How do I get the RPM @ 60 to 75 mph?
07-03-2014, 11:45 PM
#1
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How do I get the RPM @ 60 to 75 mph? I would like to compare what my DD does vs where I'm @ now with this comb.
3.91 rear
4L80e trans 4000 stall
18x35x305 tire
3200lbs G-body.
Now listening 2 Drake 0 - 100
3.91 rear
4L80e trans 4000 stall
18x35x305 tire
3200lbs G-body.
Now listening 2 Drake 0 - 100
07-04-2014, 05:52 AM
#4
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Thanks.... off 2 work. Got a $5000 check in yesterday..Darn bank is closed. LOL.
I got a long way to readline even in 3rd. I was thinking 4th gear on the FWY...
Thanks again:
Paco
I got a long way to readline even in 3rd. I was thinking 4th gear on the FWY...
Thanks again:
Paco
07-04-2014, 10:10 AM
#5
to determine RPM vs MPH you need tire circum..tranny ratio and your rear end ratio. i made a table to help me determine what rear end ratio i wanted and to stay within my torque peak between shifts....
07-04-2014, 11:43 AM
#6
rpm=336 x rear gear x final drive ratio of trans x MPH / rear tire diameter
RPM= 336 x 3.91 x .75 x 60 MPH divided by actual tire diameter.
This should be within a few hundred RPMs. You can change out the #s to figure out desired tire diameter at a given rpm or mph etc…
RPM= 336 x 3.91 x .75 x 60 MPH divided by actual tire diameter.
This should be within a few hundred RPMs. You can change out the #s to figure out desired tire diameter at a given rpm or mph etc…
07-04-2014, 12:05 PM
#7
TECH Addict
Or you can take the tire info to get diameter.
Example:
305/35-ZR18
Width in mm/ profile of width in % - speed rating- rim diameter in inches
305mm/25.4= 12.007"
12.007" x .35 = 4.202"
4.202" x 2= 8.404"
8.404" + 18"= 26.404"
So a 305/35ZR18 tire is approx. 26.4" Dia.
Then you take engine RPM / selected gear ratio / rear gear ratio x (tire diameter x 3.14 or Pi) x 60 = Inches per hour
Then it's inches per hour / 12 = feet per hour
Feet per hour / 5280 = miles per hour
So, at 3300 rpms in 3rd gear on an A4 with 3.91 gears and 305/35ZR18's you'll be at 66.27 mph, theoretically. 3500 rpms will put you at a theoretical 70 mph.
The speed will actually be slightly lower with the tq. converter locked because the actual radius of the tire will be less due to the weight of the vehicle. Unlocked tq. converter will be further off (lower).
Example:
305/35-ZR18
Width in mm/ profile of width in % - speed rating- rim diameter in inches
305mm/25.4= 12.007"
12.007" x .35 = 4.202"
4.202" x 2= 8.404"
8.404" + 18"= 26.404"
So a 305/35ZR18 tire is approx. 26.4" Dia.
Then you take engine RPM / selected gear ratio / rear gear ratio x (tire diameter x 3.14 or Pi) x 60 = Inches per hour
Then it's inches per hour / 12 = feet per hour
Feet per hour / 5280 = miles per hour
So, at 3300 rpms in 3rd gear on an A4 with 3.91 gears and 305/35ZR18's you'll be at 66.27 mph, theoretically. 3500 rpms will put you at a theoretical 70 mph.
The speed will actually be slightly lower with the tq. converter locked because the actual radius of the tire will be less due to the weight of the vehicle. Unlocked tq. converter will be further off (lower).
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07-05-2014, 09:46 AM
#14
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You too huh? LOL.
2 more, with the set up listed in the first post;
@60mph you'll be at about 2250rpms in 4th
@65mph you'll be at about 2450rpms in 4th
@70mph you'll be at about 2650rpms in 4th
@75mph you'll be at about 2800rpms in 4th
2 more, with the set up listed in the first post;
@60mph you'll be at about 2250rpms in 4th
@65mph you'll be at about 2450rpms in 4th
@70mph you'll be at about 2650rpms in 4th
@75mph you'll be at about 2800rpms in 4th
Last edited by hrcslam; 07-06-2014 at 06:04 PM.
07-05-2014, 10:08 AM
#16
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Yes sometimes DRO + DOS EQUIS
I JUST HAPPEN 2 LIKE N/A HP and a # ain' t s*** if it don't hook.
Think about how much I as a person have spent 2 get a number
cheap cheap cheap
lol...
I JUST HAPPEN 2 LIKE N/A HP and a # ain' t s*** if it don't hook.
Think about how much I as a person have spent 2 get a number
cheap cheap cheap
lol...
07-05-2014, 10:09 AM
#17
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thanks
again U -all
trying 2 shake off a Charlie Sheen buzz .... so you no that I get lifted just @ my home.
again U -all
trying 2 shake off a Charlie Sheen buzz .... so you no that I get lifted just @ my home.
Last edited by lil john; 07-05-2014 at 10:22 AM.