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K04 Conversion - Looking for opinions & posting my progress/info about the swap

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OllieVRS:
EDIT: Oops I put the values in the wrong way around, but it still calculates the same hp  :grin:

I'll use https://www.omnicalculator.com/conversion/torque-to-horsepower for a conversion to metric hp.

I took the values from the first log at 5760RPM and 274Nm, as I think they're the most reliable from your log:



Horsepower can also be estimated by multiplying the MAF g/s reading by 1.25, as the engine aims to burn 1.25g of fuel for every 1.0g of air taken in, creating 1 horsepower.

So at that same RPM point it's using 172g of air, 172*1.25 = 215hp. So your real hp number (I estimate) is somewhere around 215-225hp.


Your boost is definitely too low, that the first thing to investigate. Are there any engine error codes? But if you've smoke tested and replaced the DV there's only thing left it could be.

If your planning on going K04 instead of just replacing or repairing your K03, remember you need to think about the additional costs. A K04 upgrade needs S3 injectors, HPFP upgrade (I think) and S3 intercooler. As well as supporting mods like DV relocation kit and tune.

ZoliWorks:
Yeah I've used the same calculator. 215 to 225 is what I'd say it feels like. I can definitely feel that low end instant torque surge of the K03 but due to it being faulty, it dies off quite fast and proceeds to pull slightly better than a stock GTI. My money is on the wastegate actuator but we'll see when I pull it off and inspect it.

Now as far as options go, I've been thinking about them for the past few weeks and it's very hard to decide.

K03 - €1100
CHRA is most likely faulty as I and my mechanic both think there's too much oil in the intake, and the exhaust manifold appears to be cracked but could just be a streak of rust cause if that crack was real, it would already be in 2 pieces. Repairing the turbo would cost no less than 400 euros. Turbo repair/refurbish shops here only provide 1 year warranty and their reviews are evenly split between either 1* and 5*, I dont really want to take a chance. Getting a turbo from another car costs aprox 240 euros and nobody guarantees that it works, it isnt cracked internally, it isnt eating oil or that it'll last, so that's also out of the question. Getting a replacement turbo is pretty much the same deal as getting a refurbished one. Opinions are very split between mechanics but the general consensus is that you either go OEM or you go home. And they cost around 500 to 700 euros. OEM turbos cost upwards of 1k euros.

K04 - €1300
What I said about the K03 also applies here, however, I'm much more confident about a 2nd hand K04 than I am about the K03. Problem is, people know how much potential these turbos have and they are so rare that you can barely ever find them at any reseller. After searching for a week, I only found a single yard selling one for 500 euros. Now I did find brand new Borg Warner K04's for sale locally but they cost anywhere between 1200 and 1500 euros.

Downpipe - €300
Now as far as running the K04 will go, I'll be getting a downpipe with a 200 cell cat anyway to help turbo longevity since OEM I have 2 cat's and they are quite restrictive, but I wont be getting a full performance exhaust because I want my car to stay relatively quiet. Sports downpipe is imo the perfect middle ground between keeping the sound relatively stock, no drone, and providing room for power. Found an Aliexpress kit for 300 euros incl shipping which I'm fine it. At the end of the day it's just a pipe and if the cat lasts 2 years, I'm happy, given that just a sports cat is half the price of that downpipe here and they dont last any long either.

Intake - €200
Found an Aliexpress intake but dont quite like that due to the way it mounts so I'll be going with a German one, Ta-Technix, for 200 euros. It secures onto the vacuum pump so it doesnt bend in the middle like the Chinese ones do, has a heat shield and a filter. What more do I need?

DV relocation kit - €50
Aliexpress, 50 euros for the whole thing incl shipping.

Injectors - €400
With just the turbo, I can get tuned for 305-315hp. No injectors, no fuel pump, no pressure valve, or sensor. however, I will look into this when the time comes and get them all fitted. In all fairness, I don't estimate these to cost more than 400 euros, brand new (excluding the pump).

Upgraded fuel pump internals - €600
If I go down the K04 line, I'll get this. Didnt really research brands and prices cause it aint a priority right now. Between 500 and 800 euros.

Forged piston rods - €900
Arguably the second most expensive part of the whole process right after the turbo. If I'm serious enough about the K04, this will have to be done in order to safely reach 350HP. I'll probably slap in cams and pistons too.



TLDR
So in the end I really only have 3 options

K03 - €1100
Get my turbo replaced with an OEM one and know that I'll be set for life and that the car will have great low rpm torque and acceleration but will lack past 100kph and wont have any room for more power

K04 basic - €1200
Get a used OEM K04, downpipe, intake, DV relocation kit and remapped, making 310 or so HP with room for improvement. Car will probably lack low-down, wont have the same kick, but middle and top end should feel vastly different. Should be quite good when accelerating past 100 and I'll also have a much more reliable and better built turbo.

K04 all out €3000 to €4000 ontop of K04 basic
Gonna cost a lot but would max out the car. 350 to 360hp and over 500nm torque before hybridizing the turbo. Will get everything from above plus boost pipes and a twincooler setup with an S3 intercooler. Should be quite fun honestly and a pretty decent sleeper build. Not quite sure if worth it tho so I'll continue to think about my options for a while longer.

As things are right now, I'm split between K03 or K04 basic. Even if I stay K03, I'll be getting the downpipe, intake, S3 cooler and likely boost pipes too cause those were leaking. I've fixed them temporarily but I want a proper setup. So all in all my K03 plans might as well turn into a K04 job since I'll be running 70% of the required mods anyway.


This brings me to my original post and why I made this thread. K03 or K04? 03 pulls stronger down low and it's great for city driving that I do a lot but 04 provides more middle and top that comes in handy when I go on longer roads. Not quite sure about the low end but I dont think it'll be as punchy as the 03.

breeze:
What about going for stage 1 K04? Injectors and turbo with the pipework but retain intercooler and existing downpipe. To me that is quite a good value route.

On K03 vs K04… I think you will definitely notice the loss of low down torque. It is quite obvious. Not terrible but you do feel it. The K03 engines have slightly higher compression which will offset this but also limit the top end if you want big power.

From the R-Tech site:
All the factory k04 engines use a compression ratio of  9.8:1,  the AXX is 10.5:1 and the BWA 10.3:1.

ZoliWorks:

--- Quote from: breeze on March 27, 2024, 06:09:17 am ---What about going for stage 1 K04? Injectors and turbo with the pipework but retain intercooler and existing downpipe. To me that is quite a good value route.

--- End quote ---

So what you're saying is, ditch the downpipe in favor of the injectors? I'll have to check but brand new replacement injectors shouldn't cost that much as I have a few contacts to source them from.
Tho I feel like the downpipe might allow the turbo to breathe better and in return spool faster so I wont feel that torque loss quite that much.


--- Quote from: breeze on March 27, 2024, 06:09:17 am ---On K03 vs K04… I think you will definitely notice the loss of low down torque. It is quite obvious. Not terrible but you do feel it. The K03 engines have slightly higher compression which will offset this but also limit the top end if you want big power.

From the R-Tech site:
All the factory k04 engines use a compression ratio of  9.8:1,  the AXX is 10.5:1 and the BWA 10.3:1.

--- End quote ---

Huh I heard the exact opposite. Because of the higher compression rates, these engines (BWA) will hold power better at higher rpm's. Tho I could have heard wrong cause I havent really looked into it, just saw it mentioned here or on vortex somewhere.

OllieVRS:
Many options there, your final biggest option is probably worth more than my whole car  :grin:

Up to you what path you go down, but as the HP increase the money required to get more HP exponentially increases, if you get what I mean.

If you're talking about upgrading pistons, keep in mind how much time and money that that full engine rebuild will cost too. Factory pistons are fine up to 350hp according to others on this forum.

You don't necessarily need the S3 intercooler upgrade, but performance will suffer if you're doing more than just 1 pull from traffic lights, due to heat soak. Essentially as the heat from the extra fuel being burnt can't dissipate fast enough, the car automatically reduces power to contain the heat. E.g. the first dyno run will get you a high number, but the second much lower. Or on a race track the car will lose performance after a few turns. I wonder what @breeze thinks about this. He also has a good point about torque, you may have to start revving higher when driving after upgrading. But that's down to personal preference whether you prefer balanced torque through the whole rev range or more high end torque and less low end.

Downpipe costs money, but it's a good HP value upgrade after the turbo. It normally gets 15hp extra on stock cars (on high octane maps), it got me 10 extra hp on 95 octane. Not to mention my 200 cel cat really improved the exhaust note of mine even with the rest of the exhaust being stock, it sounds like a fancier raspy race car engine rather than the boring 4 cylinder that it is  :grin:. Mine is from MPDevelopments UK, €600. It does cause a check engine light which has to be coded out by your tuner though. Haven't put it through an emissions test yet, but I've kept the original downpipe just in case.

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