What does X look like. Motor Addition

B6/7 S4/RS4
#1

This post will have both the S4 and RS4 motors in here for you to look at.

While both The RS4 and S4 motors share the same fill frame aluminum composite motors the motor structure, the motors are not the same.

The RS4 seems to be the Next generation of aluminum motor. The web walls are stronger and thicker then the S4. Components like the pistons and rods are different. Some say this leads to no cylinder wall score issues. I tend to lean towards that as well. The RS4 takes what the S4 motor did great and beefs it up a bit.

The good thing is that when people start to build the S4 motors, if they know and can identify the changes added to strengthen the RS4 motors these little additions (those that can be implemented) will really help.

Lets start with a quick picture of all 4 generations of the Audi aluminum motors.

On the top left, Gen 1 thats the 3.0 motors for the A4 and A6 motors. That motor is very strong and they have metal selves to help keep the strength up.

Top Right, Gen 4 the RS4 motor. The latest in the list of evolved Audi motors.

Bottom left. Gen 3 the S4 motors. This is the first attempt to use the special hone and not a wall coating to be able to eliminate the Gen 1 metal sleeve and the Gen 2 wall coating.

Bottom right, Gen 2 V8. This motor came in a few cars. It was the first aluminum Audi motor to not have the sleeves. Some reports came back saying that there were a few motors that started with the metal sleeves and then Audi used the Wall coating to strengthen the walls. A common practice in the Porsche aluminum motor series.

http://audirevolution.net/addons/albums/images/915909378.jpg

When we look closer On the S4 and Rs4 we will see that they went to a two piece, main girdle design. This adds a ton of strength to the motor as a unit.

http://audirevolution.net/addons/albums/images/984997505.jpg

If you have never seen the full face of the S4 motor you will see its ALL aluminum.

http://audirevolution.net/addons/albums/images/290097915.jpg

While Ive never been a big fan of the Cut away motor pictures. Looking at the S4 and the RS4 together like this really puts the jump from one motor to another in perspective.

S4

http://audirevolution.net/addons/albums/images/87305023.jpg

RS4

http://audirevolution.net/addons/albums/images/660096015.jpg

The good thing, at this point in time is that the Aluminum Audi motors have held there ground for quite sometime. The neigh Sayers of the past have been proven wrong when it comes to the strength of the aluminum motors, or at least the blocks.

#2

Good info. fwiw from what I’ve found the S5 motor is a gen IV with forged internals and the same high compression, just not the built up cylinder heads.

#3

Love this info, keep it coming. Very simplified as well, so anyone can understand the differences. That makes for a great starting point and I look forward to hearing more of the technical differences and design processes that separate the two motors as well as other Audi (or non-audi) motors.

#4

Also, to elaborate what was touched on before, the main difference for the cylinder walls between the gen II and gen III is the switch from a chemical treatment to a mechanical treatment.

Both blocks use a high silicon aluminum alloy called Alusil; a material which allows for linerless aluminum block constructions. While there are other methods for linerless construction, primarily the nikasil coating process, Alusil is different because it does not work by added material, rather removed material. In the final bore processing steps the aluminum is removed from the alloy which precipitates out very hard silicon crystals with microscopic pores between the crystals. These pores hold oil, and this process results in the characteristic matte finish of Alusil bores.

The Gen II motors used a chemical treatment which stripped the aluminum, but the Gen III switched to a special hone tool and paste which achieved the same effect. The main driving force between the switch was that the mechanical treatment can be performed immediately after the standard cylinder bore operations with the same equipment (albeit with an additional tool added to the hone machine). This reduced waste and cost, and additionally created a smoother cylinder bore because the microscopic silicon crystals are ‘smoothed’ by the repeated passes of the hone tool, whereas the chemical treatment does not have this effect.

Hope this clears up some confusion, all of the info is directly from Kolbenschmidt Pierburg Group publications

#5

Thanks beem I was hoping you would step in and add that. I have some of the tech information but I Wanted to almost cut and paste. With as little time as I have its amazing how hard it is to just load pictures and give a brief description.

I would just like to add and sumerize.

Gen I aluminum blocks metal sleeves.
Gen II aluminum blocks nikasil coating process
Gen III aluminum blocks special hone machine work added
Gen IV aluminum blocks special hone machine work added

#6

OMG more please! This is great information. Can anyone go further in to the sleeved motors? Is this something that we need when we make more power?

#7

No problem, I was under the impression though that the Gen II was Alusil processed by Chemical Stripping and not Nikasil

#8

No, not necessarily. The Alusil is plenty hard, the only issue is it limits material selection for the pistons since they need to wear against the walls in a particular manner.

#9

Very cool post beem. That picture of the S4 motor sitting on the pavement makes me want to go clean my motor.

1st post here. woot

#10

Here is a example of the metal sleeve and a chemical sleeve

http://audirevolution.net/addons/albums/images/922245416.jpg

Thanks to maddog for the correction.