Random thoughts thread

[Spd229]

Originally Posted by 7thgear

I CRAVE DRAMA AND INTRIGUE

NOMNOMNOM

NOW KISS?

[kanundrum]

Ah Yes going to a nationals game

Should be fun

[kanundrum]

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[Shagaliscious]

Baseball games are always fun. A buddy at work went to one a few weeks ago and said the prices are outrageous at the Nationals ballpark. It is a beautiful ballpark though.

[Nevermore]

Originally Posted by Nevermore

Just put some noob questions in the engine/exhuast forum. Let's see what happens.

I have returned unscathed!

[OrbitalEllipses]

Originally Posted by 7thgear

I CRAVE DRAMA AND INTRIGUE

How typical.

[serialk11r]

Originally Posted by Dimman

Ow, my brain...

Parts that look horribly inefficient to me are the flow through the ports (two sharp 90° turns? No thanks...) and how combustion pressure seems to also push partly against the direction of of the rotor

My conclusion, (based on not being an engineer, briefly viewing the vid, and generally disliking EVERYTHING to do with rotaries), us that BMEP will be atrocious, the lack of 'overlap' control (? Rotary cam phasing) is the same issue as wankels, and rotor temp control point to this being just another virtual motor that won't get past (or even to?) the prototype stage.

From your friendly neighbourhood, highly opinionated, traditional, change-fearing pessimist.


Heh...

To be fair, a piston engine's poppet valves are probably much worse than a 90 degree bend. BMEP should not be a problem, but having the combustion happen over such a long period of time would probably be a detriment on spark ignition engines at low speed like I said.

The only serious problem I see is the rotor cooling. Can't oil cool it since the exhaust would just burn the oil up. Steam injection into the power stroke might work, but that adds a lot of complexity obviously.

The exhaust/intake timing issue can be taken care of with a supercharger :P Go Eaton.

I like this one more than the rest of the engines I've seen, since it doesn't involve using extra pistons and connecting rods and such. Opposed piston designs use double the number of pistons and 2 cranks but get no balancing benefits from them, so it only makes sense to change something like a 12 cylinder truck engine into 2 inline 6s put together. The Scuderi engine thing is again a waste of cylinders and pistons, although NVH is not as bad since you get power strokes every 180 degrees per power cylinder.

[Dimman]

Originally Posted by serialk11r

To be fair, a piston engine's poppet valves are probably much worse than a 90 degree bend. BMEP should not be a problem, but having the combustion happen over such a long period of time would probably be a detriment on spark ignition engines at low speed like I said.

The only serious problem I see is the rotor cooling. Can't oil cool it since the exhaust would just burn the oil up. Steam injection into the power stroke might work, but that adds a lot of complexity obviously.

The exhaust/intake timing issue can be taken care of with a supercharger :P Go Eaton.

I like this one more than the rest of the engines I've seen, since it doesn't involve using extra pistons and connecting rods and such. Opposed piston designs use double the number of pistons and 2 cranks but get no balancing benefits from them, so it only makes sense to change something like a 12 cylinder truck engine into 2 inline 6s put together. The Scuderi engine thing is again a waste of cylinders and pistons, although NVH is not as bad since you get power strokes every 180 degrees per power cylinder.

Poppet valves are really, really well developed when it comes to flow. Look at a cross section and how the valve seat and back of the valve stem produce a very nice venturi (radially around the valve, picturing it in 3d) starting at low lift, all the way to full open. Plus porting is pretty much almost a straight shot.

As 7thgear pointed out, the sharp corners are probably not helping either, by creating turbulence and making the flow area effectively smaller. Vena contracta is probably much more severe because of those corners. Maybe.

The thing that is a major pain with rotaries is the inability to separate intake and exhaust timing from crank position.

As to your Eaton (pretty sure they ran out of a unicorns before they could get small TVSs out to the public...) doesn't that just add to the heat issue? One step at a time...

[serialk11r]

Originally Posted by Dimman

Poppet valves are really, really well developed when it comes to flow. Look at a cross section and how the valve seat and back of the valve stem produce a very nice venturi (radially around the valve, picturing it in 3d) starting at low lift, all the way to full open. Plus porting is pretty much almost a straight shot.

As 7thgear pointed out, the sharp corners are probably not helping either, by creating turbulence and making the flow area effectively smaller. Vena contracta is probably much more severe because of those corners. Maybe.

The thing that is a major pain with rotaries is the inability to separate intake and exhaust timing from crank position.

As to your Eaton (pretty sure they ran out of a unicorns before they could get small TVSs out to the public...) doesn't that just add to the heat issue? One step at a time...

That's true...darn. Well, torqueless wonder it is.

The thing with poppet valves is that the valve seat and valve may have a nice shape but the way the air flows after it gets past that area is ugly.

[Dimman]

Originally Posted by serialk11r

That's true...
The thing with poppet valves is that the valve seat and valve may have a nice shape but the way the air flows after it gets past that area is ugly.

It's not as bad as you might think. The chamber shape also factors into flow, shroud distance (valve to wall), angle of entrance (swirl vs tumble). I think the issue is the over century head start. You have all that gradual progress and refinement and knowledge base to fight against with the new designs.

(Plus stubborn traditionalists such as myself saying 'Never!' at the drop off a hat...)

One decision they made that seems really ignorant/naive of manufacturing, though. And it bugs me. They claim that the whole thing is designed to be machined with only 3 axis. It sounds great, but production-wise it is silly because casting is the major production method, and you can produce complex shapes relatively easily ( assuming, like all engines, that mass production economics are the target).



Also, because rotary.

[fatoni]

crazy patient:"nice tan. it looks so natural. where do you go?"
me:"well my dad is black so..."

[7thgear]

Originally Posted by OrbitalEllipses

How typical.

[M-17]

Originally Posted by OrbitalEllipses

Because cheaper than an M3 and M5, which is the type of vehicle it seems like it's competing against.

is that what you think or did GM mention that. Cause I was actually thinking the same thing then I couldn't help but find that comical.

Originally Posted by Shagaliscious

Baseball games are always fun. A buddy at work went to one a few weeks ago and said the prices are outrageous at the Nationals ballpark. It is a beautiful ballpark though.

Prices at any of the top professional sport leagues are mostly overpriced. I heard that beer and some food was going to be cheaper this year at Fenway park, but I wouldn't be surprised if it were $1 or $2 cheaper. SMH

[OrbitalEllipses]

Originally Posted by M-17

is that what you think or did GM mention that. Cause I was actually thinking the same thing then I couldn't help but find that comical.

I didn't read anything GM said about it...but the comparison is easy to make.