temp will produce a known force acting on the flap. An increase the number of molecules will increase the force, resulting in a greater deflection of the flap. Also higher temps will mean the molecules will strike the surface of the flap with greater energy, not sure how that will affect the reading though.

[Lloyd]

Ignore this, confusing myself

[jondee86]

Of course it's a mass flow sensor. Each molecule of air (well not exactly as air is a mixture) at a known temp will produce a known force acting on the flap. An increase the number of molecules will increase the force, resulting in a greater deflection of the flap. Also higher temps will mean the molecules will strike the surface of the flap with greater energy, not sure how that will affect the reading though.

What have you been smoking dude

An AFM measures airflow (or volume/time) and the mass flow is
calculated by the ECU using separate temperature and (possibly)
barometric pressure sensor inputs.

Cheers..... jondee86

[Bazda]

ok what have you all been smoking..

the 4agze afm works on air flow there is a flap inside that gets pushed.

And YOU CAN RUN IT BLOW THROUGH if you think not then ur a friken idiot .
I ran my car like that for 2 years on 18psi on my 4agte with the standard ecu + extra injector.

putting the 4agze afm suck through is more of a restriction.
On a nissan sr20det their afm's dont have that flap inside thats why it can be run suck through.

[slighty_sykotic]

Do you need the extra injector? and how did you control it?

Thanks bazda.

--Sykotic

[Bazda]

to run over 11psi you need an extra injector as you can see in the pic.

I used a powerlink to control it.

[slighty_sykotic]

hmm, thats sweet then. Im planning on 8-10 max at the moment, so you reckon it will be sweet left as stock with a blow through?

If so, great news

--Sykotic

[fivebob]

Of course it's a mass flow sensor. Each molecule of air (well not exactly as air is a mixture) at a known temp will produce a known force acting on the flap. An increase the number of molecules will increase the force, resulting in a greater deflection of the flap. Also higher temps will mean the molecules will strike the surface of the flap with greater energy, not sure how that will affect the reading though.

What have you been smoking dude

An AFM measures airflow (or volume/time) and the mass flow is
calculated by the ECU using separate temperature and (possibly)
barometric pressure sensor inputs.

So tell me oh wise one, what will the results be with a flow 1m3/sec of air at 100kPa, vs 1m3/sec at 200kPa, will the output be from the afm be the same in both cases. I think not, but perhaps I am lacking the enlightenment which I seek.

Secondly how does volume without reference to mass deflect the flap? What happens if I flow 1m3/sec and near total vacuum, will it still deflect the flap as much at 100kpa?

NB the volumes I refer to are at the pressures stated, not the equivalent volume at STP.

Have a think about it then share your illumination with us mere disciples of the Greater Reunification Church of Toyota

[Bazda]

hmm, thats sweet then. Im planning on 8-10 max at the moment, so you reckon it will be sweet left as stock with a blow through?

If so, great news

--Sykotic

Yes that will be fine, mixtures run at the max on 12psi so I ran 10psi until I got the extra injector.

[NA Drifter]

well, we have tried a blow tru on a RX7 AFM and it sux... car run like %$&^... and we change it back straight after...

[Akane]

What have you ALL been smoking?

There might be a few here who tells you that "I have been running my setup for 2 years at so and so PSI and it's fine", then GOOD FOR YOU.

But I strongly suggest you DO NOT run the AFM after the turbo. They might tell you it creates less restriction. Alright, let's step back a bit and think for a second:

Why does it have less restriction? Is it because now you're forcing COMPRESSED air through the AFM?

It takes the same force to PUSH the air through something, as opposed to PULL. Why would this matter.

secondly, if you start pushing COMPRESSED air so more air can fit through the same amount of space (restriction), now how the hell is the AFM going to tell how much air you're pushing through?

1cm^3 of air @ 18psi is VERY DIFFERENT to 1cm^3 of air @ 0psi. If the AFM is already fully opened (starting to have restriction), and then you pump some more air through the AFM (AFM's still fully opened, but now more air being "processed" since the air is compressed, how is the AFM going to know? that little temp sensor compensation ain't going to figure jack shit out.

If you have this "push through" setup and it works great, congrats to you and your rangi setup. But do I suggest you doing it? Hells no, leave this rangi crap to the bros with Mazda 323's.

BTW, the AFM on the 3S-GTE is good over 300hp+ Unless you're making more than 320, I don't see why you think it's such a restriction.

Feel free to correct me, afterall I ain't no Engineering student. I'm just going through common sense.

[Malcolm]

I used to run it on my GT-Four, and it's quite possibly the post you saw about it a while ago.

I have heard a lot of conjecture about whether the AFM measures mass flow or volumetric flow. Most evidence I've seen suggests it's a volumetric device. On this page on the Bosch homepage it calls it an air-flow meter and directly beneath it there is an air-mass sensor
http://www.boschautoparts.co.uk/pcPetr10.asp?c=2&d=1

I wont do it again.

[fivebob]

II have heard a lot of conjecture about whether the AFM measures mass flow or volumetric flow. Most evidence I've seen suggests it's a volumetric device.

How can something that relies on force to swing a flap open be a volumetric device? Take it to the extremes , if the flow is at near total vacuum what happens to the deflection? if you use a very dense liquid what happens to the deflection?

The fact that it works when used under pressure should tell you it's a mass flow device, otherwise it would make the engine way too lean if it only measured volume

[Malcolm]

yes this is something I've puzzled over too, and what you're saying is basically the reasoning I used when I originally did this. I wonder if the denser air does cause more deflection for a given volume, but not to the same ratio as the increase in pressure, so air at 2bar abs. might increase deflection 50% more than air at 1bar abs. for instance.

I'm doing a bit of a search right now for more info