The exhaust ports are all the same efficiency wise.
The No.1 exhaust manifold branch does have a slightly tighter turn, however whether the efficiency losses are more than fractional I very much doubt. Even if the manifold was very poorly designed, the significance of the restriction wouldn't be enough to increase combustion temperatures to melt a plug.
There is very little in the way of cooling airflow to the engine anyway, putting the charger in front of cylinder No1. ain't gonna make much difference.
I bet if you could put a temperature probe into each of a G40's standard cast manifold primary pipes, the EGT's in all four would be very similar indeed.
This is either a plug related failure or for some reason the engine momentarily ran very lean on No1 cylinder.
I partially agree, but what you say isn't strictly ture.
The exhaust ports themselves are the same efficiency wise, the exhaust manifold itself isn't. The increase in pumping energy required on Cyl. 1 to clear the tight radius will have an effect on EGT after a few cycles. I agree with you about it not being significant enough to melt the plug. The charger brackets etc do make a differance on block distortion, they're basically a heatsink for the exhaust, and as such retain alot of latent heat, don't be so quick to rule things out.
Personally I think it's a bad plug. I've not seen it yet but even with Robin's state of tune (circa 160bhp) a W5DPO should withstand the increase in EGT. Also there would be evidence on other plugs of a failure about to occur if fueling or ignition timing where indeed the case.
The injectors have been flow tested a few times and came out fine, the fuel rail can't really go wrong either, it's a plastic rail! and Cyl. 4 is furthest away from the intake anyway, so I expect this would experience the biggest pressure drop.
I no longer run Bosch plugs, and havn't for a long time as they don't like nitrous and I find when you go boyond the relms of W4 they like to missfire when cold. NGK are far better (and cheaper) one of the few things people pay attention to until they go wrong like this!
