Induction
Direct Injection requires a large, mechanical fuel pump at the back of the engine with hard line plumbing used to accommodate the over 2,000 psi fuel pressures required to inject at high engine speeds. Also note that the fuel pump required a slight relocation of the upper bellhousing bolt hole (arrow).
In addition to the major changes, the LT family also uses a longer thread reach spark plug (right) compared to a typical LS plug (left). This moves the plug even closer to the center of the combustion chamber.
The switch to direct injection means that the injector has moved from the intake manifold port to the cylinder head. Plus, with a much larger intake port opening, this demanded revisions to the Gen V intakes. We mentioned this at the beginning of the story but it’s worth noting again that the L86/L87 6.2L truck engines use a completely different intake manifold, front accessory drive, and oil pan compared to the passenger car LT1. However, internally these engines are the same, which means compression, cam timing, and cylinder heads have not changed from the LT1. So if there is a Gen V engine in your future, consider looking for an L86 truck version as potential engine swap material.
As you might expect, the truck intake manifolds feature longer runners to enhance low-speed and mid-range torque compared to the Corvette or Camaro intakes that emphasize peak horsepower. As mentioned, these intakes completely interchange. Both the L86 and LT1 engines employ an 87mm throttle body.
In terms of aftermarket upgrades, MSD now has a very nice, two-piece polymer material intake that offers a 103mm throttle bore opening for a larger throttle body although the stock unit will work. Testing has show up to a 20 horsepower improvement over the factory LT1 intake. This would make a fantastic upgrade for the L86 truck engine as a swap candidate into an older muscle car.
The 2020 LT2 Corvette engine offers an updated manifold that is 3 inches taller than the LT1 version but still retains its 87mm drive-by-wire throttle body. Chevrolet claims the manifold adds three percent power to the LT2 engine with significantly improved port-to-port air distribution compared to the LT1. The LT2 runners are all equal length at 210mm (8.26-inches) in length while the LT1 runners vary a bit. This runner equality may be one of the reasons (along with a larger plenum) for the power gains above 5,200 rpm. While it appears the LT2 manifold will interchange with previous Gen V engines, this has yet to be confirmed.
The LT2 in-cylinder fuel injectors are dramatically larger in flow capacity and operate at exaggerated pressures compared to electronic port fuel injectors. LT1 injectors are rated at 114 lbs/hr at 2,205 psi maximum operating pressure while the LT4 supercharged engines employ a larger 143 lbs/hr injector. These output numbers may seem extremely high but keep in mind that direct injection engines are limited to extremely short injection duration periods, so the injector output volume must be very high along with the injection pressure. A typical multi-point factory fuel injector located in the intake manifold of a Gen IV 6.2L LS3 for example is 42 lbs/hr, but this injector has far more time to inject fuel than in-cylinder injectors.
Remaining on the topic of injectors, The LT5 supercharged engine that we will discussion in the next section employs both the same in-cylinder direct injection but then adds port fuel injectors to supply the additional fuel required to make the LT5’s added horsepower. The LT4 and LT5 engines use the same injector, verified through Scoggin-Dickey.