Crampy wrote:How do we work out or know the ideal length for a Blacktop, other than chuck them on a dyno and look at the power deilvery?
Depends for what purpose you are wanting the trumpets. And what other work has happened to the engine internally as well as what ecu you have running the engine, before you can really define what is 'ideal'
The factory ones i measured crudely at around 125mm in length. Although even with the same length ones, you lose resonant frequencies that having the chamber around them creates (Helmholtz) There is a large amount of science around it that i dont understand properly.
In my very limited experience with mucking around with the trumpets, the longer you go, the lower down the rev range the torque curve will move, and the shorter they are, the higher up it will go.
A large school of thought shared by many here says that the best trumpets to use are the factory ones with the airbox and intake chamber.
I'm planning on buying a couple of those 150mm sets from efihardware for my race car with blacktop 20v in it, and gradually decreasing the length of the trumpet from standard to see which is going to be the most effective for me with the engine setup i have.
