How rpm varies with engine speed

[BocaDave]

I haven't done much highway driving with my Genesis 3.8, but recently was pleased to note how the engine was loafing around at 2000 RPM while I was cruising on flat ground at 70 MPH with the A/C off (per my speedometer, not GPS).

My last two cars were 4 door sedans and ran at 2,500 to 2,750 RPM at 70 MPH if memory serves me correctly.

That should bode well for engine life, I would think, since fewer RPMs = less wear on many engine parts and lubricants (valves, cylinders, alternator, probably oil, transmission, etc.).

I wonder what YOU have experienced with your Genesis Sedans at various speeds (and with other cars), particularly highway speeds.

For those of you who like "hard numbers," I looked up an example of how engine speed varies with RPM (but couldn't find data for the Genesis). Here are the numbers per Wikipedia in terms of "Inches per revolution (for a Corvette Z06).

http://en.wikipedia.org/wiki/Gear_ratio

Vehicle Speed per 1000 RPM:

1st gear 8.1 inches 7.7 mph / 11.3 kmh
2nd gear 11.6 inches 11.0 mph / 17.7 kmh
3rd gear 16.8 inches 15.9 mph / 24.1 kmh
4th gear 24.0 inches 22.7 mph / 35.4 kmh
5th gear 28.6 inches 27.1 mph / 43.4 kmh
6th gear 42.9 inches 40.6 mph / 64.3 kmh

(remember, to convert inches per second to mph, multiply by approximately 1.5, so 40 inches /second = 60 MPH (+/- 1%).

 

[ctrcbob]

Huh???

Engine Speed IS RPM!

Don't know if you mean car speed vs RPM. You have me confused. Even more confused when you talk about Inches at an RPM.

Again, HUH?????

 

[mcginnpm]

I had my speedo recalibrated into furlongs per fortnight...

 

[JOwest]

I had my speedo recalibrated into furlongs per fortnight...

My onboard fuel consumption now displays litres per 1 million spark ignition.

 

[BocaDave]

Hey guys, don't shoot the messenger (although it was MY message and I was carrying it).

The inches per RPM is how they expressed it on the Wikipedia web site from which I took the quote.

Now, I told you how to convert it to MILES per 1,000 RPM (multiply by 1.5).

Yes,I should have re-written their chart into Furlongs or Feet, or Miles...

But I though I'd save time by publishing the exact quote.

Whatever time I saved, was just lost now because I had to write this note.

Is it fun yet?

 

[flyboy2]

Bocadave I figure I have to take a piss about every hour when on the road. Every .75 hours if I've had a mocha. How many revolution do you think took place in between pit shops if I inched along at 65 mph and only had my regular coffee? If I travelled 75 mph miles and stopped at the 65 mile point would drinking a mocha afford me less engine resistance or more engine resistance? How about I pour my mocha directly into the tank so it by passed the middleman. Would my engine have more or less resistance? Then I could travel 100 miles in between pits stops. Darn this stuff is fascinating... Do you have the answers? Please let me know when you do. I'm out playing golf--

 

[mcginnpm]

If I shoot the messenger with my Sig Sauer P229 .357SIG, which has a barrel twist of 1:15 and a muzzle velocity of 1450 fps, and the messenger is at a distance of 2.6 chains from me when I pull the trigger and traveling away from me in a Corvette Z06 (w/the A/C off) at a constant 6000 rpm in 5th gear, how many times will the bullet rotate before it impacts the messenger? To simplify the math you may ignore the effect of air friction on the bullet.

flyboy2 - You must complete this math assignment before you finish drinking your mocha, but you must finish drinking your mocha before it reaches a temperature of 305.4 degrees Kelvin. Otherwise you will receive no credit and you will have to re-take this class next semester. The mocha must be in a standard Starbucks biodegradable cup with one (1) cardboard sleeve installed, and consumed in a room not warmer than standard day, sea level temperature.

 

[flyboy2]

Mike l like Marines. No quite an Army Airborne/Ranger... but close.

 

[bradyb]

I haven't done much highway driving with my Genesis 3.8, but recently was pleased to note how the engine was loafing around at 2000 RPM while I was cruising on flat ground at 70 MPH with the A/C off (per my speedometer, not GPS).

My last two cars were 4 door sedans and ran at 2,500 to 2,750 RPM at 70 MPH if memory serves me correctly.

That should bode well for engine life, I would think, since fewer RPMs = less wear on many engine parts and lubricants (valves, cylinders, alternator, probably oil, transmission, etc.).

I wonder what YOU have experienced with your Genesis Sedans at various speeds (and with other cars), particularly highway speeds.

For those of you who like "hard numbers," I looked up an example of how engine speed varies with RPM (but couldn't find data for the Genesis). Here are the numbers per Wikipedia in terms of "Inches per revolution (for a Corvette Z06).

http://en.wikipedia.org/wiki/Gear_ratio

Vehicle Speed per 1000 RPM:

1st gear 8.1 inches 7.7 mph / 11.3 kmh
2nd gear 11.6 inches 11.0 mph / 17.7 kmh
3rd gear 16.8 inches 15.9 mph / 24.1 kmh
4th gear 24.0 inches 22.7 mph / 35.4 kmh
5th gear 28.6 inches 27.1 mph / 43.4 kmh
6th gear 42.9 inches 40.6 mph / 64.3 kmh

(remember, to convert inches per second to mph, multiply by approximately 1.5, so 40 inches /second = 60 MPH (+/- 1%).

but i drive 90mph and sometimes 125mph. could you recalculate for theses speeds?

 

[flyboy2]

What's interesting is to look at your speed while turning 2,000 rpms in 6th gear. Looking at a GPS would be more accurate of course. Then figure our your top rpms to redline or until the speed governor kicks in. Then using your math you can figure out the top speed of our vehicle... or come close.

One way of figuring out top RPM is to floor it in 1st gear. At the top, the transmission will automatically switch into second gear. Note RPMs when this happens. This might give you an idea of when the governed RPMs will cut in when in 6th gear. Of course the only way to figure out top end is to take it to Bonneville or a runway--

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[Mark_888]

I was specifically promised by the Hyundai dealer salesman that no math was required to drive a Genesis.

 

[Disaster]

If I shoot the messenger with my Sig Sauer P229 .357SIG, which has a barrel twist of 1:15 and a muzzle velocity of 1450 fps, and the messenger is at a distance of 2.6 chains from me when I pull the trigger and traveling away from me in a Corvette Z06 (w/the A/C off) at a constant 6000 rpm in 5th gear, how many times will the bullet rotate before it impacts the messenger? To simplify the math you may ignore the effect of air friction on the bullet.

First of all the .357Sig is a useless round and when you have an actual Sig chambered for it, your Sig fanboy status is out there for everyone to see. Pick up an HK45 and don't worry about bullet revolutions or whether the darn thing will penetrate a denim jacket.

 

[XBOHDPuKC]

I was specifically promised by the Hyundai dealer salesman that no math was required to drive a Genesis.

sorry wrong thread

 

[ctrcbob]

This is one of the most worthless threads, if not the most worthless thread, I've seen on this BB.

RPM is, and always has been, ENGINE SPEED!!

 

[flyboy2]

This is one of the most worthless threads, if not the most worthless thread, I've seen on this BB.

We really don't care about your opinions. If you don't like a thread don't read it.

 

[QCTLG]

We really don't care about your opinions. If you don't like a thread don't read it.

Look who's talking !!

 

[flyboy2]

Here are some preliminary speed numbers for those that are interested.

Car is a 2009 Genesis V-8 with 6,000 miles, stock tires, a K&N air filter. Engine airtake valve (don't know the official name) has been removed. No GPS used.

At 2,000 RPM car does approximately 74 mph At sea level in 6th gear.
With two runs in 1st and 2nd gears, tachometer will reach 6,300 RPM before shifting.
6,300 RPM is approximately 3.15 times 2,000 RPM

The vehicle is capable of 233 MPH in a no wind, no drag scenario.
But in a real world you will have parasite drag, compression, density altitude, etc.

And of course there is that speed governor--

 

[ctrcbob]

If the subject was "how RPM varies with car speed", that would make sense,
however "how RPM varies with engine speed" just does not make sense.

RPM and Engine Speed are the same thing. (at least outside of Santa Cruz <grin>).