Numbers scribed on the compressor housing, Anybody identify??

[BetMinesFaster]

Hey guys, bought a used turbo from this site, Supposed to be a Precision PT70GTQ, The numbers scribed on the discharge nozzle tell me its likely a PT71GTQ? they are 7180H, Im assuming the "H" stands for the H cover, 71 is inducer and 80 is the exducer?? The inducer is obviously a machined wheel not cast by appearance, You can see all the marks from the cutting bits, and the exducer protrudes from the housing so that signifies a GTQ...any input would be nice! Thanks, Ryan

 

[8AV8]

Measure the wheel with a micrometer and see if its 70 or 71mm.

 

[RUQWKNF]

Here you go.

71 = 71mm inducer, billet cnc machined compressor wheel.

80 = 80 trim GT-Q turbine wheel.

The 71mm billet cnc cut compressor wheel is a high efficiency wheel, that has a useable boost range of 25-40psi. It doesn't make hardly any more power vs the 70mm wheel below 25psi. The only downside is, the typical built Buick V6 will not handle boost levels much past 35psi before lifting the heads or blowing a gasket. This is the main reason why the 70 GT-Q has been the optimum choice for 109 stoker motors, and or TSM builds. This does not include Stage 1 or 2 motors, as they have more bolt holes than you stock 109 blocks.

Other than the numbers on the compressor cover, it is very easy to distinguish between a 70 GTQ and a 71 GTQ because of the billet aluminum CNC cut compressor wheel. That turbo pictured, looks like one of the original ones from the start, as it has the older Holset style compressor cover. The builders typically engraved a born on date onto the backing plate, just behind the compressor wheel. That version was built between '03 and early '06 when the new Precision logo compressor covers came out. FWIW, the 71 GTQ was very popular with the Supra, crowd which can run 30-40psi of boost no problem
HTH

Patrick