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Location:
Rockhampton, Queensland
Registered:
October 2004
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map vs. afm?
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Sun, 10 October 2004 08:34
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Hello,
i am doing up a custom 4A-GTE engine and i was wondering which is most suitable for a forced induction setup? AFM or MAP?
i have been told MAP is but have not received a justified answer from anyone.
Could anyone please help me out with this issue?
Kind Regards,
Daniel
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Location:
Brissy QLD
Registered:
March 2004
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Re: map vs. afm?
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Sun, 10 October 2004 12:21
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MAP would be better... tempted to leave it there but i won't
the reason why map is better is the same reason as the NA car too its restrictes less, the air flow isn't restricted as its "sucked" ~as my my physic teacher taught me nothing is sucked its always a change in pressure~ less restriction means more air more air means better combustion assuming its getting enough fuel.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: map vs. afm?
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Sun, 10 October 2004 12:33
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think of it this way, which is a better measure of how much air goes into the motor (since that is what they do)
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Location:
Montrose, VIC
Registered:
May 2002
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Re: map vs. afm?
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Sun, 10 October 2004 14:28
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And why on earth would car makers use the more expensive idea of airflow meters when they could all use MAP.. hmmm.. But then maybe they just don't know anything ey?
Or MAYBE it's because there is actually an advantage in the accuracy.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: map vs. afm?
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Sun, 10 October 2004 14:34
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hey shinnny - this is something that has plaiged me for a while. Do you know to what positive pressure the bigport GZE ECU is mapped out to?
I know the smallport is restricted by the use of a 2 bar MAP sensor, but i dont know where the limits of the bigport are.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: map vs. afm?
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Sun, 10 October 2004 14:56
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All the bigport GZEs I've ever seen have had the flap AFM on them, therefore aren't really mapped to any boost pressure as such, only airflow.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: map vs. afm?
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Sun, 10 October 2004 15:03
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yeah i know this donghead 
oh nevermind... will take to long to type and im tired! 
avast matey! bed calls.
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Location:
Newcastle
Registered:
August 2003
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Re: map vs. afm?
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Sun, 10 October 2004 15:23
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Donghead!!!!!!! HAHAHAHA
Funni shit.
But yes when doing the querying of AFM VS MAP.
I do recall someone saying they switched to MAP cause it was cheaper to manufacture on large scale. But other people say MAPS are better, I have seen a few AFMS that seem a bit restrictive... but.. ugh
Still confused.... (from when I first started asking these Q around a year ago)
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Location:
Melbourne
Registered:
May 2002
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Re: map vs. afm?
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Sun, 10 October 2004 15:54
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According the NZers on twincam and toysport NZ, it's best to use the AFM cause the MAP ones have some issues over a certain PSI limit and the stock MAP ECU can retard timing after 5500...
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Location:
South Australia
Registered:
July 2002
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Re: map vs. afm?
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Sun, 10 October 2004 16:00
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Just go to Phil Bradshaw's page.
AFMs are good because they can calculate the air flow based off of - well - air flow. It's not an overly complicated story but the explanation is pretty long winded I guess. I think there is a bit of a debate as to how useful they are at like 3000m above sea level but I think that conjecture is kinda unfounded.
AFMs CAN be a restriction, but it's hard to say how much as most people with 'proof' only have dyno results that aren't conclusive, as opposed to a proper flow-test which is conclusive. Compared to some other restrictions in the engine (example throttle size, port sizes etc) it's not a huge part of the equation, I'm guessing around about 1% or thereabouts.
If you can get a hot-wire type AFM then you are laughing, but they aren't cheap. Couple this with a boost sensor (wide band MAP sensor somewhere) to handle correction factors to the a/f ratio and you are laughing even harder.
AFMs are MUCH more accurate at calculating air-flow IMHO and thus the chances of getting the correct amount of fuel to the engine (to ensure more than just good power, but also longevity of the componentry) are greatly increased. Sure maybe you could get higher air-flow and thus break dynos better with MAP, but an AFM will give you more consistent a/f ratios - which is what it's all about. Why else would we have EFI if a/f ratios weren't important!
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: map vs. afm?
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Mon, 11 October 2004 00:13
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A good hot-wire AFM is about as good as they get. Very accurate, and SFA restriction. Compared to the vane-type AFM on a 1G, they make a WHOLE lot of sense.
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Location:
Rockhampton, Queensland
Registered:
October 2004
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Re: map vs. afm?
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Mon, 11 October 2004 00:49
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So it doesnt really matter whether i get afm or map, as i am in the process of ordering a GZE halfcut and need to decided whether i want map or afm? the GZE goes up to 2 bar i believe i read somewhere in this thread, and i am wishing to run 1 bar of boost, so i guess i am safe with the map half cut?
or am i ?
Daniel
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Location:
South Australia
Registered:
July 2002
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Re: map vs. afm?
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Mon, 11 October 2004 01:55
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A 2-bar MAP sensor means it'll read pressure from 0 to 2.0bar...what you have to realise though, is that a 2.0bar reading is approximately equivalent to 1.0bar of boost. The pressure reading from a MAP is basically 1.0bar (atmospheric pressure) + whatever boost you are running, so you are effectively limited to 1.0bar of boost (ie 2.0bar of total manifold air pressure)
Go with AFM, have you read anything anyone has said here????
AFM ensures much better a/f ratios, putting a MAP sensor on is only good when you are worried about space in the engine bay, or maybe the cost of componentry. If you don't care about a/f ratios and only want maximum power at only ONE narrow range of throttle application and RPM then why not stick carbies on? 
If you want really good smooth reliable engine operation with really good power and good torque, then use AFM/EFI.
jcmf - the actual restriction placed on the engine from having the spring-loaded flap is quite small - what is a restriction is the overall cross-sectional area of the flap-type AFM and it's shape. Last I checked, squares are the second worst polygon for surface area vs. circumference - and if you know much about airflow, you would much rather air flowing through a geometrical shape that has high cross-sectional area for a given circumference, the best shape just happens to be a circle but it's an impractical shape for the job.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: map vs. afm?
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Mon, 11 October 2004 01:58
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if you are converting to turbo, its a matter of preference really.
AFM has following features:
# Bigport head, thus needs TVIS intake manifold for turbo
# 8.0:1 pistons
# 3-rib block
MAP sensor has:
# Smallport head, thus need a 100kW intake mani for turbo
# 8.9:1 pistons
# 7-rib block
# piston oil squirters
these would be the things you are more intersted in if you were to be doing a Turbo conversion....
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: map vs. afm?
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Mon, 11 October 2004 02:14
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what they all said 
what was said when Megasquirt was developed was:
although AFM may be a better measure of air, for 95% of applications the difference is small enough to be negligible.
MAP is much easier to set up for a variety of engines, whereas making a circuit to couple to a variety of AFM's is not so easy.
a MAP sensor is good, but will suffer when you have large overlap cams and poor idle vacuum. not a prob for you.
a MAP sensored ECU will only be as good as it's tune to the particular state of the engine. if you modify the motor (intake, exhaust etc) then it can go out of tune easily, since it is tuned to the manifolds pressure, rather than airflow directly.
with AFM, you are tuning to the amount of air going in, so unless you have massive air leaks, the AFM will be able to respond to a large range of engine mods WITHOUT retuning.
ideally, you would get a vane type AFM, which is large enough to not pose a restriction (the square hole, not the vane), and has nearly full vane defleection at max rpm-WOT.
if you have an AFM with a 1" square hole, of course it will "literally" suck.
with hot wire AFM's, need to remember to have good temp compensation, as different air temps will change the cooling effect on the hot wire.
Cya, Stewart
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: map vs. afm?
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Mon, 11 October 2004 02:16
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| THE WITZL wrote on Mon, 11 October 2004 11:58 |
if you are converting to turbo, its a matter of preference really.
these would be the things you are more intersted in if you were to be doing a Turbo conversion....
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thats prolly the answer he was looking for 
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Location:
South Australia
Registered:
July 2002
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Re: map vs. afm?
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Mon, 11 October 2004 02:34
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If you want the engine to run for 200,000+ks then you might be better off with AFM, the state of most engines flow changes quite a bit over the years!
I think WITZL has pointed out perhaps some more pertinent points, though, in regards to which half-cut you should get.
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Location:
south east - melbourne
Registered:
March 2004
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Re: map vs. afm?
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Mon, 11 October 2004 05:47
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RICE ATTACK 
if u want the flutter noise from the turbo go for the hotwire afm or the map sensor ,
the vane afm wont give u much flutter
cheers
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Location:
u.s.a. south
Registered:
April 2004
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Re: map vs. afm?
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Wed, 13 October 2004 23:26
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I've seen bov wreak havoc on hi-boost vafm cars. No fun when u don't have a lot of spares to source.
Seen excellent results from map + piggyback on turbocharged gze & ge.
My buddy dumped his gze vafm electronics for na 4age map electronics + piggyback tuning. On a t3 turbo, its still spinning the rear wheels thru second and third gear, automatic tranny. Runs flawless on 440s.
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Location:
South Australia
Registered:
July 2002
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Re: map vs. afm?
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Thu, 14 October 2004 02:37
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| Quote: |
I've seen bov wreak havoc on hi-boost vafm cars
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Err - how?
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Location:
u.s.a. south
Registered:
April 2004
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Re: map vs. afm?
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Thu, 14 October 2004 06:32
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somehow shockwaves between the turbo inlet/vafm was still too violent for the afm door/spring assy (as explained to me). This is at 24+ psi, while trying settings on different bovs. Did it on the toyota (and a ford 2.3 T4@28psi/same type vafm).
My buddy solved the toyota prob by going map na 4ag elctronics + piggyback tuning. Doesn't run the oe map sensor either. I didn't investigate the vafm any further... too impressed with the way the map + piggyback runs. He gave me a spare complete map setup from a 4age motorset also
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