Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 2017 Plus 4 GDI - better manifold, cat and map

I have owned my first and only Morgan (so far) for just on a year and it has been intriguing to read about the performance improvements that many others have made to their GDI engined Plus 4s. Inspired and informed by all this, I have now joined in and hope it might be of interest to report on my experiences.

The car started with the bog standard set up of the rather basic exhaust manifold/catalytic converter, together with the standard ECU map, so the performance and driveability was not all it should be:



So I got MMC to install the "Enhancement Flash" and this improved the drive qualities, with power delivery being smoother and fuel consumption improving noticeably (from low 30s mpg up to 36ish).

Reading about the significant benefits of a better exhaust system, I considered going the whole hog and getting the AR manifold, cat, silencer and Clubsport map. But reports of substantially louder noise put me off, so I have opted for the Librands/Piper sports manifold and cat, which I had fitted by Matt at Lifes Motors in Southport at the same time as an annual service (he did an excellent job, as well as putting up with me watching/ getting in the way and asking lots of questions).




As others have found, the old manifold and cat have to be cut in two to be removed easily:



The results are that the exhaust note is a little louder, especially when making use of the power freed up with the bigger manifold pipe diameters. There are also more pops and crackles. It's nicer to drive with more torque available from lower revs than before and the fuel consumption has improved again, up to around 40 or so mpg.

I couldn't resist satisfying my curiosity about the actual power output following these improvements, so took it to a rolling road dyno for a power run, which produced this graph:


Accepting issues around calibration etc of dynos, it is interesting to see the power is around 15bhp more than stock, with a smooth delivery curve - in contrast to some of the other power curves seen by others, particularly with the original basic map.

I'm content with the improvements in how it drives versus exhaust noise. And the better fuel consumption has almost convinced the CFO that it was worth the few quid it cost!