Question about AFR tuning and WOT..
11-01-04, 09:55 PM
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777** The Anti-rice
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Question about AFR tuning and WOT..
So...i learned in my automotive technology class WOT it doesnt really monitor the fuel thats going into the engine , it closes off vacuum and just dumps fuel in at full injector/fp capacity.
Is this true with rotaries/RX7's as well? and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
Is this true with rotaries/RX7's as well? and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
11-01-04, 10:25 PM
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Originally Posted by DEZERTE
So...i learned in my automotive technology class WOT it doesnt really monitor the fuel thats going into the engine , it closes off vacuum and just dumps fuel in at full injector/fp capacity.
Is this true with rotaries/RX7's as well? and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
Is this true with rotaries/RX7's as well? and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
11-01-04, 10:44 PM
#4
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Originally Posted by DEZERTE
So...i learned in my automotive technology class WOT it doesnt really monitor the fuel thats going into the engine , it closes off vacuum and just dumps fuel in at full injector/fp capacity.
Is this true with rotaries/RX7's as well? and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
Is this true with rotaries/RX7's as well? and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
11-01-04, 10:53 PM
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777** The Anti-rice
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Maybe I misunderstood or something, cuz the guy is pretty knowledgable.
So is there a difference in WoT vs not WoT as far as AFR's go? And do people usually tune the SAFC for WoT?
So is there a difference in WoT vs not WoT as far as AFR's go? And do people usually tune the SAFC for WoT?
Last edited by DEZERTE; 11-01-04 at 10:58 PM.
11-01-04, 10:54 PM
#6
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Originally Posted by DEZERTE
So...i learned in my automotive technology class WOT it doesnt really monitor the fuel thats going into the engine , it closes off vacuum and just dumps fuel in at full injector/fp capacity.
Is this true with rotaries/RX7's as well?
Once the ECU knows you're at heavy load (i.e. WOT), it reverts to a fuel map.
This fuel map uses the air flow meter is it's primary load sensor.
So, the ECU knows how fast the engine is spinning (i.e. RPM's via the CAS) and how much air it's ingesting (the AFM), it goes through a look-up table (i.e. the fuel map) to calculate the proper fuel injection duration.
and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
The AFM is the primary load sensor for the FC3S.
This is another question, but not as important as the first: Can you tune the SAFC2 for both low throttle and high throttle, or does it matter.
I would concentrate on the high throttle stuff first.
-Ted
11-01-04, 10:57 PM
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Originally Posted by RETed
That's a very rough description of what is happening.
It is to a point.
Once the ECU knows you're at heavy load (i.e. WOT), it reverts to a fuel map.
This fuel map uses the air flow meter is it's primary load sensor.
So, the ECU knows how fast the engine is spinning (i.e. RPM's via the CAS) and how much air it's ingesting (the AFM), it goes through a look-up table (i.e. the fuel map) to calculate the proper fuel injection duration.
See above - the S-AFC adjusts the AFM signal.
The AFM is the primary load sensor for the FC3S.
I don't think the low throttle is as important at the high throttle settings.
I would concentrate on the high throttle stuff first.
-Ted
It is to a point.
Once the ECU knows you're at heavy load (i.e. WOT), it reverts to a fuel map.
This fuel map uses the air flow meter is it's primary load sensor.
So, the ECU knows how fast the engine is spinning (i.e. RPM's via the CAS) and how much air it's ingesting (the AFM), it goes through a look-up table (i.e. the fuel map) to calculate the proper fuel injection duration.
See above - the S-AFC adjusts the AFM signal.
The AFM is the primary load sensor for the FC3S.
I don't think the low throttle is as important at the high throttle settings.
I would concentrate on the high throttle stuff first.
-Ted
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11-02-04, 05:21 PM
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Originally Posted by DEZERTE
So...i learned in my automotive technology class WOT it doesnt really monitor the fuel thats going into the engine , it closes off vacuum and just dumps fuel in at full injector/fp capacity.
The fuel dump is usually called acceleration enrichment, which is just a way for the ECU to fudge the amount of extra fuel needed under acceleration. I don't know of any systems that dump the fuel at the full rate, but I guess you could look at it that way to simplify the process. Anyway, this enrichment is added to injector pulse width specified in the ECU base fuel map, as the base fuel map is only set up for static conditions (constant load and constant rpm). The faster the acceleration, the more enrichment is added to the base map injector pulse width value.
The throttle position sensor (TPS) is usually used to determine the acceleration value, so this is usually what controls the acceleration enrichment. If the TPS is not very accurate (S4 RX-7), and more like an on/off switch, then the ECU will not be able to have a very refined acceleration enrichment function. If the TPS sends a more refined signal (S5 RX-7), then the acceleration enrichment can also be more refined. The refined signal allows for better on/off throttle, partial throttle, and gradual throttle changes. The advantage to more accurate acceleration enrichment is that smoothness and power are increased because too rich of a mixture will cause the engine to bog a bit, and a less-accurate acceleration system is usually set a bit on the rich side just to be safe against a possible lean situation.
Originally Posted by DEZERTE
and if this is true, how are you supposed to tune the SAFC or whatever for WOT when the car doesnt give a **** either way and lets the fuel flow at full injector capacity?
However, in the case of a generic EMS application, you would first set up a static fuel map (usually on the dyno). Then, you would make acceleration runs to set the acceleration enrichment. The acceleration enrichment is a little more difficult to set, and usually requires a knowledgeable tuner.
11-02-04, 09:37 PM
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Originally Posted by DEZERTE
So...i learned in my automotive technology class WOT it doesnt really monitor the fuel thats going into the engine , it closes off vacuum and just dumps fuel in at full injector/fp capacity.
On a stock engine, if the car was run WOT and the EFI actually went 100% duty on the injectors, the car would just stall and die and if its a rotary, probably flood itself, heh. I doubt our injectors on a stock rotary see over 70ish% Duty cycle @ WOT... STOCK.
EDIT: well damn... the above post sounds smarter than mine, read it.
Last edited by Kenteth; 11-02-04 at 09:40 PM.
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