S4 decat pipes

both id say. remap to compensate the de cats. take the pre cats out aswell or theres no point. also tha lambdas need deleting whist on. just done this on my 3.0 v6 petrol quattro sport. lovely difference
 
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Just out of curiosity Paul, how does the ecu control A/F ratio if you delete the lambdas ?
 
You only delete post cat lambda. Front remain in place controlling fueling
The rears only look for cat function anyway
 
The other thing is if you need to replace the cats for mot does it need to be returned to standard map to pass or would it pass with remap and cats on
 
more hassel in my opinion especially if you havnt access to the right tools. as for the DIY'ist getting the pre cat down pipes off can be a pain. swapping them over time again isnt ideal in my opinion
 
I use to run mine with the decat pipes I just ran it with the EML light on up until I got the JHM tune which then sorted it. Any company that can remap can get rid off the code tho. If you want to go for the JHM tune I currently have a flash cable which is being passed around so let me know if you need it and I can forward it on to you.
 
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the pre cat and main cat are actually together
i did mine by gutting the pre cats and remapping to eliminate codes
i would advise against the milltek front pipes as they have had a lot of cat failures
 
Paul @ Unit 9 Remaps said:
more hassel in my opinion especially if you havnt access to the right tools. as for the DIY'ist getting the pre cat down pipes off can be a pain. swapping them over time again isnt ideal in my opinion
Click to expand...
Yeah I know what you mean img mechanic mate will swap them for £50 for mot don't think I would do it myself like you say to much hassle
 
dsmclark40v said:
I use to run mine with the decat pipes I just ran it with the EML light on up until I got the JHM tune which then sorted it. Any company that can remap can get rid off the code tho. If you want to go for the JHM tune I currently have a flash cable which is being passed around so let me know if you need it and I can forward it on to you.
Click to expand...

Thanks will let you know
 
why remove both and then have to swap to get the car an mot
unless you are going for a very high stage of tune then there is no benefit to removing the post cat as the flow is more than adequate
the problem on s4,s is the pre cat not the post cat

gut the pre cat and either map the existing lines out with your current tune or
go for something like a ccc tech tune or jhm tune which eliminate the check engine light by opening up the parameters
 
dualmono21 said:
why remove both and then have to swap to get the car an mot
unless you are going for a very high stage of tune then there is no benefit to removing the post cat as the flow is more than adequate
the problem on s4,s is the pre cat not the post cat

gut the pre cat and either map the existing lines out with your current tune or
go for something like a ccc tech tune or jhm tune which eliminate the check engine light by opening up the parameters
Click to expand...

I have another set of these headers if anyone is interested, https://daviem.wordpress.com/s4-transplant/
 
audi upgrades
dsmclark40v said:
Nice build! makes me miss and want another B6 S4! what headers are those? and how come you used the stock downpipes with them? albeit with out the pre cats of course
Click to expand...

The headers are RS4 so a perfect fit and much better than what comes on an S4 but I had them modified to fit the S4 heads, then the RS4 downpipes or cats as they are high flow as they are about 60mm, they finnish up in the perfect position to fit an RS4 system or Milltek or other, I recon if the RS4 is a high reving engine then the headers and cats are good enough for what my engine will put out, and I wasn't wrong, it really bursts into life, loads of torque and wants to rev, and does, I had a few of them modified while I was at it if others want a set.
 
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