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saucer
09-04-2008, 05:37 PM
I've got a new ATP downpipe on the way and I'm a bit concerned about my fuel economy. (little late now huh?)

As I understand it, our cars have two sensors on the downpipe - one behind each cat. These sensors measure the difference in oxygen levels (and maybe other gasses) after each scrubber to make sure they're doing their job and keeping all of our trees green and happy.

Since I can't afford to get tuned just yet, I'm gonna have to trick the second little bastard with a spacer to thin the amount of passing exhaust.

So my question is: Is the fuel mixture a fluctuating ratio - dependent on the sensitive o2 sensor telling it just how lean or rich to inject? Or... is the o2 sensor simply a precautionary, passive device, letting the driver know that something must be wrong with the exhaust, and therefore just triggering a CEL? :iono:

TIA :biggrin:

07Noside
09-04-2008, 05:38 PM
Its passive you'll have no ill effects but a light on your dash.

dbduke
09-04-2008, 06:22 PM
Really? Damn, I wish I knew that before I took my car into VW to have my blown O2 sensor fixed.

07Noside
09-04-2008, 06:23 PM
Really? Damn, I wish I knew that before I took my car into VW to have my blown O2 sensor fixed.

you didn't notice any ill effects right? I ran my car on stg1 software with the ATP d/p+ CEL but didnt notice anything.

dbduke
09-04-2008, 06:26 PM
I thought I noticed a drop in mpg, but maybe I'm just crazy :iono:.

vrsix kevin
09-04-2008, 07:25 PM
fsi has 2 o2 sensors
1 right after the turbo
1 after the 2nd cat.

DarkstaR
09-04-2008, 07:36 PM
Search "wayne angle block" or "o2 sensor"

saucer
09-04-2008, 07:51 PM
Yeah emailed him today. Wayne ships em out for $38.

I'm curious how the sensors work though... if they're off/on, or if they effect the fuel ratio on the other end. I read somewhere that the code from a catless dp notes the car is running rich. I guess if the sensor is passive, it just thinks the car is running rich, but doesn't actually tell the injectors to compensate??

saucer
09-06-2008, 05:41 PM
bump for answers and proof.

I'm still hearing people argue that the o2 WILL affect the air-fuel ratio :iono:

wannagofast
09-06-2008, 06:19 PM
bump for answers and proof.

I'm still hearing people argue that the o2 WILL affect the air-fuel ratio :iono:

The first or front 02 sensor is the one that reads AFR. The angle block is for the second or rear 02 sensor. The second sensor is monitoring emissions.

dbduke
09-07-2008, 01:04 PM
I think the front O2 sensor does in fact affect your AFR. My car is not driing correctly and I have a blown front O2. The tech at VW said that the car is burning rich, but threw a hissy fit regarding a dispute about warranty coverage before explaining how he came to that conclusion.

saucer
09-07-2008, 02:42 PM
And the 1st sensor is post-cat correct? Cause the 1st cat on the stock pipe is directly after the turbo...?

What sort of problems could this cause w/o a stage 2 tune? I'm really worried about throwing a new downpipe on with out some new software...

DarkstaR
09-07-2008, 02:45 PM
And the 1st sensor is post-cat correct? Cause the 1st cat on the stock pipe is directly after the turbo...?

What sort of problems could this cause w/o a stage 2 tune? I'm really worried about throwing a new downpipe on with out some new software...

fsi has 2 o2 sensors
1 right after the turbo
1 after the 2nd cat.

If you decide to run a downpipe without software or with GIAC then I would recommend getting a wayne angle block.

saucer
09-07-2008, 02:49 PM
If you decide to run a downpipe without software or with GIAC then I would recommend getting a wayne angle block.

Ordered one last week. :biggrin:

DarkstaR
09-07-2008, 02:53 PM
Ordered one last week. :biggrin:

:thumbsup:

Did you send him a message via email?

saucer
09-07-2008, 03:35 PM
Yeah - got his info while searching for answers to my concern about AFR. Still waiting for some solid answers to come through on the subject before I install the 3" though.....

saucer
09-16-2008, 07:33 PM
Another question about running catless..

Will the lifespan of the o2 sensor at the top of the downpipe be dramatically reduced after removing that first cat?

junker
11-06-2008, 01:08 AM
The 1st oxygen sensor is after the turbo before the cat. The cat is downstream.