You probably haven’t heard much about direct injection unless you’re a diesel guy, since all diesels operate as compression ignition where the fuel is injected into the cylinder at the highest point of cylinder pressure. When the fuel is injected, ignition automatically occurs. What’s already arrived in many OE engines like the GM Ecotech and Ford’s EcoBoost engines is a similar feature for a normal gasoline engine except that these engines still use a spark plug to initiate combustion. Of course, we first have to give it an acronym—gasoline direct injection (GDI). This process uses very high common rail line pressures of more than 2,000 psi.
While there are serious power advantages to GDI, it first came to the forefront in the mid-’90s with applications aimed at improving fuel mileage. Apparently, these engines can run at very lead air/fuel mixtures—we’ve seen claims as lean as 65:1 in cruise conditions. The real fun comes when direct injection is combined with variable valve timing and turbocharging. That’s what the Chevy HHR engine does, and the advantages are amazing. Ford also has a GDI four-cylinder called the EcoBoost. This little engine pulls much harder than it has a right to, mainly because we’ve heard that the engineers can play with ignition and valve timing along with injection points to really spool up the turbo very quickly, making for a very efficient and responsive engine. I don’t know of anybody in the aftermarket who is playing with direct injection, but imagine a small V-8 like a 4.8 or 5.3L LS-series engine with a turbo and GDI. Would that be an animal or what?