Onetrack:
Using BSFC figures, can you point me to any motor vehicle engines that are 30% more efficient than an aircraft engine?
27/09 - I was actually referring to a 30% fuel efficiency gain over the last 60 years in automotive engines - which has been driven by legislation, not by any effort on the part of auto manufacturers.
The legislation was more than likely driven by the understanding that the corporate inertia to introduce improved engine efficiency was unlikely to be overcome without legislation, when you have auto manufacturers and oil companies sharing directors on the company boards - as is, and has long been, the case....
......I don't know how you can expect an engine that has had virtually no engineering development/advances in technology since its inception in the early 1950's, to seriously compete with a modern automobile engine that utilises a wide range of efficiency improvements in its design - such as high-tech fuel injection systems, VVT-i, multiple OHC's, low-friction rings and pistons, high compression ratios, CGI and high-tech alloys in blocks and heads, fractured metal caps for bearings, sintered iron powder for conrods. The Lyco is a dinosaur.
Onetrack. You are talking complete and utter bollocks.
You do not understand the concept of the duty cycle of an engine - the spectrum of torque and rpm over which the engine is expected to operate. An engine designed for automotive use has a completely different duty cycle to an aircraft engine and many of the automotive "developments" you speak of have no useful application to aircraft engines and they are heavy as well.
Variable valve timing and overhead cams for example have no relevance to a direct drive engine that is going to spend its entire life at 55% + of full power at 2500 rpm.
Manufacturing techniques such as fractured bearing caps, etc. may be relevant if they are amenable to quality control and reliability and maintainability considerations.
As for fuel injection, I am deeply involved in the process of commissioning an aircraft with a Rotax fuel injected engine for an alleged fuel economy increase of around 10%. I can assure you that the installation is neither cheap nor simple because of the complexities of ensuring an uninterruptible high pressure fuel flow and that relies on an uninteruptable electrical system. The engine is heavier than a carbureted engine as well.
The engine has two alternators, two ECUs, eight injectors, a raft of sensors (knock, MAP, temperature, etc) and a raft of built in logic devices to provide fail-over and alerting. It is not a trivial exercise to wire and plumb this thing.