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Recap of the SAI circuit

Old 09-15-2011, 01:56 PM
  #61  
tropheus
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I'm signing up for 2 assembled.

Jack
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Old 09-15-2011, 04:09 PM
  #62  
NP993
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Originally Posted by Lorenfb View Post
"Why does that mean we can't remove the SAI pump and system from our cars?"

Yes, you could remove just the pump, but why? When you remove system
components, it no longer looks stock, i.e. A possible future sale or an
overly committed emissions inspector/tester.
Ah, okay. So what you originally said is not correct. Thanks for clarifying.
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Old 09-15-2011, 04:14 PM
  #63  
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I'm also in for two units. Rennlist is a great place... Thanks
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Old 09-15-2011, 05:02 PM
  #64  
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I'm in for one. I can compare it to my "home made" version.

I loved those Heathkits!
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Old 09-15-2011, 05:08 PM
  #65  
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+1
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Old 09-15-2011, 05:21 PM
  #66  
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Count me in too pls.
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Old 09-15-2011, 09:30 PM
  #67  
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add another one to the list! I'm in.
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Old 09-15-2011, 09:36 PM
  #68  
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wasn't there a thread awhile back about same that was removed as it was possibly not legal especially for states with smog refs....
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Old 09-15-2011, 09:39 PM
  #69  
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Originally Posted by 600RR View Post
Despite being responsible for every problem in every early CS, Lewis is great. Take that PCNA!
Problems or Easter Eggs...it's a fine line
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Old 09-15-2011, 11:09 PM
  #70  
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+1
I sent you a pm earlier... please count me in for one on the first batch !

thanks !...and....very cool.
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Old 09-16-2011, 08:10 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
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Old 09-16-2011, 08:41 AM
  #72  
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Default SAI

Please add me to the list.

Thanks
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Old 09-16-2011, 10:10 AM
  #73  
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Originally Posted by aaronutk View Post
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
I was going to use old school through hole parts, simply because it makes it easier for DIY soldering.
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)
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Old 09-16-2011, 10:32 AM
  #74  
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"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.

Last edited by Lorenfb; 09-16-2011 at 11:46 AM.
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Old 09-16-2011, 01:21 PM
  #75  
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Originally Posted by Lorenfb View Post
...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..
It would be a simple circuit to design for this (voltage change), assuming the voltage levels were provided.
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