Replacing Bosch WB 4.2 with 4.9

[hb93]

I don't see any differences in their output. Is there any issue with updating the AFR from stock (99.5 A4 2.8l) to the modern 4.9's? I'm installing 02 monitoring and it makes more sense to use the existing bungs rather than drill and weld new bungs into my headers... thoughts?

[Mad Cow]

LSU4.9 isn't backwards compatible with 4.2, so no. Literally the first result when you google lsu4.9 explains exactly why it won't work, read up./ The 30v is narrowband too, so I don't know where you got the idea that you can swap in wideband sensors. Not there there's any point in going wideband unless you're working on a FI setup and need to get it tuned anyway.

[fed0ra]

I don't see any differences in their output. Is there any issue with updating the AFR from stock (99.5 A4 2.8l) to the modern 4.9's? I'm installing 02 monitoring and it makes more sense to use the existing bungs rather than drill and weld new bungs into my headers... thoughts?

Their circuits are quite different. As Mad Cow said they are definitely not backwards compatible with Bosch 4.2. He is also correct in that your car is narrowband, not wideband. If you want wideband for a gauge then you would go with whatever your controller called for. If this is what you are going for most wideband controllers offer a "simulated narrowband" output where it sends a signal mimicking a narrowband sensor so you can put the wideband sensor in place of a narrowband primary sensor without losing functionality.

[hb93]

Yeah, that's what I get for trying to figure stuff out at 4am... :P I'll drill and weld my headers for the 4.9's.. thanks.

[hb93]

I did get the PLX wideband sensor kit, it does do narrowband emulation pass-thru... I was trying to avoid sporting for a second one of them but thinking that maybe that's my best bet....

[Mad Cow]

Why are you so dead set on LSU4.9? Just use a 4.2 with that wideband controller and connect the emulated narrowband to the stock ECU.

[hb93]

I did get the PLX wideband sensor kit, it does do narrowband emulation pass-thru... I was trying to avoid sporting for a second one of them but thinking that maybe that's my best bet....

[hb93]

Why are you so dead set on LSU4.9? Just use a 4.2 with that wideband controller and connect the emulated narrowband to the stock ECU.

The PLXDevices kit came with the 4.9... and I had another 4.9 already.

[hb93]

My new question is, is there any value to monitoring both headers? Or any disadvantage to only monitoring one? I have the sensors so I only need one more 'reader' to round it out, but I'm a bit over my planned budget for the month (by a bit over a grand) on this project so am trying to avoid spending more on anything that is truly extraneous.

[Mad Cow]

It's best to monitor both banks, much safer that way. Also the latency of the narrowband passthrough might mess with the stock ECU, it'll see one bank responding slower and could try to compensate somehow or throw a code. I didn't notice your wideband controller is made for 4.9, why ask about 4.2 then? I'm really confused.

[fed0ra]

It's best to monitor both banks, much safer that way. Also the latency of the narrowband passthrough might mess with the stock ECU, it'll see one bank responding slower and could try to compensate somehow or throw a code. I didn't notice your wideband controller is made for 4.9, why ask about 4.2 then? I'm really confused.

The wideband cars (at least the 1.8T) uses a Bosch 4.2 sensor. He may have thought that his car was equipped with them.