Sams TFSI turbo conversion (maybe!?)

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Been meaning to get something up on this for a while. I wanted to actually finish it first but now figure why not live dangerously and do a blog on the conversion as its actually happening (or failing?).

So what I'm doing here is sorting out a turbo conversion from the stock K03s to an IHI RFH5 from a Golf Mk6 Gti. Here's a little rundown of this turbo and its relatives:

- Golf Mk5 Gti, EA113 engine = Borg Warner K03
- Golf Mk5 Golf Pirelli & Golf Mk6 'R', EA113 engine = Borg Warner K04-064
- Golf Mk6 Gti, EA888 Gen1 engine = IHI RHF5

So from what I understand IHI are the parent company of Borg Warner or at least the American arm of it. From this turbo onward it seems VW went over to running IHI's after their longstanding relationship with BW turbos. The IHI turbo in the newer Mk6 Golf Gti engine is a very close reproduction of the BW K03 in the Mk5 Golf Gti. Ive had mine side by side with the BW and they are only subtly different outwardly. eg wastegate actuators. The compressor wheels are virtually the same but the later IHI has fewer blades but a bigger hot side wheel so may be better up top?. But put simply the IHI RHF5 in the Mk6 Gti is often referred to as "K03" despite very definitely not being a BW turbo. Its just that the name fits since its big brother the 'R' still carried a BW K04.
So what all these turbos have in common despite being on earlier EA113 engines or the later EA888 Gen 1 and 2 engines is that they have the same exhaust manifold designs in that they outwardly appear to be 4-1 long runner designs fit to the head by sitting in a 'rail' on the underside of the exhaust manifold and then pivoting up to meet studs on the top side.
Their manifolds are also integral castings with the turbo hotside which gets you away from the crappy exhaust manifold to turbo connection gasket leaks that especially K03s's suffer from and the manifolds themselves look to be a very free flowing design in comparison to the choked down 1.8T 20V K03/K04 designs.
And what makes this conversion possible? Our 1.8T 20V has the exact same port sizes and port spacings as both of the later engines mentioned above, so with an adapter plate between the head and the exhaust manifold of the turbo, they fit on the 1.8T 20V.
What got me interested in this conversion was first seeing guys in the UK doing a similar conversion with the larger BW K04-064 in Audi A3's, Golf Mk4's etc. I'm sure people will be wondering why I would do the conversion with the Mk6 Gti turbo rather than the K04-064, well there were a few reasons:

1. the BW K03, IHI 'K03' and BW K04-064 are all very similar dimensions. The smaller two of the trio actually carry very similarly sized housings meaning that a Mk6 Gti turbo that fits now, can easily be plug n played with a bigger K04-064 down the track.
2. I don't have rods yet! I actually have all the bits together for a proper rebuild of my spare engine. I could have waited to rebuild that and then swing it all in with a K04-064 attached but that would realistically have been a good year+ away. Instead I figured I'd get this turbo up and running, the car will still be a good step quicker than what I've had but shouldn't bend the stock rods in my existing engine if we're careful with the tune. But yeah the eye is definitely on the K04-064 out of the Golf R in the long term.
3. There's a fair bit involved in the conversion so I wanted to get it all squared away and not be stuffing around trying to get things to work on a new rebuilt engine later. Ive seen rebuild engines hit brick walls with tunes, hardware problems and development etc, in and out of work shops, way too much idling and bore glazing when what they should be doing is turning the key and getting quality run in kays on the motor. I wanted all the little things eg intercooler pipework, MAF sizing/placement, boost solenoid compatibility, whether the thing will even fit in the little Polo engine bay! etc, to be sorted before a rebuilt engine goes in.
4. ha ha and I was basically gifted a nearly brand new Mk 6 Gti turbo which gave me a decent bump in that direction!

and as for why this turbo in comparison to a K04-022/023 from an Audi S3 Mk1:
1. they have horrible OEM exhaust manifolds, maybe even worse looking than the Mk golf/Polo Gti.
2. The stock manis have tiny little collectors at the exhaust to turbo connection that incinerate gaskets and come loose no matter what you do.
3. I've never liked the look of the aftermarket K04-022 manis. runners directly facing each other at the collector, no gas guides down into the turbo etc
4. Id seen pretty reputable people in the UK saying that the smaller TFSI turbos outperform K04-022/023's because they can do everything the other turbo does on less boost, with more timing advance and lower EGT's. Mine is a turbo specced by the factory for a 2.0L engine so constitutes a performance and generational upgrade all at once.

So there you go. After all the work so far It may not even fit into the Polo engine bay. The only other people I could see who had done this conversion in a Polo were in Greece. They are left hand drive with no brake booster/master cylinder in the way, so it could be that with a RHD Polo that i'll run into some serious dramas. But what the hey, I'll try!

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So the first piece of the jigsaw is the ADAPTER PLATE. Mine was sourced from CB Auto Solutions in the UK. There are a few companies that are doing them. The reason why I chose this one is that it was the only one that that exactly copied the OE fitting method of the TFSI turbo exhaust mani. eg. the top row of bolts are correctly angled to match the angled face on the mani. Other brands have square fitting studs and then rely on angled washers to fit against the manifold, but to my mind unless they were precision made the washers after many heat cycles could shift upward and/or during tightening if this happened there would be an upward sheer placed on the stud.
Other brands copied the factory's lower rail idea but used it directly on the 1.8T 20V head. That's fine but then the top row of bolt holes didn't line up requiring drilling of the factory manifold and using wide washers in some areas so that one bolt could pin down a wide area of the manifold. The CB adapter was also a bit thicker than the others. This may come to bite me later if say the turbo wont fit against the firewall or master cylinder, but it does mean that the adapter is beautifully port matched between the 1.8T 20V exhaust ports and the new turbos exhaust mani runners.

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The nest thing I tackled was the turbo cores OIL AND WATER LINES. Now what you need to do before you start looking to see what lines up etc is to get the turbos core oriented correctly. The 1.8T 20V in my Polo sits canted back 15 degrees as measured off the cam cover. But the turbos core wont be vertical bolted to the engine as is off a MK6 Golf Gti. Thos engines must sit a bit more upright which puts the core orientation off on a 1.8T 20V. You need the core (in particular the oil drain) to be vertical, so make sure you release the exhaust housings V-band clamp and clock the core so it sits correctly. On my TFSI turbo it wouldn't clock. I had to remove the CHRA from the exhaust housing and remove a small removeable pin from the mounting face that had been locking its position. Remove the pin and you'll be able to move the core to wherever you need it relative the the exhaust housing which is obviously fixed to the exhaust mani.

So the lines are as follows:

water inlet line:

If you source this turbo make sure you get the lines with it. The OE water feed line from this turbo will mate up with the 1.8T 20V block. The hardline needs a slight massage around the turbo which is no big deal, just hand force, but then its banjo connection unfortunately sits out from the where it needs to connect to the block. So you need two things - a longer banjo bolt and a spacer to go between the banjo and the block. So the longer banjo is no problem. When you remove your K03/K03s from your Mk4 golf, Polo Gti etc make sure you hang onto the banjo bolt from its water feed. On the K03 in those cars the water feed goes into the top of the turbo core via a tall post in the hard pipe which uses a long banjo bolt. This bolt can be used now but on the connection to the block. I just made up a spacer on the lathe to fit.

sorry you're just going to have to tilt your head to the left.

water outlet line:

You're in luck. The line that comes with the turbo fits. Again just a bit of 'realigning' of the hard tube with you hand and it'll feed neatly around the back of the head and come out right where the original turbos had.



oil inlet pipe:

So far I was able to either adapt/or just plain use a line that came with the turbo. Its a bit different with the oil feed as the one that comes with the turbo will not work. The Mk6 Gti turbo gets an oil feed off an oil gallery in the block but our 1.8T 20V only supplies it from the oil filter housing. so-

1. throw away the OE 1.8T 20V K03s oil feed line
2. throw away the OE TFSI turbo line
3. You need an adaper that screws into the top of the turbo core. Its part number is VAG #N0207043
4. you need to buy the oil line off a Passat I believe. Its part number is VAG# 06B145771N/P
Itll just bolt onto the oil filter housing just like the 1.8T 20V one did using the original banjo bolt, runs around the back of the cam cover attaching where the 1.8T 20V heat shielding does and then screws onto the adapter.

sorry again. my rotated pics just wont upload in the correct orientation.

Oil return line:

This one requires doing a cut n shut with a twist on the OE 1.8T 20V K03s oil return line. Basically the line you already have needs to be cut off up near where it attaches to the turbo. The flange end that bolts to the turbo needs to be rotated 90 degrees roughly and welded back together. I needed to remove a small section of the pipe or else it would have been in compression and you also have to pay attention to the braided hose section to ensure it stays clear of where the driveshaft will run.

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SUPPORT BRACKET

Neither your 1.8T 20V or TFSI one (if it came with the turbo) wont fit. You have to make one. I had some old pneumatics mounting fittings and rose joints on hand. The ones that worked were 10mm thread on one end and 8mm on the other so I just welded a 10mm bolt to some 8mm threaded rod and I was good. With the spacers I got them to line up perfectly and also not get in the way of anything else including the Polo driveshaft boot grease shield that still fits and is a nice reference to know that the driveshaft wont be hitting anything.

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WIRING/N75 BOOST CONTROL

From what I can gather from people who know stuff overseas the Polo's ME7.5 Bosch ECU will be able to run the N75 Boost control solenoid that comes with the TFSI turbo's. It is situated physically on the compressor housing though, unlike the Polo's. It has no polarity just like the original N75 valve.
So your choice is:

1. decide to retain the original N75. pro- no wiring needed con- the TFSI's N75 will need to have its pneumatic connections to the compressor housing removed and then lines run from those take off points up to the original N75 and inlet pipe.
2. run the TFSI N75. All the pneumatic connections are already made. You just need to extend the Polos wiring to reach down to it. As I said the N75 is not polarised so you can just cut off the existing plug, solder on 2 leads and run them to a plug to fit the TFSI N75. What I was lucky to discover was that the plug needed to fit the TFSI N75 is the same plug off either an N249 or SAI delete. I had a plug tail left over from when I removed all that crap and what do you know it fits!

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HEATSHIELDING

The TIP for this turbo will run directly across the top of the exhaust manifold. So too does the oil infeed line, so I wanted something to protect both the oil infeed line (to make sure uncooked oil is getting to the journal) and the TIP to obviously keep inlet temps as low as possible.
First thing is to keep the OE heatshield from the 1.8T 20V's K03/s. It only needs a bit of a trim with tin snips to be able to be retained. This shield has a convenient angled lip on it. So I folded up some thin aluminium sheet and basically rivetted that to this lip to form up a good enough shield.
As for firewall shielding I think that'll be a bit of work. Further along you'll see that this turbo sits lower and further across under the master cylinder than the stock one does. That puts the comp housing right against the firewall in spots and the old reflective skinned fabric isn't going to cut it. I cant really build any firewall heat shielding though and have it pre-emptively fitted because there's every chance I'll have to more clearancing so this part of the heat shielding story will have to wait until fitment day I think.

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CLEARANCING

So the single biggest issue with this swap is going to be how close the new compressor housing sits to the firewall. In particular the part of the firewall that bubbles out to clear the point where the steering column uni joint fits onto the steering column on the inside of the footwell.
from the inside
on the firewall side (after a bit of hammering)

So after deciding on core position (which affects some of the line banjos) and in particular comp housing clocking, I filed down any protrusions on the comp housing that might cause problems (learnt from UK sites) and then made up a 'jig' so that I could simulate where the new turbos extremities will be against the firewall. I'd also previously removed the air con compressor and heat exchanger and now thought I get rid of the AC lines on the firewall. I dont think the latter is particularly necessary but with the other stuff already out of the car it was superfluous anyway. The jig revealed clearancing issues so hammering ensued!! And yes I was constantly checking on the inside that the steering column knuckle wasn't going to get near fouling on the sheet metal.

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COMPRESSOR HOUSING

So the comp housing has some inherent issues that were worth tackling now and also some fitment issues for the Polo engine bay. The former concerns the TFSI turbos diverter valve (DV) setup.

DV:

The OE TFSI turbos use electric diverter valves mounted directly on the comp housing. The Polo ME7.5 cant run an electric divereter so you have two options, both of which are pneumatic only.
1. remove the TFSI DV and replace with a pneumatic DV that bolts into the same spot on the comp housing. This is all very neat and only needs a vacuum line run from the plenum down the back of the engine. GFB and Turbosmart make them. But for me there were two problems. First was the issue of space. The electric DV was massive and never would have fit, but so too the pneumatic DV replacement you can buy are quite bulky and sit out up to 25mm in the direction of the firewall and I already have problems there. Also when you actually look at the size of the hole that the DV exhausts through in the comp housing, it is miniscule. Literally my pinky only just fit.

Now the 1.8T 20V with a measly K03s fitted even had a 25mm DV fitted (OK I.D was 22.5mm but still) and that was from the factory at 9psi! So I didn't think once this turbo gets boosted up and is really moving some air, that that tiny little DV was going to cut it. Which leads me to the next option..

2. Use a blanking plate to delete the compressor housing mounted DV altogether and go to a remote DV location. This suited me because I'm already running a pre-throttle body 25mm Turbosmart DV which is a superior position for a DV/BOV in performance applications, it allowed me to run 25mm pipe work for the DV system (vs 16.5mm in the Mk6 Gti turbo) and it ruled out any clearancing issues too. The blanking plate seen in the pics is for an Astra VXR (very similar turbo) and seals off the DV hole. I just need to find some Viton seals for it (don't trust a china site that says Viton) and its good to go.



COMP HOUSING EXIT

The IHI RHF5 runs a turbo muffler canister on the compressor housing outlet much like the Polo Gti's K03s. Its integral exit turns a tight 90 degrees and utilises one of those press to click/spring clipped fittings where the intercooler (IC) pipework plugs into it. At first it looked to me that with some modding that I could use it but clearance against the chassis rail below the brake booster/master was proving difficult.
this
to this

I'd hoped the straight piped exit to the muffler would work because it was expanded to 2 inch at the pipe which would have flowed way better than stock which is 39-40mm the whole way through which is pretty anaemic, but even a tight 90 degree silicon pipe off that wouldn't clear the chassis rail. That modified turbo muffler is now for sale if any Golf Mk6 Gti guys are interested!
The main problem was that the whole turbo muffler canister itself was adding too much length to the compressor exit, so things had to get a bit more choppy.


So basically the canister was cut off retaining the machined surface for welding onto later. Then the surround was removed and tidied up A thick walled tube ID 41mm OD 48mm was found onto which a mate welded a bead. I then chucked it on the lathe and spun its inside to open out from 42mm to 46mm. Same mate then welded this pipe to the comp housing and ported everything out at the transition.
A stock IHI RHF5 on a Golf Mk6 Gti is ID 39-40mm all the way out to the 90 degree bend. Now its ID is 40mm prior to where the canister was, opening out to 46mm at the exit. The pipe I'm going to use is actually the comp exit pipe off a K03/K03s 1.8T 20V! I had a low kay one on hand so that turns out into 2/1/4inch pipe at its exit now, difference being that it holds tight to the engine and will clear the chassis.

BEFORE using my modded turbo muffler. wont clear due to exit pipe way outside of crank pulley.

AFTER - note how the 90 degree joiner sits in much tighter to the engine and will clear the chassis rail.

So this part is still a work in progress. The car currently runs a 2 inch pipe in this position out to the SEAT Sport IC. I'll be changing that for 2/1/4 inch. The 90 degree pipe in the pic will feed into an aluminium pipe that I'm still waiting on bits for before I get it welded up and fitted.

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exhaust/dump



So just to check if I was going to be lucky I thought I'd see if a Golf Mk6 Gti dump would fit. It wouldn't as the cat moved the dump way to far off to the passenger side. In addition it chokes down behind the cat to what couldn't be more than 1/3/4 inch pipe so...…..nup.



what I did use it for though was its flange. That lead to the next issue. The flange has an odd 80-81mm ID and I wanted to use a 3inch dump 76mm. So I managed to use a plumbers flaring tool (usually used for brass pipes) and with a lot of heat added managed to falre the end of my pipe to fit flush with the flange so it can be welded nicely.

From what I can tell, off the 90 degree bend I have now I'll need to use two 45 degrees to offset the exhaust to line up with cyl 3 which is roughly where the tunnel is. I found this grainy pic of a K04-064'd Audi and its exhaust. The Polo's firewall will be tighter than in that car but it'll probably end up looking something like this:

either way this is where its all sitting now:

Once I get the turbo in I'm honestly not sure how the hell I'm going to get the car down to my mates workshop for the exhaust to be finished. Hopefully I can leave the dump pipe bend sitting inside the flange (loose but it is captive) and cable tie the O2 sensor at it opening so the car will run, and hopefully not set fire to anything. we'll see I guess!

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exhaust housing & wastegate actuator/flapper

So I don't want to run the stock Mk6 Gti Golf wastegate actuator. Not only do they have a pissy spring tension eg 5-6psi that's going to be inadequate if this will be pushing 20psi, but the whole setup on these turbos inc the wastegate flapper have some pretty inherent problems. see here:

https://www.youtube.com/watch?v=Cl4AuMc8zfg

So because my turbo only had 14,000km on it the wastegate flapper arms bush hasnt worn into an oval like they do on higher kay cars yet. While I'm thinking that this turbo will be temporary before a K04-064 goes in down the track, part of me still worries that I might actually be 100% happy with it once its in and then I'll regret not having future proofed the wastegate flapper bush. Given that the turbo isnt in a car, the 150 bucks for the kit to fix it seems like cheap insurance now, so I may just tackle it.
heres the flapper repair kit:
https://www.ebay.com/itm/2-0T-VW-Audi-IHI-RHF5H-Wastegate-Rattle-Flapper-Rebuild-Kit-2009-2010-2011-2012/123471075185?hash=item1cbf731771:g:0EcAAOSwSupbq5h u

and here's the procedure for fixing it: (different car but exact same principle)

https://www.youtube.com/watch?v=1ON-UVZI7Z8

and just as a side not here is a pic of the closely related but early Borg Warner K03 TFSI off a Golf Mk 5 GTi:

https://www.ebay.com/itm/2-0T-VW-Audi-Ko3-Ko4-K04-K03-Wastegate-Rattle-Flapper-repair-Kit-2005-2009/113352250497?hash=item1a64521481:gr0AAOSwqcJbq8oH

Note that the Mk5 BW has preload adjustment in the wastegate actuator arm but the IHI Golf MK 6 one doesnt. The latter just has a pin end that 'should' pull out about 3mm preload before it pops into the hole in the flapper arm.
But here lies the other major drama with the MK 6 actuator that I can see. The pin is made of an inferior steel, softer than the flapper arm and wears away to the point where the pin goes oval and then mm by mm you start to loose your pre load. eg my pin measures 8mm diameter but at the point where it pushes on the flapper arm it has worn down to 7mm, and thats in only 14k km's which is pretty pathetic. There are two band aids for this problem. One is a compression clip that goes over this connection to dull rattling sounds that you'll get from insufficient pre load and secondly you have to bend the actuators bracket where it fits onto the turbo to force more pre load back into it.

So to me thats way dodgy so I'll be transplanting my Turbosmart IWG-75 actuator thats in my car now onto this turbo. Ive already sourced a stainless rod thats long enough. I'll just need to tear a 1/4 inch thread onto it so it'll fit into the actuator piston, I have a choice of springs to use (I'll probably run the single 10psi spring), and then I only have to figure out a better connection onto the flapper arm. Need some advice here as I was actually thinking I'd use a small rose joint. The ones I have are a stainless ball in a brass race. The only issue would be if different expansion rates in the metal would cause it to bind? I'm all ears from racing peoples for advice on that.

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turbo inlet pipe (tip) & filter


see Page 4, post #34

[GRP]

Great read.

Hope it all goes to plan.

[JTop]

this is actually a brilliant idea sam <3 hope to see this running soon!!
not sure if your tip and filter post has any content attached to it btw

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no the ones left blank are pending, but will be filled out as progress is made

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So I put up a bit of an ad but may as well get it on here too. Putting out to the 1.8T 20V people of the world...... I need a stock K03s wastegate actuator. To move forward on this TFSI turbo conversion I need to modify/use the turbosmart wastegate actuator which is on the daily. So to keep my daily running around while I get the good actuator sorted for the conversion, I need a spare I can throw in in its place. Any help would be greatly appreciated. I can do it as a loaner and give it back to you once the conversion is in (if its your spare on a shelf) or outright buy it off you.
let me know!!!
sam