My data proven point is while IATs do rise at idle with an open filter setup, as soon as you move off and the engine starts shifting air the IATs instantly return to normal operating levels. One correction though, I do now believe the peak IAT of 47c I saw was a consequence of rad fan activation, on closer review the log definitely shows a correlation between the two with a rise from 40c to 47c as the fan blew hot air into the closed engine bay at idle. Because the car was sat at the lights there was litrally no other air flow in the enclosed engine bay other than the super heated air pushed out by the rad fan, so the IAT rise is to be expected.

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However, once again as soon as you open the throttle and move away the IATs fall rapidly,TBH if I had my time again I would probably have asked my fabricator to build my inlet manifold with the throttle body facing forward, this would have likely necessitated fitting a longer throttle cable and added other minor complications but it would have placed the air filter up front to receive cool incoming air. However, the benefit would have been very small and only likely seen at idle where in terms of power production higher IATs are largely irrelevant.

On Saturday 27th Jan I will be visiting Surrey Rolling Road to put Monty on the rollers for the first time, this will not only give me outright peak horsepower and torque figures but because a proper graph is supplied I'll be able to see where the torque peaks in the rev range, and how long its sustained for. This is what I'm paying to see, as far as I'm concerned peak horsepower numbers are more for pub bragging rights while torque and the shape of the torque curve demonstrates far better how the car genuinely performs in the real world out on the road.

However, despite SRR running a huge fan in front of the car it is afterall a static test, so I'll be recording a log during the run so I can analyse my IATs and all other data feeds after the event. I'll be comparing these figures with what actually takes place during real world driving, should my intake temps on the rollers be say 15c higher than my true temps out on the open road it's safe to say the engine's real world output could be as much as 5% more than the graph will indicate.

My personal data supported thinking is there really isn't anything to worry about in terms of real world driving power loss if you fit an open filter up the back of the engine bay, but I do strongly suspect the Mondeo airbox will start to become a restriction above 172hp so that would mean a K&N or similar could be a worthwhile mod for anyone going further than just a decent exhaust manifold on their Duratec Plus 4.

The GDI of course has what looks like a better coffee can type filter enclosure with a cold air feed, while this feed does sit over the hot exhaust manifold my data shows once the engine moves off idle the inrush of air will solve that issue more or less instantaneously. I'm not sure what type of filter resides within the GDI's coffee can but I suspect whatever it is the setup will happily support the Club Sport tune that I understand takes the engine to 185hp, and as 185hp represents the practical tuning limit of a GDI I'd recommend the OP saves his money and leaves the standard setup in place.

Actually the stock cold air fed GDI setup looks pretty good to me, so I might even copy it on Monty thumbs

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Last edited by Montegue; 04/01/24 09:54 AM.