Several pilots here report they only get the fuel smell momentarily when leaning is described as
too quickly, or
aggressively, or a similar description. Question for you...Does this rapid leaning with fuel smell go so far as to cause the engine to stumble, or more specifically, include a loss of RPM?
I'm looking for some phenomenon which would explain a momentary reversal of nozzle deltaP due to rapid leaning.
Break.
I imagine a few readers are wondering how a "turbo injector" is different from the standard.
Actually, the nozzle body and restrictor is the same for both standard and turbo. The difference is in the shroud assemblies. A standard nozzle has a simple bell-shaped shield covering a brass screen. A turbo shroud is sealed to the nozzle body with o-rings, and the bleed air is supplied via a pipe and hose.
This is the nozzle itself. Note the air bleed hole in the side of the nozzle body. Air enters there and entrains with the stream of fuel from the small diameter passage in the restrictor, mixing as fuel and air pass through the larger diameter passage and into the intake tract.
Here are the shrouds, standard on the left, turbo on the right.
So why the piped bleed air with a turbocharger? Manifold pressure is higher than plenum pressure by a large margin, so plenum pressure won't work as a bleed air source. Instead, bleed air is supplied from a tap downstream of the turbocharger.
Now to the EAB application. We can install turbo shroud assemblies on our normally aspirated engines, and supply the feed tube (the "rail") with a ram inlet to ensure high bleed pressure. There are two theories in play here. One is that higher bleed pressure results in better mixing and atomization in the nozzle, resulting in less cycle-to-cycle variation when deeply LOP. The other is that the ram bleed pressure source is consistent, rather then suffering from random turbulence and variations in local pressure at each nozzle location on top of the engine. I don't know that anyone has absolutely
proved either theory, but a lot of users have reported better overall engine behavior, including myself. FWIW, it's also impossible to vent fuel from the nozzle bleed into the upper plenum, as seen in the video link of the Bonanza engine. If there is any reversal, the fuel is trapped in the shroud and returned into the nozzle.
This is the current installation on my RV-8. Don Rivera at Airflow Performance can supply all the major parts.
Another partial installation, customer photo courtesy of AirFlow Performance. The stainless steel rail (the long tube), short hoses, shrouds, etc are kit parts. Builder adds a custom ram inlet tube from the blue fitting forward, bent to suit the cowl inlet.