Originally Posted by UsedTaHaveA68
This seems to be a very common misconception. Fast foward to 0:25. You will notice that fuel is sprayed into the cylinder on the intake stroke. If it were sprayed at the top of the compression stroke, it wouldn't be very effective in cooling the intake charge. That and it would probably spontaneously ignite, causing the engine to "diesel."
EDIT: Why can't I ever get these damn videos to embed?!! Here's the link:
Your right but there may be more to this than you think.
* Ultra lean burn mode is used for light-load running conditions, at constant or reducing road speeds, where no acceleration is required. The fuel is not injected at the intake stroke but rather at the latter stages of the compression stroke, so that the small amount of air-fuel mixture is optimally placed near the spark plug. This stratified charge is surrounded mostly by air which keeps the fuel away from the cylinder walls for lowest emissions. The combustion takes place in a toroidal (donut-shaped) cavity on the piston's surface. This technique enables the use of ultra-lean mixtures impossible with carburetors or conventional fuel injection.
* Stoichiometric mode is used for moderate load conditions. Fuel is injected during the intake stroke, creating a homogeneous fuel-air mixture in the cylinder. From the stoichiometric ratio, an optimum burn results in a clean exhaust emission, further cleaned by the catalytic converter.
* Full power mode is used for rapid acceleration and heavy loads (as when climbing a hill). The air-fuel mixture is homogeneous and the ratio is slightly richer than stoichiometric, which helps prevent knock (pinging). The fuel is injected during the intake stroke.
I read it on the internet, it must be true
Seems like to tune this would be pretty complicated especially when you add in the variable valve timing. With so much computer controls on this thing I wonder if it would mostly just tune itself? Just add more air. Which may be why a CAI and exhaust improve this thing so much.
Diesel by the way (at least my engine) uses a two phase injection on compression where the first(small) charge starts the burn and the main charge is then delivered. Compression is much higher (upwards of 24:1) for diesel.
Ok just food for thought. Like I said I'm no tuner but I do understand the basics. I've been studying this engine for a while and.... me likey