Trying to jack the AFM open and use an S-AFC is a HACK.&nbsp The S-AFC doesn't have enough resolution to make this run anywhere near reasonably well.&nbsp I install and tune Haltechs for a living.&nbsp I can install and tune a Haltech in my sleep.&nbsp I find the Haltech a much more effective solution than trying to get cheap.&nbsp The stock fuel control (i.e. airflow meter) does an admirable job.&nbsp I don't know why you want to get rid of it and be cheap at the same time.&nbsp The gains are not worth more than 10hp on a mildly modded FC - exhaust will give you more power, easily.&nbsp This mod ends up sounding like bragging rights to see if you could - this is not what I would call a "performance upgrade".


-Ted

 

Wow Ted, I thought it was much more of a retriction than that. Learn somethin new everyday.

 

OK, I got the goods on this mod. It's the old-skool method to up the performance with Japanese HKS add-ons (heaven forbid you use an Aussie standalone instead of a billion Japanese products, hehehe). Here's what you need (besides the FMIC)...

AFM relocated and return spring tension readjusted
HKS PFC F-CON
HKS FCD
HKS GCCII
HKS Twin Power Ignition

Of course, for the same price you could buy a standalone EMS, throw the AFM in the trash, and still have some cash left over, but then you couldn't put lots of HKS stickers on your car and look cool at the import meets.

 

And have a bunch of punks ask if you drift every 10 minutes, since you have mAd TyTe JdM pArTz Y0!!1

 

Nice job RETED and Felix

 

So has anyone actually moved their afm to the IC piping? How did it work out? Can the afm even stand the pressure?

 

Its been claimed a few times. Personally I don't see how it would work without other mods as the AFM is calibrated for operation at 1 atmosphere of pressure. It will measure lean as boost rises.

Henrik
87TII

 

I've heard this several times before and it makes no sense. Airflow before the turbo is exactly the same as airflow after the turbo (obviously), and restriction is related to airflow, not pressure or temperature. If you measured the pressure drop (a measure of restriction) across the AFM in both locations it'd be the same, because the airflow's the same.
I've yet to see anyone offer any proof that this makes any difference. That means before and after dyno runs with no other changes made. Any takers?

 

No, you've got it backwards.
ECU's with airflow meters are actually measuring the air they're ingesting, so thay can calculate the exact amount of fuel required to give the A/F ratio the ECU's fuel maps specify for the particular rpm/temp/etc conditions at the time. Flapper and sliding cone type AFM's like the FC's can't measure mass flow, only volume flow, so they have a built-in temp sensor so the ECU can calculate mass flow from volume flow and air temp. If you change the VE (intake and exhaust mods, porting, etc) with an AFM system the higher airflow is measured by the AFM and treated normally.
ECU's that use MAP (manifold absolute pressure) sensors as the load sensor (spped-density) have maps that basically say at X manifold pressure and Y rpm there is supposed to be Z airflow, and then calculate the fuel required from there. But they are only estimating the airflow based on the values found by the programmers experimentation on the stock engine and bolt-ons. If you change the VE, the relationship between manifold pressure and flow changes and this introduces errors in the ECU's airflow estimates. This is why speed-density systems (including aftermarket ECU's) are less tolerant of mods that AFM systems.

 

My friend did this mod he's running the factory computer with a custom fuel set up .this is the part that gets me , THEY CUT OFF THE BOOST SENSOR.THIS IS HOW HE RUNS 12.3
550 CC PRIMARES
1600 SECONDARIES
SX FPR
STOCK COMPUTER
FRONT MOUNT WITH THE AFM MOUNTED RIGHT AFTER THE TURBO
AND TWO SS BOV'S MOUNTED RIGHT AFTER THE THROTTLE BODY , SO THE AFM DOESN'T BLOW UP AFTER HE **** OFF THE THROTTLE.
oops sorry forcaps lock. he also is runing a full to4.
i will try to take sum pix if he let's me.

 

man thats crazy.

 

can you bore or widen the AFM and adjust it via the set screw inside?

 

So would the afm survive if it was placed right before the TB after the BOV?

Im sure it would have better response with that position then before the turbo. And i dont think you need all those HKS piggybacks to mount the afm in that position.

 

From what Ive been told I have gathered the understanding that if you place the AFM after the turbo and before the TB you run into the problem of innacuracies in that the air there is essentially backed up when under pressure and doesnt really move past the flapper b/c a constant supply is going in as coming out or something to that degree. Also it sounds rather cheap and worthless

 

How does it sound cheap and worthless? The engine changes its sound because of this?

And no, the afm would deffinetly open, the column of pressurized air is moving into the engine except when the throttle closes and the BOV vents. Thats when response is improved and no more hesitatrion after a shift.

 

LOL, you are missing the point. The stock AFM measures the airflow prior to the turbocharger heating the air, the intercooler cooling it, and the rest of the intake taking its pressure drop toll. Therefore, the ECU must estimate the temperature and pressure of the air in the manifold. In English, the stock AFM has absolutely no idea what is really happening in the intake manifold. An aftermarket speed-density EMS can calculate this better with sensors which are actually mounted in or near the manifold. This is also why mounting the stock AFM downstream of the IC would allow for more accurate operational information, assuming that some type of piggy-back ECU could take advantage of this information.

 

Sorry, NZConvertible has got it right. What your missing is that the AFM measures airflow AND temp at a common point. Add altitude (air pressure) and you can calculate the mass of the air at that point. Since the system is closed after the AFM (excepting for the wonderfull vacuum leaks) the mass flow is the same through the remainder of the intake regardless of what the turbo does pressure and heating wise. Once you know the mass, just add fuel to match.

Henrik
87TII

 

I thought there was an air temp sensor on the TB elbow anyhow?

 

Hey guy's when you figure this one out give me a hollar...... I foud in a auto salon 2 mag i believe that was the mname .they were using skyline afm's after the turbo????

 

i'll have to find it a gain you just need to ba able to read jap... all the good **** just in mazda language..... if i could read japanese.. i'd be in heaven....

 

It must be there so that the ECU can compensate for vacuum leaks.

 

I don't know what its for. I just know I must have unplugged mine 500 times when pulling the upper intake.

 

i left mine unplugged one time when i was setting my TPS and i made it about 5 miles and broke down.

 

Let me try this from another angle. If I add a very large FMIC to my TII, will it cause a reduction in throttle response and/or lag? If so, why?

 

the temp sensor in TB isnt it for measure temp of coolant flowing thru it? for the 3000rpm rev thing