another turbo question

[dmmotes]

I am hoping that somebody can help me make some sense of the two turbos that I have. Both were I think aftermarket banks sidewinder kit turbos but they are different. 1 is a banks with a 1.00 stamped one the exhaust inlet, the other is a rotomaster a/r 60 with a 1.16 on the ehaust inlet. Can somebody help. I want to know which one I should use and what the ratio means and what the difference is between the two. Thanks in advance Don

[Stray Cat]

The exhaust housings have different A/R ratios. The smaller the number, the tighter the ratio; the larger the number, the higher the ratio. A tighter ratio means that you are forcing the same amount of exhaust through a smaller space. That will make the corresponding turbine spin up sooner and faster. The exhaust turbine drives the compression turbine that produces boost. So, if the exhaust turbine spools up sooner and faster, it will provide more boost and sooner. Because a tighter ratio is forcing the same amount of exhaust through a smaller space, it also causes more back-pressure, and therefore more heat in the engine. You need to find the correct balance for your engine and application. Because the exhaust and compression turbines are interactive, both need to be considered. Just as the exhaust turbine dimensions changes performance, so does the compression turbine. A small comression turbine will add boost sooner, but move less air. A larger comperssion turbine will move more air, but requires more pressure on the exhaust turbine to build boost. So, they both need to be matched to your application. The 1.0 ratio exhaust turbine is the one Banks uses for the 6.2L application, and is conservative. You can go tighter than that without a problem. I don't think you will be happy with the 1.16 ratio turbine housing; it will do little for you on a 6.2L. I am testing a 0.84 ratio exhaust turbine vs. the 1.0 Banks on a dyno. The results are being reported in the "6.2-TD Engine Experiment" post of this forum. I am sorry that this is not a simple answer, but there is no simple answer. You just have to find the best set-up for your desired results.

[ 03-06-2005, 02:30 PM: Message edited by: Stray Cat ]