Editing VVT-i (section)

=== D-4S ===
[[File:2GR-FSE.jpg|thumb|The 2GR-FSE engine, the first to feature D-4S]]

'''D-4S''' (Direct Four Line Superior) is a twin injection fuel system that is an improved version of the previous D-4 system, combining both indirect and direct injection. It uses a traditional manifold fuel injector on one end for low pressure and a direct injector on the other for high pressure. It also works in conjunction with VVT-i (as well as its variants). This system debuted in the ''[[Toyota GR engine#2GR-FSE|2GR-FSE]]'' engine used in the [[Toyota Crown (S180)|Toyota Crown Athlete]] and the [[Lexus IS (XE20)|Lexus IS 350]], which was also the first engine overall to combine both traditional fuel injection with direct injection. This system was also used in the ''[[Toyota U engine#4U|4U-GSE]]'' (''[[Subaru FA engine#FA20|FA20]]'') engine found in the 2012–2021 [[Toyota 86]] and [[Subaru BRZ]] as well as the ''[[Subaru FA engine#FA24D|FA24D]]'' engine used in the 2022–present [[Toyota GR86]] and Subaru BRZ, both working in conjunction with Subaru's [[AVCS]] system. The D-4S system provides much more cleaner exhaust emissions than with D-4,<ref>{{cite web|url=https://www.tomorrowstechnician.com/toyota-d-4s-port-fuel-or-direct-fuel-injection-why-not-both/|title=Toyota D-4S: Port Fuel Or Direct Fuel Injection? Why Not Both?|date=2019-03-21|first=Andrew|last=Markel|website=Tomorrow's Technician|access-date=2025-03-24}}</ref> while also helping with providing more peak power at high rpms.

It is important to note that the "S" in the D-4S name does '''not''' signify a [[supercharged]] engine, as engines using the D-4S system such as the 4U-GSE and the 2GR-FSE do not have superchargers. Traditionally, supercharged engines are denoted as "Z" under Toyota's engine naming scheme (e.g. ''[[Toyota A engine#4A-GZE|4A-GZE]]'', ''[[Toyota G engine#1G-GZE|1G-GZE]]'' and ''[[Toyota TZ engine#2TZ-FZE|2TZ-FZE]]'').

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