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Recap of the SAI circuit

 
Old 11-28-2011, 09:48 AM
  #361  
air993
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Lewis, do you have to clear out any codes before/after the installation or will this over ride any preexisting codes related to the SAI?
Lucas
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Old 11-28-2011, 07:27 PM
  #362  
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Originally Posted by air993 View Post
Lewis, do you have to clear out any codes before/after the installation or will this over ride any preexisting codes related to the SAI?
Lucas
I would defer to flying_low, as I don't work on these cars, nor do I have any OBD diagnostics tools.

My guess would be to clear the codes, since I doubt they would self clear after a few cycles (like some emission codes do, like loose gas caps).
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Old 11-28-2011, 07:33 PM
  #363  
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Just a quick 'theory of operation' for this circuit and implementation....

It can be thought of as a 1 input, 4 output electronic switch, nothing more than that.

When 12V is applied to the Blue wire and GND is applied the Grey wire (on the 2 terminals on the left side of the PCB), the signal is divided down and turns on the 4 FETs (field effect transistors) simultaneously.

A FET can be thought of as a simple voltage controlled switch.
With NO voltage applied (just sitting on your desk), if you took an ohmmeter, you would measure an OPEN circuit between any of the O2 (black wire) outputs and GND (grey wire, remember all 5 GND terminals are exactly the same), since the FET is "OFF"
With 12V applied, the same ohmmeter would now read a short circuit (actually about 1 ohm or so), since the FET is now "ON"

BTW, there is no magic to 12V, it could be 9V, it could be 18V .... it really doesn't matter. You can use any voltage source/battery to test the operation of the PCB out of the car.
If you damage an output FET, it is a simple matter to determine which one (using the above technique), and order/solder in a new one.

If anyone wants more in depth analysis (can't understand why), I would be more than happy to enter the schematic into LTSpice (free download program) and provide you the files so you could 'play' with the circuit on your computer.
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Old 11-28-2011, 07:43 PM
  #364  
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Thanks Lewis that helps. Cannot wait to quit seeing that check engine light!
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Old 11-28-2011, 08:25 PM
  #365  
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Default 28 November shipping list -- 19 units

Hi,
The following RL members' orders have been packaged and are going to the post office tomorrow morning (thanks again to my bride again for helping with logistics):

2ndof2
jaguarandi
deekay911
v33
beagling
richard lee
michaelh993
dan v
mike cap
southsong
911dave
pnogc2s
kraftsman
slapshot
nels415
bprasmsn.com
e3photo
tropheus
mdamen


These have been shipped based on first come/first served receipt of PM's with shipping info for those who are on the first list.

Please watch your mailbox for a 6x9 manila envelope from Massachusetts.
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Old 11-28-2011, 08:29 PM
  #366  
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Default Remaining open orders from first list

Hi,
If my list is correct, the following members have not provided mailing information; the units are assembled and waiting to be shipped.

TheBen
JPS
cdmdriver
SimonM_98
CAHRERA
sdrake
Matt Lane
Jim W
dbog
bootman

Please PM me:
Name
Street
City, State, Zip

I will try and ship the units out as soon as I have the information.

Happy Holidays.
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Old 11-28-2011, 10:28 PM
  #367  
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Received my units last week! Check was mailed today as first order of business after returning from holiday.

Many thanks, Lewis!

Tony
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Old 11-29-2011, 12:53 AM
  #368  
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Hi Lewis,
Was wondering if the one heading my way had an enclosure? I PM'd you a few days ago but didn't see the update on Ash's list. Either way, thanks for your efforts!
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Old 11-29-2011, 05:11 AM
  #369  
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Originally Posted by 2ndof2 View Post
Hi Lewis,
Was wondering if the one heading my way had an enclosure? I PM'd you a few days ago but didn't see the update on Ash's list. Either way, thanks for your efforts!
Unfortunately, no.
I believe your request for enclosure came after Ash closed the list and I had ordered parts.

In this thread, you can find a link to the enclosure, which you can purchase from Mouser Electronics (electronics distributor). I believe the enclosure is about $1.75 for a single piece, plus whatever they charge for shipping (which will unfortunately be much more than the cost of the unit)
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Old 11-30-2011, 07:43 PM
  #370  
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Originally Posted by air993 View Post
Lewis, do you have to clear out any codes before/after the installation or will this over ride any preexisting codes related to the SAI?
Lucas
The short answer is I don't know if the codes will clear once the circuit is installed. My suspicions say you will have to reset the CEL registers which will clear all the flags and start the testing cycle again.

I'm interested to know if someone has the CEL turn off and how long it takes after connecting the circuit.
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Old 11-30-2011, 10:32 PM
  #371  
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Flying low,
I plan to have the codes cleared, but if they turn off before I will let ya'll know. I have only driven a few miles since installation, but nothing yet!
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Old 12-01-2011, 07:06 PM
  #372  
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Default 01 December shipments -- 1 unit

JPS
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Old 12-01-2011, 07:08 PM
  #373  
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In anyone needs any additional screws (PCB mounting or enclosure cover), I have some left over.

Just send a PM with what screws you need and I will send them in a small envelope.
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Old 12-02-2011, 08:38 PM
  #374  
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Lewis,
Thank you for replying to my earlier post but could I get on the second list? Also, did anyone verify if this will work on a 97 993 (see end of my post) ?

I am in a state of indecision right now given I pulled the motor out of 97 993 thinking I could just clear the ports but it looks like 2 of them are fully clogged and one is still slightly clogged. Since I live in California I have to get rid of the P0410 check engine light problem. Which means I am probably going to have to remove the heads, send them out to be cleaned and then drill out the carbon. My car does not really burn oil so the valve guides are still good. I might find that not to be true (78K miles) and will end up doing a top end job - never did one on a porsche motor. A bit more then I was looking to invest in (time and dollars) given I travel for work a lot and that means my car will be off the road for some time now. Maybe I should just "suck it up :-)

From what I can see from earlier posts is everything I need from a parts list perspective in the following to attempt to build this myself if you never get to the "second list" - assuming I go to Radio Shack with printed PDFs and order the enclosures in the links you provided (see below) ?

RL_993_SAI_AW.pdf
RL_993_SAI_SCH.pdf

Link to the enclosures:
http://www.mouser.com/Search/Product...y546-1551RFLGY

Link to the PCB mounting screws:
http://www.mouser.com/Search/Product...546-1551ATS100

Link to the enclosure cover screws:
http://www.mouser.com/Search/Product...y546-1591TS100

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.

(BTW: a MaxJax is a really good investment if you have the cash - www.maxjaxusa.com)
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Old 12-03-2011, 08:05 PM
  #375  
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Hey Guys,

I signed up for one of these and I hope it is not too late to cancel my order. If not I will be glad to pay for it and offer it up to someone else that needs it. Just let me know what I need to do. Sorry for the confussion - just decided to go another way instead of buying another 993.

Thanks all,

Tim
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