Pascal said:
I doubt there will be much benefit from this on a turbo engine... The intake plenum temperature is governed by the gobs of boosted air being rushed through it, doesn't matter if it's in contact with the head or not.
In a natural aspirated application it's great though, since you can make the intake charge 100% cool fresh air, you don't want that passing through a hot intake plenum.
There are a lot more thermodynamic gains to have in making sure the turbo's hot side is well insulated (blankets, etc) and the intercooler system is efficient.
And what are the differences between the combustion process of the F/I engine, when compared to the N/A engine ?
Whether the engine is turboed or not, cool intake air will make it perform better and the intercooler of a turboed car, is there to cool the intake charge for when it enters the plenum.
Therefore, having a cool plenum for the cooled intake air to go through, will certainly help performance.
Bottom line is, it doesn't matter whether the engine is turboed or not, a cooler plenum will benefit it !