K04 Turbo upgrade, what all is needed?
 

I am seriously considering buying a 2001 S4 with 105k and was thinking about upgrading the turbos right away. I found some k04 turbos with the inlet and up pipes for about $1400. I was wondering what else is needed to complete this upgrade? I'm not looking to cut corners, but at the same time want to keep the cost as low as possible, so I'm only looking to buy the absolute necessary components. What kind of hp increase can I expect from this upgrade? I saw that AWE tuning has a kit available with these K04 turbos and it produces about 460hp, but the kit is way out of my price range and includes a lot of stuff, which I'm not sure is totally necessary. Would it be possible to get something close to this performance without paying the $8k AWE wants for this kit? Thanks

You will need a fueling kit - inejectors, hitachi-maf, rs4 airbox, etc. Plus an reflash of the ECU to change the program to utilize the new components. Without the ECU and fueling you will get zero additional HP.

You can typically buy the fueling kit separate from the turbos. Be aware that the 460hp advertised might include their exhaust manis, down-pipes and other upgrades, but you should expect around 450 crank horses with a proper fueling kit from K04.

search the forums for RS4 fueling. Also try homebrew tune.

Sane minimum list:
K04s
inlets
injectors
bigger maf housing
RS4 maf accordion pipe
clutch (a must, you will fry stock one guaranteed)
ECU re-program

highly recommended:
new Diverter Valves
new tranny+engine mounts (aftermarket, stock or RS4 are just too soft)
bigger rims/wider tires
brakes tune
new fuel pump
new fuel filter

recommended:
new N75
new TBB
bigger and better intercoolers

Add ons:
meth injection

RS4 motor mounts are too soft? Why would you want to rattle your teeth with solid motor mounts?

Bigger rims/wider tires? Why?

Brakes? Why?

I don't see why you would highly recommend items that would simply be personal preference and in no way are close to being needed with a K04 setup.

RS4 are too soft for stage 3, been there done that. The fact is that Sterns or 034 mounts poly mounts are close to stock in feel but a major improvement in limiting drivetrain travel.

Re tires/brakes.
These are in recommended group, not "a must" so chill.

#1 Handling, safety, the car will have pretty much 2x as much horsepower as stock car so that would only make sense.

#2 I didn't tell him to get BBK, I just advised a tune up.

What's wrong with these suggestions, they make more than just a little sense?

It makes perfect sense to upgrade the brakes, tires and suspension when you're talking about adding that much more power. Most people recommend it. It's not necessary as part of a K04 build, as that is mostly seeking engine performance, but it would be recommended for the overall benefit of the car.

From stock, about $10k to do it right.

RS4 motor mounts are perfectly fine on a Stg3 car. Too soft? Are you kidding, again, why do you want engine mounts that are just going to transfer engine vibrations into the frame so you can enjoy them in the cabin?

Getting larger wheels/tires does not make sense, how exactly are they improving the safety and handling? Stock size wheels and tires are just fine.

Getting the brakes checked out would be smart, but that doesn't have anything to do with a K04 setup, just a good thing to do with any car.

I don't think any of those suggestions make sense when it comes to essential upgrades with a K04 setup. A better clutch is about the only essential, aside from the components necessary to actually get a K04 setup running.

Upgrading to a BBK only makes sense if you plan to track the car or you want the look. It isn't going to provide any benefit in DD situations.

How exactly does engine HP relate to the suspension choice? Spring rate is one of the key attributes of a suspension, what spring rate is recommended for K04 power level? If there's a recommended upgrade, what is it? For instance, I'd advise getting a better clutch, at the TQ levels a K04 car makes there are clutches rated to handle that much TQ, so you find a clutch that can take the force. What grade of suspension component should one get with a K04'd motor?

Most people recommend these upgrades because they don't really understand how the components interact. Not that there is any harm in putting upgraded components on the car, but the logic of adding more power requiring these upgrades doesn't make sense.

I'll just toss in my brief 0.02. Find a kit/setup that you will be happy with, not based on price. Buying twice is always more expensive. If you love tuning and doing it yourself, by all means do it yourself. If you want it right the first time, buy a well sorted kit.

PS, these cars have cheap-ass detectors and spit crap parts back at the owner.

When you accelerate, what does the weight of the car do? That's right, it shifts back. Guess what takes that force. That's right, the suspension. Excuse my attitude, but the fact that you question these recommendations like we're idiots is kind of annoying. Go try to tell a true drag racer that suspension doesn't matter. If they know anything, they will laugh.

Generally if you're upgrading the engine to have more power, you want it to go faster. If you're going faster, you should make the appropriate upgrades to stop faster as well. Of course, from the same speed it's not much of a difference, but it's just generally a good idea. At the very least you should consider upgrading your pads if they're stock.

Tires affect handling and grip. It's generally recommended to upgrade tires with power output. Sure the stock size is capable, but you'd be better off improving your traction. If you only want to go straight, traction helps. If you want to turn, traction helps. Even if it's able to handle the power, it's a lot closer to the limit of the tire's performance, which is not optimal.

That's why these things were listed as recommended. Yes, a clutch upgrade would be considered more required, but doesn't have as much to do with safety as much as the delivery of power.

The S4 isn't a drag race car, it's a passenger sedan. What's good for a true drag race car doesn't necessarily equate to something that is good for the S4. Most component changes involve tradeoffs. Increasing HP doesn't necesssarily mean the suspension must be changed. Back to my question, what level of suspension upgrade is needed with K04 power? My answer, is that it depends on what you want from the car, and it will involve tradeoffs. Your answer is?

There's a distinct difference between going faster and accelerating faster. The stock S4 was electronically limited to 143 mph, more than fast enough for the street. I expect a lot of people upgrade beyond stock not so that they can do 160, but so that they can accelerate faster. In that case upgraded brakes are not necessary. Like I said, track use, where the car will experience repeated heavy braking, where fade would become an issue, is where you might think about upgrading the brakes.

"Even if it's able to handle the power, it's a lot closer to the limit of the tire's performance, which is not optimal." What size tire upgrade is needed? What's the increase in lateral g's that the car can handle when upgrading from stock size tires? You say that at K04 power level's the vehicle is closer to the limit of the tire's performance. Could you quantify the limit and how close the car is to it?

Flyboy, seriously. Read my post again. And again, and again. Essentials are listed in first group, if you have anything to say about these, go ahead. Rest is listed in recommendations section. You don't like it, fine. But don't put your own words into my mouth as nowhere did I say that tries, brakes and mounts are required.

At this point I just regard you as a person who's personal agenda is just to have a last word regardless of what others say. Additionally you seem to have some sort of comprehension problem so please work on that.

Everyone who has stage 3 (+) car will tell exactly the same thing I did. Broken engine mounts (even RS4), smoked clutches, crashed cars due to inadequate handling for torque/speed can be amended with proper upgrades and prevention.

I also don't understand your fear of aftermarket mounts. I personally have soft solid stern engine mounts and the car doesn't get any noticeable vibrations in the cabin so that's why I would highly recommend these over oem junk.

Julex - yeah, I've noticed that too about Flyboy but I've stayed out of it until now.

Flyboy: I don't know if you are trying to be a Troll or if you just have a problem with communication. Either way, there's no need to jump into a thread and start swinging wildly at other posters. This is not the only thread where you have done this.

I think your input is appreciated as is and your opinions are regarded as on par with anyone elses. There is no need to undermine the opinions of others...

There's not a set minimum limit that I could declare and be realistically accurate to what would be best. The weight shift on stock springs with stage 3 acceleration is ridiculous. It is not required, but recommended. That means it might be a good idea if you are able to, but you don't absolutely have to have it in order to do a stage 3 car. I didn't say that it had to be a drag set up, I was just explaining how the suspension plays a role in acceleration as well.

Yes, I realize that from the same speed you need the same braking power. When you can get to a certain speed faster, you're more likely to see that speed in the car. It greatly depends on the driver, but as an assumption, it might be a good idea for most people to upgrade braking as a result of the increased ability to reach higher speeds. Notice again that it's recommended, not required. Better brakes are safer no matter the power of the car. A car that can more easily see higher speeds would be safer with better brakes, unless the driver does not change their habbits while driving the car.

It all depends a lot on the specific tire. Traction is the limiting factor I'm talking about here. What size tire can the stock wheels run? 225? Since it's awd, a typical stage 3 set up might not inherently lose traction, but you'd be pretty close. I'll admit, I have no where near the ability to tell you how much force every tire model can handle at every size, but I know that it does not take much to break traction with the stock size (decent tire) and stage 3 power.

Let's assume he wants the car to have good handling as well. Guess what turning requires, on top of acceleration. Traction! While you should not be applying power through the turn, you'd be able to safely start applying power earlier while coming out of a turn with better tires. This also applies to even subtle changes in direction.

Fact of the matter is, with greater power you'll eventually require better tires. Going from 225 to 245 or 255 with minimal weight increase is going to be a significantly better set up (assuming relatively equal tire models) than the stock set up. Unless you're trying to be a ricer and do burnouts, you're losing the ability to accelerate or turn properly if you lose traction. Drifting is not a faster form of racing.

You make some good points. My personal experience is that I've not been able to break traction with my stock size tires even when on race gas. I'm not doing 5000 rpm clutch drop launches, so likely how one decides to drive the car comes into play. For a street setup Stg3 I've never found the stock size tires to be lacking, but you point out clear benefits to going with a larger tire, even if they're not realized.