Now that I have an R8 engine, the other thing I've been doing recently is comparing the RS6 and Lambo / R8 engines, and I think I've been able to answer my original question about whether the RS6 V10 was capable of revving to 8000rpm. Why would that matter? Look in the list of engines in the previous post. They're the engines that everyone gets excited about these days, the engines with character, the engines that make a car, and make you drive for the sake of driving. They all sound great (GT3, 812, LFA, M5, Huracan etc - the sort of cars where people say they're worth it for the engine alone) they all happen to have high bmep, high specific outputs, and they all rev very high - 8000 to 9000 rpm.
The easy thing to get out the way is that the 5.0 RS6 is closely related to the R8 / Gallardo / Huracan 5.2, and is not closely related to the older Gallardo 5.0.
Seen side by side, you'd say that the similarities were striking, but the older engine has 88mm bore centres, and the newer one is 90mm - like all 90-degree VAG engines.
Looking externally, the engines are similar, but have the following differences:
The R8 has a dual clutch gearbox, so the rear timing cover is completely different to match (but is interchangeable with the RS6 timing cover).
The R8 has bearing housings for the prop-shaft to the front axle, and the RS6 does not.
The R8 starter motor is behind the engine, but alongside on the RS6.
The R8 power steering pump is behind the engine, but alongside on the RS6.
The R8 has a stiffening web to the bellhousing flange on the block girdle, but the RS6 does not.
Apart from that, they're very similar. For comparison, here's the S8 5.2 V10, which has a wet sump:
Here is the Gallardo / Huracan / R8 5.2 V10, with the dry sump removed. The red arrow shows the stiffening web that the RS6 doesn't have:
And here is the RS6 5.2 V10, which has a dry sump:
They're all quite similar, but the RS6 bottom end is much more like the R8 than the S8. You can even see a row of 6 cross-bolts right at the bottom. These hold the cast iron bearing cap
inserts more securely into the lower block girdle or bed plate. Every V10 has a block girdle with cast iron inserts (stiffer than alloy, and lower thermal expansion). This all gives a very strong and stable bottom end, one that UGR took to over 2300whp in 2015 before they introduced their billet block.
The current Lambo and Ferrari and Mercedes V12 engines also have block girdles, but the Italian engines don't have the cast iron inserts or the additional cross bolts. The S4, S5, S6, S8, RS4, RS5, RS6 C7 and RS7 C7 also have block girdles, but don't have a dry sump or cross bolting. Cross-bolting is a typical construction technique for high performance V engines that have conventional deep skirt block and individual bearing caps, and this strengthens the bottom end. It's used on all the recent Audi / BMW / Bentley / Lamborghini / Mercedes / Porsche twin turbo V8's.
Almost all road car engines are wet-sumped, including the RS4 & S6, and at high revs the oil tends to froth, getting air into the oil, which obviously hurts the lubrication. Dry sumping is a cost-no-object solution that helps to get round this by minimising the frothing in the crankcase in the first place, and with an air-oil separator in the return to the oil tank. The outlet to the pump is taken from the bottom of the tank and gives the best possible oil feed, especially under sustained high g-forces. Keeping air out of the oil feed to the bearings at high engine speeds is great way of safeguarding a high-performance engine, and is generally used on racing engines, Ferraris, Lamborghinis, the R8 V8 & V10 - and the RS6 V10.
A block girdle is also a preferred, cost-no-object solution, but only the Lambo/R8 V10 and RS6 V10 have a block girdle AND cast iron inserts AND cross bolting. They also have a shallow cast alloy oil tray with individual compartments for each crank throw that forms part of the structure of the block and further strengthens the girdle from underneath. Indeed, this bottom cover is bolted onto the girdle by the same 24 x 10mm bolts that secure the block girdle, plus the bolts around the edge, so the girdle is sandwiched between the bottom cover and the block. Ever noticed those bolts heads sticking out of the bottom of the engine? They hold the whole of the bottom end together.
This means the crankshaft is to all intents and purposes encased in one big solid alloy casting that is only cut way to allow just enough room for the crankshaft and con rods to move, and no more, and this is only possible with a dry sump. To illustrate this, here is the R8 / Huracan girdle, which is the same as the RS6 except for the few differences that I listed at the top:
By contrast here are the S6 and RS4 girdles respectively - very similar and very good, but not the same as the R8 / Lambo:
What does this mean? The RS6 doesn't just have a good bottom end, I think it's the best.
Internals next.
