3k rpm at 80mph 6th gear?

darkseed · 12-03-2009, 05:54 AM

Anybody know if this is right? When I'm driving on the freeway in 6th gear my RPMS are almost about 3K even when I'm not on the gas pedal. Feels like I'm in 5th gear really and also feels like its burning my gas like no other

darkROAM_1 · 12-03-2009, 07:59 AM

Compared to a 350Z or a G35, it's lower than those from what I've heard. There's nothing wrong with it. Hell my car gets GREAT gas mileage at about 73mph on extended trips.

Red370 · 12-03-2009, 08:57 AM

I avg. 30mpg on the highway at those speeds, nope, not burnin nuffin.

DooDooBrown · 12-03-2009, 09:04 AM

That is right! That is the speed I am at 80% of the time with my baby! I was getting about 21.0, but have put about 6000 miles on her, and it is slowly creaping up... Currently at 23.8

WhiskeyHotel · 12-03-2009, 09:27 AM

Here's how to calculate it:

mph = (rpm * cir) / (gear * final * 88)
mph = (3000*6.96)/(0.794*3.692*88)
mph = 80.9

where:
rpm = engine rpm (We'll use 3000)
cir = tire cicumference, in feet (We'll use 83.5" or 6.96' for 19's)
gear = gear ratio of your car (Assuming an MT in 6th, this is 0.794)
final = final drive ratio of your car (Assuming an MT, this is 3.692)
88 = combines several conversion factors

To work it backwards, using 73 MPH:

RPM = (mph * gear * final * 88) / circumference
RPM = (73*0.794*3.692*88)/6.96
RPM = 2706

This should get you close!

kenchan · 12-03-2009, 02:02 PM

my G's 6MT rpm is considerably lower rpm than my Z.

my FitSport's 5MT cranks over 3.5K at 70mph.

hahaha.

WhiskeyHotel · 12-03-2009, 02:14 PM

Quote:

Originally Posted by kenchan

my G's 6MT rpm is considerably lower rpm than my Z.

my FitSport's 5MT cranks over 3.5K at 70mph.

hahaha.

The final drive on the G is 3.538. Assuming all else is equal, the RPM's should be about:

3.538/3.692 = 95.8% of the Z at the same speed.

kenchan · 12-03-2009, 02:21 PM

about 95.82% to be exact.

elmz · 12-03-2009, 02:31 PM

Yep that's correct. In my 350 it was a little higher. Just remember the redline is 7.5k so there is plenty of gear left.

12-03-2009, 05:54 AM	#1 (permalink)
darkseed Base Member Join Date: Nov 2009 Location: SoCal Posts: 86 Drives: 09 370Z PG M6 Rep Power: 16	3k rpm at 80mph 6th gear? Anybody know if this is right? When I'm driving on the freeway in 6th gear my RPMS are almost about 3K even when I'm not on the gas pedal. Feels like I'm in 5th gear really and also feels like its burning my gas like no other __________________ 09 PG M6 w/NAV - 307RWPH - FI mods

12-03-2009, 08:57 AM	#3 (permalink)
Red370 A True Z Fanatic Join Date: Jul 2009 Location: Kaiserslautern, Germany Posts: 4,391 Drives: your mom to church Rep Power: 296	I avg. 30mpg on the highway at those speeds, nope, not burnin nuffin. __________________ 2011 Mustang 5.0 \| 3.55's \| Lethal Performance off road H-Pipe \| Magnaflow Muffler Delete \| JLT CAI/Bama tuned 417whp/ 404 ft/lbs

12-03-2009, 09:27 AM	#5 (permalink)
WhiskeyHotel Track Member Join Date: Nov 2009 Location: Oklahoma Posts: 530 Drives: 2015 GT-R PW Premium Rep Power: 17	Here's how to calculate it: mph = (rpm * cir) / (gear * final * 88) mph = (30006.96)/(0.7943.69288) mph = 80.9 where: rpm = engine rpm (We'll use 3000) cir = tire cicumference, in feet (We'll use 83.5" or 6.96' for 19's) gear = gear ratio of your car (Assuming an MT in 6th, this is 0.794) final = final drive ratio of your car (Assuming an MT, this is 3.692) 88 = combines several conversion factors To work it backwards, using 73 MPH: RPM = (mph gear * final * 88) / circumference RPM = (730.7943.69288)/6.96 RPM = 2706 This should get you close! Last edited by WhiskeyHotel; 12-03-2009 at 09:30 AM.*

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12-03-2009, 07:59 AM	#2 (permalink)
darkROAM_1 Base Member Join Date: Nov 2009 Location: Oak Cliff Posts: 78 Drives: 09 MB 370 base/sport Rep Power: 15	Compared to a 350Z or a G35, it's lower than those from what I've heard. There's nothing wrong with it. Hell my car gets GREAT gas mileage at about 73mph on extended trips.

12-03-2009, 09:04 AM	#4 (permalink)
DooDooBrown Base Member Join Date: Jun 2009 Location: Ranson, WV Posts: 178 Drives: 09 370 Touring w/spt Rep Power: 16	That is right! That is the speed I am at 80% of the time with my baby! I was getting about 21.0, but have put about 6000 miles on her, and it is slowly creaping up... Currently at 23.8

12-03-2009, 02:02 PM	#6 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141521	my G's 6MT rpm is considerably lower rpm than my Z. my FitSport's 5MT cranks over 3.5K at 70mph. hahaha.

12-03-2009, 02:21 PM	#8 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141521	about 95.82% to be exact.

12-03-2009, 02:31 PM	#9 (permalink)
elmz Track Member Join Date: Feb 2009 Location: San Diego, CA Posts: 674 Drives: 2014 Porsche Boxster Rep Power: 17	Yep that's correct. In my 350 it was a little higher. Just remember the redline is 7.5k so there is plenty of gear left.