The 2.7-litre six-cylinder engine now develops 240bhp, 12bhp more than previously.
The Boxster S, which will be launched simultaneously, has 20bhp more at 280bhp from its 3.2 litres. The Boxster takes 6.2 seconds to reach 62mph, while the S model achieves it in 5.5 seconds. Top speed is 159mph for the Boxster and 167mph for the Boxster S.
It will be priced at £32,320 (including VAT) and the Porsche Boxster S at £38,720.