MAP vs AFM (splitted from smallport sale topic)

[krijn]

looks like an AFM? Shouldn't this be a MAP based engine?

[banpei]

Well, the seller mentions it is a non-tvis 4age but you will never know for sure. One way to find out: contact the owner.
Krijn: the inlet is different and doesn't have a variable inlet system, so the only thing you care about then is the airflow, thus the engine needs an airflow meter.

[SutteR]

banpei the smallport version also is available with MAP. Don't ask me about which were for which market I don't know for sure. I'm only sure that I've just bought a MAPped smallport from GB.

[banpei]

SutteR Wrote:banpei the smallport version also is available with MAP. Don't ask me about which were for which market I don't know for sure. I'm only sure that I've just bought a MAPped smallport from GB.

Ofcourse the MAP is very possible on a non t-vis system, but the t-vis system needs a more complex calculation thus the map system is more efficient for the tvis system. The afm system is simpler and cheaper so for a non t-vis system it would be expected to have an afm.

[SutteR]

Some people might agree with you but I'm happy with that MAPped smallport. The AFM versions have the EGR valve and the O2 sensor and such things to reduce the power output in order to save the nature...

[SekiguchiUeno]

banpei Wrote:

SutteR Wrote:banpei the smallport version also is available with MAP. Don't ask me about which were for which market I don't know for sure. I'm only sure that I've just bought a MAPped smallport from GB.

Ofcourse the MAP is very possible on a non t-vis system, but the t-vis system needs a more complex calculation thus the map system is more efficient for the tvis system. The afm system is simpler and cheaper so for a non t-vis system it would be expected to have an afm.

banpei are you sure about this? writing mistakes happens, but is hard for beginners to select whats true and whats not, when they come here and search for info

[NoHachi]

Very subtle Sekiguchi...I like it. (You're right by the way)

[banpei]

SekiguchiUeno Wrote:

banpei Wrote:Ofcourse the MAP is very possible on a non t-vis system, but the t-vis system needs a more complex calculation thus the map system is more efficient for the tvis system. The afm system is simpler and cheaper so for a non t-vis system it would be expected to have an afm.

banpei are you sure about this? writing mistakes happens, but is hard for beginners to select whats true and whats not, when they come here and search for info

Well, this is getting a bit too offtopic this way. So I decided to split the topic.

From what I understood the equations on AFM are simpler than on MAP:

- AFM measures the air flow, thus measuring the air volume and temperature you know what airmass entered the engine
- MAP measures the manifold pressure and combined with temperature and knowing how large the intake is you crudly know what airmass entered the engine

AFM has the drawback it actually needs the air to push a flap which measures the airflow, thus slowing down the air.
MAP has the drawback you need to do more calculations and the old ECUs don't have the power to do such math, thus using lookup tables

Given the t-vis system it opens the extra butterflies when the engine needs more air, thus sucking in more air. The ecu needs to pick this up and see how much air entered the engine but since the AFM system actually needs to pick up on the increased airspeed the MAP system should be more responsive in picking up the dropped pressure.

For a non t-vis system you don't have a sudden drop in pressure, so a AFM should be sufficient enough.

Then again: I'm no engine expert and this is just knowledge I picked up by reading stuff about engines. Correct me if I'm wrong, I'm glad to learn.

[NoHachi]

With an AFM you measure the exact amount of air going into the engine at any time. From a systems controll standpoint it is vastly superior over MAP, no conversions to be done, no corrections, no mistakes.
TVIS opening might cause a leanspot due to throttle body dynamics (where the non-compressible fluid assumption goes overboard) but that would be easy to iron out by enrichening or compensating around the correct RPM.

[banpei]

I agree with you that the AFM is superior over the MAP on all points you give there, and you can indeed compensate for that taking the throttle position in account.

However the AFM of the hachi does not measure the exact amount of air, it measures the volume. So you still have to do a conversion on that against the temperature.