# 4.2L V8 into a B5 Audi S4?



## chris_72 (May 27, 2008)

Hey guys, I just got my paws on a 2001 Audi A6 4.2L and I have a 2000 Audi S4 that's just sitting around... I love the sound of a warmed up 4.2L... By now I'm sure you get where I'm going with this. 
I have seen it done. And physically I have no problem fabricating all parts needed to make it work. It's the electrical Side of things that gets me worried. 
Questions like what ecu do I use, how do I get past the immobilizer, How do I join the 4.2L engine harness with the B5 S4 body. 
Any info on this would be great.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

Its virtually plug and play with an A6 donor, as they both use the same basic wiring scheme. Search 'the russian' on Audizine as he's done one with the A6 motor. You hardly need to fabricate anything  

Very likely you can swap the cluster from the A6 to keep the immobiliser matched to the ECU (obviously swap the transponder chips to the S4 keys too). If its a pre-facelift A6 (borderline for a 2001) then it will probably just swap over. If its a facelift then it will have CAN-BUS so you'll need to do a bit of wiring for that. Either way, you definitely have the easiest donor :thumbup:


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## chris_72 (May 27, 2008)

Well that sounds like some good news! Ill check out this Russian character you speak of.


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## 1999.5GTIVR6 (Jun 15, 2011)

Now I haven't looked into this enough, but I was considering buying a allroad 2.7t a a while ago. With a blown moter, my plan was to make it an rs4, but when researching I found out they made the 4.2l body a bit bigger to squeez it in. Not saying it won't fit with out modification, but I do also remeber seeing a few a6s with the 4.2 stock and they were called "widebody" so before sinking money into the motor and possibly rebuilding parts I'd highly reccomend looking at spacing


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

You are correct that the 4.2 A6 has wider track and also a different front panel to make more room for the 4.2, however with a little bit of cunning it fits fine in the A4. It has been done many times before  Curiously the 4.2 Allroad doesn't have the wide-track setup, although I suspect it does have the different front end. 

The only clearance issue in the A4 is getting hoses to fit the radiator as it is very close to the front of the motor. You can either move the rad forward (what The Russian did) or use an alloy one with right-angle outlets (what I'm doing). 

Here's mine: 










:thumbup:


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## antichristonwheels (Jun 14, 2001)

You can have the ECU hacked to remove the immobilizer (and whatever else you might not want to be concerned with)


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## chris_72 (May 27, 2008)

Wow, Mikkijayne! That looks like a serious build! Do you have a build thread for that car? It looks awesome!


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

No build thread sorry. Its basically a '90s BTCC replica but with a V8 instead of an I4. I'll be using it mostly for hillclimbs and trackdays


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## chris_72 (May 27, 2008)

*Ok, back from the dead...*

Hey guys, 
So I'm back from the dead here. Started my own business, so time was not on my side for the last year and a bit. Anyway, I've started on my swap. I was going to buy a B5 with a blown 2.8 V6, but my S4 popped the transmission, so it was coming apart anyway. So far all I've done was get the engine/trans out of the S4. Now I'm cleaning, and prepping for all modifications and getting ready for the 4.2!


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## magics5rip (Mar 17, 2004)

I've been considering the same swap recently with my 2001 A4 (its basically a S4 shell). According to a thread on motorgeek the ART 4.2L should be nearly plug and play...I plan to start my swap in about 3 months. 

Motorgeek Thread


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