How high can the V10 rev?

[welwynnick]

I'm slowing getting to appreciate what a monster engine Audi made, only to detune it to just 650Nm and 572 bhp with things like compression ratio, cam duration and modest boost.

I believe peak power starts at 6250rpm, and the redline is 6700, yet the S8 peaks at 7000, and that's an inferior engine - longer stroke, wet sump and split crankpins.

The S8 engine was near state-of-the-art at the time, with a specific torque output of 103Nm/l, and has much in common with the RS4 & R8 engines - which rev over 8000 rpm.

Perhaps those limits are only achievable if you don't have a torque converter, but the RS6 won't be worse than the S8, and the 6R80 variant of the 6HP26 is successful in drag racing.

The stock RS6 engine will probably run out of breath at very high speeds, but I know that many tuned engines do have higher rev limits.

I'm not trying to prove that the RS6 can actually rev to 8000, I expect it would need pistons/rods/valves for that, but I'd just like to find out what's been safely done before.

So does anyone know just how high the RS6 can rev?

Thanks,

Nick

Edit - yes I am trying to show that the RS6 could actually rev to 8000!

[welwynnick]

To answer my own question, SSP 377 describes the differences between the regular FSI V8 and the high revving engine in the RS4 and RS5 (and perhaps the Lambo engines as well):

The main technical differences between the base engine and the high-revving engine lie in the following modules:
– Cranktrain
– Timing gear
– Cylinder head
– Oil supply
– Engine cooling
– Intake path
– Exhaust system
– Engine management

I think this means that on the whole, apart from the extravagant lubrication and cooling systems, the RS6 engine has more in common with the regular V8 FSI engine than the high revving engines.

The RS6 engine has an advantage over the S6 engine with the shared cranks pins and the dry sump, but is at a disadvantage because of the unequal firing pulses and consequent greater vibration. However, in these respects it's the same as the Lamborghini and R8 V10 engines, so it can't be much of a disadvantage.

Nick

[Covkiller]

Until your valves bend

[welwynnick]

Other minor differences:

Secondary air injection system
Master-slave engine management system
Engine speed sender
Throttle valve increased from 82 to 90mm
Colder spark plugs
Larger fuel injectors
K-wire diagnosis

[welwynnick]

I suppose the questions I really want answering are:

1. Does the RS6 really have a Lamborghini engine, like all the sales adverts claim?
2. If it does, can it make as much power as a twin turbo Lamborghini?

1. It's a V10 and it's 5.0 litres and the Gallardo had a 5.0 V10, so they must be the same, give or take a few details, mustn't they? Well, I don't think they are. In fact, I don't think they have much in common at all. The Audi has a bore and stroke of 84.5 x 89.0 and 90mm bore spacing, while the Lambo was 82.5 x 92.8 and 88mm. I believe the Lambo 5.0 was also an even-firing engine - so split crank pins. The Lambo 5.0 also has the Lamborghini name cast into the block, while Audi engines have four rings.

However, the Lambo 5.0 was a bit of a red herring and caused some confusion. Forget about that for a moment, and everything falls into place. The Gallardo 5.0 was replaced by the 5.2, and that has plenty in common with all the Audi V10s, and the FSI 4.2 V8 as well. The 4.2 and 5.2 engines have exactly the same bore, stroke and spacing - 84.5 x 92.8 and 90mm, and the RS6 V10 is just a short stroke version. They even have the four ring logo cast into each block - even the Lambo engines.

Audi said the RS6 V10 was based on the Audi 4.2 V8, not the Lambo 5.0 V10. And the Lambo 5.2 was based on the Audi 5.2 - as well as identical capacity 5204 cc, they even had identical torque - 540 Nm. So rather than saying that the RS6 has a Lambo engine, it would probably be better to say that Lambo used an Audi engine, albeit heavily modified - probably along the lines of the modifications Audi made to the RS4/5 engine, listed above, plus the different inlet, exhaust, transmission etc.

So do the S6, S8, RS6 and R8 use essentially the same engine as the Gallardo and Huracan 5.2 V10? Yes they do.

2. So can the RS6 make as much power as a twin turbo Lamborghini? For stock engines at least - no - I think it can make more. The Lambo and R8 engines are much higher revving, and you'd have to upgrade the pistons, rods & valves to redress that. However, doing that would undermine the benefit of the stock engine - the relatively low compression ratio. Twin turbo Lambos with stock engines don't make much more power than stock despite huge revs, huge turbos and huge charge coolers, because they can't take much boost.

The RS6 has a state-of-the-art (sorry for repeating myself) engine that in naturally aspirated form is good for 103Nm/litre specific torque, yet breathes well enough to peak at nearly 7000 rpm, but can still take lots of boost. There's no other way THT Performance can get 1431Nm torque and 1050 bhp at just 5700 rpm, which all suggests to me that the best is yet to come.

Nick

[don0301]

I suppose the questions I really want answering are:

1. Does the RS6 really have a Lamborghini engine, like all the sales adverts claim?
2. If it does, can it make as much power as a twin turbo Lamborghini?

1. It's a V10 and it's 5.0 litres and the Gallardo had a 5.0 V10, so they must be the same, give or take a few details, mustn't they? Well, I don't think they are. In fact, I don't think they have much in common at all. The Audi has a bore and stroke of 84.5 x 89.0 and 90mm bore spacing, while the Lambo was 82.5 x 92.8 and 88mm. I believe the Lambo 5.0 was also an even-firing engine - so split crank pins. The Lambo 5.0 also has the Lamborghini name cast into the block, while Audi engines have four rings.

However, the Lambo 5.0 was a bit of a red herring and caused some confusion. Forget about that for a moment, and everything falls into place. The Gallardo 5.0 was replaced by the 5.2, and that has plenty in common with all the Audi V10s, and the FSI 4.2 V8 as well. The 4.2 and 5.2 engines have exactly the same bore, stroke and spacing - 84.5 x 92.8 and 90mm, and the RS6 V10 is just a short stroke version. They even have the four ring logo cast into each block - even the Lambo engines.

Audi said the RS6 V10 was based on the Audi 4.2 V8, not the Lambo 5.0 V10. However, the Lambo 5.2 was based on the Audi 5.2 - as well as identical capacity 5204 cc, they even had identical torque - 540 Nm. So rather than saying that the RS6 has a Lambo engine, it would probably be better to say that Lambo used an Audi engine, albeit heavily modified - probably along the lines of the modifications Audi made to the RS6 engine, listed above, plus the different inlet, exhaust, transmission etc.

So do the S6, S8, RS6 and R8 use essentially the same engine as the Gallardo and Huracan 5.2 V10? Yes they do!

2. So can the RS6 make as much power as a twin turbo Lamborghini? For stock engines at least - no - I think it can make more. The Lambo and R8 engines are much higher revving, and you'd have to upgrade the pistons, rods and valve gear to redress that. However, doing that would undermine the benefit of the stock engine - the relatively low compression ratio. Twin turbo Lambos with stock engines don't make much more power than stock despite huge revs, huge turbos and huge charge coolers, because they can't take much boost.

The RS6 has a state-of-the-art (sorry for repeating myself) engine that in naturally aspirated form is good for 103Nm/litre specific torque, yet breathes well enough to peak at nearly 7000 rpm, but can still take lots of boost. There's no other way THT Performance can get 1431Nm torque and 1050 bhp at just 5700 rpm, which all suggests to me that the best is yet to come.

Nick

TL;DR

The RS6 C6 block has a Lambo bull stamp

[IanH755]

Just to add my thoughts -

1a. Lambo 5.0 V10 vs RS6 5.0 V10 - As you said we know the Lambo 5.0 V10 and RS6 5.0 V10 do not use the same block, internals or accessories but it's understandable why folks (incorrectly) think the two are linked just due to the name.

1b. Lambo/Audi 5.2 V10 vs Audi 5.0 V10 - As you suspected the Audi produced RS6 study guide confirms that the RS6 V10 uses a short-stroked 5.2 V10 bare block and, as the 5.2 V10 is an Audi/Lambo rework of the original Lambo only 5.0 V10, again I can see why folks claim it's a Lambo engine.

However when Audi built the RS6 5.0 V10, the bare 5.2L V10 bare block and a few bolt-on accessories they used were still built by Lamborghini at the time, it means they do have the Lambo "bull" cast into the them (quite a few pics of RS6 blocks/parts with the Lambo Bull in the cast) but to me at least, as everything internal to the engine is solely Audi designed, stamped and built and only the bare block is Audi/Lambo designed & Lambo built, this makes it an Audi engine rather than a Lambo one, but again I can see where people can claim otherwise.

Additionally, while I agree with some of what you said here about the Audi and Lambo 5.2 V10 being the "same" I think it's only regarding a small portion of the fully built engine, as Audi and Lambo used different piston materials, different duration camshafts, different crank design etc so I don't you could say the S6 & S8 5.2 V10 engines are the "same" engines as the Gallardo and Huracan 5.2 V10 due to differences internally.

2. Stock Engine TT Lambo vs RS6 max power - I'd say that the RS6, would be able to make more on an engine dyno just due to the higher compression of the Lambo causing issues but once you start to crack open the engine and upgrade things I'd think that a modded RS6 engine should be able to match the mental power levels as the US Twin Turbo'd Lambos - approx 2000hp+ - if you used the same parts but I think it'd "ONLY" work with the engine out of the car and on an engine dyno as it's the car itself that is the most limiting factor in extracting max HP out of this setup, not the engine strength as those Drag Lambos prove.

[BW_90024]

Sent from my iPhone using Tapatalk

[BW_90024]

Bit of a scruffy photo, but Lamborghini stamp on the engine block


Sent from my iPhone using Tapatalk

[Jim Haseltine]

That's on the water pump, mine has one as well. Some (maybe all) blocks have a Lambo badge somewhere on the bottom near the oil pump sealing flange - not found it on mine but then I've not been looking for it.
In my opinion the releationship between the Lambo and Audi V10 engines is a bit like a Hollywood film that has been 'based on a true story' - close or even spot on in places but way adrift in others. Some parts are the same, even down to the part numbers but they aren't any of the real working bits.

[welwynnick]

What happens when you do rev too high....

[welwynnick]

Thanks for the replies.

I think it's clear that the 5.0 & 5.2 were based on the 4.2, and the 4.2 came first.

It's probably best to think of the 5.2 V10 as being a joint venture.

As far as the 5.0's capability is concerned though, it has most things in common with the regular 4.2 FSI engine used in the Audi and VW SUVs. So there aren't any reasons why the RS6 shouldn't rev like the S6.

Nick

[IanH755]

As far as the 5.0's capability is concerned though, it has most things in common with the regular 4.2 FSI engine used in the Audi and VW SUVs. So there aren't any reasons why the RS6 shouldn't rev like the S6.

Nick

Compression is the reason - turbo cars use a lower compression than NA engines and therefore tend to (but not always) have a lower rev limit than an NA version of the same engine.

[welwynnick]

Because the compression protects the con rods at high speeds? Many years ago I heard the story that racing drivers were taught not to lift off at the red line because it removed that measure of protection (though how you brake at the end of the end of the straight I don't know). That only works when the engine is under load, and it hardly affords any protection on the exhaust stroke. It's something that I've always been very sceptical about.

It's hard to believe that any modern motor manufacturer will expect their customers to refrain from closing the throttle at max revs, and then blame them for breaking the engine. I'm sure that manufacturers have to accept that liability, and will design the engine appropriately. I believe that the RS6 has forged steel conrods anyway, which is reassuring.

One final question from me, though. Does anyone know whether the RS6 has cast or forged pistons? VAG say the 4.2 FSI V8's have forged pistons, but the S6 V10 has cast pistons. I read somewhere that the RS6 has cast, but that source also said it had a split pin crank, so I'm not sure. Does anybody know for sure?

Thanks, Nick

[IanH755]

The OEM pistons are cast Ali alloy but the con-rods are forged. I looked into getting a forged set of pistons, con-rods etc from FCP Engineering during my rebuild but the price was £4k+ at the time.