Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) "Burning" smell when driving hard

Most likely your manifold and turbo getting nice and hot ie working temp, most mogs never get properly hot when they just tootle along under light load and throttle

It would be worth checking that no ancillaries or wiring near either of the above are too close as the CX engine bay is very tight

I'll check that out today

Shame I can't upload the odour to help identify it

Just a thought, could it be the age old Morgan problem of fumes getting into the cabin?
I’ve had 4 different Morgans and they have all done it, the latest CX Plus Four being the worst of the lot!
Get the engine warm then bury the throttle, when you have reached a decent speed lift of the throttle totally, you will get a good whiff of Shells finest and it does actually smell a little like you describe.

Sir P

The CAT on my plus 4 still stinks with 47 k on the clock, but only after pushing hard or blasting up steep hills.. It’s a sulphur type smell and I often think that the stories of fumes from the exhaust are more related the cat.

Yes that's how to describe the smell - sulphur like. I guess it is the CAT then - does that mean it's faulty or leaky or is it just a "feature" or "factory specced optional extra"

I'm 99.9% certain it's not fuel. I had a Westfield (built by me) on the road for 20 years with a 1600 xflow in it - I'm familiar with the smell of fuel in the cockpit

On saloon cars, most cats are well hidden, so the smell is not so prominent, whereas on a Morgan it it is much closer to the driver with not a lot of barriers to restrict the flow of smell. However, if you google smelly cats, it is ONE of the signs of a failing cat. But, googling is a bit like looking up the medical dictionary when you have a pain in the belly!! You start to make a will right away.
As I said, under hard driving, mine did it from new and still does it 12 years later and has never had emission issues for an MOT. I guess if it starts to smell after a “normal”, gentle run, then it may need further investigation.
Sulphur Dioxide can be detected by the average person in concentrations of 1 p.p.m or less, and when you think of the mechanical joints on an exhaust system, it does not take much for minuscule amounts to creep out at joints.

Sulphur dioxide has an irritating smell similar to a struck match. Brake/clutch linings smell similar to burnt toast although I find it more acrid. Both well defined - OP suggests the latter.

My plus six did have some strange odours at first, when pushing on, I put it down to the insulation. Not so much now, but still get a whiff when the turbo is working hard.

My car also has this smell after hard acceleration. It cleans the catalyst.

It just occurred to me. Being a modern BMW engine and WLTP emissions and all that, I would assume you have a GPF - Gas Particulate Filter. All petrol BMW engines now have this. If I understand it correctly, the filter burns off the particulates during normal driving, assuming the car is taken at motorway speeds at times and for a decent distance. Assuming it has one, the CPU take over if it deems that the filter needs cleaning. Assuming it has one and being a Morgan they are normally driven on shorter drives vs. long motorway journeys, it could be it's going through a cleaning cycle.

Might be worth checking the manual for any mention of a GPF.

BMW GPF

GPF FAQ