Help choosing piston configuration (making dream engine blueprint)

[BHoffman97]

Hello, I am new here. I am still in school, I want to pursue a career in a sort of automotive engineering. I think about these things to get away from everything else, take my time and I don't allow it's challenge to stress me. Doing so I come up with a lot of crazy ideas, some I really want to see how they'd work. That is why I'm here, I'm making a virtual engine (it will take some time). I only think, so I'm not exactly familiar with the advanced math, I could do it if I knew what I was doing though. All I'm doing is a learning experience.

So, to the engine. I am creating a piston engine beyond Formula 1 tech (or at least the tech FIA allows). 12 cylinder, 4.0l, high bore/stroke, 1 centrifugal supercharger, 1 large turbo or a sequential setup, throttle body before compressors, direct injection, actuated valves (no cams, like the Koeniggsegg models), 5 valves per cylinder, dis, dry sump lubrication. Those are some of the technologies I want to incorporate into this drawing. First problem: what piston configuration do I use. I was thinking about an H configuration, but I don't know it's balance. I could simply go with a 90 degree V engine because I like the fact that it is balanced, the downside is the crankshaft is ridiculously long. An H configuration would shorten the crankshaft, but is it balanced? Those 2 things really bug me and I must have the best of both worlds, don't ask why... it's just a fun drawing. Any other configurations I should be aware of? I'm not doing a radial, that would be awkward to have in a car.

See I have pet peeves, and they are all going to be silenced here because I will find what I want. Bear with me, I'm trying to learn and dream at the same time. Also, pardon my ramblings.

 

[BrianPetersen]

Here are some things to mull over for your thought-experiment.

Centrifugal superchargers don't develop boost until higher revs. Turbochargers also don't develop boost until higher revs. I don't see the point of using both. And if you are going to have a turbocharger, that's the way to go.

An inline-six has good balance characteristics. If you make a V12, it is a combination of two inline-sixes. You can make the bank angle anything you choose, and because each inline-six is well balanced, two of them will also be well balanced. A flat-12 is a V12 with a 180 degree bank angle. The length is not affected - you have six cylinders in a row either way.

If you want to use 5 valves per cylinder plus direct injection, where are you putting the injector and the spark plug? Direct-injection engines have all gone to 4 valves per cylinder and the injector is frequently between the two intake valves aimed almost horizontally inward. You may wish to study why all previous proponents of 5 valves per cylinder (notably Yamaha and VW/Audi) have all gone back to 4 valves per cylinder, even in MotoGP, and why current F1 engines use 4 valves per cylinder.

Finally ... what's the application? It would seem like your target power output will be beyond what any current roadracing series uses.

Personally, I am more impressed by the engineering behind a small-displacement high-efficiency low-emissions engine that can be a benefit to everyone, than by anything with monstrous power output and monstrous thirst ... Many racing series, rightly or wrongly, are starting to limit the fuel usage, whether directly or indirectly; efficiency matters ...

 

[BHoffman97]

Ok then... changes. I need a roots supercharger and if I can't have direct injection I'll just do semi direct right before the valve. No application, I just feel like making this, it's not real and might not ever be real. If it was real it would be ridiculously fun. I like power efficiency, I grew up with the "no replacement for displacement" muscle car guys and I want to prove them wrong someday with a small displacement engine (or a lot smaller than the 572ci hemi and 512ci built-to-high-hell big block Challenger sitting in my dad's garage).
Still nothing with the H configuration, I know they aren't used hardly at all any more, I'd like to see it come back to life if it's balanced like a V12. If I did a V12 or something of the sort I'd do a boxer, it sounds more interesting and I've always liked the old Ferrari Berlinetta Boxers.

 

[timiacobucci]

I'm not doing a radial, that would be awkward to have in a car.

Ohhh, I beg to differ,

https://www.youtube.com/watch?v=z8InG6T9pxs

I mean if a critical criteria is fun to draw how can you beat that?

If not radial is a flat 12 not exotic enough?

I think you've got the idea with a roots positive displacement for twin charging but a lysholm is more efficient. I vote flat 12, turbo > lysholm > ITB

On the subject matter of small engines with high output and for a real world version of something very crazy and very successful along these lines using one of my personal favorite engines the 4g63, see this thread

http://www.eng-tips.com/viewthread.cfm?qid=267889

That evo has to be one of the all around most impressive setups I've ever seen.

 

[Lou Scannon]

The H configuration adds bulk, weight & complexity due to the dual crankshafts and gearing in-between. One of the most successful H engines was the 24 cylinder Napier Sabre aero engine from the 1940's. It was only ever used fighter applications, but was one of the most powerful and highest power density aero engines ever, whether by displacement, physical size, or weight criterion. Of course, even more notable than the H layout was the sleeve valving, which experienced a meteoric career in british aero engines in the 1930s and 1940s, further examples being the Bristol Hercules and Centaurus, and Rolls Royce Eagle (which never achieved production status).
I assume a 12 cylinder H layout can have excellent balance, as it is merely a pair of flat sixes, but I haven't checked.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[tbuelna]

A 12 cylinder H-configuration would be two flat 6 cylinder engines stacked vertically with the cranks coupled. If you are doing a conceptual design study loosely geared towards F1 racing, then the H configuration is a poor choice in terms of weight, packaging and efficiency.

For an unlimited boost 4.0L recip engine you might consider a V8 or V10 arrangement with more modest bore/stroke ratio. You'll get a better balance between weight, size, efficiency, and throttle response by using fewer cylinders, lower bore/stroke ratio, lower rpm, and extremely high boost.

 

[drakem4]

What about opposed piston opposed cylinder? Seem to be the next big thing in engine design

https://www.youtube.com/watch?v=uP7gGUCPJj0

 

[140Airpower]

Its so nice to have a clean sheet, no requirements, unrestricted and unfettered dreams. But....
The IC engine is over 150 years old and among what you see today is what's just about the best of 150 years of clean sheets.
In F1, the V10 seemed to be the best compromise in maximum breathing from multiple cylinders and weight from compact design. The V10 looked better than the V12 when both were allowed. Already mentioned is that the H is extra heavy and more complex. Also, the flat engine is a weaker structure than a V as well as being heavier. In a car, the flat engine also suffers somewhat from restricted exhaust due to ground clearance and it tends to interfere with ground effects channels and diffusers.

IMVHO, the sleeve valve engine of WWII proved to be inferior to the poppet valve engine after the dust cleared. The main deficiency that cannot be overcome is that the sleeve control mechanism is complex and rpm restricted, probably severely rpm restricted relative to today's engine speed requirements.
Note that the opposed piston engine usually relies on sleeve valves and this engine is essentially a flat engine that has two crankshafts and two crank cases instead of two heads. Guess which is heavier. Also, two heads probably breath better relative to the displacement than the central induction system of the opposed piston engine (but I'm not sure). Just a note that the opposed piston engine is very difficult to air cool, but this may be a moot point for you.

 

[drakem4]

Rotary valve 2-stroke engine

Look at the Mercedes-Ilmor 2-stroke Rotary Valve V8 that was banned from F1

 

[140Airpower]

"Look at the Mercedes-Ilmor 2-stroke Rotary Valve V8 that was banned from F1"

Saying "banned from F1" could be like saying steam engines are "banned from F1" or bicycles or moon rockets. Those were never under consideration. 2-strokes are not considered and rotary valves are not either. They are not "banned".
I will be impressed with this engine when Mercedes puts it in their passenger cars.

BTW, as far as I know rotary valves that are exposed to combustion pressures leak, they attempt to seal the port from the outside of the chamber and are lifted by the pressure -unlike poppet valves that are forced into their seats therefore seal very well. Sleeve valves also seal very well.

 

[BigClive]

If we are talking about the same engine - it was a 4-stroke not a 2-stroke. It was intended for the V10 engine. Despite some claims to the contrary there was probably only a single cylinder test engine built.
The gear train to each rotary valve doesn't look very practical.

http://home.people.net.au/~mrbdesign/PDF/AutoTechBRV.pdf