Quote:
Originally Posted by CamaroSpike23
as for why DI motors use high press fuel injectors, its because they are in the combustion chamber, not in the intake manifold. what does this mean? basically that the injector has to be able to withstand the immense compression of the cylinder and still be able to spray the fuel and atomize it properly in a given amount of time.
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The DI engines need high pressure injectors (& fuel pumps) because they do inject during the compression stroke in certain modes Mostly light loads and cold starts not high loads where knocking is a threat. Here is a pretty good article on them:
http://autospeed.com/cms/title_Direc...0/article.html
They mention about half way down that the computer opens the throttle wider in the first mode (Stratified Charge Mode) to reduce pumping losses.
The higher pressure should also produce smaller droplets which would in turn provide more cooling of the air (actually just faster, but time is limited).