Jump to content
SAU Community

Placement Of Afm

Color_Of_Green
 Share

Recommended Posts

LTHLRB Grand Master

LTHLRB

Posted
Posted

its placed where the intake is. The amount of air the turbo is sucking in is sensored by the afm, which the data is given to the ecu. As long as the afm has air passing through it, your car will run fine.

Correct me someone if im rong.. A MAP sensor is placed inside or where the inlet manifold is. Manifold Apsolute Pressure.

xRHETTx Mentor

xRHETTx

Posted
Posted

They talked about this (at least putting in the intercooler cold piping) in a recent issue of HPI magazine.

Seems like a good idea, as long as the AFM can hold up to the increased pressure (which I'd assume it can, we are talking in almost every case of less than 2 bar)

Gav Mentor

Gav

Posted
Posted

AFMs work best with an even flow of air through the body. If the AFM is too close to points of sudden air pressure and volume changes (eg throttle bodies, blow off valves, inlet manifold etc) then you get "reversion" flow through the AFM body. This is perhaps most noticeable in an uneven idle or in near stalling on sudden deceleration. One of the functions of the mesh in AFMs is to ensure a smooth flow of air through the body.

Busky2k Veteran

Busky2k

Posted
Posted

I like the idea of the AFM on the cold side of the intercooler. Better throttle response (due to less air volume between the TB & AFM) and the fact that atmo BOVs don't affect it (if you place the BOV before the AFM) are reasons why I'd like to give it a go...

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
90% of vl turbos have the afm in the intercooler piping. If your fussed about the size of your afm.. Q45 or Z32 is the way.. Alongside a PFC

thats a pretty bold statement.

coming from a VL years ago, its definately not the case

Craved Grand Master

Craved

Posted
Posted
and the fact that atmo BOVs don't affect it (if you place the BOV before the AFM) are reasons why I'd like to give it a go...

want to explain how this works?

my thoughts are : regardless of where you put the AFM it reads whats going through it.. so an atmo BOV stills lets air out, the turbo still forces air through the piping to this opening... hence still having the AFM read air flow. so it would be exactly the same

if anything it just makes it harder to have a recirc style BOV..

Sydneykid Grand Master

Sydneykid

Posted
Posted
the fact that atmo BOVs don't affect it (if you place the BOV before the AFM) are reasons why I'd like to give it a go...

Hmmm, I reckon no matter where you place the AFM an atmospheric (vented) BOV will affect its readings.

If the BOV is after the AFM, the AFM will measure air that doesn't end up in the engine. ie, whatever the BOV vents to atmosphere

If the BOV is before the AFM, then the air that has already gone past the AFM will reverse direction and get measured twice.

Either way = short term rich running (maybe stalling) after the BOV vents.

:O cheers :)

Busky2k Veteran

Busky2k

Posted
Posted

Well my theory is a bit different to you guys about the BOV.

Lets say the AFM is 3" from the throttle body. The BOV is about 5" away from the TB, ie placed just before the AFM.

On full boost we close the TB, and then we get a slight about of reversion which the AFM reads. But the AFM is is pretty close to the TB so we could say 3" x 3" of piping is not really a significant volume which contradicts SK's theory somewhat.

So.. the pressurised air between the turbo and BOV (ie FMIC etc) is all vented out through the BOV. But the key is that the AFM had never measured the vented air in the first place, so thus it won't go overrich.

Does my theory make sense?

Craved Grand Master

Craved

Posted
Posted
Well my theory is a bit different to you guys about the BOV.

Lets say the AFM is 3" from the throttle body. The BOV is about 5" away from the TB, ie placed just before the AFM.

On full boost we close the TB, and then we get a slight about of reversion which the AFM reads. But the AFM is is pretty close to the TB so we could say 3" x 3" of piping is not really a significant volume which contradicts SK's theory somewhat.

So.. the pressurised air between the turbo and BOV (ie FMIC etc) is all vented out through the BOV. But the key is that the AFM had never measured the vented air in the first place, so thus it won't go overrich.

Does my theory make sense?

so your assuming that the air between the TB and the BOV doesnt move at all

and any air coming its way routes through the BOV without affecting the air within the AFM ..

i see your point but is that true?

The Dan Grand Master

The Dan

Posted
Posted

I have been running the AFM after the IC for a couple of years now and the results are much nicer than you would think. Throttle response improved and no more rich spot when the BOV let go. I ran over 20psi through mine and it had no adverse effect on the AFM at all.

The whole thing with the BOV not effecting it is because the air between the air filter and the turbo acts like a giant spring. This is what causes the AFM to go psycho and cause the engine to stall. When the throttle snaps shut, the BOV opens and the air passes out. While it is doing this, the turbo is still pushing some air. This is still measured by the AFM but the air doesn't bounce around like a spring as it would before the turbo. Then when the BOV shuts the throttle is open again and the air continues to move.

Busky2k Veteran

Busky2k

Posted
Posted
so your assuming that the air between the TB and the BOV doesnt move at all

and any air coming its way routes through the BOV without affecting the air within the AFM ..

i see your point but is that true?

Well the air between the TB and BOV is still insignificant at 5" of piping as in my theory. Its certianly faaaarrr less than the capacity of FMIC and its associated piping if the AFM in its factory position which causes it to run rich.

Also in reference to your second point, the TB is shut. No air is going to pass through the AFM when the BOV vents. I mean how would it? Its a dead end.

I guess 3lit3 32's experience reinforces my theory. I also noted that my car ran rich when backing off on full boost, even with a recirculating BOV.

I'm real tempted to try this on my car. But I'm just to pansy to hacksaw the filter flange of my Z32 AFM lol.

TTT Grand Master

TTT

Posted
Posted

On my next skyline I want to play around a little with this.

Upon pulling apart the afm on my rb20 to re-solder it, I found it’s nothing more than a circuit board with wires and sensors etc.

And offcourse the hot wire below.

I plan to get a spare afm and cut it apart and make something up so that I can just have the hot wire sensor sit in the intercooler piping.

Not sure how I will do this just yet as I don’t have a spare lying around.

But I’ll give it a go eventually.

I don’t want to actually have the hole AFM unit… just the element and circuitry above it.

Craved Grand Master

Craved

Posted
Posted

good way to do it GTST ..

then again, all you need to make is a flange to bolt on a 3" or whatever piece of piping to the std bolt holes ..

then just use a sealant between the AFM and flangee, then silicon hoses as normal

as the to Dead end .. your saying that the air stops dead and doesn't move when you start forcing air into that dead end .... it would have to move .. especially if it was after a bend where the air would be force more to the external side of the bend..

aphid Proficient

aphid

Posted
Posted

hah, i was always under the impression vl's didn't have factory fitted intercoolers, hence the low 7.0:1 (or there abouts) comp ratio.. you learn something new every day :O

90% of vl turbos have the afm in the intercooler piping. If your fussed about the size of your afm.. Q45 or Z32 is the way.. Alongside a PFC
Craved Grand Master

Craved

Posted
Posted
hah, i was always under the impression vl's didn't have factory fitted intercoolers, hence the low 7.0:1 (or there abouts) comp ratio.. you learn something new every day :O

the intercoolers are aftermarket

as per

http://www.turboclub.com/turbocars/gm/GMH/gmh_vl.html

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • sinn3r
      R34 Skyline climate control unit transistor

      By sinn3r · Posted

      I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • MBS206
      R34 Skyline climate control unit transistor

      By MBS206 · Posted

      I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • GTSBoy
      R34 GTR Seats / No longer reclining

      By GTSBoy · Posted

      Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • GTSBoy
      Questions on potential new purchase

      By GTSBoy · Posted

      Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • GTSBoy
      Ethanol Content Sensor - Always at 11%?

      By GTSBoy · Posted

      Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...