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Re: Drivetrain loses revisited, 900 vs 9000 Posted by Kevin K [Email]  (#374) [Profile/Gallery]
(more from Kevin K) on Tue, 3 Dec 2002 15:27:57
In Reply to: Drivetrain loses revisited, 900 vs 9000, Ryan B, Tue, 3 Dec 2002 00:35:05 Members do not see ads below this line. - Help Keep This Site Online - Signup |
regarding 3rd or 4th gear dyno runs and/or acceleration:
900 is less efficent because it has:
- chain and sprockets
- 2 gear meshes (to and fro layshaft), vs 1 mesh for 9k
- 90 deg bevel final gears, vs helical for 9k.
Based on many diff dyno sheets for various stock FD rx7's I have seen, usually 3rd gear, rwhp was typically 222 +/-2 vs 255 at eng, for 13% loss. This has bevel final gears and 2 meshes in 3rd (1 in 4th).
for the 900, add couple percent for chain, gets u mabe 15% losses ( wheel hp x 1.18 = eng hp, at 15% loss).
for 9k tranverse design, no bevel and 1 less mesh, mabe 10% losses, (1.11 multiplier).
These loss values, 15%, 13%, and 10%, are based on near stock hp. Part of these losses are load dependent and some aren't. If you are at 2x stock hp, mabe knock 15% off these corrections.
The recently posted values of ~20% for the 9k were based only on non-load dependent effects like tire friction, from coast down tests, meaning predicted total losses would be even higher. These are very high %'s, and many, many shops do not use coast down values. I do recall one test where an engine dyno was also used, and coast down values were too high, and actual losses were consistent with my loss values.
figure 20-25% losses for awds.
posted by 67.201.228...
, Tue, 3 Dec 2002 15:27:57 <-- Viewing This Message, Tue, 3 Dec 2002 23:16:37
, Wed, 4 Dec 2002 13:56:56, Wed, 4 Dec 2002 15:10:30, Wed, 4 Dec 2002 15:43:00, Wed, 4 Dec 2002 16:02:15, Fri, 6 Dec 2002 00:32:39
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