Some people swear up and down that eBay parts are a cheap, quick path to mechanical woe and suffering, but automotive test guru Richard Holdener isn't one of them. In fact, after torture-testing this $163 cheap eBay knock-off of a Garrett GT45 turbo on eight different engine configurations, he's convinced that it's proof that you don't have to spend tons of money to make more power and have some more fun adding a turbo to your car.
Holdener's test included some of the most popular engines to turbocharge: a 2.4-liter Honda K-Series inline-four, and of course, multiple versions of General Motors' ever-present LS V8. Some old-school engines were thrown into the mix as well: the 455 Buick V8, the 302 Ford Small-Block V8 and the 454 Chevy Big Block V8—the latter of which was tested with both single- and twin-turbo setups.
It's a pleasingly wide variety of enthusiast engines, ranging from the 2.4-liter Honda to the 7.4-liter 454. It could have been a bit more responsive on the small 2.4-liter engine, and he probably would have remedied that with a different, smaller turbo, but the fact that it worked really shows its versatility.
Likewise, backpressure—where there's more exhaust pressure flowing into the turbo than there is boost flowing out—was an issue on the larger engines. This is a sign that you should typically upgrade to a larger turbo for what you want to do—or in the case of the Chevy 454 test, Holdener's cue to add a second GT45 clone to the test. That's right: twin-turbos.
Holdener notes in the video that multiplying the naturally aspirated power output of an engine by the pressure ratio of the turbo, it should give you a good idea The 300-horsepower K24, for example, should have around 600 horsepower when you throw 14.7 pounds of boost into the formula. The real-life build tested in the video made 585 hp, which checks out. A turbo like this where this simple math exercise works out horsepower results is said to "follow the formula."
"If it's following the formula, you know that things are working the way that they should—that the turbo's fairly efficient, that the combination's working, that your tune is fairly spot on, that all that stuff is working," Holdener explained.
None of the tests were on pump gas, but rather, they were tested with E85 or race gas. He doesn't add too-crazy amounts of boost in these tests considering that some engines had older stock blocks, but he gets results. The wildest result, of course, was the twin-turbo 454, with 1,039 hp and 1,028 lb-ft of torque at 16.5 psi of boost.
Holdener's test turbos came from an eBay store called DNA Motoring and another store called CXRacing (which also sells on eBay, if you're curious), but he said that cheap GT45 knock-offs can be found all over eBay and Amazon. When the real version from Garrett typically costs over $2,000, this $163 eBay special is an incredible value.
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