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]

TWM makes Weber clone throttle bodies for several carb styles, including the IDF.

The only issue with these, or any other individual runner induction system, is measuring manifold vacuum for speed density systems (like the Megasquirt). Just one port has too much pulsing to be read reliably. A MAP plenum can be used, or you can use only the throttle position as the load input, which comes with its own set of problems. As a rule, you can get such a system working great for racecar needs, but getting good low-speed drivability is a real challenge for a street setup. The most effective setups use both throttle position and MAP for load, based on RPM (Megasquirt only uses throttle for acceleration enrichment out of the box).

[Mark Henry]

TWM makes Weber clone throttle bodies for several carb styles, including the IDF.

The only issue with these, or any other individual runner induction system, is measuring manifold vacuum for speed density systems (like the Megasquirt). Just one port has too much pulsing to be read reliably. A MAP plenum can be used, or you can use only the throttle position as the load input, which comes with its own set of problems. As a rule, you can get such a system working great for racecar needs, but getting good low-speed drivability is a real challenge for a street setup. The most effective setups use both throttle position and MAP for load, based on RPM (Megasquirt only uses throttle for acceleration enrichment out of the box).

You just tap all of your manifold runners for a small vac. line and run them to a single point. Then run a hose to your MAP sensor.
If you have problems (big cam) with your MAP, stick a mig welder (.023) tip in your hose, just before the MAP.

TWM, Jenvey and CB perforamce make TB's. CB's is the cheapest, but both the TWM and Jenvey are of better quality.

They have the same problems as dual carbs as far as the linkage goes, where as a single TB system doesn't.
Also I prefer direct injection over the injector in the TB, as all these TB's have.

[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.

[crash914]

This is what I am going to use....I plan on placing an order in the next couple of days....

Megasquirt all the way!! (IMG:style_emoticons/default/aktion035.gif)

Oh yes....2.6 liter of headbanging fun.....