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RPM reading @ 110km/h, survey
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sam_01
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 Oct 18 2008, 12:32 AM
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New Member
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My perdana V6 shows ~2800 revs at 110km/h.
To prove it:
Perdana v6 gear ratios:
Gear Ratio 1st = 2.846
2nd = 1.581
3rd = 1.000
4th = 0.685
Final Gear Ratio = 4.350
110km/h change to meters/minutes = (110 x 1000) / 60
= 1833.3 meters/mins
Speed reduction at Final gear = 0.685 x 4.35
= 2.979
Meaning 1 tire rotation equals 2.979 engine turns.
Tire circumference (stock perdana v6 205/55 R16) = 1.986 meters.
Tire revs per min = 1833 / 1.986
= 922.96 tire revolution / min
Engine revolution per min = 922.96 x 2.979
= 2749 revs / mins
So the calculated engine revs is close the reading on the rev meter (-51 revs).
But that was when my auto gearbox is ok.
Now using manual gearbox becoz my auto box kong already.
Manual tranny reads 3100 @ 110 km/h.
Not sure what are the gear ratios on the manual tranny.
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sam_01
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Nov 6 2008, 10:15 PM
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New Member
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QUOTE(V12Kompressor @ Nov 5 2008, 07:53 PM) Wira/Satria 1.3 doesn't come with OEM rpm meter. They get speedometer in the middle, fuel meter on the right and engine temperature on the left only. Sad.  BTW, sam_01, how you get your tyre circumference? As I remember, tyre circumference is diameter of the tyre+rim x pi. So your Perdana's tyre circumference should only be 0.759mm.  There are lots of webites that can do the calculations. You can find your tyre circumference HERE. Or you can take a measuring tape and measure your tyre circumference yourself if you want to be really sure 
Added on November 6, 2008, 10:24 pmQUOTE(sjz @ Nov 5 2008, 07:04 PM) You must be expert in Maths...  Help me to calculate with this... Kembara. st: 2.730, 2nd:1.526, 3rd:1.000, 4th:0.696. Rev.:2.290 What is the final drive ratio & Kembara tire size ? This post has been edited by sam_01: Oct 25 2010, 09:04 PM |
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sam_01
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Nov 8 2008, 01:44 AM
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New Member
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QUOTE(V12Kompressor @ Nov 7 2008, 12:41 AM) BTW, Kembara 4AT final gear ratio is 5.857Tyre size is 205/70 R15 BTW, took the hassle to calculate 110 @ ? rpm for Kembara. Answer turns out to be 3,505 rpm.  Thanks! Pretty huge reduction at final drive.....1 tire rotation equals 4.076 engine revs. |
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sam_01
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Oct 25 2010, 08:36 PM
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New Member
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QUOTE(J1@l_ l_l l\l @ Jan 22 2010, 11:00 AM) Does the calculation above applies to automatic box as well since it's using torque converter which means indirect drive unlike manual tranny tht is driven directly by the engine. The calculation is based on the Perdana V6 automatic gear ratios with the assumption that 100% of the power from the engine is transfered to the gearbox. In real situation, I believe there will be a power loss, hence, you will get a slightly higher RPM reading. |
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