Question about 545i specs
02-25-2006, 07:32 PM
#51
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Originally Posted by EBMCS03' post='246136' date='Feb 25 2006, 11:22 PM
Humm since the final drive gear in manual is smller than step doesnt that mean the manuals rpm should be lower than the step at the same speed? Thus giving better economy in 6th? OR am I over simplifying things?
Step--.69 X 3.38 = 2.3322 < .87 X 2.93 = 2.5491--SMG/Manual. Thus, the effective rear-end ratio of the step is lower numerically, and, thus, its RPM in 6th would be lower.
02-25-2006, 10:50 PM
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Originally Posted by Znod' post='246140' date='Feb 25 2006, 08:32 PM
Yep, a bit of oversimplification. You have to consider the gear multiplication factors.
Step--.69 X 3.38 = 2.3322 < .87 X 2.93 = 2.5491--SMG/Manual. Thus, the effective rear-end ratio of the step is lower numerically, and, thus, its RPM in 6th would be lower.
Step--.69 X 3.38 = 2.3322 < .87 X 2.93 = 2.5491--SMG/Manual. Thus, the effective rear-end ratio of the step is lower numerically, and, thus, its RPM in 6th would be lower.
Oh so thus the Step gets better gas milage in same speed cruising... assuming with same tire setup...
what about acceleration? So the step has better gearing to do 0 to 60 sprints?
02-26-2006, 07:53 AM
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Originally Posted by EBMCS03' post='246172' date='Feb 26 2006, 02:50 AM
Oh so thus the Step gets better gas milage in same speed cruising... assuming with same tire setup...
what about acceleration? So the step has better gearing to do 0 to 60 sprints?
what about acceleration? So the step has better gearing to do 0 to 60 sprints?
02-26-2006, 11:09 AM
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Originally Posted by Znod' post='246259' date='Feb 26 2006, 08:53 AM
In principle, the Step could get better mileage, IMO, since the tranny efficiency loss should not affect things incrementally much, if any, when crusing. You've probably seen it by now, but I discussed the second issue on the "Straight-Line Performance" thread.
Yes Thanks I saw the second issue in the other tread already.
As for effieicncy loss with the step I personally dont think there is any anymore... they make autos soooooo good now. I have no data to back it up but just my own gussing.
02-26-2006, 11:12 AM
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Originally Posted by EBMCS03' post='246136' date='Feb 25 2006, 11:22 PM
Humm since the final drive gear in manual is smller than step doesnt that mean the manuals rpm should be lower than the step at the same speed? Thus giving better economy in 6th? OR am I over simplifying things?
SMG/Manual = 0.87 * 2.93 = 2.55
Step = 0.69 * 3.38 = 2.33
Advantage for mileage = Step
Ooops - I did not see the previous answers when I did this- sorry
02-26-2006, 11:18 AM
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Originally Posted by EBMCS03' post='246317' date='Feb 26 2006, 03:09 PM
Yes Thanks I saw the second issue in the other tread already.
As for effieicncy loss with the step I personally dont think there is any anymore... they make autos soooooo good now. I have no data to back it up but just my own gussing.
As for effieicncy loss with the step I personally dont think there is any anymore... they make autos soooooo good now. I have no data to back it up but just my own gussing.
02-26-2006, 11:31 AM
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Originally Posted by Znod' post='246325' date='Feb 26 2006, 12:18 PM
Manuals usually are assumed to have a 15% efficiency loss, while autos usually are assumed to have a 20% efficiency loss. I hope you are right about the Step. If so, then it give nothing back to the SMG/manual in the performance arena because of incremental inefficiency. And, by the way, I don't have a guess about the efficiency loss of the Step. I have been assuming implicitly that it would be the same as for the manual. But, ?????
Thats what I ment I guess... I ment the autos have no exta loss over the manuals anymore. If you want to talk about loss what about the loss over the drivetrain too? LOL
02-26-2006, 11:32 AM
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Originally Posted by cobradav' post='246319' date='Feb 26 2006, 12:12 PM
You need to multiply the 6th gear ratio times the final ratio to get your "equivalent" final ration
SMG/Manual = 0.87 * 2.93 = 2.55
Step = 0.69 * 3.38 = 2.33
Advantage for mileage = Step
Ooops - I did not see the previous answers when I did this- sorry
SMG/Manual = 0.87 * 2.93 = 2.55
Step = 0.69 * 3.38 = 2.33
Advantage for mileage = Step
Ooops - I did not see the previous answers when I did this- sorry
Just to make your answer feel better.
Thanks cobradav! your answer was much better and much clearer than Znods!
02-26-2006, 12:09 PM
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Originally Posted by EBMCS03' post='246335' date='Feb 26 2006, 03:31 PM
Thats what I ment I guess... I ment the autos have no exta loss over the manuals anymore. If you want to talk about loss what about the loss over the drivetrain too? LOL
02-26-2006, 12:11 PM
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Originally Posted by cobradav' post='246319' date='Feb 26 2006, 03:12 PM
You need to multiply the 6th gear ratio times the final ratio to get your "equivalent" final ration
SMG/Manual = 0.87 * 2.93 = 2.55
Step = 0.69 * 3.38 = 2.33
Advantage for mileage = Step
Ooops - I did not see the previous answers when I did this- sorry
SMG/Manual = 0.87 * 2.93 = 2.55
Step = 0.69 * 3.38 = 2.33
Advantage for mileage = Step
Ooops - I did not see the previous answers when I did this- sorry
And, anyway, shouldn't you be out gathering data? You're not swabbing the deck again are you?