CTS K04 vs. CTS K04-X

[CycloSteve]

AZ thoughts on the CTS K04-X version as compared to the standard CTS K04? Other than $450 more and likely needing a custom tune beyond the standard K04 tunes out there, wondering if anyone has experience (good or bad) with either.

[Jayz691]

Seen a few people in my FB groups running them(k04x), but could never get a data log from anyone, to compare MAF peak readings to my reg CTS K04.
There's no info if comp wheel is any bigger or not. I know it has clipped turbine, so should flow a little better up top. But like I said, no real data to compare..

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[CycloSteve]

Hmm, not interested in adding HP near or at redline, but rather to have the turbo be more efficient. Not sure if the "X" version does that or not.

My driving style and preferred HP curve is more like the zero-sixty launches to get up to speed, or carving back roads, passing on two lanes, etc. Rarely get over 5k rpm, as one of my other rides is a turbo-diesel Landcruiser, thus I like usable mid-range torque.

Leaning towards the standard K04.

[oVeRdOsE]

maybe get hybrid one, intake k04 turbine only.


imo the most reliable mod you can do is a stage2 unitronic flash. not the hpfp one, since it wears the cam follower faster assuming you use a kit to mod the oem hpfp.

people willing to put $ for a ko4 kit, should do balancer shaft delete, oil pump conversion and legit hpfp upgrade. And at this point, it just wont worth the money to get around 330bhp...


It cost not much more to built my 600whp N54, and my B7 (265bhp) feel like a slow ass econobox now in comparison.

[CycloSteve]

N54, LOL, my 335 is a ton of fun to drive in summer, but what a pain to keep from breaking - and it is bone stock and is the only car that I think truly hates me.

I figure whatever setup I go with will eventually eat the motor, thus will be sourcing and building another to hang out in my shop for that day (or when I get bored).

[Jayz691]

A K04 build can be reliable on a stock block, been running mine for 2-3 years now.
The HPFP upgrade itself is fine, just check your follower, most utilize the stock spring, but higher rail pressures more often will add stress, but not a big deal.
Balance shaft delete is good no matter what. If your pump assembly is in good shape, $150 for a WASA freewheel, new hardware, and 3 of the 4 piston cooling jets and done. The jets fail, and will cause lower idle pressure. Don't do the 1.8t conversion or anything like that, and you'll be fine.
It is quite a bit of $ for what ya get, but it's fun..

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[oVeRdOsE]

I dont say the car wont work, it's just already putting money on turbo, exhaust, fuel pump control module, hp fuel pump, injectors and tune ; I would address all the 2.0t possible issues.

and to get overtaken by lot of modern car on the highway

I'm thinking to put more power on my B7, since I decided to keep it, and it feels slow now. Might get a used kit one day.
I've completed a bmw swap, now I'm tempted to do a vr6 swap on the b7

[Jayz691]

Well yeah, no matter what, it's a 20yo 4cyl luxury sedan. It's not gonna be fast. If you want a "fast" car, you don't buy a b7.
For me and a lot of others, it can be a fun car that's great in bad weather(snow, etc), and fairly comfy.
After having my auto sedan for 6-7yrs, everything done to it, my girl basically hates it(harsher ride, etc). Now my recent purchase of my 08 manual TI avant has made me(and my girl) fall in love again. Kinda liking the wagon, and drives/rides beautiful. It's completely stock, and unmolested.

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[AudiB720TS]

Have you checked the that the “X” isn’t transverse only (different flange, no DV?)?

To make the most out of a K04 you’d want to have supporting mods. It gets expensive. At that point you might as well throw in some more cash.

I’m several years into running a K04 hybrid. Car is very fast and lots of fun. No complaints other than wanting to have a fast automatic gearbox instead of all this damn shifting in city traffic… Might migrate to an S3 and swap engine over.

[Jayz691]

Have you checked the that the “X” isn’t transverse only (different flange, no DV?)?

To make the most out of a K04 you’d want to have supporting mods. It gets expensive. At that point you might as well throw in some more cash.

I’m several years into running a K04 hybrid. Car is very fast and lots of fun. No complaints other than wanting to have a fast automatic gearbox instead of all this damn shifting in city traffic… Might migrate to an S3 and swap engine over.

They make a long and transverse model.
1050x is transverse, 1070x is for longitudinal cars.
I wouldn't say a b7 with a K04 is "very fast", but it's def fun.

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[vce1232000]

Ive had my KO4 installed since late 2013 till now. still a fun car to when I do.

[oVeRdOsE]

Well yeah, no matter what, it's a 20yo 4cyl luxury sedan. It's not gonna be fast. If you want a "fast" car, you don't buy a b7.
For me and a lot of others, it can be a fun car that's great in bad weather(snow, etc), and fairly comfy.
After having my auto sedan for 6-7yrs, everything done to it, my girl basically hates it(harsher ride, etc). Now my recent purchase of my 08 manual TI avant has made me(and my girl) fall in love again. Kinda liking the wagon, and drives/rides beautiful. It's completely stock, and unmolested.

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but it can be fun.

I drove a stage 2+ Unitronic with a k04, and the fun factor was definitively not better than my stage 2 k03 b7.

A fun b7 is ; a flash tune, basic mods, drop, swaybar and good tires.

Now a rare B7 like a Ti avant 6mt, could very benefit of a 2.7tt swap. But this engine, while more powerful than a 2.0t, it's no match of the 2020-era sports cars. I did a excel sheet to built either a E91-n54 or B7 avant 3.0T, and the E91 was hands down cheaper and faster (and arguably more reliable).

Also power is so relative now, a friend got a brz and find it quite quick and some got a tuned G80 M3 automatic and they said it's slow...

[Sa12_gecko]

Interesting…my wallet likes to hear this haha

[CycloSteve]

Going with the standard K04 after reading the B8 experiences with the X version. The "should be able to support" answer from 034 about the X did not give me confidence on the software side, where the standard K04 seems to be a sweet spot for most tuners.

https://www.audizine.com/forum/showt...-CTS-TR-1070-X

[Jayz691]

but it can be fun.

I drove a stage 2+ Unitronic with a k04, and the fun factor was definitively not better than my stage 2 k03 b7.

A fun b7 is ; a flash tune, basic mods, drop, swaybar and good tires.

Now a rare B7 like a Ti avant 6mt, could very benefit of a 2.7tt swap. But this engine, while more powerful than a 2.0t, it's no match of the 2020-era sports cars. I did a excel sheet to built either a E91-n54 or B7 avant 3.0T, and the E91 was hands down cheaper and faster (and arguably more reliable).

Also power is so relative now, a friend got a brz and find it quite quick and some got a tuned G80 M3 automatic and they said it's slow...

Unitronic k04 is also kinda neutered like APR. Most OTS K04 files are extra "safe" for obvious reasons on a stock block. If you think a K04 setup wasn't any more fun than a "stage 2", something was wrong there..
Even on the safe side(stock block) it's an extra 50-60hp, and prob similar added tq. With rods and a custom, more aggressive tune, could be more like 70-80+ more.
Now, is it worth the money, that'll depend on the person. That's an opinion, but it's definitely "more fun"..

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[Nizmo]

APR k04 file with S3 injectors is a lot of fun. All 333bhp of it

[oVeRdOsE]

Unitronic k04 is also kinda neutered like APR. Most OTS K04 files are extra "safe" for obvious reasons on a stock block. If you think a K04 setup wasn't any more fun than a "stage 2", something was wrong there..
Even on the safe side(stock block) it's an extra 50-60hp, and prob similar added tq. With rods and a custom, more aggressive tune, could be more like 70-80+ more.
Now, is it worth the money, that'll depend on the person. That's an opinion, but it's definitely "more fun"..

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the main concern here, is I dont own a k04, but test drove one.

For a car guy, even get 10 more hp is a very enjoyable goal.

the second concern is now I own a way more powerful car, you know, you don't know you ''need'' power until you have power.

[Jayz691]

the main concern here, is I dont own a k04, but test drove one.

For a car guy, even get 10 more hp is a very enjoyable goal.

the second concern is now I own a way more powerful car, you know, you don't know you ''need'' power until you have power.

Lol, very true indeed..

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[Cyrik]

Now, is it worth the money, that'll depend on the person. That's an opinion, but it's definitely "more fun"..

Not trying to get off topic here since this is a K04 thread... Sorry in advance.

If I may chime in on this... I think most B7 owners share the same sentiment that for the money it really isn't worth it to go all out on this platform. I'm at a crossroads with my car at the moment, currently Stage 2 JHM, and if I wanna add any more power I have to spend upwards of 3k on a car that's worth 5k to go K04 (upgraded fuel pump, injectors, and turbo).

The way I see it, in today's day and age why not do drop-in rods for an extra $700 and some labor and go a bigger turbo instead? Also in my case, the TIP trans becomes more of a limiting factor at those power levels from what I've heard. And at that point why bother doing any of it at all when, for example, a C6 A6 with the 3.0T is less than 10 grand nowadays and you START at the power level a Stage 3 B7 already is.

By no means am I trying to shit on the B7 platform, this is the best car I've ever owned, but it's really starting to show it's age in today's market. Probably why I'm going to move on in the near future unfortunately.

the second concern is now I own a way more powerful car, you know, you don't know you ''need'' power until you have power.

I think this is what has led to my above sentiment, being "spoiled" into faster cars/platforms that are more affordable now that they've aged a bit. I have a couple friends with 335i's and my car can't hold up against them at all. It makes me question why I spent all the time and money on my car in the first place. Hell, my friend's Z28 Camaro with the 427 put out over 400whp on a dyno (at altitude mind you) with barely any mods done to it. Some say that's like comparing apples to oranges, as both of those platforms are much different than an Audi A4, but I digress.

[Nizmo]

I am not saying that a B7 will appreciate to that of an RS4, but there is a reason that car has aged and appreciated so well. B5 S4's rock bottom hit about 4k, now go look. EVO's etc. Its a time old crossroads. Some will stay, most will go. Sadly.

[Jayz691]

Not trying to get off topic here since this is a K04 thread... Sorry in advance.

If I may chime in on this... I think most B7 owners share the same sentiment that for the money it really isn't worth it to go all out on this platform. I'm at a crossroads with my car at the moment, currently Stage 2 JHM, and if I wanna add any more power I have to spend upwards of 3k on a car that's worth 5k to go K04 (upgraded fuel pump, injectors, and turbo).

The way I see it, in today's day and age why not do drop-in rods for an extra $700 and some labor and go a bigger turbo instead? Also in my case, the TIP trans becomes more of a limiting factor at those power levels from what I've heard. And at that point why bother doing any of it at all when, for example, a C6 A6 with the 3.0T is less than 10 grand nowadays and you START at the power level a Stage 3 B7 already is.

By no means am I trying to shit on the B7 platform, this is the best car I've ever owned, but it's really starting to show it's age in today's market. Probably why I'm going to move on in the near future unfortunately.



I think this is what has led to my above sentiment, being "spoiled" into faster cars/platforms that are more affordable now that they've aged a bit. I have a couple friends with 335i's and my car can't hold up against them at all. It makes me question why I spent all the time and money on my car in the first place. Hell, my friend's Z28 Camaro with the 427 put out over 400whp on a dyno (at altitude mind you) with barely any mods done to it. Some say that's like comparing apples to oranges, as both of those platforms are much different than an Audi A4, but I digress.

Well, I can give some feedback for my reasoning anyway. Let's forget about just the power factor, and jumping ship to a dif platform. Personally I love the b7, and after 6-7 years of ownership, I know the platform pretty well. Also, I have a lot more done that I'd have to either part out, or take a huge loss. That's why I recently bought a manual TI avant. It's in MUCH better shape, lower miles, and will hold much better value than my base sedan. I'll use my sedan as a donor for parts, then likely sell it.

Now for power.. I did mine in stages so it wasn't such a big chunk of $ at once. Also it was my daily, so couldn't have the car down for long. When I went from stage 1(Motoza) to stage 2, I also upgraded rail sensor, prv(APR), and map sensor in preparation for a K04. When I went to a K04 later, just needed turbo, injectors, and re-tune. Once you have a solid K04 setup, won't take much to go to a smaller full frame setup.
My sedan is at 250k+ miles so was looking to rebuild/refresh, and found a deal on new IE rods and free rings with them. Collected parts for a refresh, but didn't get around to it. Also picked up a top mount JDL tubular manifold and PTE6266/WG for dirt cheap. Was gonna rebuild with rods, and re-tune to push the K04 for now. Sell the 6266 and get a gt28 or similar for a little more power, but still be a good daily.
Now things have changed since I got the new avant..
Been running the CTS K04 for a few years, on stock block, and it's been great.
My car is also a tip car, got the JHM tcu tune and haven't had any issues with the trans. The 6hp19 is a pretty solid trans. Only issue is the TC, with the common hunting issue. I bought a built TC to remedy it, and hold power better down the road, but no longer need it cuz the new ride is manual. TC is from VAST, and now for sale.
Know I got off topic a bit but basically, if you like your b7 and wanna keep it, a K04 setup is a very nice bump, without needing to do any block work. If you do rods, you can actually push the turbo. With all the supporting mods done correctly, it won't take much to do a smaller BT setup down the road, if ya wanted. That was my thinking.
If you can park you car and spend a few months fully building it, then just do it in one shot I guess. Dif situations, dif routes.

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[CycloSteve]

Like Jayz, I find the B7 to be a good combination of reliability, relatively easy to work on, comfortable, decent fuel consumption (getting up to 500 miles on a tank), and have the ability to produce good usable power. In fact, I am picking up a Ti sedan later this week with 125k on the clock and some nice upgrades for the Mrs. to use...and will be selling the 335i and my B5 Avant as I am tired of tossing money into those two cars as they age...yes, they both were really fun, but it is time to hand them off to someone else to enjoy. Will have three B7's in the stable soon.

Back on topic - my K04 and other parts for the Avant should be arriving later this week or next. It may be a month until I tear it all down and build it back up, but that event horizon is approaching.

[Nizmo]

Like Jayz, I find the B7 to be a good combination of reliability, relatively easy to work on, comfortable, decent fuel consumption (getting up to 500 miles on a tank), and have the ability to produce good usable power. In fact, I am picking up a Ti sedan later this week with 125k on the clock and some nice upgrades for the Mrs. to use...and will be selling the 335i and my B5 Avant as I am tired of tossing money into those two cars as they age...yes, they both were really fun, but it is time to hand them off to someone else to enjoy. Will have three B7's in the stable soon.

Back on topic - my K04 and other parts for the Avant should be arriving later this week or next. It may be a month until I tear it all down and build it back up, but that event horizon is approaching.

Loaded 06 S-Line. Back when that meant something LOL. That's my keeper B7. I Have a 07 CVT I got to pull the engine to build out. 06-08 A4 was the most beautiful A4 ever made. Yea I said it.