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12-20-2012, 09:46 PM | #1 |
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Dynod today with 20 inch wheels -hp loss?
Just a quick question. I dyned today and pulled 496.5 hp with 20 inch cv3. Vossen wheels.
How much loss -if any- would you say my 20 inch wheels contribute? I would like to hit the 500 hp club. Thanks If I switched to stock 19 inch Wheels would that help? |
12-20-2012, 10:27 PM | #2 |
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Yes...they rob you of power. I saw a significant difference on the dyno
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12-21-2012, 01:17 AM | #4 |
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Mustang dyno or Dynojet dyno? Which SC kit did you get? What are all your mods? Do you mind posting your dyno for us? sorry for all the questions but that way, maybe we can evaluate the gains you'd get by putting back the stock wheels.
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12-21-2012, 11:56 AM | #6 |
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To give you a little perspective using my car as an example.
All Stock - Dynos 362 whp on a DynoJet Full Exhaust HFC's, tune and 20" wheels - The car dynoed 347 whp on a DynoJet So there is a significant difference |
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12-21-2012, 12:21 PM | #8 |
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I have to thank you aswell. Your xpipe with hfc produces amazing hp
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12-21-2012, 02:40 PM | #10 | |
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Good luck with your build.
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12-21-2012, 03:27 PM | #12 | |
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As an extreme example, a very light 20" wheel could have less inertia than a very heavy 19". In that case, the dyno would read better with the 20" wheels. However, this situation it is not very likely. Without knowing the inertia difference between a specific 20" wheel/tire combination compared to a specific 19" or 18" wheel/tire combination, it is impossible to assess the relative loss (unless someone already ran back to back dynos of Vossen 20" vs stock 19" on the same car ![]() Last edited by CanAutM3; 12-21-2012 at 03:43 PM. |
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12-21-2012, 03:50 PM | #13 | |
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Rotational inertia (polar moment of inertia) varies with the square of the distance to which mass is located from the centre of rotation. So even if the wheel weighs less, if the mass is distributed farther from the centre, it could still have more rotational inertia. |
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12-21-2012, 04:13 PM | #14 |
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You can't just consider the wheel weight, but also the weight of the tires. 20" tires will tend to weigh significantly more than a 19" tire and a lot of that weight is at the worst possible place.
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12-21-2012, 04:22 PM | #15 | |
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![]() For a given rolling diameter, increasing the wheel diameter actually reduces required tire sidewall. This reduction in tire sidewall material is most likely offset by the material needed to compensate for the structure stiffness. But, in my opinion, not to a significant extent. Comparing different sizes weights on Tire Rack could confirm this... For example Michelin PSS: 265/40R18=27lb 265/35R19=25lb 265/30R20=26lb 275/35R19=27lb 275/30R20=27lb Last edited by CanAutM3; 12-21-2012 at 05:00 PM. |
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01-27-2013, 12:50 PM | #17 |
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wow! i did not know 20s" made that big of difference in horse power.
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01-27-2013, 01:44 PM | #18 |
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Time for the 17" wheeler dyno queen! Seriously, makes a very strong case for using a hub dyno only if one wants to get as close to reality (what hp the engine is actually producing pre/post mod) as possible.
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01-28-2013, 09:32 AM | #22 |
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The hp loss is related to the increase in centrifugal force of the 20" wheels. The greater diameter of the wheel the further the weight of that wheel is away from it's center, requiring more force to spin or stop that object. In essence, a heavy 18" wheel would be easier to spin than a lighter 21" wheel. You dig?
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