Skiddell/Pmac Airbox

[toopy]

Did look at those but can't see much difference in what I have. I already have the trumpets so don't really want to spend another £80+ on some more. In fact i now have longer 75mm trumpets which seem much better. The short ones tend to suffer from drawing in hot air from the engine bay which affects the power. I'll stick with what I have.

I would have liked one of the Skiddell/PMac airboxes but couldn't see where I could route the intake pipe through the radiator panel. There is no room between the rad and the cabin vent pipe on my car and I didn't want to do away with the vent.

I think what Ian was pertaining to above, is that with the rubber seal holding the mesh in place, you are effectively taking the rolled lip of the trumpet out of the equation, which is rather the point of the trumpets in the first place. The other ones linked above, obviously still have the mesh but you also still get the effect of the smooth airflow over the trumpet lip. How much difference that actually makes to a standard engine i wouldn't know.

 

[Farmer42]

I think there are 2 types of trumpet. One is the rolled lip type which I understand to be straight used on Dellortos etc. and there are the ones like mine that don't have a rolled lip but narrow towards the carb so that the air speeds up a bit like a venturi. If I don't have a rolled lip trumpet I don't understand how air would be affected by the rubber. There is no difference in performance with or without the filters.

 

[toopy]

Like you say, with or without the filters, performance is the same on your engine, however on a tuned engine at high revs they would likely be restrictive.
I couldn't find a decent diagram, so i drew a crude example to show with the rubber on the mesh filter causing air flow turbulence and hence a possible drop in maximum performance at high air intake speeds.
Not that any of this really matters in this case, i just felt like drawing, badly, and trying to explain, badly, how air flow and velocity could be negatively impacted

 

[AliK]

Agreed mr @toopy - I had to return a set of trumpets for a refund to Merlin as they claimed to be the right size by they narrowed to less than the carb mouth by about 4mm. On mine, I DEFINITELY felt the performance drop at the top end.

It was the noticeable performance drop that made me suspicious and got my callipers out!

Ps. Great scribbles!