4.0TT Build limit questions (S6)

[InvisibleFrisby]

I've got 132,000 miles on my 2013 S6, been running APR downpipe and accompanying 93 octane tune since about 70,000 miles and it's run well. I'm starting to get some oil burn which I assume to be the weak rings that seem to be on all Audi engines of this era. I'm considering doing a rebuild and going for more power, but I can't seem to find much information about people building on these engines to see what the limits are.

Does anyone have information on what kind of power this block can hold reliably? What the 7 speed DCT can hold?

[brad281]

I've got 132,000 miles on my 2013 S6, been running APR downpipe and accompanying 93 octane tune since about 70,000 miles and it's run well. I'm starting to get some oil burn which I assume to be the weak rings that seem to be on all Audi engines of this era. I'm considering doing a rebuild and going for more power, but I can't seem to find much information about people building on these engines to see what the limits are.

Does anyone have information on what kind of power this block can hold reliably? What the 7 speed DCT can hold?

How many miles are you going before being prompted to add oil?

Oil burn is very common on Audi turbo engines, especially the 4.0T with cylinder on demand. Mine had been using a quart of oil every 1500 miles or so since I got it with 29k miles on it. I switched to Motul Xcess 8100 oil and now it's requiring a quart every 2500-3k miles. Unless you're using oil more frequently than this, I don't think you've got anything to worry about.

Sent from my SM-A716V using Tapatalk

[ItsLarryG]

The DSG is a weak point at higher hp unless you start going with aftermarket clutch packs, not sure what the next driveline weak point is once that is addressed.

If you are going through the time/cost/effort/whatever of a rebuild, anyone know if you can swap pistons for RS7 to lower the compression to help with the heat issues in the S engine? This talking point usually comes up when someone is asking whether to buy and RS or save money on the S, but I would assume you already own this car outright and not really considering trading it in for an RS7.

[InvisibleFrisby]

When I purchased the car at about 60,000 miles, through about 100,000 I would change the oil every 10,000 miles and not see any prompting to add oil. The last couple of iterations I've seen the message around 7,000 miles.

[InvisibleFrisby]

The DSG is a weak point at higher hp unless you start going with aftermarket clutch packs, not sure what the next driveline weak point is once that is addressed.

If you are going through the time/cost/effort/whatever of a rebuild, anyone know if you can swap pistons for RS7 to lower the compression to help with the heat issues in the S engine? This talking point usually comes up when someone is asking whether to buy and RS or save money on the S, but I would assume you already own this car outright and not really considering trading it in for an RS7.

Yes, the car was paid for outright when I drove it home from the seller in 2017. Perhaps moving to the RS7 with the better transmission and a higher starting point would be the best.

[brad281]

When I purchased the car at about 60,000 miles, through about 100,000 I would change the oil every 10,000 miles and not see any prompting to add oil. The last couple of iterations I've seen the message around 7,000 miles.

Change your oil every 5k, especially if tuned.

Sent from my SM-A716V using Tapatalk

[OlyS6]

I've got 132,000 miles on my 2013 S6, been running APR downpipe and accompanying 93 octane tune since about 70,000 miles and it's run well. I'm starting to get some oil burn which I assume to be the weak rings that seem to be on all Audi engines of this era. I'm considering doing a rebuild and going for more power, but I can't seem to find much information about people building on these engines to see what the limits are.

Does anyone have information on what kind of power this block can hold reliably? What the 7 speed DCT can hold?

The DL501 DSG has been able to deal with at least 700whp and 700 ft-lbs of torque reliably for many folks on this platform. My clutches slipped at well under that, but I’m pretty sure it was just a case of a faulty clutchpack. Several folks have snapped axles when launching with higher levels of torque.


Sent from my iPhone using Tapatalk

[Alabama]

The DL501 DSG has been able to deal with at least 700whp and 700 ft-lbs of torque reliably for many folks on this platform. Several folks have snapped axles when launching with higher levels of torque.

Great point. How do you reconcile the folk who claim their DSG fails at moderate driving when others break the axle while the transmission holds?

[MattyMarkey]

Great point. How do you reconcile the folk who claim their DSG fails at moderate driving when others break the axle while the transmission holds?

I would think proper/prior maintenance and driving characteristics/conditions might be a factor. Also, maybe those who have a TCU tune vs those who don’t?

Throwing out some wild guesses. Similar to the oil screen; it could fail tomorrow, or never fail, but it’s a weak point and ya never know! Haha


Sent from my iPhone using Tapatalk

[OlyS6]

No idea. I'm sure some DSG failures on the lower end of the spectrum may be faulty production, or potentially poor choices while driving in manual mode. I know I experienced clutch slip at pretty early mileage on just the APR Stage 3 tune (around 600 awhp). The axle issues are sometimes more associated with wheel hop on a violent launch. I don't know enough about how force is translated between the transmission and the differentials/axles to be able to explain why one or the other may be more likely to fail on these cars. Thus far my axles have been fine (knock on wood), but I almost never launch the car either. That said, I'm currently at roughly 700 awhp, and recently developed 'clunking' from my driveshaft, despite having an upgraded driveshaft bearing carrier installed. Turns out there is some rubber buffer between inner and outer tubes of the driveshaft that when it breaks down can cause 'clunking' felt under the driver's seat with deceleration and/or acceleration.

[digdah]

Your wording seems to describe the exact issue I am having. Mine only happens under heavy acceleration, at least for now. So I am currently no longer seriously looking into changing out my carrier bearing but will have my shaft examined? Always an adventure with this car, sigh.

No idea. I'm sure some DSG failures on the lower end of the spectrum may be faulty production, or potentially poor choices while driving in manual mode. I know I experienced clutch slip at pretty early mileage on just the APR Stage 3 tune (around 600 awhp). The axle issues are sometimes more associated with wheel hop on a violent launch. I don't know enough about how force is translated between the transmission and the differentials/axles to be able to explain why one or the other may be more likely to fail on these cars. Thus far my axles have been fine (knock on wood), but I almost never launch the car either. That said, I'm currently at roughly 700 awhp, and recently developed 'clunking' from my driveshaft, despite having an upgraded driveshaft bearing carrier installed. Turns out there is some rubber buffer between inner and outer tubes of the driveshaft that when it breaks down can cause 'clunking' felt under the driver's seat with deceleration and/or acceleration.

[OlyS6]

Your wording seems to describe the exact issue I am having. Mine only happens under heavy acceleration, at least for now. So I am currently no longer seriously looking into changing out my carrier bearing but will have my shaft examined? Always an adventure with this car, sigh.

I'd try the driveshaft carrier upgrade first. If the clunk remains, then the driveshaft. (You do need to cut off the current drive shaft carrier and the rubber surrounding the carrier bearing). As of right now, new driveshafts for our cars need to come from Germany and can take a bit (fingers crossed mine will get here this week).

[IowaRS7]

I haven't been on this site for quite a while but I am working with Silly Rabbit on options for building the motor. I have been waiting for forged pistons from almost 10 months and I have also been working with a couple of companies on sleeves and pistons for blocks that need to be sleeved. Because there really hasn't been many options to date for this, it has been a process to develop and work through all the steps to create forgings and so on. The good news is we are in the home stretch and after all our first runs are done, it shouldn't take nearly as long to order more going forward. If you have interest in building the motor, let me know by sending a message.

[brad281]

I haven't been on this site for quite a while but I am working with Silly Rabbit on options for building the motor. I have been waiting for forged pistons from almost 10 months and I have also been working with a couple of companies on sleeves and pistons for blocks that need to be sleeved. Because there really hasn't been many options to date for this, it has been a process to develop and work through all the steps to create forgings and so on. The good news is we are in the home stretch and after all our first runs are done, it shouldn't take nearly as long to order more going forward. If you have interest in building the motor, let me know by sending a message.

I thought the RS7 already had forged pistons. No?

Sent from my SM-A716V using Tapatalk

[IowaRS7]

I thought the RS7 already had forged pistons. No?

Sent from my SM-A716V using Tapatalk

Pretty sure from pictures I have seen they are cast aluminum, which is typical of OEM internals for mass production. The forged ones will be lighter as stronger.


Sent from my iPhone using Audizine

[Alabama]

I thought the RS7 already had forged pistons. No?

Sent from my SM-A716V using Tapatalk

From the 2012 4.0 engine self study program: "Cast pistons with a cast-in ring carrier for the compression ring are used in all engine versions. The principal difference in pistons for the engine variants is the shape of the piston crown." The difference in the accompanying pictures appears to be a larger diameter concave area in the center of the piston crown for the high horsepower variant. Mahle makes aftermarket forged pistons for smaller VW/Audi engines, but not for the 4.0t. In an old AZ post, DeerHunter wrote "Cast pistons are not terrible, in of of themselves. If knock is kept under control, there are essentially no downsides (and many upsides, since cast pistons wear better, are quieter,etc.). The fact that Audi uses cast pistons for all versions of the engine (including the S8 and RS6/7) speaks volumes for how tough they are. This wouldn't be one of my concerns, unless you're planning of building a 1,000 hp monster, in which case you're better off starting with another car."

[IowaRS7]

Mahle is the company we have been working with for months to make a forged Aluseal piston for the 4.0T stock block. The forged piston paired with forged pins and rods will allow for more power and higher revs with upgraded valve springs. With the tight tolerances and lower weight of the forged pistons with the aluseal design, we think this will be a great solution for high HP builds. There is also a sleeve/piston combo on its way for builds where cylinder wall damage has occurred and drop in pistons will not work. Similar build but using an iron sleeve and pistons designed for the iron sleeves. There has been quit the waiting period given the pandemic and high demand on these companies so very excited to finally see it all coming together.

I would agree overall that cast pistons are good, but if you want to build a motor for high performance with higher revs, using forged internals is the standard. Stronger, lighter and tighter tolerances to withstand much more abuse.


Sent from my iPhone using Audizine

[Burkeomatic]

From the 2012 4.0 engine self study program: "Cast pistons with a cast-in ring carrier for the compression ring are used in all engine versions. The principal difference in pistons for the engine variants is the shape of the piston crown." The difference in the accompanying pictures appears to be a larger diameter concave area in the center of the piston crown for the high horsepower variant. Mahle makes aftermarket forged pistons for smaller VW/Audi engines, but not for the 4.0t. In an old AZ post, DeerHunter wrote "Cast pistons are not terrible, in of of themselves. If knock is kept under control, there are essentially no downsides (and many upsides, since cast pistons wear better, are quieter,etc.). The fact that Audi uses cast pistons for all versions of the engine (including the S8 and RS6/7) speaks volumes for how tough they are. This wouldn't be one of my concerns, unless you're planning of building a 1,000 hp monster, in which case you're better off starting with another car."

For 99% of street builds, a cast piston is absolutely fine. Now will a forged one give you more margin of error for preignition or other irradic events that can kill a piston? Absolutely. When I built the engine in my miata, I did a rods only build. Everyone knew that you would ventilate the block at around 300whp from the rods breaking, but folks just went ahead and replaced pistons as a precaution, but swore up and down you would need them. My car made 350+whp for years before I finally got rid of it. Everyone swore my shitty little $800 short block with $150 valve springs and ported by me heads was going to grenade any minute, but it wasn't to be. That engine is currently throwing down 400whp in another car. That is like a 4.0t making over 800whp with port injection, wasted spark, and crappy cast pistons designed in the 80's.

However, if you want to rev higher, and have lighter pistons, and more margin for error, then by all means get them. I just couldn't justify increasing the cost of a build 160% for something not proven to be needed, and it turned out I actually didn't. If your tune is on point, the pistons will be fin, and I am pretty sure that logic applies from carbs to direct injection.

[IowaRS7]

Who wants to be the one to prove they are needed and at what power level 🤪 not me, so I will spend a bit extra for the added insurance while the motor is out. I am planning for 1300awhp though so it’s a no brainer.


Sent from my iPhone using Audizine