The Ultimate Guide: Gasoline Direct Injection

Everything you need to know about Gasoline Direct Injection - the good, the bad, and the opportunities for the automotive aftermarket.

Engines equipped with GDI first appeared on the market in 2007, and by 2008 they were installed in 2.3% of all light-duty vehicles produced. Ten years after introduction, GDI was used in about half of all light-duty vehicles produced. Throughout 2020, GDI installations continued to rise, reaching a new high of 55.3%.

So, what is gasoline direct injection, and how does it work? We've rounded up the facts so you don't have to. Read below to become your shop's newest GDI expert.

What is Gasoline Direct Injection?

What are the advantages of GDI?

So, what's the catch?

Here's why you should care.

What is Gasoline Direct Injection?

Gasoline Direct Injection (GDI) engines work very differently than their predecessor technology, namely, Traditional Port Injection (PFI) systems.

GDI engines work by injecting fuel at high pressure directly into the combustion chamber, like common rail diesel injection. GDI engines operate at pressures up to 3,000 PSI, with pressures varying based on engine operating conditions. These injection systems operate at higher voltage – typically at 65 volts or more.

On the other hand, PFI injection systems inject fuel into the intake manifold above the intake value, with constant pressure relative to the intake pressure, typically operating at 36-43 PSI.

What are the advantages of GDI?

GDI has seen mass adoption as a result of the rise in demand for fuel-efficiency and reduced emissions. Because GDI provides an increase in power output compared to traditional fuel injection, it is often coupled with turbocharging and smaller displacement engines to maintain customer performance expectations.

Marketed as Ford EcoBoost, Mazda Skyactive, GM Ecotec, VW TGDI, gasoline direct injection is the next generation of gasoline fuel injection, and for good reason.

  • Better Fuel Economy: Allows engine down-sizing, especially when combined with turbocharging, variable valve timing and stop-start technology.

  • Reduced Emissions: Tighter control of air fuel ratio on a per-combustion event basis. Higher start-up combustion temperatures cause faster light-up of the catalytic converter.

  • Higher Power Output: Direct injection provides air charge cooling, reducing peak combustion temperatures, which allows for more aggressive ignition timing maps and higher compression ratio engines.

So, what's the catch?

While GDI technology is great, it is certainly not perfect. With the emergence of GDI technology, comes several unintended consequences.

  • Higher Particulate Emissions: Hot spots, combustion geometry, rapid combustion events not giving fuel time to atomize. Same challenges as diesel engines.

  • Carbon Build-Up on Intake Valves: Lack of fuel spray on intake valves prevents cleaning. Crankcase vapors and EGR gases create carbon deposits.

  • Complete Engine Failure due to LSPI: Low speed pre-ignition (LPSI) caused by trapped oil vapors and cylinder wash-down from direct injection and higher compression ratios.

  • Injectors & Pump More Susceptible to Fuel Quality Issues: Tighter injector tolerances and the addition of precision high pressure pump compared to PFI systems.

  • Diagnostic Challenges: Carbon build up can be easily misdiagnosed as faulty injectors.

Here's why you should care.

Many vehicles manufactured with GDI are now coming out of factory emissions warranty, representing a significant service opportunity for independent repair shops and the automotive aftermarket.

According to the US Department of Energy, over fifty percent of vehicles manufactured in 2018 were equipped with GDI. Because GDI operates directly in the combustion chamber, it is subjected to extremely high pressures and high temperatures - all of which make the injector more susceptible to contamination and eventual failure.

Thus, GDI technology has increased fuel injector replacement rates both at the industry level, as well as among newer vehicles. The combination of an older population of vehicles and more vehicles experiencing fuel injector failure earlier in their life cycle due to the nature of GDI technology has led fuel injector replacement rates to be higher than ever, jumping from 0.85% in 2017 to 1.28% in 2020, an increase of 50%.

With injector failure rates on the rise, GB has you covered as the market leader in providing 72 premium remanufactured GDI part numbers covering over 4,600 vehicle applications.

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