MPH & RPM's

Stock4Evr · 07-04-2014, 03:07 PM

Where can I find a description of MPH and the relationship with RPM's? As I do not know how to present this question I would like to know, say I want to go 30MPH what should be the RPM's? So say 1st gear the best RPM is 1500 at then at 40MPH the best would be 2500... I would like to know if there is a chart relation the two readings? I hear that some race cars do not have a speedometer so in order not to exceed exit speeds from the pits they must go, say 2000RPM's. Am I making any sense?

N88888_dawg · 07-04-2014, 05:27 PM

I'm not entirely sure what you're asking.
Are you asking for gear ratios to help calculate your speed?

Stock4Evr · 07-04-2014, 05:55 PM

Quote:

Originally Posted by N88888_dawg

I'm not entirely sure what you're asking.
Are you asking for gear ratios to help calculate your speed?

I think I have the gear ratios
1 - 4.780
2 - 3.056
3 - 2.153
4 - 1.678/1
5 - 1.390/0.846
6 - 1.203/-1
7 - Nothing that I have found

I guess I would like to know in what should the rpm's be in all the gears. Say that when I am in manual 1st gear I should run around 1500 rpm's and when in 4th gear around 3000 rpm's. Does this clear it up a little?

6-speed manual (7-speed DCT)
4.110 (4.780) / 2.315 (3.056) / 1.542 (2.153)
1.179 (1.678) / 1 (1.390) / 0.846 (1.203) / - (1)

BEAR-AvHistory · 07-04-2014, 10:15 PM

Why not take a drive & find out for yourself, should only take a few minutes. Someone else might have a different gear package or tire size so their numbers would be no good for you.

Andrewcoja · 07-05-2014, 08:20 AM

Quote:

Originally Posted by BEAR-AvHistory

Why not take a drive & find out for yourself, should only take a few minutes. Someone else might have a different gear package or tire size so their numbers would be no good for you.

Aside from figuring out the math for yourself (we don't know your wheel/tire diameter), this is the easiest way to do it. Set up a camera to record your dash and go through the gears on an empty road (mind the speed limit).

Vigilante375 · 07-05-2014, 11:32 AM

Here, pick which one you want to use to find out what you need:

https://www.google.com/?gws_rd=ssl#q...tio+calculator

For something like that, you're better off searching the internet.

Ski Killset · 07-05-2014, 12:10 PM

Just search for auto math calculators. I have yellow bits of tape on my tach in my race car to mark speeds in a given gear.

Stock4Evr · 07-06-2014, 10:33 AM

Thank you for all your comments. I will work with each of your recommendations. Thanks again.

07-04-2014, 03:07 PM	#1
Stock4Evr RetNavSpook 67 Rep 398 Posts Drives: 2012 135i - 2016 320i Join Date: Jan 2014 Location: Canyon Lake, Texas iTrader: (0)	MPH & RPM's Where can I find a description of MPH and the relationship with RPM's? As I do not know how to present this question I would like to know, say I want to go 30MPH what should be the RPM's? So say 1st gear the best RPM is 1500 at then at 40MPH the best would be 2500... I would like to know if there is a chart relation the two readings? I hear that some race cars do not have a speedometer so in order not to exceed exit speeds from the pits they must go, say 2000RPM's. Am I making any sense?
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07-04-2014, 05:27 PM	#2
N88888_dawg Private First Class 8 Rep 166 Posts Drives: none Join Date: Feb 2014 Location: UK iTrader: (1) Garage List 2008 BMW 135i [0.00]	I'm not entirely sure what you're asking. Are you asking for gear ratios to help calculate your speed?
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07-04-2014, 10:15 PM	#4
BEAR-AvHistory 2020 Z4 M40i - 2022 M4C Convt 3127 Rep 5,264 Posts Drives: 2020 Z4 M40i - 2022 M4C Convrt Join Date: Jun 2011 Location: Raleigh, NC - OIB, NC iTrader: (0) Garage List 1965 COBRA (FFR rep ... [8.57] 2023 Jeep Wrangler ... [9.50] 2009 Yamaha V-Star [0.00] Cars 2-BMW, 2-FORD, ... [0.00] 2023 Ford Expeditio ... [0.00] 2020 Z4 M40i [10.00] 2022 BMW M4C [7.25] 1998 FORD Ranger 4X4 [0.00]	Why not take a drive & find out for yourself, should only take a few minutes. Someone else might have a different gear package or tire size so their numbers would be no good for you. __________________ Kevin Dravit Gray, Black Leather, Moonlight Roof, Red Calipers 2022 M4C - 2020 Z4 M40i - 2023 FORD Expedition XLT Max 4X4 400BHP - 2009 V-Star - 1998 Ranger 4X4 5MT - 1965 Cobra (R) 5MT - 2023 Jeep Wrangler Sport S 6MT
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07-05-2014, 11:32 AM	#6
Vigilante375 Major 116 Rep 1,158 Posts Drives: 2012 AW 6M 135i Join Date: Sep 2011 Location: WA iTrader: (0)	Here, pick which one you want to use to find out what you need: https://www.google.com/?gws_rd=ssl#q...tio+calculator For something like that, you're better off searching the internet.
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07-05-2014, 12:10 PM	#7
Ski Killset Second Lieutenant 25 Rep 293 Posts Drives: 08 AW 135i Join Date: Mar 2014 Location: Portland, Or iTrader: (0)	Just search for auto math calculators. I have yellow bits of tape on my tach in my race car to mark speeds in a given gear.
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07-06-2014, 10:33 AM	#8
Stock4Evr RetNavSpook 67 Rep 398 Posts Drives: 2012 135i - 2016 320i Join Date: Jan 2014 Location: Canyon Lake, Texas iTrader: (0)	Thank you for all your comments. I will work with each of your recommendations. Thanks again.
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