Hi there,
No tests on F7R as yet. Those ones are 45mm shaftless throttles as we couldn't use the same kind of twin body we normally do. Very wide ports making that difficult.
As far as I know we never did any 38mm ones for the renault engines. We had a misprint on the website for a long time as the guy who did it just copied one lot of information for each throttle body kit.
The F4R ones are 42mm. Can now be fitted with a taper to 50mm if you like, although someone who tried that didn't make any more power. The 42mm sized shaftless throttle has been used up to 300bhp on a duratec. I'm not entirely sure why the jenvey's aparently made more power as it would be unique in the testing we have done on lots of other engines. One thing I did notice a while back is the opening on the throttle was the same size as the RS inlet manifold. Everyone is familiar with the port matched inlets, releasing an extra few bhp. The new ones we make are the larger size of the head (like a port matched inlet) so if that was the missing few bhp the jenvey's had then I guess that isn't a problem anymore. We were originally designing the system to the requirements of the customer, if we're not told about things like this we can't make the improvements necessary. All seems to be water under the bridge now though.
Anyone with a williams may like,
Thanks,
John.