Autocross Champion
Denver, CO, USA
I don't really understand the difference between this new "FSI" engine and a conventional turbo-charged engine. I tried looking at the VW site, but didn't find anything too technical. It basically says that they are taking technology that makes a turbo-diesel so efficient and powerful and applying that to a turbo-gasoline engine. If anyone has any explanations or links to external information, that would be very much appreciated. Thanks.


Touring Car Champion
Ok, I'll do my best to explain the difference. There are basically two general types: Direct Injection and Indirect Injection (Such as Throttle Body Injection, Multi-Port Injection or Central Port Injection). The main difference is basically where the Fuel is injected. I'll go over a few below.

Throttle Body Injection: An earlier method to replace the carburetor. This method injected the fuel into the throttle body of the engine where it would then pass through the intake runners, almost the same path as a carbureted engine.

Multi-Port Injection (Modern Cars Generally Use This): Some times referred to EFI, injects the gasoline directly ahead of the intake valves by way of a single injector per cylinder. The cars computer electronically manages how much fuel gets sent based on air/fuel ratios and other variables.

Direct Injection (Diesel Engines and FSI on the VW/Audi): The fuel is sprayed directly into each cylinder's combustion chamber at a higher pressure instead of ahead of the intake valves. Provides cleaner emissions and is more fuel efficient as well as a higher power output.

Quote from :
FSI, however, incorporates a mode known as "stratified charge", which gives the fuel-air mixture in the cylinder an extra swirl to create an electric charge (much as a thunderstorm is created) at the point it reaches the spark plug. This allows for a leaner fuel-air mixture, using less fuel, and the excess air forms an insulating layer in the cylinder to guard against heat energy losses.

Well I did my best to explain the differences I hope that it's helped some. If it's confusing or what not let me know, i can try to explain it differently or better or something.


Drag Racing Champion
Very nice post I am new to VW so now I understand how it works alot more thnx!


FIA GT Champion
Wow. Nice explanation. I tried to explain it to some body and they looked all glossy eyed at me. I asked if they were lost and he was like yeah....pretty much from the beginning.