S6 ABT engine displacement

[doncecone]

Hi guys,

I have two question which come out hard to be answered.

How can i know for sure if my engine is 2.0 or 2,2? It is an ABT version, 250 hp, automatic in the car papers.

If it is a 2.0 do you know if the only difference is the crankshaft, which in the 2.0 version is taken from the NM engine. And if that is so, swapping it with one from AAN or NG will increase the engine stroke and respectively the displacement to 2.2.

Thanks a lot!

Tsvetomir

[UrS4boy]

Hi guys, I have two question which come out hard to be answered. How can i know for sure if my engine is 2.0 or 2,2? It is an ABT version, 250 hp, automatic in the car papers. If it is a 2.0 do you know if the only difference is the crankshaft, which in the 2.0 version is taken from the NM engine. And if that is so, swapping it with one from AAN or NG will increase the engine stroke and respectively the displacement to 2.2. Thanks a lot! Tsvetomir

There is another forum member with an ABT 2.0L "AANM" (my term) that was for the Italian market. We thought it probably used an NM crank but we asked Abt and they don't have any documentation on it or whether there were different pistons and rods used.

PM me with your email and I will provide some Abt-related info.

Dave F.

[caterpillar]

the VIN nr build plate or the service book label will tell you... Fx.. NM CBL AEU.... or similar code...

[UrS4boy]

the VIN nr build plate or the service book label will tell you... Fx.. NM CBL AEU.... or similar code...

Normally I would agree but in this case, the build tag will say AAN but nothing about the lower displacement. I have documentation on an Abt UrS6 Avant and the TUV approval document from Abt in Kempten, Germany says AAN but for the displacement it says 1993 cc. I am sure that the NM crank is involved but I've never figured out if the rods and pistons had to be changed as well.

Based on current data, the AAN, 3B, ABY and ADU all used the 034105101S crankshaft whereas the NM used a 034105021G crankshaft.

The AAN, 3B, ABY and ADU used the 034107065M 81.00 mm diameter pistons. Although the NM pistons were still 81.00 mm, their PN was different, i.e. 034107065F (the 7A used 82.5 mm dia pistons so the differences between the 7A and NM is not just the crank shaft). There is a listing for the connecting rod, PN 027198401C, that says it was the same for the NM, 7A, 3B, AAN, ABY and ADU.

On this basis, the work done by Abt probably involved an NM crank but might also have involved NM pistons. No way to tell (Abt doesn't remember how they did it - Alessio checked).

Dave F.

[doncecone]

Dave, my reductional thinking is that if there were more modifications that the crack there would be technical data and spare parts for that engine. Crack on these engines is very hard to brake but pistons much easier. And there is nowhere information about them. So if rods are the same, crank is different and it say nothing in any catalogue about pistons i don't think there is other thing but the crack.

If i dissemble the bottom of the engine, which is pretty easy and decide to check the number on the crack do you know whee exactly it is located?

[caterpillar]

have out a sparkplug; then easy have å long thin thing...( of wood/ steel att least 1 meter) then turn the engine by HAND/ small tools, the see the stroke ...86,4mm or 77,4mm

[UrS4boy]

... So if rods are the same, crank is different and it say nothing in any catalogue about pistons i don't think there is other thing but the crack.

Crack? I think that is what some people smoke.

As for the craNk, rods and pistons, you missed the point I was trying to lead you to by posting that information:

If you decrease the displacement from 2223 cc to 1993 cc and the piston diameter stays the same (81.0 mm), then you had to use a crankshaft with a smaller throw. The ratio of 1993/2223 = 0.8965. When you multiply 0.8965 times the crank throw of the AAN, i.e. 86.4 mm, you get 77.46 mm, which is remarked close to the NM crank throw of 77.4 m. So that leads to a conclusion that they (Abt) probably used NM cranks (which were already available in the Italian and Portguese (and maybe Spanish) Audi parts systems because of the NM engine being used in B3 Coupe Quattros in those markets).

If you change the crank to one with a smaller throw, i.e. from 86.4 mm to 77.4 mm and you use the same rods as the stock AAN, then to make the compression the same, i.e. run the pistons up towards the head as high as the used to be with the full displacement AAN pistons, then you have to use pistons that have the wrist pin/gudgeon moved down by 9.00 mm. As a result, different pistons other than the AAN pistons had to be used. I don't know enough about the NM pistons to say that they were selected for duty or not. The pistons could have been bespoke (one-offs) made by or for Abt for these Italian/Portugese market-destined UrS4s and UrS6s.

Try caterpillar's suggestion to check the crank throw.

Good luck.

[UrS4boy]

Just found a previous thread that I started on this topic.

I had forgotten that the compression ratio was down to 8.8 instead of 9.3. This might mean that the pistons are the same as the AAN except that they don't go 9 mm as high (but that is a lot lower so that can't be right either).

The thread also includes the response I got from Abt, i.e. we threw the info out and/or we are too lazy to find it again.

http://www.s2forum.com/forum/showthread.php?t=53046&highlight=NM+pistons

And here was me guessing in Post 8 of this thread:

http://www.s2forum.com/forum/showthread.php?t=52687&highlight=s6

[UrS4boy]

Curiousity got the cat. I decided to do the math on where the top of the piston had to be on the "2.0L" Abt AAN. Is it lower or higher than the AAN. I used 77.4 mm stroke and 8.8:1 compression ratio (CR) for the Abt motor (Some documentation says 77.0 mm). The math is shown below. The answer appears to be that the piston is as high or higher than with the AAN. With a 77.4 mm (or 77.0 mm) stroke, this can only be achieved with new pistons with a lower gudgeon/wrist pin location (say by EDIT: 4.5 mm (9 mm/2) (ish)). (or 4.4 mm if the new stroke is 77.6 mm not 77.4 mm)

BTW, *THIS* is where you use that algebra that you thought was useless.

[doncecone]

Thanks a lot for the detailed explanation. I checked it and it seems to be 77,6 the throw, exactly as stated in the brochure.

I looked at the compression ratios and the one on the ABT is actually 8,8:1, lower than the stock 9.3:1.

Are sure about your calculation of 9 mm increase as the piston movement is due to the full rotation of the crack?
I'm not an engineer but i think if we increase the crank radius by 1 mm them the stroke increases by 2 mm as the piston will be going 1mm higher at TDC and 1 mm lower than before.

So in our case the piston will be going 4,4 mm higher and 4,4 lower. So they needed to compensate only for the 4.4 mm at the top. Maybe I'm wrong, I'm not sure.


Now the 1 million dollar question is: Are these 4,4 mm the key to the lower compression ratio or there have been user other pistons.

ABT Compression of 8,8:1 out of 398,6 cc which means means that there is only 45.3 cc left, which is exactly the size of the chamber.

Standard AAN compression is 9,3:1 out of 445,2 cc means there is 47,9 cc left little more than the chamber.

That means that ABT TDC is even higher than standard AAN.

Obviously not enough room so they've definitely used 4 or 4,4 mm taller pistons which they manufactured or 4 mm shorter rods?

It's hard to believe they manufactured special pistons for 1000 units sold in Italy and Portugal.

[doncecone]

I've been writing my post for 2 hours doing the math you've posted.

[caterpillar]

make another bottom, and have it the car.....and take out the complete unit.....lots of any bottom around...( stroker 2,6 ^^)

[UrS4boy]

Are sure about your calculation of 9 mm increase as the piston movement is due to the full rotation of the crank? I'm not an engineer but i think if we increase the crank radius by 1 mm them the stroke increases by 2 mm as the piston will be going 1mm higher at TDC and 1 mm lower than before....
It's hard to believe they manufactured special pistons for 1000 units sold in Italy and Portugal.

My 9 mm came from 86.4 to 77.4, if you say it is 77.6 then it would be 8.8 mm. And yes, I messed up , you are correct. The stroke is made up of two halves, i.e. one half below the crank centerline and one half above. As a result, to keep the top of the piston in the same location as the AAN piston, the gudgeon/wrist pin would have to move down not 8.8 mm but 4.4 mm.

They seemed to use the same rods as the stock AAN so I am guessing that in addition to the NM crank, they used NM pistons. BUT that is a guess and I won't know until somebody posts up photos of an NM piston a beside a stock AAN piston.

[doncecone]

Dave is right, there is no other option but the NM pistons and crank. The bore is the same 81 mm, the stroke ration is the same as 7A vs NM (86,4 vs 77,4).

So if i want a 2226 cc i need the AAN pistons as well. In that case I'll thinking in the caterpillar proposal for the future - go 2,5+