AudiWorld Tech Articles

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.

I've also installed Bosch Silver F2CS spark plugs (purchased separately from elsewhere) which are a cooler heat range to help curb detonation.

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.

But, if you had visions of showing your tail lights to that pesky ///M3 you see on the way to work every now and then you'll need just a little more out of the little 1.8T unless you catch the guy (or girl) gawking at themselves longingly in the mirror, the M3 is equipped with a slushbox (a sin for sure... they deserve to get dusted) or the other driver is just not on the ball. My car is fast but it's not quite into the ///M3 neighborhood.

Comments from Steve Brown:

Well, Don came over on Saturday & was brave enough to let me drive his car (my last three vehicles were autos & my manual experience comes from my fathers TR4A & his MGA (no syncros to get back to first!). Anyway, I'll let him tell the tale of how he got the car to where it is now, but I'll tell you, his car is now (1) fast, (2) stable, engine wise, throughout the rev range, (3) fast, (4) fun, (5) fast.

The car gets up and moves! (He might try to say there is a bit of hesitation as you spool up the turbo off the line, but it's MINOR). Cruising at anywhere from 25-60 (no place for HIGH speed test), you could basically aim the car & GO, RIGHT NOW!

My humblest apologies to Don's clutch, getting moving & 1-2 were VASTLY different from a 75hp 30 year old car.

Wow...I realize now two things: (1) The 1.8T is an amazing piece of work, (2) I'd be completely in debt modifying one if I had it.

There is a turbo whistle, but I only noticed it when I was outside the car. The car sounds like a MACHINE, but not at all offensive (still stock exhaust).

A consolation: My horns are WAAAAAY louder than his.
Donp: [That's for damn sure... I was shocked! Really loud! I need these!!]

Steve
98.5 2.8

Testing I've done so far has resulted in 1/4 mile times of 14.61@93.30 mph and 0-60 runs of around 6.01 seconds. These were the first runs I'd done with this configuration -- I suspect I can shave a tenth or two off of these times once I learn the powerband of the car and where to shift to squeeze out the most performance. If so, that would put me in the high 14.40s or 14.50s. That aint bad for a 3600 lb car with a 1.8 liter engine. I have not had time to do in-gear testing yet but I suspect those times will be good too. Yes my friends I've now got a sleeper -- A mild mannered looking A4 with a split personality. My goal has been accomplished.

Update: Since my initial 14.61 1/4 mile run I've done additional runs. My best time so far: 14.49@95 mph.

I did find that the car runs perfectly with the stock (ie. factory) prom installed. I wanted to verify I could run the stock software as I heard that the car would not run correctly with a K04 -- mine does just fine. Smooth (albeit slow) factory power right up the the rev limiter.

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.

Torque: Stock v Chipped v K04 Chipped
				Change
RPM	Stock	Chip	Turbo	stock v chip	stock v turbo
2500	160	185	209	25	49
3000	160	222	245	62	85
3500	160	230	255	70	95
4000	160	235	255	75	95
4500	160	227	252	67	92
5000	158	212	242	54	84
5500	147	185	223	38	76
6000	135	160	200	25	65
6500	118	136	175	18	57
7000	-	92	135	-	-

Horsepower: Stock v Chipped v K04 Chipped
				Change
RPM	Stock	Chip	Turbo	stock v chip	stock v turbo
2500	75	90	100	15	25
3000	90	125	137	35	47
3500	108	155	170	47	62
4000	123	180	195	57	72
4500	138	195	216	57	78
5000	151	200	230	49	79
5500	155	195	235	40	80
6000	155	185	230	30	75
6500	146	172	220	26	74
7000	-	155	180	-	-