Atkinson cycle engines?

[Hank]

14 minutes ago, A64Pilot said:

There are improvements, but water cooling for example adds a lot of weight and lots of complication, it’s been done, but I don’t think it worked as well as hoped. Wasn’t there a “liquid rocket”?

Yes, the Liquid Rocket was a modified M20-L, using a large 350-hp engine to replace the Porsche engine due to Porsche's withdrawal from the aviation market. Seems like only a handful were made.

Here's one I ran across. Note the size if the radiator exhaust hole below the N number (on both sides).

[A64Pilot]

I thought so, so why aren’t new Cirrus’s liquid cooled? I’m thinking the motor didn’t work out as well as hoped?

Obviously it was Certified and Liquid cooling should have done wonders for longevity, with it you can keep an engines temp very stable and not have hot spots etc.

So something happened? I’ve never seen one myself so I assume there weren’t many motors built?

[A64Pilot]

Decent article on liquid cooling aircraft engines

https://www.aopa.org/news-and-media/all-news/2002/july/pilot/airframe-and-powerplant-(6)

So where are they?

 

[Hank]

31 minutes ago, A64Pilot said:

I thought so, so why aren’t new Cirrus’s liquid cooled? I’m thinking the motor didn’t work out as well as hoped?

Obviously it was Certified and Liquid cooling should have done wonders for longevity, with it you can keep an engines temp very stable and not have hot spots etc.

So something happened? I’ve never seen one myself so I assume there weren’t many motors built?

Not due to lack of engines, but to lack of useful load after the swap, which didn't include a gross weight increase. Extra weight came from the radiator, the coolant, a pump to push it around, mounting brackets for the radiator and pump, probably an overflow jug like in your car, ductwork from the radiator to the huge exit holes, etc. That, plus the hurricane that totaled many of the L models parked waiting on one conversion or another . . . . .

[A64Pilot]

So why not on new aircraft? 

You know in truth I’m sure as I think many others are that a Modern design aircraft engine could burn car gas and not weigh any more than these Diesels being proposed, and TBO should go way up, I’m not talking high RPM with reduction gearboxes, but direct drive. 

Autos are producing high HP, with 11 to 1 compression with car gas, so it can be done without high octane, because it is being done