Rover 820 airbox versus the ITG Maxogen

Ever want to know how the Rover airbox compares with the ITG Maxogen? I took the picture opposite, astonished at the remarkable similarity between the two structures. Dimensionally, the two are surprisingly close - 20mm is all that separate them in terms of diameter of the airbox enclosure proper. The inlet 'choke' (the narrowest point of the air intake) is identical.

The ITG does have advantages though. It appears as though that intake 'trumpet' is designed to accelerate air into the airbox - and presumably increase top end power. The Rover 820 airbox does not have this feature - it may even make the airflow turbulent at higher engine speeds where the ITG might be expected to excel.

Unfortunately, I have yet to try the Rover 820 airbox mod on the same car as the ITG, but we have tried both filters on two separate cars (mine and Tom Randell's) on the same day at Dave Walker's rolling road (just before it moved from Brixton to Norfolk).

Some of the differences in the power curves could be explained by Tom having a slightly 'better' engine to start with, but what IS interesting is how both the power and torque curves overlie one another up to about 4,500 rpm. That scrapyard air box is performing as well as the fearsomely expensive ITG! Above this point, however, the ITG comes into its own, and shows where you've spent those extra pennies - on an additional 4 bhp. Are those extra horses value for money? You decide...