Seneca I with turbo question

[tathepilot]

I got checked out in a Seneca I with rayjay turbos. They are manually controlled. When I apply the turbo I noticed the fuel flow drops off ? Why does this happen? Can the reduction in fuel flow be use in flight planning purposes ?

I asked the mei why does that happen, he said.....it just does.
go figure.

Can any one shed some light on this.

 

[rumpletumbler]

With my extremely limited understaning of turbo charging...isn't it just increasing the air pressure inside the engine so that it operates as if at sea level to a certain altitude? I would think that would increase fuel flow. But....ignorance will fool ya every time.

 

[unreal]

Yeah, that is weird. On the turbo I fly, we keep the mixtures up full-rich on takeoff, and then lean for TIT in the climb. By no means does fuel-flow drop off at any point...the thing guzzles like nothing other.

 

[TrafficInSight]

A Fuel flow gauge is actually a pressure gauge marked with flow numbers. It could be that flow is actually going up but pressure is going down... Is this a Seneca I with Lycomings and a turbo STC?

I'm looking for my book on fuel injection... but I can't find it.

 

[philo beddoe]

I would try to call the aftermarket turbo manufacturer.

My limited understanding is that fuel and air burn in an exact ratio according to weight. If you are stuffing more air into the engine, my logic says that more fuel is required to maintain a burnable mixture. The above post may be right, assuming that there may be some effect on the flow guage from the turbo. You would think that the STC would have had to take this into account, but I guess you never know.

 

[TrafficInSight]

The fuel injector nozzles themselves have bleed ports to allow bleed air into the fuel stream. This helps with atomization.

Change in the amount of bleed air can cause changes in fuel flow indication. That might have something to do with it.

At any rate... a fuel flow decrease with turbo application sounds like BAD NEWS to me. High boost with lean mixture is a recipe for detonation. Though, as long as there's enough fuel flow for the given mixture it's okay I suppose.

 

[tathepilot]

A Fuel flow gauge is actually a pressure gauge marked with flow numbers. It could be that flow is actually going up but pressure is going down... Is this a Seneca I with Lycomings and a turbo STC?

I'm looking for my book on fuel injection... but I can't find it.

correct