A single cylinder research engine, based on the Paxman Valenta RP-200, was constructed with the aim of achieving high levels of mean effective pressure and investigating the problems involved. Experimental work on the engine has achieved up to 35.4 bar BMEP. Firing pressure has been limited to values no higher than normally experienced on multi-cylinder engines by a reduction in compression ratio 8:1.Full details of the engine performance, e.g. air and fuel consumption, exhaust temperature and exhaust clarity, etc. are presented for a range of speeds and compression ratios with varying boost pressure.