G40R questions
Discussion
Apologies for hijacking the thread but would be interested to hear of any solutions anybody has found for fumes/smell in the cabin. Have read a number of times that this is common so i am not alone. Mine has had the small deflector plate fitted to the diffuser that was supposedly part of the factories solution. However, I have conducted a few tests and I am fairly convinced that the cabin fumes are not exhaust gases, certainly not from the tailpipe entering the boot. I suspect engine related fumes. I would love to find a solution as it’s my only bug bear with the car. I think the car desperately needs a fresh air feed, the air con cools but does nothing for the air quality, I’m just not sure of the best solution.
Yeah, to be fair it only bothers me on long drives. If you managed to drive from Leeds to Aberdeen without bother maybe I’m just being soft. But if I drive far enough I get headaches and can taste it so perhaps there is something more to it with the older cars. Mine is also worse with windows down, I presume this draws air from the car creating a low pressure area in the cabin which then draws in fumes from somewhere. I spoke with one of the teams that run G40 race cars and they have had similar issues on cars with atmospheric oil breathers badly positioned but the duratec cars all breath back to inlet so I can’t see where else the fumes might originate.
kwak82 said:
Apologies for hijacking the thread but would be interested to hear of any solutions anybody has found for fumes/smell in the cabin. Have read a number of times that this is common so i am not alone. Mine has had the small deflector plate fitted to the diffuser that was supposedly part of the factories solution. However, I have conducted a few tests and I am fairly convinced that the cabin fumes are not exhaust gases, certainly not from the tailpipe entering the boot. I suspect engine related fumes. I would love to find a solution as it’s my only bug bear with the car. I think the car desperately needs a fresh air feed, the air con cools but does nothing for the air quality, I’m just not sure of the best solution.
have you got a pic of the plate fitted to the diffuser? I don't know if mine has one. 
Not sure if pic will work, first attempt to upload anything. Essentially it is a piece of 90deg black angle aluminium riveted perpendicularly to the rear diffuser so it protrudes into airflow presumably to somehow cause turbulence or disrupt the air as it passes the diffuser. As with all G40 info it seems shrouded in mystery. However, I have read bits and pieces referring to it as a factory fitted solution to the fumes. I agree that the bluff tail of the car does draw fumes from central exhaust up boot face, hence the sooty rear that a lot of G40’s have. My confusion with the solution is that I have attempted to put strong smelling substances in the boot and the smell never makes it into the cabin. I cannot see how fumes would make it from the boot to cabin as there is no obvious flow path. From above the space around the fuel tank yes I can see it but from the boot I can’t. I would love to know what the factories intention was.
I have a 2015 car and no plate on rear diffuser...
I have never had fumes in the cabin, I have the rear wing.
I suspect the smell may well be hot catalytic converter and hot GRP?
On my car the heat shield around cat was touching the cat and the grp and so when it got hot the smell was a mixture of hot cat and hot grp which is quite fumey.
I have cured it be making the cat shield independent of the cat with a small air gap. No more fumes although on a good run the I can ostill smell the cat - they do just stink - and it is sat on the other side of the bulkhead.
I have never had fumes in the cabin, I have the rear wing.
I suspect the smell may well be hot catalytic converter and hot GRP?
On my car the heat shield around cat was touching the cat and the grp and so when it got hot the smell was a mixture of hot cat and hot grp which is quite fumey.
I have cured it be making the cat shield independent of the cat with a small air gap. No more fumes although on a good run the I can ostill smell the cat - they do just stink - and it is sat on the other side of the bulkhead.
Another thing to check is the v clamp on the manifold pre-cat - mine was tight but not holding the joint closed and it had been assembled dry without exaust paste. This meant exhaust gases were escaping at that joint that would likely quickly find their way into the cabin from the front?
I would be interested to know if the rear wing makes any difference to either this fumes problem or stability of the back end as I would prefer to remove mine to be a bit more discrete about town....
I would be interested to know if the rear wing makes any difference to either this fumes problem or stability of the back end as I would prefer to remove mine to be a bit more discrete about town....
My car runs very rich, which seems common, and has burnt out at least two cats previously. Because of this I have a cat replacement pipe fitted. So it can’t be the cat causing fumes in my case. The v clamp is a possibility but I can’t detect a leak here, albeit the car is stationary when I’m checking it. If I ever get another manifold made I would be keen to redesign this section so I could discount it causing fumes.
As for the rear wing, I have one too and have read various comments about it improving fumes. I guess it must put some downwards force on bootlid which might potentially seal it better, but as I said I cannot find a path that fumes could travel from boot to cabin. With that in mind I don’t see how it could improve cabin fumes? No idea about it’s aerodynamic effectiveness. Would be interested to know.
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