SAI bypass circuit
01-31-2006, 09:24 PM
#31
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Okay, but the circuit still doesn't look like it will work with those diodes.
The other issue with the circuit is what is the amount of current that you are clamping? It looks like you are shorting an active sensor. That is, you may draw too much current in the first circuit, and the second circuit will not clamp enough with the steering diodes in place.
The other issue with the circuit is what is the amount of current that you are clamping? It looks like you are shorting an active sensor. That is, you may draw too much current in the first circuit, and the second circuit will not clamp enough with the steering diodes in place.
Originally Posted by hoggel
Doh!! I typed it wrong as you suspected. A lean condition is <.45 Volts. I corrected my original post.
01-31-2006, 09:42 PM
#32
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Originally Posted by Marv
Okay, but the circuit still doesn't look like it will work with those diodes.
The other issue with the circuit is what is the amount of current that you are clamping? It looks like you are shorting an active sensor. That is, you may draw too much current in the first circuit, and the second circuit will not clamp enough with the steering diodes in place.
The other issue with the circuit is what is the amount of current that you are clamping? It looks like you are shorting an active sensor. That is, you may draw too much current in the first circuit, and the second circuit will not clamp enough with the steering diodes in place.
However, does anyone have any specs for the O2 sesnors? I would also worry about the current draw.
I have a car with the SAI CEL, and will definately will be trying this soon. It would be nice to see if there is a cleaner way to install everything, without the T's.
01-31-2006, 10:02 PM
#33
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I am a big fan of clean air so I would like to keep the SAI functional. But the Porsche bad design of the ports needs a remedy. I would certainly not criticize anyone who kluged the system. The pressure is off me (pun intended) since I found my CEL was not clogged ports.
I'm going to look into a mechanical bypass in case the clogged ports issue come up later in the life of my car. I think a thin plate between the head and the heat exchanger could accomodate ports with enough airflow to keep the system operating. The air line could be disconnected where it routes into the cam carrier and connected to a custom manifold that would feed the plate.
I'm going to look into a mechanical bypass in case the clogged ports issue come up later in the life of my car. I think a thin plate between the head and the heat exchanger could accomodate ports with enough airflow to keep the system operating. The air line could be disconnected where it routes into the cam carrier and connected to a custom manifold that would feed the plate.
02-18-2006, 04:31 PM
#36
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You guys are great. Been following this thread (and others) with great interest.
The circuit seems simple enough, but what is the existing circuit like (before the mod)? IOW, where do the O2 sensors go in an unmodified car?
Am I correct that pin 3 of the O2 sensors are tied to ground (perhaps directly through the exhaust piping) and pin 4 is the sensor's signal (voltage source)?
I like the circuit with the 4 transistors because I think this one will do the best job of shunting the sensor's voltage to ground. The other one with the single transisitor and 4 isolation diodes may not pull the signal low enough.
Also, does anybody have any idea how much current needs to be sunk??? I imagine the O2 sensors, being active devices, don't produce a significant amount of current and the 4 transistors might be replaced with a CMOS integrated circuit.
Finally, where exactly in the car would this device have to be located??? Just trying to figure out where it would have to be spliced into the wiring harness.
Thanks all.
993's forever and death to the EPA. Anarchy now!!!
The circuit seems simple enough, but what is the existing circuit like (before the mod)? IOW, where do the O2 sensors go in an unmodified car?
Am I correct that pin 3 of the O2 sensors are tied to ground (perhaps directly through the exhaust piping) and pin 4 is the sensor's signal (voltage source)?
I like the circuit with the 4 transistors because I think this one will do the best job of shunting the sensor's voltage to ground. The other one with the single transisitor and 4 isolation diodes may not pull the signal low enough.
Also, does anybody have any idea how much current needs to be sunk??? I imagine the O2 sensors, being active devices, don't produce a significant amount of current and the 4 transistors might be replaced with a CMOS integrated circuit.
Finally, where exactly in the car would this device have to be located??? Just trying to figure out where it would have to be spliced into the wiring harness.
Thanks all.
993's forever and death to the EPA. Anarchy now!!!
02-18-2006, 04:38 PM
#37
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I am just waiting for the hammer to drop....this bloody damn
SAI just cost me close to $2,800 the past few months. 1st I did a pre-emptive SAI valve change...a month later the air mainfold the SAI sits in blew a freeze plug, fried the new SAI and one of those cheesy chrome air lines broke off....that fix was closer to $1,300 + the first fix...
Now I find out because the air conditioning compressor has been slammed around so many times being loosed up to get at the SAI, an airconditioner hose is broken...the cost of the hose. $600, + 3 to 4 hours of labor to put it all together again.
If some electronic fix come along, I am on for it!
This nickel dime crap keeps coming up. I hate it!
Now I find out because the air conditioning compressor has been slammed around so many times being loosed up to get at the SAI, an airconditioner hose is broken...the cost of the hose. $600, + 3 to 4 hours of labor to put it all together again.
If some electronic fix come along, I am on for it!
This nickel dime crap keeps coming up. I hate it!
02-19-2006, 02:20 PM
#39
I'm in for sure. My back is killing me, my fingers are torn up- all from trying to remove that stupid valve. I've modified a 1 inch crow's foot and seem to have a good grip on the valve, I've been soaking it with pb blaster and AeroKroil.
Here's the best way I can get grip on the valve, sorry if the photos don't show much. I'd appreciate any ideas. If I'm applying pressure in the wrong way, please let me know. I needed a 1/2 inch drive socket wrench to get the extension in the right place, the breaker bar would not allow me to place it in the right spot. The red arrow just points to the one air injection line that keeps me f rom putting the crow's foot in that area, seems like it has to be place from the rear of the valve to grab the valve and not grab anything else...
Sorry, no intention of hijacking this thread, just thought this might be a good place to ask this question. Thanks
Here's the best way I can get grip on the valve, sorry if the photos don't show much. I'd appreciate any ideas. If I'm applying pressure in the wrong way, please let me know. I needed a 1/2 inch drive socket wrench to get the extension in the right place, the breaker bar would not allow me to place it in the right spot. The red arrow just points to the one air injection line that keeps me f rom putting the crow's foot in that area, seems like it has to be place from the rear of the valve to grab the valve and not grab anything else...
Sorry, no intention of hijacking this thread, just thought this might be a good place to ask this question. Thanks
02-19-2006, 03:27 PM
#40
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Originally Posted by CentralCoastC4S
I'm in for sure. My back is killing me, my fingers are torn up- all from trying to remove that stupid valve. I've modified a 1 inch crow's foot and seem to have a good grip on the valve, I've been soaking it with pb blaster and AeroKroil.
Here's the best way I can get grip on the valve, sorry if the photos don't show much. I'd appreciate any ideas. If I'm applying pressure in the wrong way, please let me know. I needed a 1/2 inch drive socket wrench to get the extension in the right place, the breaker bar would not allow me to place it in the right spot. The red arrow just points to the one air injection line that keeps me f rom putting the crow's foot in that area, seems like it has to be place from the rear of the valve to grab the valve and not grab anything else...
Sorry, no intention of hijacking this thread, just thought this might be a good place to ask this question. Thanks
Here's the best way I can get grip on the valve, sorry if the photos don't show much. I'd appreciate any ideas. If I'm applying pressure in the wrong way, please let me know. I needed a 1/2 inch drive socket wrench to get the extension in the right place, the breaker bar would not allow me to place it in the right spot. The red arrow just points to the one air injection line that keeps me f rom putting the crow's foot in that area, seems like it has to be place from the rear of the valve to grab the valve and not grab anything else...
Sorry, no intention of hijacking this thread, just thought this might be a good place to ask this question. Thanks
Looks about right to me. Couple of things you might try...
1. Why does the extension junction look like it is a swivel/universal joint? You want to try to keep the pressure that is exerted as direct (90 degrees) to the crowsfoot as possible. It does take a great amount of force to break that corroded joint loose.
2. You are turning so the bar is traveling towards the fender(counter clockwise), correct? lefty loosey, righty tighty??? Sorry for asking the obvious. Others have added that sometimes trying to tighten it a bit, then loosening will sometimes help to "break" the joint loose. Mine wasn't all that difficult to remove, but it did require sufficient force and a repositioning of the crows foot on the valve base a couple of time to get things lined up just right to apply the force needed.
3. Put a blanket or towel on the fender to protect it so if it does break loose suddenly you don't end up with a nice gouge mark from the beaker bar in your fender.
4. How long have you soaked the valve w/ penetrant? If less than a couple of hours, you might want to liberally spray the base of the SAI valve again and let it soak for a few hours before retrying.
5. Watch out not to apply pressure to that pipe that is arrowed in the picture. It is connected to the SAI valve manifold and have been known to crack if pressure is applied to it when turning the extension bar. Beware.
Good luck... let us know how it turns out.
02-19-2006, 03:50 PM
#41
Kelly, thanks for your response. Agree on the extension, I'm going to change that one out for a straight non-wobble extension. Yes, the force will be going toward the fender and I'm going to place towels as you mentioned, makes good sense. I've been adding the penetrant for about 4 days now, just not sure how much of it is getting to the threads...
I've narrowed the crow's foot down to the point where it's contacting only the
valve and not the body of the manifold but it's so hard to see down in there that
you really have to be careful. I'd rather not replace that manifold.
I'll keep you posted. It's a nerve-wracking job, not enjoying it that much!
I've narrowed the crow's foot down to the point where it's contacting only the
valve and not the body of the manifold but it's so hard to see down in there that
you really have to be careful. I'd rather not replace that manifold.
I'll keep you posted. It's a nerve-wracking job, not enjoying it that much!
...go ... go ....go. 
02-19-2006, 07:51 PM
#44
Still working on the valve, as I apply pressure with the breaker bar I can detect deflection of the entire aluminum manifold and that makes me a little nervous.
What would you guys think of cutting off the valve just above the 27mm nut using a dremel cut-off wheel? I realize that particles from the cutting process would probably go down into the manifold, what if vacuum was applied to the upper end of the valve to counteract that tendancy? I'm just a bit paranoid about breaking the manifold, my valve seems frozen in place.
Of course and engine drop would work as well and probably is not a bad idea, just exploring all my options before I do something that might require
CPR....
What would you guys think of cutting off the valve just above the 27mm nut using a dremel cut-off wheel? I realize that particles from the cutting process would probably go down into the manifold, what if vacuum was applied to the upper end of the valve to counteract that tendancy? I'm just a bit paranoid about breaking the manifold, my valve seems frozen in place.
Of course and engine drop would work as well and probably is not a bad idea, just exploring all my options before I do something that might require
CPR....