Guide, how to convert an Audi S2 inlet manifold to a 4pot.

Ok! It's been done many times, I have just gone through this convertion myself and thought I would post up how I went about it.

First off you need an Audi S2 inlet manifold. It is from a 5pot, but luckily for us they used the same spacing and bolt pattern so when fitting to a 16v 4pot (ABF,KR,9A etc) all you have to do is cut off one cylinder... lol





I used a band saw to remove the extra runner, it gave a square cut and was easy, but you can acheive this with a hacksaw and elbow grease. I cut just on the very edge of runner No5. I tried to keep the plenum as big as possible. Once cut I flattened of the part with a band facer.



In the picture you can see a shiny area that has been sanded. This was a bulge that had a thread for a bolt in it. I cut it off and sanded it smooth. The inside of the plenum has three tubes running through it.



For the interested parties here is the removed runner and the size measured.



Ok, once cut up you need to start adding bits back on. It helps if you can TIG weld aliminium or have a friend who can, otherwise you need to pay someone to does this, and it helps if you have access to a machine shop, or otherwise you will need to pay someone to make you a few parts.

The most inportant part is the flange for the trotter body (TB) to mount to, the shape of this will be determined by the position you cut the manifold and the TB you are going to use. I used an ABF round TB which is 68mm ID.

Becuase of the odd shape it needed to be i firstly made one square flange, also i will used this on my setup later. To make the flange (either) I marked it out, drilled the bolt holes, then milled the centre out.







Once I cutout both flanges (square and plenum shaped) I bolted them together and turned on the lathe to get a perfect match. On the inside (plenum side) of the plenum flange I added a radius to help the air transition.





If using a TB on the plenum, you could bolt the flange onto the TB and turn it to match the TB ID.



This is the only pic I have of the plenum flange, it's the odd shaped one!



I then cleaned up the plenum with a finger sander and welded the flange in place. Before welding on one side of the plenum I had to fill weld and file it back, very straight forward. Then I welded it.

 

Well done, you have read this far! You maybe think, job done its all over? Well not quite yet. Because you removed the OEM flange you also removed the nipples used for vacuum and the air inlet temperature (AIT) sensor mount.

I refitted these as follows.

On a separate piece of plate, (beause the S2 manifold is to thin - it has thickness added when cast where take offs are) I drilled the holes for the nipples and pressed the nipples in a vice - ouch!

This is then ready to be welded in place - note, you will need to drill out the manifold with corrisponding holes before hand!








For the AIT sensor I use an OEM 1.8T jobbies, it's 15mm centres between the hole and thread, M6 thread and 12mm hole. Again I made a plate, drill manifold and welded into position on the underside of the TB.



And finally I also added a vacuum take off for the brakes. I turned this on the lathe and then welded into the opposite end to the plenum, which is handy because there is a core plug that can be removed (leaving a 20mm hole) and the brake servo is on that end.





For my application I needed to support intercooling pipe work and a charge cooler. To do this I used an existing mount on the plenum, unfortunately the second mount on runner No5 was removed when I removed that whole runner. To give my mount for strength I cut of the mount from the old runner and welded it back onto the plenum runner, on the underside.





Nearly there! Ok, next was the foul rail mounts, I use a VAG 1.8T fuel rail and std (G60) style injectors, I had to make billet mounts and weld these into the correct location to support the fuel rail, I drilled and tapped an M6 hole in each.

No pics of this ATM.

 

Fantastic fabrication skills!
LOVE IT

 

Great stuff!

Brian,

 

hi mate any chance you could upgrade your photobucket so i can use your guide lol thanks