# Audi TT Wideband Conversion Questions



## swakefield (May 25, 2015)

Hey everyone, So i've done a decent amount of reading and just want to confirm that I have the right idea. I have a 2002 Audi TT Quattro 225 6 Speed. AMU engine code. They did not come with wideband sensors. BUT The 2003 BAM Engine code did! So heres my plan.

In a couple of weeks I am going to be having my 3 inch catless downpipe installed. I dont want to mess around with O2 spacers and want correct fuel measurements. From what i've read I only need 3 things:

-https://www.getunitronic.com/parts/accessories/audi-tt-18l-turbo-2002-2002-225hp-wideband-conversion-harness
- A Wideband Bosch 02 sensor
-And an ECU out of a BAE engine code tt.

Am I correct? If so, does anyone know the part number for that ECU? I can get the wideband O2 for the 2003 BAE engine through my work.
Thanks for any help in advance guys!


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## Boulderhead (Oct 21, 2012)

Any wide and ECU should work... For example mine is out of a VW AWP engine code.


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## swakefield (May 25, 2015)

Boulderhead said:


> Any wide and ECU should work... For example mine is out of a VW AWP engine code. QUOTE]
> 
> How Do I find out which ones are Wideband? And am i still correct about everything else?


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## lite1979 (Sep 9, 2005)

Going wideband doesn't get rid of the rear O2 sensor, so you may still need a bung (O2 spacer) for your catless setup to operate without a Check Engine Light.

If you get an ECU that has the rear O2 coded out, then you don't have to worry about it, but that's not my area of expertise, just an FYI.

You will also need the ECU to be immo-defeated. Your car is immo3, iirc.


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## Boulderhead (Oct 21, 2012)

Yup... Everything else looks good. I think Google is prob your best resource for finding out which ECU relies on wideband sensors. I can't speak to the spacer as my tune has secondary 02 deleted (even though I still have the hardware in place).


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## swakefield (May 25, 2015)

Boulderhead said:


> Yup... Everything else looks good. I think Google is prob your best resource for finding out which ECU relies on wideband sensors. I can't speak to the spacer as my tune has secondary 02 deleted (even though I still have the hardware in place).
> 
> 
> Sent from my iPhone using Tapatalk


Wait I can TUNE OUT, the second O2??? Is it purely tuning or something like this?

http://www.magnumtuning.com/en/detail/ez-cel-fix-oxygen-sensor-simulator/audi/tt

Because If I can avoid having to deal with replacing the ECU, I would be overjoyed. Also, does having a wideband really produce any advantage at all compared to just having it tuned out? I know that the upstream O2 measures the air/fuel ratio exiting the engine and that one is super important, but what purpose does the downstream O2 serve?


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## lite1979 (Sep 9, 2005)

The post-cat O2 measures the efficiency of the catalytic converter. With no cat, there's really no need for it.

I thought you wanted to go wideband for the sake of running a Big Turbo with a nice smooth power curve. If all you want to do is eliminate the need for a rear O2, have it coded out of your current ECU, and maybe get a tune while you're at it. You can get other stuff coded out as well, but like I said, I'm not experienced in that realm. 

I still have my original narrowband ECU with a 93 octane tune from APR from forever ago. Our AMU ECUs can only hold one tune, however, whereas the wideband ECUs can hold more than one, IIRC.

I'm pretty sure the link you posted just simulates a properly operating rear O2; not the same as having the ECU coded to ignore it.

Gonzo offers it, as does GIAC, but there are a ton of options out there, and I'm way behind when it comes to the tuning game. Some more knowledgeable posters are invited to chime in here.


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## Boulderhead (Oct 21, 2012)

Only reason to get the wideband swap is because your tuner asks for it (better control). If you only care about not getting a CEL with a castless exhaust then just get a cat and a spacer and call it a day. 


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## lite1979 (Sep 9, 2005)

^^^

High-flow cat and spacer is what I have, but it sounds like he already pulled the trigger on a cat-less setup.


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## swakefield (May 25, 2015)

lite1979 said:


> ^^^
> 
> High-flow cat and spacer is what I have, but it sounds like he already pulled the trigger on a cat-less setup.


Yea I want to go catless. I dont mind the change in exhaust smell (not like im sniffing it) and I like the open flow with no obstructions. Its not the check engine light that bothers me. If it was I would simply throw in one of the spacers we have lying around and call it a day. But I want to correctly compensate with the new setup so the engine gets everything it needs. So, most VW/Audi tuners should have the ability to tune out the downstream 02? I wont be going big turbo with this car. Thanks to everyone so far for the help!


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## Boulderhead (Oct 21, 2012)

The engine doesn't care about the post cat O2. It has no impact on fueling or adjustments made by ECU so you actually aren't compensating or doing anything which adds performance value.

Without a tune that needs these things you are just replacing parts for the sake of modding. To each their own... Just want you to understand the benefits (lack thereof in this case).


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## Boulderhead (Oct 21, 2012)

Duplicate post


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## lite1979 (Sep 9, 2005)

swakefield said:


> But I want to correctly compensate with the new setup so the engine gets everything it needs. So, most VW/Audi tuners should have the ability to tune out the downstream 02?


Deleting the rear O2 won't help your motor compensate for the larger downpipe, if that's what you're saying. I used to get a huge surge of boost around 3500rpm with my stock downpipe, but now that I have a 3" downpipe and high-flow cat (I replaced out of necessity - it was the cheapest option at the time), it's less of a power surge and more gradual.

Regarding most tuners offering a rear O2 delete, yes, most of them do.


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## swakefield (May 25, 2015)

lite1979 said:


> Deleting the rear O2 won't help your motor compensate for the larger downpipe, if that's what you're saying. I used to get a huge surge of boost around 3500rpm with my stock downpipe, but now that I have a 3" downpipe and high-flow cat (I replaced out of necessity - it was the cheapest option at the time), it's less of a power surge and more gradual.
> 
> Regarding most tuners offering a rear O2 delete, yes, most of them do.


With my setup (stock turbo, catless downpipe, minor engine mods) What would you all suggest? A rear O2 delete and tune? or spend the money to make it wideband? From what you all are saying it seems to me that making mine wideband is basically just a waste of money when talking about benefits?


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## lite1979 (Sep 9, 2005)

It's all about what you want; not what we want. Set a goal and go for it. If you want 350 wheel horsepower, there are people here who can guide you along the way. If you want a little more oomph around curves and to chirp the tires occasionally, a mild tune can get you there.

Introduce your car as-is, then we'll know what to do to achieve your goals.


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## Boulderhead (Oct 21, 2012)

When your tune calls for a wideband sensor, that is time you should convert. It takes no time at all to actually do the swap (1 hour of clean work). With your current setup, there is no reason to do anything besides install your exhaust and spacer if needed to avoid the CEL, install a cat pipe for inspection (if needed) or find someone to tune it out completely (force readiness).

The downpipe is the tip of the iceberg for modifications on turbo cars.. so hopefully you love your car and hate money like the rest of us :laugh:


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## swakefield (May 25, 2015)

Boulderhead said:


> When your tune calls for a wideband sensor, that is time you should convert. It takes no time at all to actually do the swap (1 hour of clean work). With your current setup, there is no reason to do anything besides install your exhaust and spacer if needed to avoid the CEL, install a cat pipe for inspection (if needed) or find someone to tune it out completely (force readiness).
> 
> The downpipe is the tip of the iceberg for modifications on turbo cars.. so hopefully you love your car and hate money like the rest of us :laugh:


I love the car ive already put ridiculous amounts in it haha. Had it just under a year, already done 
2 sets of new BFG G-Force Comp-2 A/S (I get them for 80 each through my work)
Both outer tie rods
coilovers in the front
both front CV's
rear shocks
rear springs
megan racing rear lower adjustable control arms
Forge Adj. BOV(which im still not sure if i like)
thermostat,
Touch screen stereo and 12" Subwoofer
New engine mount, Poly trans mount, and Poly Dog bone bushings
New fuel pump and fuel level sender (Both sides)
Electronic Exhaust Cutout,
Aux water pump last week,
and im going back to work today to put in a new power PS rack and pinion and new Ps pump as well :'(

I read everywhere these motors need new connecting rods to be able to withstand over 300HP/TQ. So for now im gonna stick with a mild tune. So if the tuner charges extra for the rear O2 delete I guess ill just stick with spacers!


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## Nooga (Apr 14, 2016)

So mine is in the shop this week and I am having a 3" cat less downpipe installed and the mechanic is going to tune out the second O2 sensor. I understand that this will keep it from throwing up a CEL, but should I be worried that it will no longer pass the emissions test? Mechanic says it will pass, but friends say that it might get caught by the emissions test.

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## MCPaudiTT (Nov 26, 2006)

If they use a sniffer you will fail guaranteed. It varies by state, so do your research. You may need to put a cat I to pass, then remove once snickered - if you can live with that guilt...


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## jsmith2015 (Mar 7, 2015)

MCPaudiTT said:


> If they use a sniffer you will fail guaranteed. It varies by state, so do your research. You may need to put a cat I to pass, then remove once snickered - if you can live with that guilt...


In California a 100 dollar bill will fix all your smog woes. 

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## Nooga (Apr 14, 2016)

Here they only plug in to the OBD connector for recent cars. Cars over a certain age also get a test at the tailpipes. 

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## lite1979 (Sep 9, 2005)

OBDII connection is all they do in Upstate NY (not sure about downstate). As long as you have no CEL and all of your readiness tests pass, then you're good to go for emissions. Mechanical is a different story, however.


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