Effects of SAI delete on HFC?

[eljay]

First off, let me provide this background to try and prevent the inevitable sh*t storm about emissions delete etc.: I bought the car with a test pipe and without SAI. If I still had SAI and all the other hardware in place, I'd keep it and I am in no way trying to say this is better since I know it's not. In fact, I've added an aftermarket cat to get rid of the fumes. I hate exhaust fumes. And I'm slowly learning about what I have on the car and how it all works.
With that out of the way...

I am looking to switch my exhaust system from current to planned:
- Current: 3" test pipe into 3" custom SS downpipe, into Magnaflow universal cat (single inlet, dual outlets) into 2.5" custom SS piping with resonators into Magnaflow rear mufflers and out with 4" tips.
- Planned: 034 HFC into 2.5" downpipe, into Borla 140100 exhaust

Relevant facts about the car:
- 2005 1.8T manual with GTRS Eliminator kit with Maestro tune.
- SAI delete, combi valve removed and blockoff plate installed.
- The test pipe still has both O2 sensors
- No CEL, but I don't know how it has been coded out and whether the tune has any "cold start" maps etc. I'm clueless on this and need to find some links to learn about Maestro etc., but that's a different topic.

My question: if I install the HFC, will I kill it (i.e. clog it) in short time due to the lack of SAI function?
If there is that danger, is there any way to check my tune for proper cold start map to somehow prevent that from occurring or is functioning SAI/combi necessary to prevent that?

Thank you.

[old guy]

The primary purpose of the SAI system was to enable Audi/VW to get a ULEV rating for the 1.8T. I suspect without the SAI that VAG could still have gotten a LEV rating. They went for the ULEV rating since this made the 1.8T the first small displacement turbo engine to get this rating. This provided a perceived (and probably real) market advantage.

So to answer your question, no I do not think you are going to kill your HFC by not running the SAI system. It may reduce the life ever so slightly. But even that can be avoided by how you start and drive your engine. Don’t start the engine and let it sit idle to warm up. Simply start it up and begin driving gently until up to full operating temperature. This increases the flow through the cat right away (similar to what the SAI pump will do at idle).

And I agree with you on running a HFC instead of a test pipe. It avoids all the stink and pollution associated with a test pipe and the performance is essentially the same.

[eljay]

Excellent! Thank you.

[diagnosticator]

I agree. I can't think of any harmful effects on the HFC from no SAI.

[Human Garbage]

As usual OG is right on the money. There should be little to no impact on the life of your HFC.

Regarding how it was coded out, well it was likely just done by modifying the scalar CDSLS to be 0, which is SAI not installed. The scalar CWKONABG is also changed which modifies the cold start behavior. With it set to 0 you won't get a raised idle on cold start due to the assumption a Cat isn't installed. With it set to 1, you will still get the raised idle on cold start to bring the Cat up to temp. This raised idle is what makes the majority of the heating, the SAI just 'assists' in getting it up to temp faster. The difference is measured in seconds when talking SAI vs no SAI though... Additionally the circuit diagnosis ESKONF needs to be changed if you want to unplug the relay for the pump or the car will throw a code. Alternately you can resistor out the circuit to fool that diagnosis.

There is another way of doing an SAI delete that involves requesting no flow using the table MSLUB (and sometimes the scalar MSLBAS). This requires the relay to still be plugged in however, so if your relay is gone, then you can assume that the SAI was deleted using the former method. This way has the advantage of passing emissions testing as the test machine can't detect the test being bypassed due to the SAI being coded out as above. That all said, I'd bet that Tapp has used the CDSLS method though...

[Mr.Avant]

These guys have got it covered on a technical aspect. Just going to throw in I've been running a HFC w/ SAI delete for 60k miles, with no problems. Mine resulted in a CEL for catalyst efficiency, and was coded out as a result (motoza stg 1+)

We don't have emissions testing here in Canada, but I did have the pleasure of using an exhaust gas analyzer. I'm happy to report it passed on all regulated emissions (CO, HC, NOx), and very little associated odour.

Sent from my SM-G920W8 using Tapatalk

[eljay]

Lots of good info. Thanks guys!

Cheers.