What do I need for a Ko4 conversion?


Registered User
Hi guys I have a 99 plate Audi A3 1.8T Sport with a ko3 Turbo

it has:

3'' downpipe
3'' de-cat
2.5'' full system
Solid state flywheel
S2000 Air Filter

The next thing I want to do is get a Ko4 turbo but after searching the internet it's hard to get an exact list of parts that are needed, hence why I've decided to ask you guys :)

I'm after getting about 280bhp from the Car eventually but for now I just want to know what is needed for the Ko4 conversion.

Thanks in advance :)


Registered User
I'm doing this at the moment on mine. You'll need the turbo, the 4 oil and water lines, k04 downpipe and cat ( or like me 3" relentless dp decat ), k04 tip, k04 manifold, I think 3" maf and injectors I think. I'm sure someone else will say if I've forgotten anything


My other car is a MINI!!!!
I'd say it depends where you want to end up ultimately, looking further ahead perhaps.

If you think 280 / 300bhp will be your limit, and you won't want for more at a later date, then I'd seriously consider a k300 hybrid given how well they're doing lately.

it'll retain your existing manifold, downpipe, lines, everything.

All you'd need is an oversized TIP, a VR6 MAF housing, and some injectors as well as the k300 turbo to get it all working.

Cost wise, I think it'd end up slightly cheaper in parts, but you get a brand new turbo, and an awful lot less labour, and slightly more power potential than a stock k04.

the k04 conversion requires a few fiddly bits, like new heater pipes and re-routing, altering the FMIC pipework, 80mm TIP's are very tight on 5spd gear linkages, and the downpipe / cat back systems need a bit of work to match up also.

In your position I think I'd be going K300 given what we know now.


Registered User
Thanks for the replies people.

I think I'd like to have the option at a later date for further development rather than being restricted to 280, it would be nice knowing that with the Ko4 there's always the option to get more power if I feel necessary, spend little more now and put in more effort/time, rather than having to do it a year or so down the line.

So if I was to walk into a shop tomorrow what exactly is the list of parts needed? I intent to use this list to purchase parts so an idiots description in a sort of bullet point list that I could use as a shopping list would be fantastic please, as I don't want to miss anything out and this all be for nothing.

The Cars off the road at the moment as I'm getting it ready for it's MOT that should be done this Month, come start of April though I will be buying everything for the conversion and making a start on that, hopefully using a parts list provided by you lovely people :)

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Registered User
Here's what I'm getting for mine.

IE rods and big end bearings
Relentless v2 manifold
Relentless downpipe decat
Badger5 billet v2.2 tip
Head rebuilt ( not sure if it's needed but getting done anyways )
Bigger injectors
Turbo and all the lines
Hester pipes
3" Maf housing
Wellycooler setup for fmic

There are a few bits I've prob forgot to list but I hope that kind gets you going and other I hope will add to the list of parts needed also


My other car is a MINI!!!!
K04 turbo

k04 fitment manifold (stock / aftermarket)

k04 downpipe (stock / aftermarket)

k04 TIP (has to be badger5 80mm really!)

VR6 OBD2 MAF housing (can use your original sensor in this housing)

Larger injectors, saab 346cc reds if you plan to never pass 300bhp, bosch 440 green if you want to have a bit of headroom for the future.

Uprated fuel pump. (i'd advise an inline knowing what I know now)

Re-worked heater hoses around bulkhead area. I used a full ko4 engined metal coolant pipe and hose connections to make it simple.

K04 oil and water lines. 2 of each. (PM me if you want to buy some ;) )

Gaskets and crush washers for all of the above, so manifold gasket, turbo gasket, downpipe gasket, 6x water crush washers, 4x oil crush washers, and a gasket for each end of the oil drain.

You'll also need various new studs and nuts throughout.

I went straight to a hybrid on mine, but the principle and fitment is all the same. It's easily doable on your driveway over a weekend.

When you do get the stuff installed, bodge up the stock MAF into the larger housing as a temp and leave your stock injectors in too. only fit the larger items once arrived at your chosen place for mapping :)