In the never ending quest for more power I present to you...
The K04-015 turbocharger
From the outside there is no visible difference between stock and the K04. I'm told it's what's on the inside that counts -- a more efficient turbine which allows higher air volume at the same boost pressure.
As you can see there is a difference between the turbines. I don't know much about turbo design but the K04 seems like it has a more aggressive blade pitch. Seems like it would take a bigger "slice" of air while rotating. Just a guess.
The K04 sounds distinctly different from the stock K03 unit. Any 1.8T owner who has been running a 0.8 or 1.0 bar chip and has a sharp ear would be able to tell something was up the first time you spooled up some boost. While the K03 has a "ffffweeeee" sound the K04 has a higher frequency "swsssss" sound. Even with the stock ECU you can hear the K04 at 7 lbs of boost. The K03 with a stock ECU is completely silent at 7 lbs. The K04 whistles like it means business... even at 5 psi. I find myself easing into the throttle just a little now and then to hear it spool... cool sound.
The 235hp turbo kit I purchased included:
I've also installed Bosch Silver F2CS spark plugs (purchased separately from elsewhere) which are a cooler heat range to help curb detonation.
It's right... finally!
If you've been following my K04 turbo installation saga you know I've had months and months of problems with the upgrade -- 4 months of problems to be exact. I had no end of trouble with the car.. it just wouldn't run correctly and performance was nowhere near the claimed horsepower. We just couldn't get the software right. The vendor kept their nose to the grindstone and eventually found the magic combination that makes my car purr... or should I say growl.
The 1.0 bar chip upgrade from stock is a much more dramatic improvement overall than a K04 upgrade. However, the K04 turned my car into feisty beast that charges hard as low as 2300 rpm and makes it presence known until 6,000+ rpm. Driving around town and on the freeway it slaughters most traffic with or without a downshift when you lean on the skinny right pedal. 4500+ performance is good and the power drop-off experienced after 5000 rpm with the K03 turbo and 1.0 bar chip is gone -- the car has a satisfying pull until you bump into the rev limiter. No increase in turbo lag with the K04. I like this setup it was just a long road to get to this point.
The Bottom Line
Do I consider the upgrade worth it? Would I do it again? Yes and yes. Although, I don't think I'd be so patient the next time.
If you are one to expect an upgrade to be truly an install, drive and forget ordeal I suggest you do your homework before you take the plunge on an upgrade of this type. I've done heavy duty engine upgrades and such before and they always have a few rough spots... it's just the nature of high performance.... this one was no different.
Here's some interesting (and somewhat puzzling) information based on published dyno data for stock, chipped and chipped with a K04 turbo. The puzzling part is the stock dyno pulls indicate the engine was performing above the factory claimed horsepower and torque. Was this engine really performing above average or do we have dyno error or some other influencing factor. Personally, I adjust the numbers based on what stock should be knock off a few HP and LB-FT as some kind of crude normalization -- I suspect would be reality numbers. Note that this data was "eyeballed" off of pictures of graphs so this data is probably not entirely accurate. Repeat: Assume these numbers are very crude (and potentially inaccurate) data. I don't want any email telling me my numbers are bogus or misleading... I worked with what was available just to get a ballpark idea. You might say bad data is worse than no data at all... probably true... but since I did the work for my own curiosity I figured some others might care to see the info too.