FSI

[Beelzeebub]

After doing a search of the entire forum, there's just not one single thread that discusses in detail what FSI is all about. All I know about it is that it is direct injection. But from my concept of internal combustion engines using fuel injectors, isnt fuel injected into the combustion chamber anyways? And how would it make it more fuel efficient if fuel is directly being injected as per the concept of FSI? Wouldn't mixing air with fuel before injection be more fuel efficient? Can anyone here explain in English, what the concept of FSI is, how is it different from systems used by Toyota, Honda (PGM-Fi), or even the current B6/B7 fuel injection systems?

[dasberd]

This is a pretty clear explanation-
Gasoline direct injection is a latest variant of fuel injection employed in modern two- and four- stroke petrol engines. The petrol/gasoline is highly pressurised, and injected via a common rail fuel line directly into the combustion chamber of each cylinder, as opposed to conventional multi-point fuel injection that happens in the intake tract, or cylinder port.
Gasoline direct injection enables a stratified fuel charge (ultra lean burn) combustion for improved fuel efficiency and reduced emission levels at low load.


http://en.wikipedia.org/wiki/Gasoline_direct_injection

[drexplode]

FSI stands for fuel stratified injection. It was tried and failed because of the complexity to control the direction of fuel near the spark plug at high rpms (>2.5k). Basically, you have a lot of unburned fuel which causes lots of emissions problems... Due to the extremely difficult control and the little benefits, it was aborted and most companies adopted homogenous injection. Or a combination of stratified at low RPMs and homogenous at the higher RPMs. Why does audi keep FSI as their trademark...who knows, probably some marketing guy really really likes it.

Read the wiki info site, it does a decent job explaining what DI is all about. In general, the fuel is sprayed directly into the combustion chamber (hence direct injection). Meanwhile, PFI (port fuel injection) is sprayed into the intake manifold and is mixed with the incomming air. With DI, the fuel is injected at extremely high pressures (40bar) which is more efficient than PFI because of various reasons: better control during intake stroke at the optimal piston position rather than in PFI it comes in with the air, and the fuel droplet size is smaller which means more burned fuel near the spark plug which is higher energy output.

The bad with DI is that it is more expensive than PFI; however, the benefits with fuel economy and emissions usually superceed the cost (at least in the US and Eu...in Latin America - not so much).

I'm sure someone else can expand on my explanation but that is all i can think of at the moment...

[dasberd]

I have also heard it has a cooling effect on the combustion chamber and air intake charge, which helps with detonation, and therefore engine efficiency.

[Beelzeebub]

I have also heard it has a cooling effect on the combustion chamber and air intake charge, which helps with detonation, and therefore engine efficiency.

interesting that you brought up the cooling effect. I used to own several air cooled type 1 VWs (beetle). and as we all know, they used carburetors. Even on hot days, you would notice condensation on the exterior of the carburetor and the intake manifold was rather cool. maybe a similar effect is achieved with FSI?

[bloodstar57]

interesting that you brought up the cooling effect. I used to own several air cooled type 1 VWs (beetle). and as we all know, they used carburetors. Even on hot days, you would notice condensation on the exterior of the carburetor and the intake manifold was rather cool. maybe a similar effect is achieved with FSI?

No FSI creates cooling pockets inside the combustion chambers. Will explain how if you really want to know