Engine and Transmission Tech

From Phillip Kuhn:

"I have been a tech at GM dealerships since 2001. I don't have the slightest clue about the other manufacturers using DI, but know a decent amount about the GM systems. So far I haven't seen any common issues at all with the GM stuff. I have seen a few injectors go bad and some issues with the high pressure pump leaking fuel into the crankcase ( just like the old mechanical pumps did), but nothing major or widespread overall. As far as the systems themselves go I will give a detailed description of how they work etc. Currently, only the Ecotec engines have DI versions, and all late model high feature v6 engines (2.8, 3.0, 3.6) are DI. They all use an in-tank electric pump running at ~60 psi to send fuel up to the high pressure pump. The high pressure pump is mounted on the engine, is driven off of a camshaft, and operates exactly like the regular old mechanical fuel pumps do ( save for the pressure output ). The entire system is a returnless system and
like most newer vehicles has no serviceable fuel filter. The supply pressure is regulated by the ecm and a fuel pump flow control module via a pwm signal to the electric in-tank pump. The fuel pressure on the high pressure side of the system is also controlled by the ecm too via an actuator mounted inside the high pressure pump. The system operating pressures on the high pressure side are 500-800 psi at idle and around 2500 psi at max output iirc. From the high pressure pump forward they use heavy stainless lines with flare and ball connections and are supposed to be a one-time use deal. Anytime we take a line loose it is supposed to be replaced, although I have reused several without any leaks. There is also a fuel rail pressure sensor located on the fuel injector rail to send pressure readings back to the ecm and there is no other means of testing pressure on the high pressure side. The injectors look like normal injectors on the fuel rail side and
use o-rings that appear to be the same size or similar to that of regular fuel injectors( I still can't figure out how the seals don't blow out at those pressures). The other end of the fuel injector is very long and narrow and uses special teflon seals to seal it into the cylinder head as they go directly into the combustion chamber through the intake side of the cylinder head. Special tools are required to install and size the teflon seals similar to the tools used for non-cut teflon seals used in transmissions. There are also special tools required to remove the injectors from the cylinder head as carbon will quickly cause them to get stuck in the close-tolerance bores. Every time the injectors are removed all of the seals have to be replaced. The injectors do require a special high voltage driver, but I do not know the specs right now. Overall, the systems operate like a regular sequential port system does and are designed similar to a diesel
system. Both fuel economy and power are improved on the engines GM is using DI on currently. The latest 3.6 in the base camaro is up to something like 317hp now. As far as being able to fit DI to any other engine, I suppose it may be possible on some engines. Even then it would require significant cylinder head modification and some fabrication. You would also have to use an ECM designed for DI and be able to modify the calibrations and flash the ecm which I am unsure if that is possible currently. Hope this answers a few questions.

Phil"

JB

Thaks for the answers, Jim. Next Big thing is supposedly, laser spark,(no plugs). I like this for a headless/opposed, engine design. roverman.