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!

Last week I drove Hawkis +4 with the sports map & exhaust. Of course coming from a 3.7l Roadster the lack of torque is obvious & being in the right gear matters far more. The petrol really need stirring!
3rd gear starts from roundabouts aren't on, sorry Gary.
But keeping it on song i.e. over 3,5k it was a very lively ride. The exhaust giving lots of pops & bangs that my standard Roadster doesn't have.

I remember on my 97 +4 that fitting the Librands manifold & exhaust really freed up meaningful mid range torque but the last time I drove that car was probably 7-8 years ago so comparing to a GDI is not on.

It would be interesting to get a back to back review of both chip & exhaust options.

The following is something all owners of "modified" cars should be aware of.


"The Department for Transport are currently running a consultation on plans to legislate on vehicle modifications which may have an impact on our hobby.

The concern is although the aim to prevent owners modifying their vehicles in a way that may be detrimental in terms of emissions and the steps are aimed at owners of new / modern vehicles, there is no provision for classic vehicles and to pass the legislation in its current form could wipe out an entire industry at the stroke of a pen.

In its proposal “The Future of Transport Regulation”, the DfT says:

“We will create new offences for tampering with a system, part or component of a vehicle intended or adapted to be used on a road. This will enable us to address existing gaps in the legislation, ensuring cleaner and safer vehicles. We will also create new offences for tampering with non-road mobile machinery (NRMM) and for advertising ‘tampering’ services or products.

This will strengthen our ability to enforce compliance in this area.

We are aware that the Law Commissions in both their first and third consultations on automated vehicles have considered tampering. We await their final recommendations and would welcome views on our proposals, as follows.

Specifically, we would look to create:

a specific offence for supplying, installing and/or advertising, a ‘tampering product’ for a vehicle or NRMM – this would apply where a principal effect of the product is to bypass, defeat, reduce the effectiveness of or render inoperative a system, part or component (the product may be a physical part or component, hardware and/or software)

a specific offence for removing, reducing the effectiveness of, or rendering inoperative a system, part or component for a vehicle/NRMM and advertising such services

a specific offence for allowing for use or providing a vehicle or NRMM that has had the operations described in the previous 2 points performed on it

a new power to require economic operators to provide information, where a service/product they have supplied amounts to or enables ‘tampering’ with a vehicle or NRMM – this would apply in any of the above senses and include requirements to provide relevant information on the quantities of products sold or modified”

A number of influential spokespeople representing Owners Clubs, Magazines, STEM bodies and Suppliers have already spoken out over the detail in the proposal and are urging classic owners to make their feelings known on the proposal via the governments own feedback system which you can visit by clicking the link below:

https://www.gov.uk/government/consu...ing-vehicle-standards#tackling-tampering

The consultations runs from 28 September 2021 until 11:45pm on 22 November 2021."

This appears to have provided the media with yet another opportunity for scaremongering.

That proposal is talking about modifications where the result is "to bypass, defeat, reduce the effectiveness of or render inoperative a system, part or component" - whereas my post is about a significant improvement in performance and efficiency, so I fail to see how it is relevant - other than as a general mention to everyone about the potential risks of removing a catalytic converter or EGR etc.

I'm going to be optimistic and judge that if such laws are introduced in the UK, then it will not be enforced retrospectively - a general principle for legislation in this country, I believe.
Also the modifications to my car are largely similar to the full sports exhaust system that MMC would have fitted, if I had chosen to go along that route - so in effect endorsed by the manufacturer.

The beauty of Morgan Trads is that nobody knows for sure what was fitted when. So the average man on the street/MoT tester will have no idea what's original, and obviously no two cars are the same.

The GDI was sold in Clubsport form with the ECU upgrade and sports exhaust anyway, so that makes this particular mod a manufacturer option.

Hi Keith, I deleted my post again because I did not want to diminish your joy (the post was about the changes to the engine and the regulations in Germany). I thought after writing that there will be other opportunities for my text. And as I wrote, we are in the same boat. I have practically all the measures implemented on my 4/4 that you have now also realized.
Let's have fun and enjoy our beautiful toys for hopefully many years.

Oh, and the heatshield from the original Cat will fit the new cat Keith.

Yes, you're right of course Dave. Matt swapped it over to the new one - I took that pic before he'd done it.