RE: AMG's new turbo V8

Friday 13th June 2014

AMG's new turbo V8

AMG reveals its all-new 4.0-litre twin-turbo V8, soon to power the GT, next C63 and future Aston Martins



It says something rather endearing about AMG that for the unveiling of its all-new M178 4.0-litre twin-turbo V8 the first 10 minutes or so of the presentation focus on exhaust noise. There is some very serious and innovative engineering in this new motor. But Christian Enderle, head of engine and powertrain development, doesn't want to talk tech until we've sat through some sound clips of great AMG V8s of the past.

'Hot-V' layout puts two turbos inside cylinder banks
'Hot-V' layout puts two turbos inside cylinder banks
Studiously we sit there, pencils poised over notebooks as the room reverberates to the thundering 300SEL 6.9 Spa race car, the W124 Hammer, the SL55, the C63 and, finally, the new M178.

Enderle nods at the end of it. "I think it is very emotional," he says, with utter sincerity.

Seems PHers agree too. Someone mentions engine noise through the speakers. Enderle and engine development manager Jochen Schmid exchange glances and grin. "We do not have this."

Flying journalists out to AMG's Affalterbach HQ to see an engine before the car it'll be installed in has even been unveiled seems a little excessive. But ahead of the Mercedes-AMG GT's official debut they obviously want some time for the new V8 to have its moment in the spotlight. And why not. This is an important engine - it'll also feature in the C63's replacement and, all being well, future Aston Martins too.

4.0-litre and 510hp V8 debuts in the GT
4.0-litre and 510hp V8 debuts in the GT
The headlines? In the AMG GT trim shown to us the M178 is a 'hot V' configured twin-turbo V8 with the inlet manifolds on the outside of cylinder banks fed by single-scroll, fixed vane turbos placed between them. This follows the format of comparable engines from Audi (the 4.0 V8 in the RS6, RS7 and Bentley Continental GT V8) and the BMW M V8 in the M5 and M6 family, the main advantages being faster turbo spool-up and catalytic converter heating for response and emissions. Dry-sumped for the GT, it gets Mercedes-patented tech like 'Nanoslide' cylinder liners, Zirconium enhanced aluminium alloy cylinder heads and third-gen piezo direct injection. Perhaps surprisingly given the stated ambition for a normally-aspirated style high-revving response it's an undersquare design with 83mm bore and 92mm stroke and has a dual-mass flywheel, apparently necessary for refinement and to work with the GT's dual-clutch transmission.

So far, so bewildering. Ready for some numbers?

Head of AMG powertrain Christian Enderle
Head of AMG powertrain Christian Enderle
As it stands it'll do 510hp and 479lb ft - impressive numbers if pegged back from the mighty 585hp and 590lb ft of the more conventional 5.5-litre M157 V8 in the E63 and others. Audi's 4.0 does 560hp and 516lb ft in the RS6, the M V8 560hp and 501lb ft in the M5. Don't be surprised to see those numbers increase as the M157 is gradually phased out and the M178 becomes AMG's core engine. And the much-loved M156 6.2-litre it replaces? 507hp and 450lb ft in C63 Edition 507 trim, 591hp and 479lb ft in M159 dry-sump form in the outgoing SLS Final Edition. All-in it weighs 209kg, just 5kg more than the M159.

This is downsizing - not a word that comes easily to the lips of AMG engineers - but very much achieved on their terms. Was anything other than a V8 ever on the cards? Briefly, until they realised they could hit the emissions numbers with eight cylinders. "It had to be a V8," says Enderle, simply. "We have a V8 DNA in our engineers - we are proud of this point!"

Engine cover directs air flow according to speed
Engine cover directs air flow according to speed
Along with noise AMG customers - and engineers - share a taste for naturally-aspirated style response and revs. Not usually happy bedfellows for forced induction but an issue, like BMW M, AMG has had to face. "The engine is able to rev to 7,200rpm - you have the sporty feeling with high revs otherwise you have the feeling more of a diesel engine," says Enderle. "And that is not what we want."

The new M3/M4 uses lots of clever features - including shutting off the ignition but keeping the turbos spinning - to maintain normally-aspirated style throttle response and, in the same mould, Enderle and Schmid affirm their engine does its best to disguise its turbocharged foundations. They're not offering specifics beyond saying there are 'strategies' within the induction system to achieve a similar effect.

Engine man Jochen Schmid worked at Merc F1
Engine man Jochen Schmid worked at Merc F1
That surprising undersquare layout helps fill the gap in low-end torque before the turbos do spool up, the fact it also means smaller pistons and the focus on reduced friction allowing the 7,000rpm-plus redline. This, the boost and the burly 10.5:1 compression put a lot of strain on the block though, Enderle keen to point out it's pressure rated to 130bar where most typical petrol engines are to 100bar. This is one lesson learned from the 360hp four-cylinder in the A45 family and strains imposed by its crazy high 180hp per litre specific output - "We have always loved V8s, now we love four-cylinder engines too!" grins Enderle.

The geekery continues apace, from the fact the Nanoslide bores (160microns thick compared to 2-3mm of conventional iron ones and better for both weight and cooling) are polished with diamonds to reduce friction and therefore oil consumption to the astonishing stat that the scavenge pump circulates the 10 litres of engine oil at a maximum rate of 65 litres per minute. Apparently that means the oil spends all of five seconds in the reservoir before going back into the engine.

M178 in dry-sumped form ready for new AMG GT
M178 in dry-sumped form ready for new AMG GT
Suitably boggled we retire to AMG's engine test bench to witness the engine put through its paces. And see, first hand, why the term hot V is so appropriate - it's not long before the turbos are glowing red hot with 900C exhaust gases as real-time driver telemetry 'drives' the engine on a lap of an undisclosed test track. We're even treated to a taste of the noise with the door opened. There's a damped breathiness to the cylinder detonations that will never equal the hard-edged crackle of the old 6.2 but it's still unmistakably V8 with an underlying bass that hits you in the chest. And, yes, contrived cylinder cut out and other tricks mean it'll bang and pop on the overrun, if not quite as manically as the A45.

Swabian modesty prevents any fist pumping or back slapping - at least in front of us - but the fact both Enderle and Schmid have worn permanent smiles throughout the presentation suggests when the proof comes in the driving we won't be disappointed. And though there's genuine remorse at the passing of the normally aspirated, big capacity era the guys at Affalterbach seem confident they've carried their V8 addiction into the modern age without sacrificing too much of the old character in the name of progress.


AMG M178 V8
Design:
V8 'hot V' configuration with two fixed vane single-scroll turbos, water to air intercoolers, direct piezo injection, dry sumped*, four-valve/twin-cam cylinder heads with variable cam timing on inlet and exhaust
Bore and stroke: 83x92mm
Cubic capacity: 3,982cc
Compression ratio: 10.5:1
Power (hp): 510@6,250rpm*
Torque (lb ft): 479@1,750-4,750rpm*
Max revs: 7,200rpm
Weight: 209kg
*As fitted to the Mercedes-AMG GT

 

 

 





   
   
   
   
   
Author
Discussion

markcoznottz

Original Poster:

4,958 posts

165 months

Friday 13th June 2014
quotequote all
You cannot help but be impressed at the engineering. But, like all these cgi films, in 15 years the tech will be old, the numbers conservative and the sound ordinary.

Zombie

1,289 posts

136 months

Friday 13th June 2014
quotequote all
All that heat. In the bowles of the engine. Engineered properly and maintained by trained techs, it shouldn't be a problem, but 10 years later in the hands of the semi-trained indi:

"What's this bd fking heatsheil here for? it's taken an hour to remove it and it does nothing. FLUNG. Not putting that ttting thing back on...."

2 years later; engine grenades.

Cause; fuel starvation due to lack of insignificant (flung) or bent heat shield - result; melted pistons?

As I see it, our UK garages can't diagnose and fix 10 year diesel tech. I see little hope for the longevity of these engines, let alone this.

Edited by Zombie on Friday 13th June 01:14

AER

1,011 posts

211 months

Friday 13th June 2014
quotequote all
Cut a big hole in the bonnet, à la GTHO Shaker, and tear down the autobahn to watch the turbochargers glow orange and white! biggrin

SimonD

444 posts

222 months

Friday 13th June 2014
quotequote all
Typo:

"Don't be surprised to see those numbers increase as the M157 is gradually phased out and the M158 becomes AMG's core engine."

Should be M178 becomes AMG's core engine....


Other than that I "think" I like it, but suprised it's even initial power output isn't higher considering it's essentially two A45 engines in a V, non?

Draexin

141 posts

111 months

Friday 13th June 2014
quotequote all
Who's fdasgfadsgIt? wink
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gumsie

673 posts

150 months

Friday 13th June 2014
quotequote all
"We have always loved V8s, now we love four-cylinder engines too!”

Of course you do Christian.

SL55 is the sweetspot though. Opinions?

Dan Trent

1,836 posts

109 months

Friday 13th June 2014
quotequote all
SimonD said:
Typo:

"Don't be surprised to see those numbers increase as the M157 is gradually phased out and the M158 becomes AMG's core engine."

Should be M178 becomes AMG's core engine....


Other than that I "think" I like it, but suprised it's even initial power output isn't higher considering it's essentially two A45 engines in a V, non?
Sorted; apologies. Likewise the placeholding gobbledygook!

Cheers,

Dan

thatdude

1,990 posts

68 months

Friday 13th June 2014
quotequote all
I often thought that shorter stroke and bigger bore facilitated higher revs...?

Prawnboy

1,326 posts

88 months

Friday 13th June 2014
quotequote all
All that work and a plastic cover on top, surely one guy could be in charge of a design some cool looking engine bay department.

Buff Mchugelarge

3,302 posts

91 months

Friday 13th June 2014
quotequote all
Am I being thick or does it makes less power and weigh more than the out going V8?


burwoodman

12,093 posts

187 months

Friday 13th June 2014
quotequote all
SimonD said:
Typo:

"Don't be surprised to see those numbers increase as the M157 is gradually phased out and the M158 becomes AMG's core engine."

Should be M178 becomes AMG's core engine....


Other than that I "think" I like it, but suprised it's even initial power output isn't higher considering it's essentially two A45 engines in a V, non?
In standard 500 ish hp guise it is a very unstressed unit. I remember reading that AMG engineers could safely coax close to 1000hp from the 5.5TT lump. The new 4.0 engine will easily be able to produce crazy numbers. Wait until the tuners get hold of it.

tram50

82 posts

81 months

Friday 13th June 2014
quotequote all
I'm sure its a very good engine. Maybe its just me but it looks more like a diesel truck engine! Whatever happened to good looking engines like Jag straight 6's and Lotus twin cams. I know emissions bits and pieces add to the complexity but still...

burwoodman

12,093 posts

187 months

Friday 13th June 2014
quotequote all
SimonD said:
Typo:

"Don't be surprised to see those numbers increase as the M157 is gradually phased out and the M158 becomes AMG's core engine."

Should be M178 becomes AMG's core engine....


Other than that I "think" I like it, but suprised it's even initial power output isn't higher considering it's essentially two A45 engines in a V, non?
In standard 500 ish hp guise it is a very unstressed unit. I remember reading that AMG engineers could safely coax close to 1000hp from the 5.5TT lump. The new 4.0 engine will easily be able to produce crazy numbers. Wait until the tuners get hold of it.

Dan Trent

1,836 posts

109 months

Friday 13th June 2014
quotequote all
Buff Mchugelarge said:
Am I being thick or does it makes less power and weigh more than the out going V8?
The M157 (5.5 twin-turbo, up to 585hp) lives on for now; the M178 is considered a replacement for the M156/M159 normally aspirated 6.2 which even in its juiciest (non Black Series) trim is the same on torque if higher on power. But, of course, wouldn't meet forthcoming emissions targets. So, in brief, it's more torquey like-for-like at two thirds the displacement and just 4kg heavier. I'd expect to see some headroom in that power figure going forwards too!

And I too was curious about the undersquare layout and high-revving thing but Schmid made the point that a bigger bore = a bigger/heavier piston and hence more inertia so it's not necessarily as clear cut as I had assumed. The Lambo/Audi R8 V10 is undersquare too and yet revs to 8K-plus. It's more about torque, as I understand it - oversquare is good for top end power and revs but less so for flexibility and low end.

Cheers,

Dan

SuperHangOn

3,462 posts

94 months

Friday 13th June 2014
quotequote all
Zombie said:
All that heat. In the bowles of the engine. Engineered properly and maintained by trained techs, it shouldn't be a problem, but 10 years later in the hands of the semi-trained indi:

"What's this bd fking heatsheil here for? it's taken an hour to remove it and it does nothing. FLUNG. Not putting that ttting thing back on...."

2 years later; engine grenades.
Mechanics always know so much better than the engineers who spent years designing and testing the bloody car in the first place!

Cheburator mk2

2,440 posts

140 months

Friday 13th June 2014
quotequote all
Dan Trent said:
... The Lambo/Audi R8 V10 is undersquare too and yet revs to 8K-plus. It's more about torque, as I understand it - oversquare is good for top end power and revs but less so for flexibility and low end.

Cheers,

Dan
And so is the S54B32 found in the E46 M3 and Z4MC. It can rev to 9000rpm in race trim but it utilises titanium conrods and ultra light weight pistons... Only Euro 4 compliant though...

keith2.2

688 posts

136 months

Friday 13th June 2014
quotequote all
markcoznottz said:
You cannot help but be impressed at the engineering. But, like all these cgi films, in 15 years the tech will be old, the numbers conservative and the sound ordinary.
Not sure you can say that the SOUND will be ordinary due to the passing of time..that suggests that old mustangs, TVR's etc sound boring because the roots of the engines are now coming close to pensionable age. A great sounding engine will always be a great sounding engine.

kambites

56,517 posts

162 months

Friday 13th June 2014
quotequote all
It's interesting to see the stats, but the only thing that really matters is how it drives. smile

Glitchy

11 posts

119 months

Friday 13th June 2014
quotequote all
Looking at the bottom left picture, what's the guy from Twilight doing having a job with AMG?

RichardD

3,534 posts

186 months

Friday 13th June 2014
quotequote all
Dan Trent said:
...
And I too was curious about the undersquare layout and high-revving thing but Schmid made the point that a bigger bore = a bigger/heavier piston and hence more inertia so it's not necessarily as clear cut as I had assumed. The Lambo/Audi R8 V10 is undersquare too and yet revs to 8K-plus. It's more about torque, as I understand it - oversquare is good for top end power and revs but less so for flexibility and low end.

Cheers,

Dan
There are guidelines for engine building regarding piston velocity and the engines above probably aren't pushing things too far.

If there are no problems with engine breathing at high rpm, then going oversquare (which allows more space for bigger valves) won't matter either. With forced induction that matters less, although better naturally aspirated breathing means less boost needs to be used.

If AMG wanted to make a 4.0 V8 that revved to 8 or 9k and made 700+bhp am sure they would have no problem doing so.

(Edited for paragraph spacing!)

Edited by RichardD on Friday 13th June 10:21