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2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
The LT5 has two sets of intake ports, with the "secondary" set having a second set of fuel injectors and a second set of "throttle body" blades. In stock form, this is controlled by the "power" key on the dash, when turned to full power, the system is active and controlled by a vacuum system. That vacuum system can easily fail, leading to the "secondaries" not working. Many people have the system set to run full power all the time with a custom chip, and if you want you can even remove (or tie open) the secondary blades so you no longer have to worry about the system failing.
Pic of the secondary port (one with the blade) next to the primary port:
2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
Yes, 8 extra injectors (16 total), and yes the secondaries have throttle blades that only open in certain situations, basically heavy throttle and/or high rpm. Under light throttle the blades stay closed and the secondary injectors are off, giving better MPG.
Yes, 8 extra injectors (16 total), and yes the secondaries have throttle blades that only open in certain situations, basically heavy throttle and/or high rpm. Under light throttle the blades stay closed and the secondary injectors are off, giving better MPG.
Ummm... I'll might take exception to the "better MPG (w/ secondaries OFF) statement", practically speaking. Oh, yes, there is technically a slight % higher torque w/ secondaries OFF, primarily in the low-mid rpm range. But, only with light throttle. With any hilly terrain, the secondaries are often opened at highway speeds.
One area that might favor the primaries ONLY running is emissions compliance. But, even that said, compliance is common with the secondary port throttles REMOVED as well. Just sayin.
(BTW, where did all the metal filings, etc., come from in that picture???)
09-22-2018, 07:04 PM
