User 122821

There has been mixed results and I believe I know why now. It's working on my '96 and another '96 but failed after a month on another '97. I also know of another '96 which it does not prevent the CEL light. I suspect the '97 and '98 are more sensitive to reading out of it's expected range than '96.

I suspect the circuit is incomplete to simulate the SAI system in the 993. The circuit reduces the voltage of the O2 sensors sending back to the ECU. The circuit times the reduction by triggering when the air pump is activated. I see now that the SAI system also has input from vacuum controlled valve between the air pump and the SAI distribution block. I suspect their are conditions which the air pump is activated but the vacuum check valve is closed and blocking air into the SAI ports. In this case the ECU throws an error as it sees low O2 voltage due to the added circuit triggering but the ECU is not expecting low O2 voltage since the vacuum valve should be blocking the air.

It's just a theory. I wish I knew more about the ECU to improve this bypass SAI circuit.

ilko

Just FYI, on my car the circuit caused a CEL. I have a 12/95 build MY96 C4S.

I installed the box and after some driving I get a CEL with codes P1410 and P1411.

After disconnecting the box and clearing the codes all is well.

jaguarandi

Hey guys, I'll chime in on my results of having this circuit installed.

I currently have:
- a daily driver MY96 coupe
- CEL for code P1411

Before having the circuit installed, I would have to constantly clear the P1411 code with my OBD2 scanner after driving for a week or so.
I got it down to where I can drive for a week and get all my readiness codes to set, thus triggering the code P1411.

So after installing the circuit and triple checking all the connections were installed correctly I gave it a go with the following scenarios. These were the steps I took.

Scenario 1:
- CEL for code P1411 was lit.
- All readiness codes were set.
- Connected the installed circuit into the prong of the SAI pump relay.
- Drove for a week. CEL for code P1411 was still lit.
- Drove for a second and third week. CEL for code P1411 was still lit.
- So that did not work.

Scenario 2:
- CEL for code P1411 was lit.
- All readiness codes were set.
- Plugged in my OBD2 reader and erased all the codes.
- Connected the installed circuit into the prong of the SAI pump relay.
- Drove for a week or so. CEL for code P1411 did not light up.
- Drove for couple of months. CEL for code P1411 did not light up.
- I Plugged in my OBD2 reader each week. Did a scan. NO readiness codes were set. NOT A SINGLE ONE WAS SET for all the months I drove.
- It seems that my results were that this circuit prevented any readiness codes to be set. I usually get a few readiness codes to set after driving for a day or two. But when I had the circuit installed it prevented any readiness codes to set.

Scenario 3 (Works for me... sorta):
- CEL for code P1411 was lit.
- All readiness codes were set.
- Plugged in my OBD2 reader and erased all the codes.
- Disconnected the installed circuit from the prong of the SAI pump relay.
- Drove for a week with my OBD2 scanner connected and monitoring to make sure all my readiness codes were set.
(Thanks to another rennlist member, I found out there is a time frame where the SAI readiness code is set but does not trigger a CEL. This was how I passed smog for my previous years.)
- After all readiness codes were set, I stopped and switched off the car. Reconnected the power to the circuit.
(I had to try the steps above 2 or 3 times. The previous times, I drove a bit too much where the CEL for code P1411 came on.)
- Drove for a week or so, no CEL for code P1411.
- Drove for a few months or so, no CEL for code P1411.
- PASSED CA smog check
- Once I disconnected the circuit, and drove again my CEL for P1411 came on.

So my results were, I can pass smog if I time it right and connect the circuit right away after all the codes were set. In CA, you can have 2 readiness codes not set and still pass smog.

The only downside is if I have the circuit connected, I can't check if some other CEL comes up such as dead O2 sensors. It seems in my case, having the circuit installed stopped having any of my readiness codes to set.

Maybe I installed the circuit incorrectly, but it seems I'm not getting the same results of other people who posted their findings.

Hope this helps.

Nick

AceMckool

Dear All,
I spoke to my Avionic Technician today about the project, and he agreed to join me for the second batch.
I just emailed ITC and we are waiting for all the info.
Once we look at the details, I will post on this same list a plan to assemble, test and ship the units.
If you are interested, go ahead and email me at: dmoinier@vih.com with on the subject line the word; SAI Device Order.
I will publish in the near future an updated price for complete units.
Let me know if you have any questions.
Cheers.

tom97c4s

I am interested in a second batch. I thought there is a list on this thread already for people on the waiting list?

It seems that some modifications are in order before they are made

AceMckool

All,
From the last list of the second round from ASH post #431, dated 01/01/2012, for 40 interested is there a new list? Also those in that list and still interested can you please confirm by email with your shipping address at: dmoinier@vih.com
Thank you

GD993C4

e-mail sent.
Thank you for putting this together for us.

JB 911

email sent. Thanks for taking over.

MHO on the reason for minimal feedback on how the first 100 worked. Perhaps many buyers were like myself and didn't have a SAI CEL light but bought it for 'down the road' then never got a SAI or sold car etc...

craig001

I just found a SAI Cleaning Kit on Pelican - http://www.pelicanparts.com/cgi-bin/...0%3C%2Fspan%3E. Yes it is $105 but has a modified 27mm crowsfoot, adapters and a coiled hose in it. Since I do not have the ability to mod a crowsfoot this makes more sense for me if I go down this road. To add to this thread, I picked up one of the units from a RLer who bought two. I never had the SEL but could not get readiness codes to set with it in after my battery died over the winter. I am being told I need to drive the car to get it set. Oh well.

Wolfk

QUOTE:
"On cold start the fresh air from the secondary air pump creates a very lean condition at the pre cat O2 sensor. The ECU compensates by injecting more fuel resulting in a fuel rich condition in the exhaust from the head. That unburned fuel in the exhaust combines with the oxygen from the SAI system and burns thereby heating the catalyst quickly to operating temperature.

In an OBDII car the ECU checks for the presence of the pump. On cold start the ECU checks that the O2 sensor signal goes through the stoichiometric, lean, rich, stoichiometric cycle with the SAI."


Does this last sentence explain why the bypass electric circuit doesn't work?
Meaning, ECU is seeing the simulated lean condition from the bypass circuit, but the bypass circuit does not address rich and stoichiometric cycle that the ECU is also looking for.
By the way, I pulled the above quote from a thread dated from 2009.

993_Targa

HELP!
Anybody out there have a diagnostic device they would sell or loan out?

The dreaded P1411 code has my '97 targa sitting in my garage. My friend's 993 is also off the road and we would both really appreciate any help. We have a ODB2 scanners in hand and would quickly get the unit back to you.

Please PM me if you could help us get our cars back out on the road where they should be.

Jim
Seattle
'97 993 targa
zenith blue metallic/grey

Past stable:
'56 356a t1 lipstick red/red
'57 356a t2 aqua marine blue/red
'63 356b red/black
'74 911s silver/red
'83 911sc silver/black

william_b_noble

what more do you need than the scanner? remove the SAI valve and check it, pull manifolds and do the flow test on the ports and clean as the FAQ says and you are on the road again - I made some covers out of aluminum so I could "super pressurize" the system and that helped, you may want to do the same - pretty simple machine work

993_Targa

Well for starters this is the SAI circuit thread not the flush thread. Plus plugging in a simple little device would be the better option for me if it worked. However I would certainly agree with you if lived in sunny, warm bikini-filled California as you do my friend. Its still too cold, damp and rainy up here to be crawling around on a cold concrete floor snapping, drilling and tapping manifold bolts. I did actually change the SAI valve out (bad shape but did not resolve the problem unfortunately.)

I will however do as you suggest if this device thing doesn't pan out by the time the sun warms my bones a bit. Bikinis on roller skates listening to ipods... now that is some real motivation indeed to go for a cruise with the top down!

The "super pressurizing" is interesting though.
Did you happen to post some details and pics you could point me to?

Jim

william_b_noble

yes, RE ^^^ - sorry - I was confused by the request for a 'diagnostic device' - I am pretty sure that the magic circuit only works on the early 993s, it certainly did not work on my 97. I found a photo of the circuits I built, but the photos I took of the "superpressureizing" thing are hiding - I may have discarded them when my car was stolen - basically I machined some 3/8 aluminum plate to match the shape of the flanges on the manifold and bolted one over all but one exhaust port so that all the flow was pretty much forced to go through one port (some leaks past the exhaust valves into the cylinders and then out the air intake, of course). I used 160 PSI air for this - I think I posted the photos here too, but I couldn't find the thread. for some reason today I cannot upload any files - every file says "this is not a valid image file" - no matter what format nor size. anyway, I made an air hose adapter to attach where the SAI valve goes, and would pour some sea foam or other magic solvent into the SAI air passage and then apply pressure - I tried to set up a recirculating pump but the seafoam ate the pump and I gave up. Now my car is gone so I guess the good news is that it isn't my problem, though I did learn way too much about trying to fix it.

Lorenfb

"In CA, you can have 2 readiness codes not set and still pass smog."

A very common misconception about how the 993 OBDII system functions
and why that statement is inapplicable.

NONE of the readiness codes (monitors) will be set (appear to an OBDII scanner)
until all the 'trips' (minmum of two) are complete. So for a 993, it's all or NONE!