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Author Topic: K04 Conversion - Looking for opinions & posting my progress/info about the swap  (Read 18511 times)

Offline ZoliWorks

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For the past month I've been split between either getting a new K03 or doing a K04 conversion (injectors, intake, sports cat downpipe) so i'd like y'all's opinion.

Long story short, my stage1 K03 is dying because it's constantly underboosting by 0.3-0.4bars. It peaks at 1.4 bars then drops down to 1.1 almost instantly. My mechanic (and tuner) thinks that it's 90% the turbo failing because almost every K03 he's worked with was either cracked internally or had a failing wastegate. We've smoke tested the engine and there are no leaks. DV is new.

Right now the car is stage 1 and it's supposed to push 270-275bhp but realistically speaking I don't think the turbo in it's current state can push more than 230-240.
Mods are as follows:
- R8 coils
- NGK BKR7EIX plugs
- Sachs X-tend OEM replacement clutch and DMF supposed to hold 430nm of torque

Compared to stock, the car is super responsive and allows me to snap around in traffic. When merging, I can floor it and it'll get up to speed fast and kick me back into the chair, which I love. Basically you see a gap, you take a gap. What the car lacks is power in the upper powerband or when trying to overtake on open roads past 100kph. It still pulls better than my stage 3 1.4 Jetta but I feel like I'm starting to want more.

Now as for the K04, would I be sacrificing this snappy responsiveness between 2k and 4k rpm for top end power? or would I retain the same low-down kick that the K03 can deliver to zip around town?
For the K04 conversion I'd go with upgraded injectors, rail pressure valve, sensor and map sensor along with a 200cell cat and an intake. I'm not very keen on a full sports exhaust because I quite enjoy how quiet the car is and would like to keep it that way. I think I've had enough of sports exhaust by driving the 1.4 for 4 years.

All thoughts and opinions regarding the K04 swap are welcome

Below are some graphs of my boost issue with wastegate duty cycle at 95%. Red is requested, green is actual boost.






« Last Edit: May 27, 2024, 10:07:32 pm by ZoliWorks »
Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


Offline OllieVRS

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #1 on: March 24, 2024, 04:16:50 pm »
I'm no expert on turbos but wanted to mention a couple things to keep in mind with HP expectations:
- R8 coils do not add more power
- NGK BKR7EIX do not help add more power (at your tuning level):
NGK BKR7EIX are a 5k Ohm restricted plug. You really should consider going back to the 1k Ohm plug (NGK 1675 PFR7S8EG) w/gaps at 0.8 mm, and allow more voltage to pass through the plug when stock as yours is. At stock there's no need to restrict the power for the arc it can generate. Because your combustion situation is not likely to disturb its arc.


Not exactly sure how to read your graph, but if this helps, here's my boost (act.) VCDS log from stage 2, intake and 200cel:



EDIT: Also, you're getting mapped and dynoing while running 99 octane, right?
'06 Skoda Octavia vRS TFSI

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #2 on: March 24, 2024, 08:01:04 pm »
I'm no expert on turbos but wanted to mention a couple things to keep in mind with HP expectations:
- R8 coils do not add more power
- NGK BKR7EIX do not help add more power (at your tuning level):
NGK BKR7EIX are a 5k Ohm restricted plug. You really should consider going back to the 1k Ohm plug (NGK 1675 PFR7S8EG) w/gaps at 0.8 mm, and allow more voltage to pass through the plug when stock as yours is. At stock there's no need to restrict the power for the arc it can generate. Because your combustion situation is not likely to disturb its arc.

Not exactly sure how to read your graph, but if this helps, here's my boost (act.) VCDS log from stage 2, intake and 200cel:



EDIT: Also, you're getting mapped and dynoing while running 99 octane, right?

I'm running on 100 octane but the map was made for 95 octane. Tuner said making it on 100 it would only add a bit more power but wouldn't behave well if I used anything lower (because i might now always have the chance to tank up on 100 or 99) so he pretty much only makes maps for 95. Also said that running 100 on his 95 map is fine.

As far as dyno goes, the car wasn't dyno-d. Guy took the stock map from the car, modified it then we went for a drive. I've been working with him for a while and he's done so many GTI's he could write a map from scratch.

Plugs and coils, the old ones were dying so I had to replace and these were the cheapest ones. On my 1.4 I've had constant misfires till I switched to this plug and coil combo so I figured it wouldn't hurt here either.

And the graph I sent, that's basically me flooring it in 3rd and then switching to 4th on the highway. Here's an excel log if that helps with anything. 3rd to 4th pull down at the bottom.
https://ubbcluj-my.sharepoint.com/:x:/g/personal/arpad_borbely_stud_ubbcluj_ro/EaMelNr8foZAu2jEjQj2aEUB0sWKGzvO_6McYF4RsmSlxQ?e=chQjX3

This log has less info but has timing
https://ubbcluj-my.sharepoint.com/:x:/g/personal/arpad_borbely_stud_ubbcluj_ro/ESgektv-s7hGrGPq-LW1OMQBbWmIgWbhIMS5MwsuXukIww?e=NpxG7f
« Last Edit: March 24, 2024, 08:10:25 pm by ZoliWorks »
Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


Offline OllieVRS

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #3 on: March 25, 2024, 12:05:13 pm »
Your boost does seem to be slightly too low from the requested boost, by a few hundred mbar. So there is definitely an issue with boost somewhere. Mine is at most -150mbar from requested when accelerating fully, usually +-50mbar.

Also remember that it's most useful to subtract ambient atmospheric pressure when talking about boost numbers, 1000mbar, e.g. my peak boost boost is 16 psi/1.1bar in my graph.

As for octane, I think mapping on that is equally at fault for the disappointing performance.

In Ireland we only have 95 octane, so if you want more octane here you have to use octane booster. So nearly everybody maps on 95 octane. Back when my car only had a cold air intake it was measured 184hp stock, then 225hp stage 1 (on dyno). When using measuring engine torque in KW via VCDS later, I estimated adding expensive octane booster to make the octane 99 only raised HP by 8-10hp on my 95 map. But the car felt a lot more responsive, and the timing was less retarded so the engine sounded more aggressive. Adding the 200 cel sports cat and another mapping raised the 95 octane power to 235hp, so max 245hp with octane booster.

Online tuners give their numbers for mapping on 98/99 octane, so if you see 'Stage 1 250hp or Stage 2 275hp' they are talking about the car running on a 98/99 map, that can't run 95. Nobody ever gives numbers for 95 octane mapping unfortunately. So if you're making ~230-240hp on a 95 map (on 99 fuel) that's probably realistic numbers.

If I had easy access to 99 octane, I would map for only 99 octane. And I would expect my stage 2 to be ~275hp. '270-275bhp' is a fantasy for stage 1 with no engine mods, your tuner may be overestimating to make his map sound better than other tuners.

Only way to know how much power it's actually making is to go to a real dyno. If that's not an option, you can log Mass Air Flow g/s (act.) and Engine Torque Nm (act.) in VCDS next time you do your log, that can *estimate* hp, but it can be inaccurate.
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Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #4 on: March 25, 2024, 06:05:38 pm »
Your boost does seem to be slightly too low from the requested boost, by a few hundred mbar. So there is definitely an issue with boost somewhere. Mine is at most -150mbar from requested when accelerating fully, usually +-50mbar.

Also remember that it's most useful to subtract ambient atmospheric pressure when talking about boost numbers, 1000mbar, e.g. my peak boost boost is 16 psi/1.1bar in my graph.

As for octane, I think mapping on that is equally at fault for the disappointing performance.

In Ireland we only have 95 octane, so if you want more octane here you have to use octane booster. So nearly everybody maps on 95 octane. Back when my car only had a cold air intake it was measured 184hp stock, then 225hp stage 1 (on dyno). When using measuring engine torque in KW via VCDS later, I estimated adding expensive octane booster to make the octane 99 only raised HP by 8-10hp on my 95 map. But the car felt a lot more responsive, and the timing was less retarded so the engine sounded more aggressive. Adding the 200 cel sports cat and another mapping raised the 95 octane power to 235hp, so max 245hp with octane booster.

Online tuners give their numbers for mapping on 98/99 octane, so if you see 'Stage 1 250hp or Stage 2 275hp' they are talking about the car running on a 98/99 map, that can't run 95. Nobody ever gives numbers for 95 octane mapping unfortunately. So if you're making ~230-240hp on a 95 map (on 99 fuel) that's probably realistic numbers.

If I had easy access to 99 octane, I would map for only 99 octane. And I would expect my stage 2 to be ~275hp. '270-275bhp' is a fantasy for stage 1 with no engine mods, your tuner may be overestimating to make his map sound better than other tuners.

Only way to know how much power it's actually making is to go to a real dyno. If that's not an option, you can log Mass Air Flow g/s (act.) and Engine Torque Nm (act.) in VCDS next time you do your log, that can *estimate* hp, but it can be inaccurate.

The car definitely feels mapped and it's a big improvement over stock but it doesn't quite run how it should. Tuners here claim 260hp for a stage 1 map, on 100 octane presumably.

The problem is that I can feel it boost then it dies off quite fast so it's definitely meeting the expected boost early on but it cant maintain it. I suspect the wastegate or the N75.

The tuner is a friend of mine so he was my first choice. This being the first car he mapped for me, I cant say if the map is good or not. I haven't dyno-d my car because this buddy is mainly a mechanic/car electrician and donesnt have a dyno and it would have cost 180 euros at a different tuner. A stage 1 map would have cost me between 500 and 600 euros so I was quite happy when he offered to do it for me for 200. (He normally makes maps for 350). He did offer to put a different map on the car just to try but said it's unlikely to change anything since he thinks it's a turbo issue.

I went for a run and measured G's and torque; The first one is a 3rd through 4th gear pull, the second is a 2nd through 4th gear pull (60-180)



Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


Offline OllieVRS

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #5 on: March 26, 2024, 04:48:47 pm »
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.
« Last Edit: March 26, 2024, 04:50:32 pm by OllieVRS »
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Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #6 on: March 26, 2024, 10:34:35 pm »
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.
Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


Offline breeze

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #7 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.

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.

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #8 on: March 27, 2024, 07:27:27 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.

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.

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.

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.
Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


Offline OllieVRS

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #9 on: March 27, 2024, 11:16:44 am »
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.
'06 Skoda Octavia vRS TFSI

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #10 on: March 27, 2024, 05:37:17 pm »
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.

If I do go down the route of forged piston rods, I might as well get the pistons themselves. My other mechanic pal who I collaborate with recommended that I replace my pistons if I do take the engine apart. A set of forged pistons should only set me back somewhere between 800 and 1k while I've seen rods as low as 700. But this is very far away tbh. I just want to get the car back up and running, putting down that 300-310hp.

And yeah, the more HP I want, the more I need to invest, which is why I think the K04 basic might be a good middleground. I'll get better middle and top end, more HP but will lose low down responsiveness all for under 1.2k, the price of an OEM K03. Anything more than this will turn this car into a money pit. I'd be fine with injectors and the fuel pump if I can safely push the engine to 350hp that way but I've heard a lot of mixed opinions. Some say stock rods should not be pushed beyond 330hp but I think it's the torque we need to limit. 500nm might be too much on stock rods. Maybe they can take 450?

On another note, I wonder if the S3, ED30 or other k04 engine's pistons and rods fit a BWA cause I can get a complete ED30 engine from the UK for under 1k

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.

Summers we get upwards of 35c here so I'll deffo make good use of the intercooler. My general driving style keeps the engine above 2.5k at all times so I should be good. Spoke to my tuner who says he drove in both k03 and k04 tuned cars and that there isn't that much difference down low. I'd want a turbo that is balanced throughout the power range but I think that's what the K04 is. If I want instant response, I might as well get a diesel  :grin:

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.

I've read that 200 cell cats wont trigger a check engine light but that's the least of my worries, we'll code it out. Passing emissions is the important part to me! I'm hoping for the same result; Improved sound, something more sporty, not your generic 4 cylinder family car but not as loud and as much drone as a full sports exhaust. Plus at 1/4th of the cost.


Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


Offline OllieVRS

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #11 on: March 28, 2024, 11:36:49 am »
"If I'm getting X I MIGHT ASWELL GET Y", the classic car guy dilemma  :grin:. Very difficult to stop yourself before you end up trying to build an engine that could do 24H of Le Mans.

Yeah I agree, the basic minimum for K04 upgrade is a good middle ground. If I didn't have plans for buying additional cars I would be looking at that myself. You may not need a clutch right away, but keep money saved for when you need it will eventually.

Also since you have high octane available in your country it would be worth considering 'switchable maps', where either OEM ECU or aftermarket ECU can be modified to support switching maps just using the in-cabin controls in the car. Not too sure how it works, but my tuner friend (who also does cheap maps like your friend) said for €500 euro he can do it, which for me just wasn't worth it. But you should do some research into it, having a 95 octane economy map and 100 octane 'fun' map would be great.

Keep in mind if you legitimately getting an ED30 engine from the UK for 1k (you must have good friends or the engine isn't running), then you will have to pay import fees/customs duty into the EU. Which can also add weeks to the delivery. All can be avoided of course if you have a sketchy friend with a van who's bringing it to you, I wouldn't know anything about that ;)

No need to worry about rods if you're going for a basic K04 set up though, and it's not like you need more than 300hp on a FWD car anyway.

...My 200 cel cat triggers the check engine light if not mapped out, not all cats are built equally. But it smells less than a decat and gives me peace of mind that I'm not a complete environmental terrorist :innocent:. It's definitely a good investment if you ask me.
'06 Skoda Octavia vRS TFSI

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #12 on: March 28, 2024, 12:42:50 pm »
"If I'm getting X I MIGHT ASWELL GET Y", the classic car guy dilemma  :grin:. Very difficult to stop yourself before you end up trying to build an engine that could do 24H of Le Mans.

True... That's how I was with the old 1.4, spent well over 12k on it and ended up selling it (to my dad) for 6k, taking off almost all the mods and selling them... minus the engine tune-up. Even tho he isn't a speedster and his old car is a 1.4 golf 4, he does like the instant power the 240hp 1.4 can deliver... But still gets beaten by a GTI with a broken turbo  :grin:

I do plan on restraining myself to just the generic K04 mods without getting into pistons and rods for the near future. Downpipe w/ sports cat, intake to make it sound cool, dv relocation kit, dv+ since I already have it and it makes a way better sound than the stock valves, r8 coils, ngk plugs, ECS complete boost pipe kit and lastly OEM S3 intercooler.

Yeah I agree, the basic minimum for K04 upgrade is a good middle ground. If I didn't have plans for buying additional cars I would be looking at that myself. You may not need a clutch right away, but keep money saved for when you need it will eventually.

I've settled with this car and dont plan on buying anything else for the next 5+ years. The 2.0 is great. Got the car for 4k total, 2.8k for the car, negotiated down from 3.650 cause the engine was running pretty bad (it was the brake booster line, it cracked), 600 for getting it home, around 500 for all the paperwork and getting it registered and lastly 100 to my buddy who spoke German and got me the deal. Spent around 4k repairing it which would have cost double if I went to other mechanics and bought parts through them.

Why all this for a GTI? Well because it's full option! It has almost everything you could put in it in 2006 and only 128k km (when I bought it anyway, made 10k since then). The clutch failed 100 meters after getting it off the trailer so I replaced the whole thing, including the DMF. I went with a Sachs X-tend performance clutch kit from the start, knowing that I'll need it in the future, so I'm all set for a while.

Also since you have high octane available in your country it would be worth considering 'switchable maps', where either OEM ECU or aftermarket ECU can be modified to support switching maps just using the in-cabin controls in the car. Not too sure how it works, but my tuner friend (who also does cheap maps like your friend) said for €500 euro he can do it, which for me just wasn't worth it. But you should do some research into it, having a 95 octane economy map and 100 octane 'fun' map would be great.

Map switching is definitely something I'll look into because I also use this car as my daily. I get 13-14 l/100km in the city which is not ideal so i've been looking into multiple maps for a while and might get an aftermarket unit for that specifically. I'll have it set up like those oldschool hueys with the flip open type switches by the shifter, where the ESP and wheel pressure button is.  :grin:

Keep in mind if you legitimately getting an ED30 engine from the UK for 1k (you must have good friends or the engine isn't running), then you will have to pay import fees/customs duty into the EU. Which can also add weeks to the delivery. All can be avoided of course if you have a sketchy friend with a van who's bringing it to you, I wouldn't know anything about that ;)

He has his ways and I don't question them  :innocent:
We'll see what he brings home, take what I need and he'll sell off the rest.

No need to worry about rods if you're going for a basic K04 set up though, and it's not like you need more than 300hp on a FWD car anyway.

Yeah that's what I'm thinking. I'll deffo need an LSD cause even right now in it's current state, I'm slipping till the end of 2nd gear, and I've got Vredestein tires on.... winter ones anyway, I'm waiting on the rims to arrive for the summer ones.

...My 200 cel cat triggers the check engine light if not mapped out, not all cats are built equally. But it smells less than a decat and gives me peace of mind that I'm not a complete environmental terrorist :innocent:. It's definitely a good investment if you ask me.

Yeah the smell is another factor why I want a sports cat and not a complete decat.


Here's the car itself. It's a 2006 Jetta with a 2.0 turbo. These pics were taken in December, the morning after I finished the Mk6 GTI front end conversion and mirror cover paintjob. I'll likely keep the car the same color, but paint the front, repair the rear bumper and cover the chrome window trims and door pillars with matte black wrap. It gives it a more sportier look. I want it to look clean from the exterior, go unnoticed cause the color is way too common. A sleeper build basically.  :grin:

The front parts are all covered in paint primer as it matches with the car's color till it gets hotter outside to paint it and I've since then painted the grille trims glossy black. Looks cleaner and sportier imo.

Next to it is the 1.4 which was in the process of getting a turbo at the time.



« Last Edit: March 28, 2024, 12:51:45 pm by ZoliWorks »
Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp


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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #13 on: March 29, 2024, 04:11:52 pm »
Quote from: ZoliWorks
The problem is that I can feel it boost then it dies off quite fast so it's definitely meeting the expected boost early on but it cant maintain it.

That is how it is with a K03, which is why I went for an Edition 30 instead of a GTI.

1.4-1.5 bar boost from a K03 creates a massive spike it can't maintain, hence why it drops again sharply. 

K04s keep going to 6500rpm easily, whereas the GTIs I drove fell off a cliff at 5500rpm.  The GTI feels more like a diesel to me, and the K04 feels a bit more like an old school 90s turbo engine. A bit of lag but much harder hitting in the mid and top end.

On my stage 1 K04, it was spooling hard by 2200rpm and usually hit 1 bar by 2750rpm and full 1.3-1.4 bar boost by 3200rpm.  That's on a stock engine. Downpipes and intakes will affect that slightly.  Doesn't sound laggy on paper but it compared to a K03, it is in practice.

K03s feel quite meaty around 1800-2000rpm. In a K04 you can't feel the boost at all until at least 2500rpm.

Another consideration with the K04 is 3000rpm surging, which is why the boost needs to be capped to 1.3 bar around there as the turbo ramps up too quickly, which the engine can't physically ingest. It feels like a massive flat spot with lots of pigeon fluttering noises from the intake.

If you have open roads where you can use the full rev band, the K04 is better.  If you live in urban areas and value quick response and punchy midrange over top end, stick to the K03.







2007 ED30 | 2009 TDI 140 | 2016 BMW 330D

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #14 on: March 29, 2024, 07:27:08 pm »
Quote from: ZoliWorks
The problem is that I can feel it boost then it dies off quite fast so it's definitely meeting the expected boost early on but it cant maintain it.

That is how it is with a K03, which is why I went for an Edition 30 instead of a GTI.

1.4-1.5 bar boost from a K03 creates a massive spike it can't maintain, hence why it drops again sharply. 

K04s keep going to 6500rpm easily, whereas the GTIs I drove fell off a cliff at 5500rpm.  The GTI feels more like a diesel to me, and the K04 feels a bit more like an old school 90s turbo engine. A bit of lag but much harder hitting in the mid and top end.

On my stage 1 K04, it was spooling hard by 2200rpm and usually hit 1 bar by 2750rpm and full 1.3-1.4 bar boost by 3200rpm.  That's on a stock engine. Downpipes and intakes will affect that slightly.  Doesn't sound laggy on paper but it compared to a K03, it is in practice.

K03s feel quite meaty around 1800-2000rpm. In a K04 you can't feel the boost at all until at least 2500rpm.

Another consideration with the K04 is 3000rpm surging, which is why the boost needs to be capped to 1.3 bar around there as the turbo ramps up too quickly, which the engine can't physically ingest. It feels like a massive flat spot with lots of pigeon fluttering noises from the intake.

If you have open roads where you can use the full rev band, the K04 is better.  If you live in urban areas and value quick response and punchy midrange over top end, stick to the K03.

True, it does feel like a diesel, especially when mapped. Instant response. My daily commute is 60% urban 40% extra-urban. I don't really accelerate past 120kph unless I'm overtaking someone and that's where I feel like the K03 falls short.

This was in 4th gear from 3k to 6k. I don't think it should fall quite this fast.


Mk5 Jetta 2.0 TFSI BWA | Mk6 GTI Front | BorgWarner K04 Turbo | Ta-Technix Air Intake | Ta-Technix 200 Cell Downpipe | Stock Intercooler | Stock Injectors | Vis Motorsport 175 bar HPFP | 300hp