Turbine Wheel Trim

[Qiuz]

Wheel trim for a compressor is-
Wheel Trim = (inducer diameter divided by major diameter) Squared x 100. Examples
T3 inducer diam of 1.674 and a major diam of 2.367 = 50 trim wheel
T4 inducer diam of 2.122 and a major diam of 3.000 = 50 trim wheel

My question is calculating turbine wheel trim for garrett turbo's. The formula for compressor wheels does not work for turbine wheels. The trim wheel # for t3's turbine with the compressor wheel formula would be stage 1 = .67, stage 2 = .69, stage 3 = .76, but they designate the number -72 for stadard turbine wheel. I have not been able to get a good answer. After talking to Innovative turbo, countless forums and reading through Maximum Boost and Turbochargers I found nothing except people telling me that its an arbitrary number or stage assigned. Some engineer had to derive this (-72) that is assigned to the T3 standard trim wheel from some formula.

 

[Ed Valvo]

I would have to agree with the manufacturers because there can be three different turbo vendors and they can all use a different part number for the exact same turbo. You'll probably never get the answer you're looking for unless you have one sent off to see what's exactly in it.

 

[Qiuz]

It’s not really a question of part numbers. You could use the Compressor wheel formula on a Turbonetics or a Mitsubishi compressor wheel and figure out a Trim number.

Turbonetics and Innovative are two different companies with different part numbers but still stock turbine wheels with the same exducer and inducer measurements. I would think they would derive a trim number from these two measurements.
I think ihi turbos actually use the compressor trim formula for the turbine wheels. I just want to know where garrett got this -72. Maybe it is an arbitrary number. Someone in garrett land must know who came up with this number.

 

[Qiuz]

ttt

 

[87GN_70GS]

So what's the formula used to come up with the "P" trim, or "S" trim, or "Super H" or...???

My vote is for arbitrary numerical/alpha assignment.

 

[Qiuz]

Yes I understand that the O, P, Q is arbitrary but on the t3 turbines they designate trim as standard or stage 2,3,& 5. The standard trim is sometimes known as -72. who dirvied that number? This is the only thing giving me hope that a formula exist.

 

[Qiuz]

The answer

Ok after posting on 5 different forums, endless searches on the net, reading through 2 books, 1 call to turbonetics, and 2 calls to Innovative turbo I give thanks to Ola from Innovative. He is very easy to talk to and very forthcoming with info. The -72 that people refer to as the standard trim turbine wheel was just a piece of the Garrett part number. They do use the same formula as the compressor wheel to designate a trim number. Its not very often you do here the turbine trim designated this way since there is a stage also arbitrarily assigned N, P, O, or Stage 2 and so on (although looking at a few other manufacturers they seem to use the compressor formula).