Attn MAF users
03-14-2005, 01:31 PM
#32
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I would suppose a MAF and signal conditioner would not affect the timing. If the MAF signal is conditioned to be what an AFM signal would also be at the same flow, then the load factor in the DME would also be the same, and thus the timing. This assumes temperature is out of the equation.
Now if you change the injectors and hope to compensate by scaling the measured airflow back as well, you will probably reduce the 'load' the DME sees. Would the timing advance? It might, at lighter loads. It might think you are at cruise using 40HP when you are actually climbing a hill using 56 HP and rather than having full advance for fuel economy you need a bit less. The knock sensors should kick in but that might not be the best way to live.
-Joel.
Now if you change the injectors and hope to compensate by scaling the measured airflow back as well, you will probably reduce the 'load' the DME sees. Would the timing advance? It might, at lighter loads. It might think you are at cruise using 40HP when you are actually climbing a hill using 56 HP and rather than having full advance for fuel economy you need a bit less. The knock sensors should kick in but that might not be the best way to live.
-Joel.
03-14-2005, 01:36 PM
#33
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Posted by J Chen:Thanks Jimbo. Contrary to what has been posted,
how do you know that timing is not compromise
when massaging the signal ?
When you massage a signal you compromise timing. The whole point of getting a maf meter sized to your injectors is to spread the timing by 37% evenly. The timing will be very close at all rpms and load points. You will have to massage the signal in some areas even with this method. But it's very minimal. I have my piggy back set to 10 witch is 0 adjustment. My fuel and timing is almost spot on. The car runs and drives like stock. I have a psc1 maf to afm piggyback. It differs from the arc2 that you have because it has a barometric sensor built in. The arc 2 has problems with cold starts and idle because it doesn't have one. But I must say that I have dialed in a pretty good fuel curve with one. As long as your climate doesn't change to harshly you can still use it with no major problems. The psc1 is superior because it can fine tune at every load point between 0.0 to 5.0 I will have to make minimal adjustments for it to be perfect. If I am at 0 and the fuel is on. What does that tell you about the timing?
how do you know that timing is not compromise
when massaging the signal ?
When you massage a signal you compromise timing. The whole point of getting a maf meter sized to your injectors is to spread the timing by 37% evenly. The timing will be very close at all rpms and load points. You will have to massage the signal in some areas even with this method. But it's very minimal. I have my piggy back set to 10 witch is 0 adjustment. My fuel and timing is almost spot on. The car runs and drives like stock. I have a psc1 maf to afm piggyback. It differs from the arc2 that you have because it has a barometric sensor built in. The arc 2 has problems with cold starts and idle because it doesn't have one. But I must say that I have dialed in a pretty good fuel curve with one. As long as your climate doesn't change to harshly you can still use it with no major problems. The psc1 is superior because it can fine tune at every load point between 0.0 to 5.0 I will have to make minimal adjustments for it to be perfect. If I am at 0 and the fuel is on. What does that tell you about the timing?
03-14-2005, 01:46 PM
#34
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Hi Jimbo,
Thanks again for the info. I have installed a temperature
sensor that connects to the original AFM connector. Does
that qualifies as a barometic sensor ?
Thanks again for the info. I have installed a temperature
sensor that connects to the original AFM connector. Does
that qualifies as a barometic sensor ?
03-14-2005, 01:47 PM
#35
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Originally Posted by special tool
And that last post proves that you have no idea what the hell you are talking about.
"Properly" installing a MAF on a 944 involves changes to the transfer function.
"Properly" installing a MAF on a 944 involves changes to the transfer function.
03-14-2005, 02:21 PM
#36
"I don't want to be a wise guy, but isn't the transfer function the same as an A/D converter? An A/D converter uses a formula (= transfer function) to translate 1 or more analog signals to a digital signal."
The A/D converter in the DME just converts the analog 0-5 volts to an 8 bit digital number
(2 to eighth (256) possibilties/levels). It DOESN'T do any of the so-called translations, that's
done by the u-processor in the DME. The key translation converts the voltage provided
by the MAF & converted to digital by the A/D to a load value. As an example, a 2.5 volt
AFM value may represent 45% load and a MAF of 2.5 volts may represent a 35% load.
So if the load table in the EPROM is not modified for the MAF voltage of 2.5 (in digital),
then the DME thinks the load is 45% when actually it's really 35%.
There's nothing complex about this process. The other approach makes the
translation at the input to the DME unit by converting the MAF voltage to a AFM
voltage that represents the correct load value. This, though, is not the best
approach because it requires a lot of tweaking (pots) and usually results in "holes"
in the load tables causing non-optimum torque curves.
Bottomline: The MAF supplier should be able to supply an EPROM to make the proper
translations. Some of the Rennlist sponsors may have this capability or a standard product.
The A/D converter in the DME just converts the analog 0-5 volts to an 8 bit digital number
(2 to eighth (256) possibilties/levels). It DOESN'T do any of the so-called translations, that's
done by the u-processor in the DME. The key translation converts the voltage provided
by the MAF & converted to digital by the A/D to a load value. As an example, a 2.5 volt
AFM value may represent 45% load and a MAF of 2.5 volts may represent a 35% load.
So if the load table in the EPROM is not modified for the MAF voltage of 2.5 (in digital),
then the DME thinks the load is 45% when actually it's really 35%.
There's nothing complex about this process. The other approach makes the
translation at the input to the DME unit by converting the MAF voltage to a AFM
voltage that represents the correct load value. This, though, is not the best
approach because it requires a lot of tweaking (pots) and usually results in "holes"
in the load tables causing non-optimum torque curves.
Bottomline: The MAF supplier should be able to supply an EPROM to make the proper
translations. Some of the Rennlist sponsors may have this capability or a standard product.
Last edited by Lorenfb; 03-14-2005 at 02:46 PM.
03-14-2005, 03:01 PM
#38
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posted by J Chen: Hi Jimbo,
Thanks again for the info. I have installed a temperature
sensor that connects to the original AFM connector. Does
that qualifies as a barometic sensor ?
No. I wouldn't use it because the temp sensor was used on a afm to detect temperature changes. The barn door can't detect denser air on it's own. The maf has a hot wire that already takes care of temp function. Using it will throw things off. The problem with past maf to afm conversions was that they lacked barometers to compensate for atmospheric conditions. That's why most had problems with settings changing every other day.
Posted by Lorenfb: The A/D converter in the DME just converts the analog 0-5 volts to an 8 bit digital number
(2 to eighth possibilties/levels). It DOESN'T do any of the so-called translations, that's
done by the u-processor in the DME. The key translation converts the voltage provided
by the MAF & converted to digital by the A/D to a load value. As an example, a 2.5 volt
AFM value may represent 45% load and a MAF of 2.5 volts may represent a 35% load.
That's why they sell piggy backs that transfer the maf signal to afm signal before it reaches the dme.
Vittesse also sells a chip that has the voltage characteristics of a particular maf meter burned to a chip to mate up timing and fuel. I must admit this is very creative. But both will do the same job.
Thanks again for the info. I have installed a temperature
sensor that connects to the original AFM connector. Does
that qualifies as a barometic sensor ?
No. I wouldn't use it because the temp sensor was used on a afm to detect temperature changes. The barn door can't detect denser air on it's own. The maf has a hot wire that already takes care of temp function. Using it will throw things off. The problem with past maf to afm conversions was that they lacked barometers to compensate for atmospheric conditions. That's why most had problems with settings changing every other day.
Posted by Lorenfb: The A/D converter in the DME just converts the analog 0-5 volts to an 8 bit digital number
(2 to eighth possibilties/levels). It DOESN'T do any of the so-called translations, that's
done by the u-processor in the DME. The key translation converts the voltage provided
by the MAF & converted to digital by the A/D to a load value. As an example, a 2.5 volt
AFM value may represent 45% load and a MAF of 2.5 volts may represent a 35% load.
That's why they sell piggy backs that transfer the maf signal to afm signal before it reaches the dme.
Vittesse also sells a chip that has the voltage characteristics of a particular maf meter burned to a chip to mate up timing and fuel. I must admit this is very creative. But both will do the same job.
03-14-2005, 03:16 PM
#39
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Originally Posted by Jfrahm
I would suppose a MAF and signal conditioner would not affect the timing. If the MAF signal is conditioned to be what an AFM signal would also be at the same flow, then the load factor in the DME would also be the same, and thus the timing. This assumes temperature is out of the equation.
Now if you change the injectors and hope to compensate by scaling the measured airflow back as well, you will probably reduce the 'load' the DME sees. Would the timing advance? It might, at lighter loads. It might think you are at cruise using 40HP when you are actually climbing a hill using 56 HP and rather than having full advance for fuel economy you need a bit less. The knock sensors should kick in but that might not be the best way to live.
-Joel.
Now if you change the injectors and hope to compensate by scaling the measured airflow back as well, you will probably reduce the 'load' the DME sees. Would the timing advance? It might, at lighter loads. It might think you are at cruise using 40HP when you are actually climbing a hill using 56 HP and rather than having full advance for fuel economy you need a bit less. The knock sensors should kick in but that might not be the best way to live.
-Joel.
03-14-2005, 03:17 PM
#40
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Originally Posted by Lorenfb
Bottomline: The MAF supplier should be able to supply an EPROM to make the proper
translations. Some of the Rennlist sponsors may have this capability or a standard product.
03-14-2005, 03:36 PM
#41
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Posted by Jfrahm: Now if you change the injectors and hope to compensate by scaling the measured airflow back as well, you will probably reduce the 'load' the DME sees. Would the timing advance? It might, at lighter loads. It might think you are at cruise using 40HP when you are actually climbing a hill using 56 HP and rather than having full advance for fuel economy you need a bit less. The knock sensors should kick in but that might not be the best way to live.
You are stretching the signal by 37% . You will not be off by 37% at the same load point. Take a 0.1 to 5.0 signal stretch it 37%. We are talking decimal points at most.
You are stretching the signal by 37% . You will not be off by 37% at the same load point. Take a 0.1 to 5.0 signal stretch it 37%. We are talking decimal points at most.
03-14-2005, 04:19 PM
#42
"Vittesse also sells a chip that has the voltage characteristics of a particular maf meter burned to a chip to mate up timing and fuel." - jimbo1111 -
the ideal & simplest approach -
the ideal & simplest approach -
03-14-2005, 05:23 PM
#44
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the ideal & simplest approach -
Not so.
Both methods work similar. Except with your method I have to buy a chip. With mine I don't. I could use the extra money I saved on a nice exhaust and know nobody has me by the ***** when it comes time to upgrade.
Not so.
Both methods work similar. Except with your method I have to buy a chip. With mine I don't. I could use the extra money I saved on a nice exhaust and know nobody has me by the ***** when it comes time to upgrade.
03-14-2005, 06:48 PM
#45
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Originally Posted by awilson40
This reminds me of that StarTrek episode where they were all stuck in a loop and kept repeating the same history over and over 