Board logo

Will I need to change trumpet lengths if I shorten the intake manifold?
Hugh_ - 12/3/12 at 07:47 PM

I've got a Pipercross PX600 airbox waiting to be fitted, the intake of which will sit a long way forward (ahead of the front of the bonnet). With my current intake manifold it will sit about 25mm outside the bodywork and will need both bonnet and nosecone to be hacked about.

I've been toying with the idea of replacing the bonnet and nosecone anyway, but if I do I would like to keep the airbox within the bodywork. If I were to change to a shorter intake manifold I would presumably lose some lower end torque, but would the combination of short intake manifold and long trumpets be likely to cause any undesirable effects as far as standing waves and power goes? Would I be better off getting shorter trumpets as well? I know that would lose me even more bottom end.

I currently have a 90mm intake and 45mm trumpets (which happens to be the maximum recommended for the airbox).

The engine spec is: 2.1 pinto, balanced bottom end with ARPs, Kent GP1 cam (3000-7500rpm range, long duration), big valve head port matched to intake manifold, Dellorto 45s.

Thanks
Hugh


Hugh_ - 22/3/12 at 03:39 PM

Anyone?


cliftyhanger - 22/3/12 at 04:13 PM

I was under the impression it was the total length, valve to intake, that mattered, so shorter manifold means a longer trumpet if you want the same "feel"
Have a look on the jenvey site, I think that is where I read it.


coyoteboy - 22/3/12 at 05:08 PM

Total length is the primary driver, shortening will move your "tuned" point upward in the range.