Borg Warner refers to both turbos as K04's. But, the S4 version apparently has a smaller compressor housing and thus different wheel. This would cause it to spool up faster. I don't know about the turbine housing-which is what will determine exhaust mating. I think they are the same. Here's what I've been told. The RS6 turbos or even the Garrett ball bearing GT25 or GT28 turbos both will allow for more air and therefore more fuel and more Hp. But theHp to the pavement doesn't occur until it travels through the drivetrain: engine--crank--flywheel--trans--diffs. The hard parts in the engine will not handle that kind of power and torque. That's roadblock number 1. The other issue is torque curve. As it is now, people say "man that car must be fast" but they equate fast to "beat a mustang 5.0 (or evo8 or 9) off the line" as fast. You know, pin you back in your seat like a roller coaster. But the reality is, my car doesn't have that kind of low end power and thus doesn't really shine until you floor it a 40mph and get to 100 real fast. Then, and only then, does my car(stock) seem "fast". I want what wammy has. That's fast! That's why I traded in my A4 2.8 for the this car (also, my son's carseat doesn't fit in the A4). The RS6 turbos, without fuel upgrades to match andtuning to bring it all together ,so it's fast off the line, isn't going to happen on its own. So they wont give me the low end torque that I want and therefore seem a wasteunless I do the fuel mods, rebuild the engine and probably the rest of the drivetrain. In short, the RS6 turbos will mount but move more air at the mid range which is exactly where I am now. In order to get the desired low end torque, you'd need the aforementioned upgrades with the RS6 turbo or a turbo with smaller ratios that spool up faster like the S4 turbos.

 

I realize that only installing ko4's or ko6's without anyother upgrades that you mentioned would be virtually pointless. You would just be running more efficient turbos. My question was more along the lines of if you installed all other necessary upgrades would you see a significant difference in power between the 2 different turbos? If so where and what would the power curve look like?

Also if you upgrade to k04's and all other necessary hardware with a tip, what part would be the first to fail and therefore be the most logical to upgrade/ is there anything that is reccomended to upgrade?

 

There would be a tremendous difference between the turbos if done properly. You can move more air and therefore burn more fuel with the larger turbo. Burning that much fuel would produce more power, so much so that I would be forced to beef up the moving parts in the engine and trans. I could use the larger turbo, limit the fuel so only produces about 475Hp but would then be gambling on being able to produce that Hp at a desirable rpm. I laugh when I see some of the car ads promoting 400 Hp in some gassers. That Hp is just before or at redline. Who the hell, besides wammy,has the vehicle at redline for any serious length of time? (that's one advantage of a diesel-bigHp, twice the torqueat lower rpm) So the s4 turbos will give me, with my other upgrades, about 470Hp at relatively lower rpms and in the first 3 gears. The larger turbo, with respective upgrades, can give me more Hp, in excess of 550or 600 but the rest of the car can't handle that. The same is true for the Garrett GT25 or GT28 turbo system. That type of set up is for serious power and requires serious money.
Put it this way, have you ever tried to get a car moving with a manual transmission in 2nd gear instead of first? What happens? It takes longer to wind out and get to peak torque, then shift to 3rd. Same thing with a larger turbo.
I'm told that you can get upto about 475Hp without getting into the engine or major trans upgrades. Depends on who you ask and if they're trying to sell you anything. My guess is that the torque converter would be the first to fail. That's why I'm upgrading mine.
By the way, there is a saying that Hp is whatspins the air conditioning condenser and pullies, torque is what breaks the tires loose!
Did I answer your question or just ramble on like I usually do?

 

Wammy congrats on getting the KO4's in and everything. I just did an oil change and noticed that my Main Seal is leaking... Which would most likely require an engine pull to fix. Looks like I need to find a bunch of money to do what you did!

How has the MPG changed since the install? And how does it feel in the 2-3500 RPM range compared to stock?

 

I get the normal highwaympg and intown mpg... If you keep it in low rpms when babying your ride during work ect. you get the same mpg i found. When flooring it you get about the same mpg as the previously APR chip I had on, 8-12 mpg . This baby flies though.. i beat a evo 9 last night from a stop :-X! The power off the line is right around 400 ft/lb torque with an extra 100-150 HP helping at the low rpms 2.5-3.5... from there up is only better with an extra 100HP+ pushing through the rest of the RPMS. The car is hands down quicker than a rs4 / rs6 if i dare say :X

 

wammy, the more you talk, the more anxious I get to get mine done. Some kid on my softball team with a newer Camaro wants to race me when I'm done--looking forward to that.

 

You should def be pumped... I have rocked an evo9 with mods, sti with mods, srt-4 FULL MODS, camaro with mods, new mustang gt( nothing special ), and RAPED my friends m3 full mods! I was prob about as anxious as you are with getting my ECU back into my car. My friend def be pumped... I thought I might be over hyping what I am getting done. I had really big worries that the moneyI spent wasn't going to be worth it.I was wrong! I was 10 times as shocked when I got into my car after everything. People try to pull up to me thinking, "hey this is a boat trying to go fast"... Then you don't see me ! I was sooooooooooooooo HAPPY i called AWE 2-3 times that day telling them how happy I was with there products Trust me I still have the same feeling everytime I hit it This leaves only1 question my friend.... How much better can the car get if we did the whole fueling!

 

so all you got from awe was the intercoolers n k04s ?? what giac program do u have


ive heard there was minimal gains unless you upgrade to fueling ... is your fuel pressure pump upgraded from stock ...

what was the grand total from awe if u dont mind me asking bc i was planning on doing this myself when i do my timing to save a couple thousand in labor

 

Yes you need the 5.0 bar Bosh Fuel pressure Pump. (awe-tuning)
I got the intercoolers from AWE.
Ko4's from prince at Vast including the inlets, hardware.

 

wammy , I have nearly identical mods to yours. I agree the car is very quick for an A6, but keep that in mind, it is an A6 (heavy). Sucessfully spanking an RS4 would be an amazing feat. I would expect that you would be able to run mid to high 13's at the track. The tip tranny is a limiting factor, it is very heavy and does not take well to launches above 2000rpm. So were in the hole off the line with most guys launching at 4500-5000rpm. Like I said, I 100% agree that 3- is way quicker than stock, but we probably wont beat any lambo's.