John is right-on, here! The limiting factor in the Explorer-22TDI's operation is EGT! The engine can be throttled well into an overheat realm at continuous duty, so Bryan has designed the drive ratios to go right up to the edge of the continuous-duty thermal limit. The 22TDI has a CAN-Cockpit RPM gage that monitors several engine parameters and allows the operator to closely monitor EGT so as not to exceed the engine's limit. During the testing phase, we hooked up the engine's monitoring port to a laptop running VAG-COM monitoring software and we were able to observe many data points involving specific fuel consumption, exhaust O2, turbo inlet/outlet, and many more to tune the drive system and get a baseline of craft performance underway at various power settings. It's amazing how precise you can get with the right sensors feeding the right instrumentation and logging software/displays!
There has been a bit of a discussion on the Hoverclub of America forum about building EFI engines with "open source" software and circuitry instead of the auto's OEM ECU. The system is called Megasquirt and has been used in aviation auto conversions, as well as Dean Polle's homebuilt SEV-styled hovercraft using an EA81 I believe. This method may also possibly be useful in driving a common-rail diesel, substituting the auto computer, but I don't have any examples of that off-hand.
Cheers,
John Carter
www.hovernut.comYou need to be careful when talking about power output - the engine at the start of this thread is rated at 36hp continuous and the VW Tdi at 80hp (3300rpm) continuous. For a reliable and long life those are the ratings that should be used on a hovercraft - not what the car brochure says 
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I doubt there are any car engines that will operate at anywhere near full rated power for very long - for one thing the cooling systems don't have enough capacity to reject the heat produced.
