IDF based EFI, purdy parts Options

[machina]

I came across these things. Says they are IDF based throttle bodies.

Is this what you fuel injection gurus are playing with in your labs?

Would be awsome to get a setup like these running.

dr

[lapuwali]

Also I prefer direct injection over the injector in the TB, as all these TB's have.

I presume by "direct" you mean "directly into the port, aimed at the valve". These days, the term "direct injection" usually means directly into the cylinder, after the intake valve has closed (like a diesel, only for gas engines).

Injector positioning seems to be a very controversial subject. Most OEM systems aim the injector at the back of the valve. Some race systems have it way up high "showerhead style", usually before the throttle. Both claim better vaporization. There was an old (70s) paper written by Lucas engineers claiming great benefits in aiming the injector upstream (away from the valve), also claiming better vaporization of the fuel.

I suspect that at-the-port positioning gives better results in low-speed conditions (less fuel on the walls of the manifold), and so would be ideal for the street, where idle and cruise predominate. Given how short typical Weber manifolds are, I'd also guess that the difference between the injectors in the TB just below the throttle (as in the TWM units), and having it 4 inches or so farther downstream is very small. No data, just speculation. For racing, the higher mounted injectors would only rarely see low-speed conditions, anyway, so high airflow velocities would take care of the manifold wetting. There have been a number of documented power increases shown with the high mounted injectors, so I suppose there's something to that. The ideal system would probably be a small injector at the port for low-speed use, and a large injector up high for big throttle openings.

This argument seems to spark as much heat as the "sequential v. batch" argument. Both sides seem to argue over very small differences.