Hotwire AFM + big intake pipe = boom?

[RomanV]

Hi folks.
My redtop 3SGE (Very similar to an Altezza motor) has a hotwire type AFM (or perhaps Karmen vortex), but I dont have the standard airbox that the AFM fits into. It isnt a flapper style AFM, which is self contained in its own pipe unfortunately.

If the cross sectional area of the new pipe that I put the AFM into is bigger than standard, the AFM will output a lower voltage than it should. Due to lower air velocity.
But since it is hard to find someone with a redtop 3SGE that I can look at, how do I get around this?
Is there a manual or something that I can reference?


Surely there must be plenty of Altezzas running pod filters out there.
(You would need to relocate the AFM to do this.)

Anyone got any ideas?

[Akane]

I'm not too sure what you're trying to explain here.

Say it's a hotwire AFM since I don't know any other Japanese cars other than the Mitsubishi uses Karman Vortex.

If you're trying to say bolting the AFM (sensor + the tubing that it sits into), onto anything, i can't see it causing any problems.

But if you're saying putting the actual hotwire, into a new tube that's not the size that's intended, then yes, you'll have trouble.

But I don't see how you end up with just the wire itself but not the casing (tubing) that it came with.

[CozmoNz]

If your putting the *unit* itself into a bigger pipe, it WILL work, granted it can only get air THROUGH the afm.

so seal around the edges, but i dont know why you would want to, the afm will always be a restriction and remove the point of having a bigger pipe (less it doubles for a reso?)

[RomanV]

I have seen the actual AFM, and it wasnt in a 'tube'. I dont have mine yet, as it is on order from Japan.

I am assuming that it does not come with the casing around it.

How big is a hot wire type AFM? Does it run a wire for say 5cm or something?

Because the AFM I saw (Which was alledgedly from a redtop) Was very small, with a very small opening. The opening looked only about 2-3 mm wide.

Hence my thoughts that it is perhaps a vortex type AFM.

I will draw a sketch of what it looked like when I get home.

Perhaps it was not an AFM so much as a temp sensor or something?

[RomanV]

If your putting the *unit* itself into a bigger pipe, it WILL work, granted it can only get air THROUGH the afm.

Thats the problem I am trying to describe, The actual AFM is a tiny wee thing that pokes down into the airflow.
Its diameter was probably smaller than an average persons finger.

So you cant flow any air through it!

So I need to put it inside a pipe. I am trying to ascertain what sized pipe I will need.

Also no air came out the 'back' of it, it only had an opening at the front.
eg. no air flows through this device, only into it.

Which seemed strange.
So im thinking its a vortex type.

[matt dunn]

[Thats the problem I am trying to describe, The actual AFM is a tiny wee thing that pokes down into the airflow.
Its diameter was probably smaller than an average persons finger.

So you cant flow any air through it!

.

I think I know the part you are on about. Similar to a late model subaru one.

Yes it will need to go into the correct daimeter pipe to make it accurate, as it measures a certain sample percentage of the air flow

Matt

[RS13]

Why bother with all of this? Putting a larger pipe will give incorrect enrichment values, as the factory AFM samples an amount of air in an X-sized pipe. If you changed X with Y, not only will it be sampling less air to start with, the lower pressure will further disrupt the signal to the ECU. If it was a good idea that worked, then everyone would do it.. but it isn't, so they don't. If you want to make the AFM less of a restriction, then do it properly, ditch it altogether and get a Link or Motec or something.

[RomanV]

I DONT want to use a larger pipe.

I am not concerned about the restriction an AFM causes in the least.

I just want to get my engine going on a reasonable budget.

So this includes using the standard AFM, and the standard computer.
But I dont have the standard pipe that the AFM fits in.

If it wasnt for the fact that the engine runs VVTI I would consider an aftermarket computer for it.

But it would take a shite load of dyno time to get the VVTI to work as well as the factory settings, so its not worth the effort IMO.

[CozmoNz]

I get what hes on about.

he has the engine, but no afm.

the afm in this case basically acts as though its a map sensor, BUT it sensors say 10% airflow through a special sized tube, this tube he does not have, and dosnt know the size of.

head down to toyota and order that inlet pipe!

get it?

[RomanV]

Yes, kind of cosmo.

I have the motor.

I have already ordered the AFM.

I have seen a mates AFM., it doesnt consist of a tube that air flows through, with a sensor inside - its just a small sensor on its own.

My mate doesnt have the 'housing' for it either.

We are both concerned that we will need to acheive the stock cross sectional area of the intake, where the AFM is.

However, this thread makes me think it might not matter:

http://forum.altezzaclub.org.au/index.p ... c=19&st=20