Reynard38

I have read with great interest the SAI issues of the 993. I myself have a '97 Carrera S and will be doing the preventative flush procedure soon (no CEL issues yet, 37K miles).
My comment is this... All this for a system that functions for 90 seconds after startup and then shuts down? At least that is the way that I understand the SAI system. If all OBD2 wants is certain voltages from the behind-the-cat O2 sensors for that 90 seconds then why not just use a relay that is switched on by the SAI pump to send that voltage to the computer via the O2 sensor wiring.
Pump comes on, x number of volts to OBD computer for 90 seconds and everyone is happy.
I am sure this is an oversimplification but lets face it... SAI is a dumb system to apease an even dumber law.
Porsche techs flame on please!

Phil

design it.....it will sell....

Howdy993

Reynard38 -

Two or so years ago, someone on this list designed a circuit to electronically bypass the SAI sensors to send an all is well signal to the 993 brain on start up - defeating the OBD II check.

If memory serves me, the problem was how to physically connect the circuit. At the time there was'nt a pool of volunteers willing to cut into their wiring harnesses.

CalvinC4S

The dream part would be a box that emulates the O2 sensors signals and plugs right into the OBD2 port from the blind side. This way you could ditch OBD2 and run aftermarket ECU. We need to pool a "get out of jail" fund for the creator!

StatmanDesigns

The main problem with this modification is that the SAI and OBD2 functions are for emmission control and, as such it is illegal to modify them. It is illegal to sell the parts to disable an emmission control system, and it is illegal to install them. You can publish the circuit, as has been done in the past, but you can't sell it. It is a complete DIY job, and you take sole responsibility for any legal ramifications. You then pass this burden on to the next owner, if and when you sell your modified car.

STLPCA

Howard's got a good memory. It was 2+ years ago that an electronic guru here (David a/k/a "993,951,944") designed just such a circuit. I kept it in case I ever face an SAI CEL which, fortunately, at 54k miles hasn't happened.

Original thread (2/03)

Howdy993

Daniel makes some very good points. The Feds would certainly frown on this type of modification and I'm sure none of us would want to buy a car with such a modification. When / If the time comes,
I'd probably get it flushed and eventually bite the bullet for a top end rebuild with some of Steve Weiners super valve guides.

Mike J

I looked into building this...the main pitfall from a logistics point of view is the connectors. You cannot source the AMP connectors in less than 5000 pc orders. I talked to AMP, to my local distributors etc and intended to build it so its pluggable in and out. I worked with another rennlister on fabricating the connectors from scratch but we could not get the temp characteristics right. I have been playing with the idea of pursing this again but am still up against the connector problem.

If the product was labelled as "off-use only" then I don't think there is much the Feds can do anyways. If someone wants to plug it in and pass emissions then no one can certainly controls this since its for off-road use...its not likely they would be caught anyways since its only for the first 15 seconds of startup. That is why I wanted the unit to be pluggable...so it can be removed and the orginal wiring restored.

I have another idea about the connectors which may work fine and am working on it. It would be plug-and-play again. But this unit would be for "off-road" use only ;-) I am also based in Canada and so our rules are different here, and if some units happen to be shipped to the US for off-road use then whose the wiser?

Such a modification will not help with worn valves etc. but just cause the 30 second emissions "warm-up" to pass fine, for off-road use of course! It will not affect any emmisions when the engine is warmed up which is wnen most emission tests are done.

Cheers,

Mike

Reynard38

Mike J.,

That is exactly what I am referring to. I would not run a car that was belching smoke for emmision reasons, but the current rules are ridiculous. As to the legality, come on guys. We drive Porshes not Volvos!

JasonAndreas

Unfortunately I'm not so sure it works that way, there is no legal use for the SAI bypass circuitry so there is no exemption. Eventually the EPA & CARB will come after you (even in Canada). The other big problem is that people have no choice but to install the device themselves. There is no way a mechanic will do it unless you remove the plates and tow the car to their premises, the fines are too large and the EPA & CARB claim to be running sting operations.

Its too bad 993 owners were/are too concerned with resale value to spend 5 minutes writing a complaint to the EPA. Nobody complained and because the OBD reporting requirements are rigged for the manufacturers the EPA couldn't really force PCNA to do anything.

Mike J

[QUOTE=JasonAndr Its too bad 993 owners were/are too concerned with resale value to spend 5 minutes writing a complaint to the EPA. Nobody complained and because the OBD reporting requirements are rigged for the manufacturers the EPA couldn't really force PCNA to do anything.[/QUOTE]

Hi Jason,

By "force PCNA" what do you mean? Do you mean that the plugging of the passages would be considered a emmisions fault and PCNA would be forced to fix it?

This device does have a legit use on race and track cars that do not have the air pump so the ODBII system does not trigger a code.

Anyone know how many times the Feds have gone after these small after-market devices with a limited audience size such as the 993? How about CAT bypasses etc? How about the older 911's where it was/is common to remove the air pumps and plug the injection ports?

I seems ludicrous that the Feds would spend lots of time/money to clamp down on a provider of a device that can be used on race engines where, even it it was abused and used on a street car, can't have an audience of more than a few hundred units.

However the US government has proved that its ludicrous before...and our Canadian one is not much better.

However if I need a bypass I certainly know how to build one.

Cheers,

Mike

JasonAndreas

Yes if there was a defect in the emissions equipment than the vehicles could have been recalled, last year the EPA had 34 voluntary vehicle recalls and 3 that were "influenced". With the 993 there were no "smog check failure patterns" noticed by CARB or the EPA so all they had to go on were the public complaints (i.e. mine was the only one) and whatever PCNA provided (nothing). Hopefully people will speak up next time. In 2003 GM had a similar problem with high exhaust backpressure causing moist air to get into the check valve/solenoid which caused corrosion and eventual failure of the AIR/SAI system (40k+ cars were recalled).
That is the same reasoning that a lot of the O2 simulator guys tried to use but the EPA has been shutting them down. Try to contact someone at the EPA in the enforcement division and get a definitive answer from them. The people at the recall division that I was dealing with sent me a sample warning letter with the fine $$$ schedule. I don't remember the exact amounts but if you wanted to cover the first fine you would have had to have sold 100 units at $300.

StatmanDesigns

Not really sure what you could possibly mean by this statement????? The disabling of an emmission control device is HIGHLY illegal. No mechanic will perform this modification for you, so it is strictly DIY. You will never be able to sell your car with this modification, so it saves you nothing in the long run, it can only delay the inevitable fix of the SAI problem.

You may think the rules are overly strict regarding the disabling of emmission control systems, and that is certainly your allowed opinion. However, no matter how strongly you believe your own opinion, it does not change the reality of this situation.

Lorenfb

More relevant than what's been mentioned in the posts is that the schematic with
the indicated semiconductors/components mostly likely won't provide the desired
results.

Mike J

Hi Loren,

I would not be so sure about that...the designer had a very good success with it. When not active it certanly isolates the clamping circuit and when active clamps just fine.

From what do you base your opinion that it won't work?

Cheers,

Mike.