Couple of Questions

[keba]

Had a couple of questions...
was reading about GDI(Gasoline Direct Injection) and it seems quite similar to a diesel engine with the fuel getting directly injected into the combustion chamber...Noticed that the compression ratios were 20-1 for diesel and between 10-13 to 1 for normal gasoline engines.


Question is ,under what conditions would a diesel engine work on petrol(without significant mods),and why are automakers not going down this path...I can see significant cost advantages

Why is the sparkplug still needed in a GDI engine(if the compressed air can be compressed enough in a diesel engine to ignite the fuel) ,why wouldnt this work in a GDI engine.one part less...one less thing to design \one less thing to fail....



Turbochargers - I see lot of bolt on turbochargers project around..;since a couple of accesories inside the engine (power brakes) ,depend on the engine vaccuum,what happens to the power assist when negative pressure(vaccuum),is changed o positive(turbo boost).or do the accesories just need some form of air pressure differential(+\-) to work?

keba

[toyomoho]

Diesel fuel is much less volatile then gasoline. In a diesel engine fuel is ignited by compression, hence the higher compression ratios of these engines.

Gasoline requires an ignition source to start burning, this normally being a spark plug. When gasoline ignites without using a spark plug it is called pre-ignition, which is not good because is uncontrolled ignition timing.

BMW and no doubt others have built GDI engines, a web search will turn these up. The result is improved efficiency.

As to the turbo effect on the brake booster, etc, can’t say for sure. The lines should have check valves to prevent a positive pressure from damaging the system. Guessing you could set the system up to use the differential air pressure at the throttle body. Some setups use the power steering pump for the booster.

[keba]

well if diesel is less volatile,then that is the one that should need a spark plug right,but it seems to be the other way around.