The JTD is a 120bhp 8v SOHC engine.
http://pictures.autotrader.co.uk/img...a?id=671931306
The JTDm includes an 8v 120bhp version (available in pre and post facelift models), a 16v 140bhp (pre-facelift) DOHC version and a 16v 150bhp (post facelift) 16v DOHC version.
http://picnic.ciao.com/uk/8582742.jpg
http://pictures.autotrader.co.uk/img...a?id=679469910
All are common rail direct injection diesel engines but the JTDm (red m-jet badge on the rear boot lid, and in the case of the 16v, additional 16v letters on rear boot lid and engine cover - see above picture) has uprated injectors which operate at a higher pressure than those in the earlier non-m JTD. The 8v JTDm engines never reached the UK though.
There's also a 16v 170bhp version of the 1.9 JTDm engine scheduled for inclusion in the Ducati version of the 147
