R33 S2 Afm - How Good Are They..

[Royalflush]

Hey guys looking @ upgrading to a Z32 but i was curious to see how good the Stock OEM R33 S2 AFM are?

Are they any SAU users here that is making over 250kw with a stock R33 S2 AFM?

Cheerz,

[paulr33]

R32/R33 std GTST AFM's are the same, will cap out around 200rwkw

they peak just near 5v at 200rwkw. you can stretch it to around 220rwkw ish if you like or even 250rwkw if your tuner is game but its not recommended

above say 220rwkw just get a Z32

[Dush]

ahh ok.. I thought they were good for around 250ish.. but i was wrong..

[DrewII]

not very good. had to change mine when shooting for a bit over 200kw. pinging problems.

[krzysiu]

My old car was running standard AFM at 250rwkw

[Royalflush]

I got a Z32 now i wanna sell it because you guys think my stock S2 one can handle around 250ish...

[217/r33]

i'd never use a stock afm for 250rwkw, thats just insanity if you ask me.

maybe tell us what your setup is then people might be able to give you more advise.

[dezz]

i'd never use a stock afm for 250rwkw, thats just insanity if you ask me.

maybe tell us what your setup is then people might be able to give you more advise.

what kind of problems would you expect when running a stock afm at that kind of power level?

[Craved]

once you max the AFM to 5V the rest is just guessing ... you can do it, but should you?

[dezz]

potential problems? knocking?

[Craved]

runs fine -- lean -- over rich --- detotanation -- boom

and maybe not in that order

the whole idea is to increase resolution as the inlet airflow is increased, so you have tunability throughout the rev range and flow potential of the turbo in that space.

to use it you need some thing tunable, so make the most of what ever the setup is.

[paulr33]

hello

there are a few things worth noting before we run along a tagent

there is no given exact RWKW or PSI rating for a given AFM maxing out

when an afm maxes out or hits its celing limit in voltage it cant show the ECU any more increase in air coming into the engine (or LOAD)

i call it LOAD as most engine ECU's refer to a LOAD axis, regardless so if its map sensor or afm, they say LOAD

so once our device (be it map sensor or AFM) max out, the LOAD signal to the doesn't increase

so

scenario #1

AFM hits 5.1v and doesnt increase from this point onwards LOAD doesnt increase (lets pretend LOAD is a made up number of say 15000)

15000 units of engine load for our given ecu. lets pretend the ECU is a powerfc as these are common and our LOAD is 15000.

this doesnt mean 15000volts or anything, its just a load index. lets say the max load index possible is 20000 for any given situation.

so at 15,000 LOAD its near 3/4 on the LOAD rating (so lets say row 15 out of 20) as its 3/4s. lets say RPM is 4500rpm

so

LOAD is 15000

AFM is 5.1v

RPM is 4500rpm

so from this point onwards until the user changes gear (and it repeats) the LOAD number never increases.

it is likely more air comes into the system even though the AFM cant say to the ECU "hey more air is coming in" - because its capped at 5v

so the only change in the map co-ordinates can be is moving to the right along the "RPM" axis as the "LOAD" axis doesnt move down.

so the tuner must from this point onwards juggle the AFR's coming out and keep the timing under control

now he MUST do this for lets say 4/5's of the throttle and the throttle 5/5's as 4/5's may be enough to max the AFM

so wether the user is hammering the car or almost hammering it the user must juggle both scenarios as both use the same axis

there is where we often hear "run out of load points" as the tuner has run out of load points, so they have to juggle any possible combination

ok so now that we know what a maxing AFM means, it basically makes it a bit harder for the tuner

the engine wont go bang, it wont melt rods, pitsons, or blow up the wastegate

youll loose some tuning accuracy, and it will be a bit more for the tuner to juggle

maxing the AFM up near the top end is ok and i would call it reasonalbe

lets say you max it at 5000rpm then i would say this is ok, as not much changes from there on

now lets look at a map sensor setup

scenario #2

MAP sensor hits 2.1v and doesnt increase from this point onwards LOAD doesnt increase (lets pretend LOAD is a made up number of say 15000)

15000 units of engine load for our given ecu. lets pretend the ECU is a powerfc djetro as these are common and our LOAD is 15000.

this doesnt mean 15000volts or anything, its just a load index. lets say the max load index possible is 20000 for any given situation.

so at 15,000 LOAD its near 3/4 on the LOAD rating (so lets say row 15 out of 20) as its 3/4s. lets say RPM is 3300rpm

so

LOAD is 15000

MAP (or PIM-1) is 2.1v

RPM is 3300rpm

so from this point onwards until the user changes gear (and it repeats) the LOAD number never increases.

it is likely more air comes into the system even though the MAP cant say to the ECU "hey more air is coming in" - because its capped at 2.1v

it is capped at 2.1v as pressure reaches target boost (controlled by the boost controller) from the time the engine reaches target boost

so lets say you hit 1.3bar at 3300rpm - from here onwards, your engine LOAD guessed by the MAP sensor setup, doesnt increase after that

so the only change in the map co-ordinates can be is moving to the right along the "RPM" axis as the "LOAD" axis doesnt move down.

so the tuner must from this point onwards juggle the AFR's coming out and keep the timing under control

now he MUST across a larger range as most engines hit target boost reasonably early (say around 3 grand) so he must do this for a wider range of thorttle and engine load "scope" but the same boost pressure etc.

there is where we often hear "run out of load points" as the tuner has run out of load points, so they have to juggle any possible combination.

so in summary, a map sensor setup it worse off and "maxes out" much earlier in the rev range -vs- an afm setup

both work ok but are tunable, will make power and so on on

its just one (the afm setup) has more accuracy and variance, thus it can use more points

~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

some tuners say its acceptable

some say its a timebomb and so on

it all depends on the car setup and whats at stake and when does the afm max

if it maxes at 3000rpm thats bad, as its heaps of juggle/guess work for the tuner

if it maxes around 5000rpm and its a fairly low powered setup then it should be ok

by low powered id say around 250rwkw ish - over these levels it can be crucial

[Trav33]

Interesting read Paul, always wondered what happened at that top end if the AFM maxed out.

[Royalflush]

This Paulr33 guy is a wizz...

Thanks for your help champ =]