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# Trim? A/R?

Discussion in 'Forced Induction' started by jimboburgess, Oct 21, 2005.

1. ### jimboburgessGo fast, Go Cheap

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Can someone explain or point to a site that shows what the signifigance of trim and a/r are i really don't know

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3. ### swannySenior Member

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For compressor wheels, trim is the ratio of inducer diameter vs exducer diameter. The inducer is the part of the wheel where the air enters it, and the exducer is the part of the wheel where air leaves. For compressor wheels the exducer is the outer diameter of the wheel, and the inducer is the inner diameter of the wheel. For turbine fans the inducer is the outer part of the wheel, while the exducer is the inner part of the wheel. See the pic I posted below to tell you which is which.

The rx7 link I provided tells you how to calculate the trim of a compressor wheel. Just a little fyi when calculating trims you can just calculate it in inches or mm it doesn't matter. Trim is just the ratio of ind/exd and the trim will come out the same whether you calculate inches or mm. The link also tells you how a higher or lower trim number determines where the compressor is the most efficient. Also check out the Garrett link and look atthe products menu and the tech menu. You can use the products->turbochargers menu to calculate the trim of the compressor wheels. Use the formula in the rx7 club site or Garrett site to calculate the trim.

http://www.turbobygarrett.com/

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