Injection questions from a carb guy

[405cubes]

Ok, so two points of the injection system make me wonder.....

Carbed, you get worse vacuum as you increase above ideal carb size- I always thought the larger throttle bores allowed a quicker equalization of vacuum, thus a quicker drop under load....
....So how does this play into a throttle bodied setup? Or MPI? I would assume the same, given the total surface area of flow...Is an injected system less prone to this, given the map communicating to alter ignition/fuel delivery?


The other thing- injector placement. Straight towards the valve? How far protruding into the port? I was thinking about it, and it would seem a bit of protrusion where airflow would whiff the fuel off at shut-down, may decrease long-term deposits/buildup... at the expense of port flow, ofcourse. Seems service life would be increased somewhat.


Again forgive my ignorance. All I know about injection is how to replace parts/ read a scanner and do basic diagnosis. Never really studied the theory, performance, etc.

[delcowizzid]

too big on the TB and they can get touchy too big on the plenum they get doughy.as far as oversizing like a carb its not as bad as you arnt trying to atomise fuel with airspeed through a carb.way massive big huge TB you could expect to see diminishing results purely from loss of airspeed through the TB

you also need to take into account TV cable for trans etc depending on what box you run.

as for injector placement generally aim them accross the short turn radius at the valve and the airstream will lift it away from the radius and hopefully cool the whole valve head.

in saying that its not allways easy to do with space constraints or port shape .just try to avoid spraying fuel straight at the port walls