V8TT will weigh more than a V10... and won't sound as good

 

let's see first. What do they weigh now?

 

too big!

 

The the S5 and the RS4 V8 already are pretty darn light. Add 2 more cylinders/pistons/rods and the associated lengthening of the crank and block, and it would be hard to believe that weight did not go up. Of course, the turbos and plumbing would add additional weight, but the designers would at least be able to place them further rearward for better weight distribution.

Having said that, I'd love to have a high revving NA V10 in the car. It would just be a bit tougher in the corners.

 

To answer this question you'd have to look specifically at those two engines. It's not as though the v10 is simply the same v8 engine with 2 more cylinders attached.

 

The High rev 5.2 V10 FSI will have a lot of light weight internals to keep the weight low.

Jarod.

 

The V10 has exactly the same cylinder pitch and spacing as the Audi V8 and V6 engines, thus the block size has to be extended by approximately 25% over the V8, thus there are 2 more sets of pistons and rods, thus the crank must be approximately 25% longer.

Both blocks use Alusil and are manufactured by Kolbenschmidt.

However, having said that the published weights (from Audi Service Training Manuals) for these engines are:

Q7 V8 - 437 lbs with Automatic Transmission

RS4 V8 - 467 lbs with Manual Transmission and dual-mass flywheel

S6/A8 V10 - 485 lbs with Automatic Transmission


The Q7 and the S6 both use a 09 Tiptronic transmission, but with different gearing ratios, thus the different designators 09E for the S6 vs. 09O for the Q7. Thus, we can use the RS4 engine as a fairly good gauge for weight difference between the Manual and Automatic transmission. If anything, any lightening of the RS4 engine will decrease the differential, where the automatic transmission is 30 lbs lighter than the manual.

From this we can compute the probable weight of the V10 with a manual transmission (assuming the manual transmission does not have to be modified to handle the additional torque) to be 515 lbs, or about 48 lbs.<ul><li><a href="http://www.rheinmetall.de/pdfdoc/praesentationen_ir/englisch/atag_engl.pdf">Alusil Blocks</a></li></ul>

 

Here are the lower weight items used on the RS4:

Intake Valves and Valve springs
Connecting Rods
Simplex vs. Roller Chain
Magnesium Intake Manifold

Crankshaft weight was increased with a dual-mass damper in RS4 for counterbalance ... "heavy metal inserts are integrated in the first and eighth crank journals by way of unbalance."

My calculations below include the weight savings from the RS4 in a conservative estimate. No matter how you cut it, a V10 manufactured with the same block technology, at the same cylinder bore and spacing, has to be heavier than a V8.

 

The V10 and V8 have the following identical specs:

Bore - 94.5 mm
Stroke - 92.8 mm
Cylinder Spacing - 90 mm
Cylinder Bank offset - 18.5 mm
Compression Ratio - 12.5:1
Block Alloy - AISi17Cu4Mg

Overall Engine Length V10 - 560 mm
Overall Engine Length V8 - 464 mm

 

The "light weight" parts will generally be in the rotating elements, like pistons, rods, valves, and valve springs, where the difference in weight is measured in ounces.

A V8TT would, of course, have added weight from the turbos and plumbing. However, I doubt it would be the additional 50 lbs that the V10 weighs, and I would hope that the mass could be positioned further back.

Having said all this. A high revving V10 would be an awesome beast!

I'm also not sure why Valve Lift would be placed into a high performance engine, with it's emphasis on fuel economy at the expense of more moving parts.