Recap of the SAI circuit
09-15-2011, 03:09 PM
#62
Ah, okay. So what you originally said is not correct. Thanks for clarifying.
09-15-2011, 08:30 PM
#67
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add another one to the list! I'm in.
09-15-2011, 08:39 PM
#69
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09-16-2011, 07:10 AM
#71
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Lewis,
Are you looking at doing surface mount (smaller) or through-hole parts? What CAD are you using for the layout, and could you release the layout files (Gerbers?) for the PCB when your done so others can make more later if needed?
Thanks,
Aaron
Are you looking at doing surface mount (smaller) or through-hole parts? What CAD are you using for the layout, and could you release the layout files (Gerbers?) for the PCB when your done so others can make more later if needed?
Thanks,
Aaron
09-16-2011, 09:10 AM
#73
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Since this is a quick project, I was just going to use Advanced Circuits PCB Artist for both schematic capture and layout, which is a free download. Ive used it a couple of times and haven't had any issues.
Again, I am doing this for the DIY aspect to help those troubleshoot their SAI, it is not meant to circumvent or violate any emissions laws or regulations. It is simply a toolbox item for RL members who work on their own cars.
I have no intention of making a single penny of profit from this project, and I will gladly distribute the design files and bill of material (which will be sourced from DigiKey)
09-16-2011, 09:32 AM
#74
"Ah, okay. So what you originally said is not correct."
Not really! You need to re-read your question and my response.
"does this enables us to physically remove the SAI system from our cars, including the OBDII ones,"
"No! All it does is fool/mis-represent what the O2 sensors 'see' when the
SAI air pump turns 'on', i.e. It basically indicates that an adequate amount
of air is reaching the O2 sensors during a cold start-up. "
The SAI system includes the not only the air pump but:
1. the O2 sensors
2. the SAI monitor diagnostics within the ODBII system
3. the relay which turns the pump 'on' and the by-pass circuit
4. air valves
So one can't really remove the SAI system!!!!!!!!
Potential Problem with the proposed by-pass circuit:
On the '97/'98 DME ECM the SAI monitor may look for a voltage
change on the O2 sensors and NOT an immediate zero volts
from the O2 sensors with the by-pass circuit. So a SAI fault
still may occur.
Bottom line: Before asssuming that the by-pass circuit is the
end-all fix for ALL 993s, thorough testing needs to be done on
all 993s, i.e. Since later/early 993 DME ECMs had different OBDII
firmwares and thus the by-pass circuit may have different effects.
Furthermore, if the by-pass circuit is not grounded in the ideal location
or the circuit is not shielded from 'noise', the circuit may not function
properly and additionally cause the O2 sensors to provide erroneous
voltages, thereby causing additional fault codes.
Not really! You need to re-read your question and my response.
"does this enables us to physically remove the SAI system from our cars, including the OBDII ones,"
"No! All it does is fool/mis-represent what the O2 sensors 'see' when the
SAI air pump turns 'on', i.e. It basically indicates that an adequate amount
of air is reaching the O2 sensors during a cold start-up. "
The SAI system includes the not only the air pump but:
1. the O2 sensors
2. the SAI monitor diagnostics within the ODBII system
3. the relay which turns the pump 'on' and the by-pass circuit
4. air valves
So one can't really remove the SAI system!!!!!!!!
Potential Problem with the proposed by-pass circuit:
On the '97/'98 DME ECM the SAI monitor may look for a voltage
change on the O2 sensors and NOT an immediate zero volts
from the O2 sensors with the by-pass circuit. So a SAI fault
still may occur.
Bottom line: Before asssuming that the by-pass circuit is the
end-all fix for ALL 993s, thorough testing needs to be done on
all 993s, i.e. Since later/early 993 DME ECMs had different OBDII
firmwares and thus the by-pass circuit may have different effects.
Furthermore, if the by-pass circuit is not grounded in the ideal location
or the circuit is not shielded from 'noise', the circuit may not function
properly and additionally cause the O2 sensors to provide erroneous
voltages, thereby causing additional fault codes.
Last edited by Lorenfb; 09-16-2011 at 10:46 AM.
09-16-2011, 12:21 PM
#75
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It would be a simple circuit to design for this (voltage change), assuming the voltage levels were provided.