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I've posted on this a few times before because somewhere along the way, some half-baked turbo rebuilder started referring to turbos just because of what compressor wheel he decided to shove into the housing.. While the compressor wheel is VERY important to a turbos performance, full potential can not be realized if you combine it with an improperly sized housing/mismatched exhaust side, etc. Here's the scoop, poop - "T28" is basically just a reference to a semi-hybrid turbo garrett produced for some limited applications - In a nutshell, its a high-performance T3 series turbo. The compressor wheel has a couple flavors, the most potent ones being in the 60 to 65 trim range, all the examples I've seen/heard about being T3 (60mm) compressor wheels. The exhaust side of the T28 is practically a universal standard - the "T28" turbine is a fairly efficient, high-trim 10 blade fan found in a variety of turbos. Where BAD "T28"'s come from, is when this great performing compressor wheel is put into a carved out housing that it is not intended for. This is a common problem to Z's, because the stock Z compressor housing is quite small - Cutting the housing from the stock ~"T22" to "T28" diameter removes some 40 to 50 percent of the compressor scroll, or "diffuser" - which is just industry terms for the ~300 degree snail inside turbo housings that aligns and smooths the rather volatile air coming off the blades (compressor) or heading towards the blades (turbine). Who cares? Well, this choppy, hot air is going to keep the turbo at hotter than normal temperatures. As the boost is turned up, the turbo begins running in temperatures far out of spec, before the efficient for the wheel is ever realized. So basically this means, once the turbo start producing good power, its cooking itself. If you keep it at nominal temperature ranges, its not producing any decent power. All of this, plus, depending on how the exhaust side is cut, can contribute to considerable backpressure on the turbine side - the compressor running inefficiently, stock T22 porting, plus the way the wheel is configured in the rear flange - you can end up with considerable backpressure. On the "Blow" stroke (suck squeeze bang blow), this immense backpressure will blow hot gas BACK IN to the combustion chamber, heating the motor - because the combustion chamber could not cool between explosions, the result is a violently hot combustion chamber. Detonation, piston failure, ring failure, overheating, etc, etc. There are a lot of "tricks" to a turbo, some of which can considerably reduce many of these effects. The way the housings are cut for the wheels, not going overly obnoxious when upsizing the wheels, alleviating backpressure, port matching, etc - Depending on how its done. This is why some T28's seemed to be plagued with problems, but other ones seem to perform quite well - Despite some of the criticism here, some of DSP's later T28 modifications hand a good handful of tricks, and are done rather well. And, just because it is a "kit", doesn't mean its a perfectly designed turbocharger, no offense. There are folks that are far more turbo-savvy than I, and I'm sure they all can tell you the strengths and weaknesses of any turbo kit you put in front of them.. HKS's 2540 is a horrible, horrible wheel mismatch. Some of Mitsu's turbine wheels are ridiculously heavy, including the TD05's. Etc...
MikeeZ
Twin Turbo, Almost BPU |
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