Engine Power Vs. Engine Displacement Vs. Engine Configuration

[pimento]

I imagine the plan behind using it was/is related to the alleged plan to use it in a car..? Or is my memory failing me again?

[RacingManiac]

I imagine the plan behind using it was/is related to the alleged plan to use it in a car..? Or is my memory failing me again?

If thats the case then its all the more laughable for AMR's effort to be taken seriously, and at the same time kept complaining about the diesels being favored.

But thats for another topic and another day...

[Ferrer]

Wasn't it actually the other way round? That the rumors of road going Astons with straight sixes started because of the racing car?

[henk4]

They use it as a stress member, if not fully at least partially. The gearbox bolts straight onto the back of the block. If not you'll need a lattice work of tubular or carbon frame around it to carry the load.

Aston Martin AMR-ONE | Racecar Engineering | Race car technology explained

The long and narrow block of the I-6 means AMR needs the trusses on the side of the engine to carry some load.

Compare that to something a bit more bespoke:
Peugeot 908 HDI FAP | Racecar Engineering | Race car technology explained
Porsche RS Spyder Evo - High Resolution Image (5 of 24)

The engine carries all the load between the gearbox and the tub.

For chassis designed with multiple type of engine, chassis bracing is usually needed since the engine may or maynot be designed to the required stiffness, and the pickup points are not necessarily the same. And the gearbox are not necessarily limited to one type.

The fully stressed engine is more "efficient" design, since you are using a part to do more work, you tried to strive for that but it may not work out all the time. AMR having a clean slate design and a bespoke powerplant and not go with something like that is one more reason why its puzzling...

For something with a unstressed motor, you just need to look at a Daytona Prototype:

Riley Mk XX Porsche - High Resolution Image (12 of 12)

OK, I checked the link from RCE (and it looks like Sam used some of our pictures but not the one I attach here. It looks and it is being described as a semi stressed engine, whereby the struts connecting the tub and the gearbox take away lots of the load. From the looks of it would be actually quite easy to insert an inline four, if they want to go the turbo way.

[RacingManiac]

I thought the I-6 is Turbocharged? The spec I think was a direct injection 2 L turbo...As you noted with the 4 cylinder note, I wonder what they gain(if anything at all, aside from maybe "prestige" with 4 banger are more commonly associated in road car with econoboxes) from going the 6 cylinder route. 4 Cylinder turbo have been used throughout the ages in prototype racing, from the recent year's AER and Mazda motor to IMSA GTP's Toyota. The 2 extra cylinder buys you nothing but really more parts and more of a PITA to package....

The whole LMP engine topic makes me think about what a waste it is for the RS Spyder's engine being unused at this point.....Would make for a perfect petrol LMP1 motor in 2011 rule, being more powerful and capable of being fully stressed if the chassis is made for it compared to ARX-01e and the HPD 3.4V8. And its direct injected....

[henk4]

I thought the I-6 is Turbocharged? The spec I think was a direct injection 2 L turbo...

The whole LMP engine topic makes me think about what a waste it is for the RS Spyder's engine being unused at this point.....Would make for a perfect petrol LMP1 motor in 2011 rule, being more powerful and capable of being fully stressed if the chassis is made for it compared to ARX-01e and the HPD 3.4V8. And its direct injected....

yes, the AMR is turbocharged, but the issue is why it should have six cylinders. A I4 turbo, such as the Mazda LMP2 from last years would be perfectly feasible.

I am sure somebody at Audi must have looked at using the Porsche engine in their prototype, but decided against it, as it would still no match for the diesels.

[RacingManiac]

Or more likely they just want to stick with the diesels for corporate marketing reasons....I am still unconvinced at the thought of diesel is the main reason why Audi/Peugeot are the dominant cars. You can't make that conclusion when no one is spending nearly the same ballpark of resources in a petrol car....

For that matter, no current petrol motor is remotely as good as the DI V8 from RS Spyder...and that car have beaten diesel Audi on Road America and Sebring outright...both of which are horsepower tracks....

[Matra et Alpine]

An I6 engine has a balance advantage having no natural first or second harmonics in the crank/pistons. Saves designers having to have counter-balances ( saves weight in rotatig parts ) and dempeners.

[culver]

I am very curious why they decided to go I6 for this car. So far it looks like no one here really knows. Off the top of my head I can only throw out these common bits of knowledge.
1. 6 smaller cylinders typically will rev higher but have more friction than 4 larger ones.
2. An I6 is narrower but longer and less stiff than a V6. The V6 is also shorter.

However, perhaps AM thought the added length wasn't a problem and thought that the potentially negative engine tradoffs could be made up for via better chassis trade offs. Hard to say but often fascinating to hear why.

[henk4]

An I6 engine has a balance advantage having no natural first or second harmonics in the crank/pistons. Saves designers having to have counter-balances ( saves weight in rotatig parts ) and dempeners.

I ma sure Baretzy is totally aware of this, given his past relationship with the BMW M1 engine, but still he has great doubts about the inherent usability of such an engine under great stress.

[Matra et Alpine]

Another BIG plus in a sports/race car is the packaging.
By having non V then the engine is narrower. This will allow the suspension mounts to be further in board and have less camber change on compression, thus aiding the grip in cornering. As well as that they perhaps feel they can use the space created to improve the aero adn esp the underfloor flow exit ?
and yeah, as already covered in the "what's bad" on the I6, getting a block able to cope is difficult -- adn keep it light
Melling managed it in the AJP and he brought his bike design experience from on eof the best I4 suzuki engine designs

[RacingManiac]

Gearbox typically drives the suspension pickup(actually, its should be backward of that), not engine, provided that you have free reign in that aspect.....and further inboard pickup design does not automatically mean better camber control. And camber variation in bump does not always drive the design consideration(as you optimize that you are trading it off in roll). And having narrow inboard pickup in my experience gives you much worse roll center control. Interesting case in point in RS Spyder again:

Porsche RS Spyder Evo - High Resolution Image (11 of 24)

Note the upper A-arm actually picks up away from the actual gearbox casing and they purposely made a stand-off pickup point....its not hard to imagine it was meant for kinematic reason....

I did think AMR might be trying to use the narrow engine to do something similar to R15 did and utilize more "internal" aerodynamic. But the pictures thus far does not suggest that, and the fact that the layout dictates that you will have asymmetry in terms of plumbing for turbo-related items, its not exactly ideal....

[Matra et Alpine]

Yes, but if you want more stability and reduce caster change and toe-in/out with movemetn then you want to widen the A or introduce a forward pickup.
That engine has a V6, so no option to do it different
Also, gearboxes are getting smaller !!
But I do concur more liekly aero.

[LeonOfTheDead]

An I6 engine has a balance advantage having no natural first or second harmonics in the crank/pistons. Saves designers having to have counter-balances ( saves weight in rotatig parts ) and dempeners.

That's correct only from a bending point of view. Inline engines are weaker when it comes to torsion and more at risk of facing resonance frequencies as soon as the pulse of the various forces acting on each piston/crank portion are close or equal to the natural pulse of the same part. Given the various harmonics all have the same phase, which is not that weird of a case.

Or perhaps I'm just too tired and shouldn't try to think about it now

[Ferrer]

That's correct only from a bending point of view. Inline engines are weaker when it comes to torsion and more at risk of facing resonance frequencies as soon as the pulse of the various forces acting on each piston/crank portion are close or equal to the natural pulse of the same part. Given the various harmonics all have the same phase, which is not that weird of a case.

Or perhaps I'm just too tired and shouldn't try to think about it now

So even the traditional plus point of the straight six is not true?