Hardest plane to take down in WW2?

[kool kitty89]

Did the V-1710 use a "pressure carburetor" and I'm not sure but does a "pressure carburetor" work like a throttle-body injection unit?

It used a Bendix produced carb, which had a larger market for "pressure carburetors" in the late 1930s leading up to WWII, or so I've read.

 

[Elvis]

kool kitty89,

Seems you're confusing some terminology here.

Robert Bosch figured out the whole "sequential" thing back in the '20's (I believe) when he came up with the idea of the Injection Pump.

Don't recall if I went into that much detail last time, but basically you have two types of injectors; the style that uses a separate Injection Pump and the style that doesn't use a separate Injection Pump (commonly known as a "Unit Injector").
The style that uses an Injection Pump is the type I believe we're working with here.
What happens is that fuel is drawn up from the tank via a typical fuel pump.
This pump sends the fuel through a filter and into the Injection Pump at "low" pressure (5-7 psi).
The injection pump can take on two forms - inline and rotary (sometimes referred to as a "distributor-style", because it looks a little like the distributor on your car).
I believe the DB601 used the inline style (trying to remember from the cutaway I've seen a couple of times).
Anyway, what happens is the pump has several small chambers each with a tiny little piston, called a "plunger". Each chamber corressponds with each cylinder on the engine.
So if you have a 6 cylinder engine, your pump is going to have 6 chambers.
If its a 12 cylinder engine, then the pump has 12 chambers. See?
Because of the small size and the fact that the injector (in this case) is basically a poppet valve in a nice shaped "case" builds the fuel up to a much higher pressure (in a diesel engine, it is not uncommon for fuel to be pressurized to around 1500 psi or more. On a modern gasoline car engine its much less, around 40-50 psi).
The combination of the higher pressure of the fuel and the shape of the opening at the end of the injector creates a fine "misting" of the fuel which allows it to burn much more readily, thus combustion is quite efficient.

With the Unit Injector (commonly seen on Detroit 2-stroke and EMD diesel engines) the Injection pump is part of the injector itself.
Basically the plunger is in the injector and fuel is fed directly into it at low pressure via the fuel pump.


MULTI-PORT INJECTION, simply means you have a separate injector at each cylinder.
The alternative to that would be a "Throttle Body" (what GM used to refer as "TBI", meaning "Throttle Body Injection").
A Throttle Body is bascially a carb, but instead of its usual jets and floats, an injector is shoved inside each venturi (assuming more than one) and fires off whenever an intake valve opens up.

So MPI and Seq. Injection are actually two different things, with the only connection between them being that they both deal with Fuel Injection.


Even today, just about every car that still uses what we now call "Mechainical Fuel Injection" (which is pretty much relagated to diesels these days) is based on the Robert Bosch design, no matter what maker's name is embossed on the body of the pump.




Elvis

 

[kool kitty89]

I understand that now (earlier I had confused a few things). I was wrong about the fuel efficiency, I'd been thinking all early systems used "simultaneous" or maybe "batched" injection and not "sequential" injection. (although those were more common on the first automobile engines using direct gasoline injection iirc)

FLYBOYJ (on another thread) described a "pressure carburetor" which sounded like a similar mechanism as single-point injection/TBI. This type of mechanism wouldn't be affected by changing G-forces (particularly -G) and since the V-1710 used a Bendix carburetor (a company known to have a strong market in "pressure carbs" leading up to the war) and since the V-1710 never seemed to have -G induced cut-out it would make sence that it used this mechanism.

It would make sence that someone would use this type of mechanism on a military a/c engine durring the war since the concept is a compromise between a carburetor and "direct fuel injection" having no problems with g-loads and being about as simple as a normal carburetor (albeit with a pressure pump) although somewhat lower performance than "direct injection" in terms of power and throttle response.

 

[FLYBOYJ]

KK just caught up to this and you are correct.

 

[kool kitty89]

Ok. Thanks, that certainly makes sence.