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Author Topic: K04 Conversion - Looking for opinions & posting my progress/info about the swap  (Read 18611 times)

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #15 on: March 31, 2024, 11:08:17 am »
Found 2 graphs on the same dyno, re-drew them as a comparison. Now I see what people meant by K03 being able to harm the engine more. I'd assume the K04 would surge just as much, if not more, if it wasn't controlled properly. Curious to see if the K04, running the same average curve as the below map, would be able to spin wheels as much as a K03 does. The graph does overall look more linear tho and the mid to top end is vastly superior.

The only area where I think the 04 might fall short is if I want to drive it with the same style as I drive the K03 in cities: Flooring it at 2k till 4k to take gaps or merge off-ramps without making people behind me have to slow down.. Or me having to slow down/stop because my car cant put down enough power to jump into a gap. I'll see how the swap goes but I doubt I'd switch back to the K03 just for the low-down power difference.


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 FatWelshBoy

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #16 on: April 01, 2024, 01:06:04 pm »
Anti-surge cores are all the rage for K04 turbos at the moment, peak torque is achieved around 500 rpm lower than the stock core as the tuner can bring the boost in harder and sooner. I think a little over 300 bhp is the sweet spot for these cars, I've probably gone too far with my car if I'm totally honest. My advice would be to go for a K04 conversion with an anti-surge core and new actuator then remap it aiming for ~300 bhp. You can go for an exhaust, intercooler, intake etc but the stock items are perfectly adequate, I'd spend the money on brakes and handling.

Offline OllieVRS

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #17 on: April 01, 2024, 02:35:25 pm »
Anti-surge cores are all the rage for K04 turbos at the moment, peak torque is achieved around 500 rpm lower than the stock core as the tuner can bring the boost in harder and sooner. I think a little over 300 bhp is the sweet spot for these cars, I've probably gone too far with my car if I'm totally honest. My advice would be to go for a K04 conversion with an anti-surge core and new actuator then remap it aiming for ~300 bhp. You can go for an exhaust, intercooler, intake etc but the stock items are perfectly adequate, I'd spend the money on brakes and handling.

Anti-surge cores? Haven't heard of them before, probably because I'm not so knowledgeable about turbos. Does that mean for those who get the occasional turbo flutter (either because of a laggy DV or custom DV setting, I have the former) won't have as loud of a flutter as with a standard mapped K03?

I know surge is not great for performance/longevity and embarrassing to some but I'm one of the less mature people who absolutely loves to hear it.





This graph actually shows quite well why the K03 makes the engine feel like it's out of steam at high speeds & high RPMs, as peak power has been passed after ~5800RPM.
'06 Skoda Octavia vRS TFSI

Offline FatWelshBoy

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #18 on: April 01, 2024, 03:35:08 pm »
Anti-surge cores are all the rage for K04 turbos at the moment, peak torque is achieved around 500 rpm lower than the stock core as the tuner can bring the boost in harder and sooner. I think a little over 300 bhp is the sweet spot for these cars, I've probably gone too far with my car if I'm totally honest. My advice would be to go for a K04 conversion with an anti-surge core and new actuator then remap it aiming for ~300 bhp. You can go for an exhaust, intercooler, intake etc but the stock items are perfectly adequate, I'd spend the money on brakes and handling.

Anti-surge cores? Haven't heard of them before, probably because I'm not so knowledgeable about turbos. Does that mean for those who get the occasional turbo flutter (either because of a laggy DV or custom DV setting, I have the former) won't have as loud of a flutter as with a standard mapped K03?

I know surge is not great for performance/longevity and embarrassing to some but I'm one of the less mature people who absolutely loves to hear it.





This graph actually shows quite well why the K03 makes the engine feel like it's out of steam at high speeds & high RPMs, as peak power has been passed after ~5800RPM.

My car is K04 and has an anti-surge core and there's zero fluttering noises. I'm not sure if there's K03 anti-surge cores available?

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #19 on: April 01, 2024, 08:42:06 pm »
Anti-surge cores are all the rage for K04 turbos at the moment, peak torque is achieved around 500 rpm lower than the stock core as the tuner can bring the boost in harder and sooner. I think a little over 300 bhp is the sweet spot for these cars, I've probably gone too far with my car if I'm totally honest. My advice would be to go for a K04 conversion with an anti-surge core and new actuator then remap it aiming for ~300 bhp. You can go for an exhaust, intercooler, intake etc but the stock items are perfectly adequate, I'd spend the money on brakes and handling.

This is probably what I'll do. Intake for the funny noises, downpipe for lower backpressure, better spool and lower EGT's, intercooler piping to fix any possible leaks and an intercooler for hot summers and consecutive pulls.

For brakes, for starters I'm just getting performance pads and disks. for suspension, I quite like the stock springs but I'm getting new shocks and probably H&R front and back stiffer sway bars.
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 Lewo

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #20 on: April 03, 2024, 01:40:31 pm »
Did you say you're running with boths cats?
Rtech advice on having a pre-cat delete done.
On mine with it done & a panel filter I got 214bhp so an easy gain and turbo spools quicker.
So if you do decide to keep standard downpipe with either turbo do the delete!

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #21 on: April 03, 2024, 10:01:38 pm »
Did you say you're running with boths cats?
Rtech advice on having a pre-cat delete done.
On mine with it done & a panel filter I got 214bhp so an easy gain and turbo spools quicker.
So if you do decide to keep standard downpipe with either turbo do the delete!

Yeah I've already ordered a downpipe with a sports cat. It's as you've said, it'll make the turbo spool faster, free up some HP and also wont hold all that heat right behind the turbo. No wonder K03's crack even on a stock car..
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 #22 on: April 04, 2024, 02:24:05 pm »
Lewo's idea of the pre-cat delete is a good one, but in my opinion the sound of a sports cat is worth the extra cost associated, plus a little more airflow over the standard main cat. And if you're lazy (like me) it's a plus, as you don't have to bash/cut/weld the pre-cat yourself, just out with the OEM downpipe and in with the new.
'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 #23 on: April 06, 2024, 12:46:25 pm »
Lewo's idea of the pre-cat delete is a good one, but in my opinion the sound of a sports cat is worth the extra cost associated, plus a little more airflow over the standard main cat. And if you're lazy (like me) it's a plus, as you don't have to bash/cut/weld the pre-cat yourself, just out with the OEM downpipe and in with the new.

Have you noticed any cabin drone with the sports cat downpipe? How much more loud is it over stock?
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 #24 on: April 06, 2024, 02:20:01 pm »
No change in drone, sometimes it leaks some (nice) sound to the cabin under hard acceleration, but normally sounds the same. It's most noticeable from the (also nice) rasp your hear with the windows down, makes my stock exhaust only a little bit louder. 
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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 #25 on: April 06, 2024, 06:31:45 pm »
No change in drone, sometimes it leaks some (nice) sound to the cabin under hard acceleration, but normally sounds the same. It's most noticeable from the (also nice) rasp your hear with the windows down, makes my stock exhaust only a little bit louder.

Glad to hear, that's exactly what I want!

On my old car I had a 2.5" catback exhaust, custom made, initially with 1, then by the next day with 2 mufflers. I've also tried 3 mufflers but regardless, the drone was killing me. You couldn't hear what the person next to you was saying if you were between 2.7k and 3.5k rpm. Tthe rest of the powerband wasn't that much better either..
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 K03MK5

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #26 on: April 13, 2024, 10:35:26 pm »
Recently completed the build with a used k04 turbo apparently from a 66k S3.  Was running fine for 2 months before the build was complete. A month down the line and the thrustmaster bearing had smashed to bits. Got it rebuilt with an uprated bearing and touchwood its been great.  Am I right in thinking this was down to a poor custom tune? The mapping company suggested a brandnew turbo so got a 2nd opinion and went for the rebuild.  I might be wrong but it seemed the mapping company was looking for more work.   This was an expensive build and no partial refund was given.  I understand it was a used turbo but I did stress it was wrking completly fine before the custom tune.

Offline ZoliWorks

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Re: K04 Conversion - Do you ever regret it? How is it for daily driving?
« Reply #27 on: April 16, 2024, 05:10:44 pm »
Update on my situation. Took down the stock downpipe to take a look at the turbo. Yeah, it's bad... No wonder it was underboosting..





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 #28 on: April 17, 2024, 01:16:37 am »


It's hard to see in the video, is it moving a lot?

There is always a tiny bit of play on a disconnected turbo as there's no oil in the bearings, but it should be fairly minimal.
'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 #29 on: April 17, 2024, 02:23:47 pm »
It's hard to see in the video, is it moving a lot?

There is always a tiny bit of play on a disconnected turbo as there's no oil in the bearings, but it should be fairly minimal.

I've compared it with my 1.4's K02 turbo with 158k km on it. That one doesn't move whatsoever. This one moves up, down, left, right back and forth. You can hear it ticking as it hits the wall of the housing.

Right now I'm split between repairing this for $200 and using it till later when I'll get a brand new oem k04 for $1400 or getting a used k04 for $400 and using that if it's in a good enough condition.
« Last Edit: April 17, 2024, 02:53:07 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