What is the optimal cruising RPM?
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I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
My auto '01 Frontier cruises at 2600rpm @ 75mph, which I still think is rather high. Since it's torque peak is at 2800rpm, I guess that's not unusual, as it never needs to downshift at highway speeds.
I guess I'm just used to older, larger engines, or vehicles that needed to downshift. One thing I clearly remember about my VW VR6 is that at highway 60-80mph speeds I could just stomp on the pedal and pass vehicles in a hurry without ever downshifting... Of course it's torque peak was at 3200rpm, which it was near (in 5th) at those speeds.
My auto '01 Frontier cruises at 2600rpm @ 75mph, which I still think is rather high. Since it's torque peak is at 2800rpm, I guess that's not unusual, as it never needs to downshift at highway speeds.
I guess I'm just used to older, larger engines, or vehicles that needed to downshift. One thing I clearly remember about my VW VR6 is that at highway 60-80mph speeds I could just stomp on the pedal and pass vehicles in a hurry without ever downshifting... Of course it's torque peak was at 3200rpm, which it was near (in 5th) at those speeds.
Hermann
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4 cyl 08 Tacoma manual. 2000 at 60 in fifth
about 2300 at 70.
about 2300 at 70.
Originally Posted By: 92saturnsl2
I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
Probably because most drivers don't mind an automatic downshifting for small grades or strong headwinds but wouldn't like to have to downshift a manual transmission for small changes in grade or to get some moderate acceleration.
Not to mention the clueless that would pull long grades at ubber low rpms with their foot on the floor.
I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
Probably because most drivers don't mind an automatic downshifting for small grades or strong headwinds but wouldn't like to have to downshift a manual transmission for small changes in grade or to get some moderate acceleration.
Not to mention the clueless that would pull long grades at ubber low rpms with their foot on the floor.
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Originally Posted By: 92saturnsl2
I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
My '89 Scirocco had two 5-speed options: a 5-speed sport transmission and a 5 Speed with an Economy 5th gear. The latter transmission achieved top speed in 4th gear, and 5th gear was purely an economy gear. I had the 5 Speed sport transmission, which I much preferred over the Economy version. I was familiar with both transmissions. As for "abnormally high RPM" (There is no RPMs, because it's always "revolutions per minute," not per "minutes") at cruising speed, if it's abnormally high, you aren't cruising!
Here's my A4's gearing chart:
I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
My '89 Scirocco had two 5-speed options: a 5-speed sport transmission and a 5 Speed with an Economy 5th gear. The latter transmission achieved top speed in 4th gear, and 5th gear was purely an economy gear. I had the 5 Speed sport transmission, which I much preferred over the Economy version. I was familiar with both transmissions. As for "abnormally high RPM" (There is no RPMs, because it's always "revolutions per minute," not per "minutes") at cruising speed, if it's abnormally high, you aren't cruising!
Here's my A4's gearing chart:
Originally Posted By: 92saturnsl2
I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
For me it's Japanese/Asian manuals:
89 Mazda 323 1.6... probably 4k RPM at 75 MPH.
99 Hyundai Accent 1.5 12V... no tach, but wheeee!
82 Yamaha Virago 748cc, 4500 RPM at 60-65 MPH
Compare to 93 Escort, 95 & 00 saturns, with "torquier" 1.9L inline 4s. It's not just the displacement, these are cammed to run out of breath about 1000 RPM lower.
Though I agree that automatic versions of ALL the cars I listed above, except the hyundai, I have experience with and have taller doggier overdrive gearing. Driving these cars is maddening as I try to nurse them up hills without kicking out of OD/ lockup, even racing through valleys to pick up steam for the next upgrade.
I should have added that most vehicles I've seen with "abnormally" high cruising RPM's have been manuals.
For me it's Japanese/Asian manuals:
89 Mazda 323 1.6... probably 4k RPM at 75 MPH.
99 Hyundai Accent 1.5 12V... no tach, but wheeee!
82 Yamaha Virago 748cc, 4500 RPM at 60-65 MPH
Compare to 93 Escort, 95 & 00 saturns, with "torquier" 1.9L inline 4s. It's not just the displacement, these are cammed to run out of breath about 1000 RPM lower.
Though I agree that automatic versions of ALL the cars I listed above, except the hyundai, I have experience with and have taller doggier overdrive gearing. Driving these cars is maddening as I try to nurse them up hills without kicking out of OD/ lockup, even racing through valleys to pick up steam for the next upgrade.
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Originally Posted By: pzev
Your gearing is very similar to mine. Whats your final drive ratio?
For the record, I have a 2.3l Ford Focus with a 3.42 final drive.
My 2.8L V6 quattro's final drive ratio is 3.889 : 1.
Your gearing is very similar to mine. Whats your final drive ratio?
For the record, I have a 2.3l Ford Focus with a 3.42 final drive.
My 2.8L V6 quattro's final drive ratio is 3.889 : 1.
IIRC our '99 Malibu with the 2.4L "Twin-Cam" runs around 2,200 RPM @ 65.
My 49 Ford with overdrive was 2400 rpm at 70mph, 2230 at 65 mph. Had to calculate that one since I got rid of it about 40 years ago.
1969 Honda CL350 was 7000 rpm at 70 mph.
1969 Honda CL350 was 7000 rpm at 70 mph.
Originally Posted By: 92saturnsl2
I remember my first vehicle, a 1978 F150 w/ the 400ci V8 would run 1500rpm at 65mph. A buddy's 1969 Ford Ranchero w/ the 302 V8 was similar.
Are you sure about that cruising speed for the truck? If the truck had 31" tires, to be doing 1500 RPM at 65 MPH you'd need a rear end ratio of about 2.15:1 (unless the truck had overdrive).
Optimal cruise RPM varies for each car. Torque peaks have gone up on modern cars, as well as RPM range for engines. Accordingly so have the cruise RPM's and gear ratios. Back in the early 80's many cars had super low (numerical) gears, to keep the cruise RPM's as low as possible to keep the fuel economy as high as possible. Some cars without OD had 2:14 axles, and with OD some cars still had 2.56:1 ratios. Of course many of these cars were equiped with low horespower V8's, but that made peak horsepower at less than 4000 RPM, and torque 2000 RPM or less. So they had the bottom end power to pull along (often just barely), but forget about top end punch.
Smaller engines always ran at higher RPM, but their torque peaks were often much higher. However, they also could run economically at 3000 RPM on the highway (try that with a V8).
My old Olds would plug along at 1500 RPM at 65 MPH with a 2.93 rear axle and OD, but it's torque peak was at 2000 RPM. Even though it was underpowered, it could still accelerate without unlocking the torque converter in OD. My 'Burb does about 1800 RPM at 65 MPH, with 3.42 gears, with peak torque at 2800 RPM.
I remember my first vehicle, a 1978 F150 w/ the 400ci V8 would run 1500rpm at 65mph. A buddy's 1969 Ford Ranchero w/ the 302 V8 was similar.
Are you sure about that cruising speed for the truck? If the truck had 31" tires, to be doing 1500 RPM at 65 MPH you'd need a rear end ratio of about 2.15:1 (unless the truck had overdrive).
Optimal cruise RPM varies for each car. Torque peaks have gone up on modern cars, as well as RPM range for engines. Accordingly so have the cruise RPM's and gear ratios. Back in the early 80's many cars had super low (numerical) gears, to keep the cruise RPM's as low as possible to keep the fuel economy as high as possible. Some cars without OD had 2:14 axles, and with OD some cars still had 2.56:1 ratios. Of course many of these cars were equiped with low horespower V8's, but that made peak horsepower at less than 4000 RPM, and torque 2000 RPM or less. So they had the bottom end power to pull along (often just barely), but forget about top end punch.
Smaller engines always ran at higher RPM, but their torque peaks were often much higher. However, they also could run economically at 3000 RPM on the highway (try that with a V8).
My old Olds would plug along at 1500 RPM at 65 MPH with a 2.93 rear axle and OD, but it's torque peak was at 2000 RPM. Even though it was underpowered, it could still accelerate without unlocking the torque converter in OD. My 'Burb does about 1800 RPM at 65 MPH, with 3.42 gears, with peak torque at 2800 RPM.
No idea what the optimal RPM is but at 65 mph, my '96 Civic commuter is just a hair over 2500 RPMs.
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