The V12 engine was swapped into a supra awhile ago by Top Secret a while ago and made insane power.Toyota even makes a v12 engine. It has been a rumor they have been using this v12 to develop a 1000hp supra. Currently tho the engine is used in a limousine that Toyota builds and in that form puts out 280 hp at 5200 rpm and 355 tq at 4000. They even make many types of diesel.
As Lotus has already said, they are starting off with the 2GR-FE. I have a feeling that they will move up to the 2GR-FSE which in N/A form makes 311 hp & 278 tq. It does this by using both direct injection & port injection for very good A/F ratio under low & medium load and under high load uses only direct injection. This engine will be far more responsive than any other v6 Lotus could have used and this is before they put on any forced induction.
Lists of all Toyota Engines (click on engine letter code to view specific family engines up close)
List of Toyota engines - Wikipedia, the free encyclopedia