RPM's & MPG

[thstone]

Originally Posted by Topless

Cruising to SD (2hrs) from my house in light traffic at about 70 mph true. The I-15 is a long straight road. I have checked the mileage a dozen times over the years and it is pretty consistent.

I had 2 kids playing water polo at UCSD so I made the trip to catch their games a lot during the season.

Dave, I am a proud graduate of UCSD, Class of 84'! Excellent school, if I say so myself.

[pesticidal]

My '05 S has averaged just over 22 mph over the 2,200 miles I've put on since I got it. About 1/2 of this has been at highway speeds. I, too, have wondered why the rpm is so high in top gear. I'm not going to say I know better than the German engineers, but I would think that the 6th gear overdrive would produce significantly lower rpms.

[sb01box]

here's my 2001 2.7 5 speed gas consumption from nov-2006 to mar-2012. 99% of the time, the top is down. 22.2mpg average
going to Las Vegas with top up and at 75+ MPH, the car gets 28.
has 120K miles on the odometer.

[Homeboy981]

Originally Posted by ProjectM96

For some reason...often going what is considered a very inefficient speed, I average 28-29mpg in my tank.

But mixed city/highway spirited I average 21-22mpg.

I'm with you almost EXACTLY! I am getting 28 on highway at 70-80+ and in the city it is right around 22 because it is hard to drive like the good doctor ordered in traffic!

All in all….pretty darn good for a sports car! Especially compared to those hungry V-8s.

[southernstar]

One can't expect the gearing on the Boxster to be the same as a Camry for several reasons:

1. The redline on the 2.7, at 7200, must be about 10% higher than the Camry.

2. While 5th gear is, in fact, overdrive, nevertheless the intention on the Boxster (as with any performance car) is to keep the gear ratio spacing closer - ie., 'close ratio', so as to provide more seemless and balanced acceleration through the gears. The Camry, on the other hand, is more concerned with acceptable performance but higher fuel economy numbers on the highway that will appeal to most buyers.

3. In addition, the advertised top speed is more important to many Porsche buyers than the advertised fuel economy numbers. Increased speed increases drag and to achieve higher speeds for a given car, it is critical to have your maximum horsepower on tap as you approach the potential maximum speed. Since peak horsepower on the engine in the Boxster is very high up in the rev range (and drops only marginally thereafter until redline), it has a higher top speed than if the car was turning only about 4800 RPMs at, say 135 MPH. Were that the case, it is likely that the car would not have enough horsepower on tap at 135 MPH to overcome the aerodynamic drag at that speed and higher speeds would likely be impossible.

4. The Boxster engine just sounds so sweet at higher RPM's!

Brad

[CoBeerToad]

I've driven stick for a while, but I always kept the RPMs low in my Ford Probe. Doing 35mph in 4th gear and such. After reading this and many other threads (inclding the one about the IMS bearing and keeping the RPMs up). Either I have been driving wrong or the Porsche is not a Ford Probe.

I know everyone drives different and different gears and different average speeds probably make this question useless, but I'll ask anyway. Where do you like to keep your RPMs when cruising? I'm under the impression that 1800 is too low and maybe just out of habit, 2800 feels to high.

[tonycarreon]

Originally Posted by CoBeerToad

...the Porsche is not a Ford Probe.

truer words were never spoken

Originally Posted by CoBeerToad

Where do you like to keep your RPMs when cruising? I'm under the impression that 1800 is too low and maybe just out of habit, 2800 feels to high.

higher RPMs sound nicer, respond better and are just more fun... so why not?

[Overdrive]

3k+ rpms as consistently as possible. In 5th gear on a 2.5, 3k is just about 75mph, and 4k is about 100mph. Anything less than 70mph I downshift.

As for the city, I try to cruise at about 45, which is again right around 3k.

[dmairspotter]

Highway driving at 70-80 mph in my 03S 6 speed is 27-29 mpg, very reliably, checked over many tanks. The higher end is when I can find real gas, lower when it's an ethanol mix.

recent highway trip- 28.6, 26.9, 27.0, 28.8, 30.5

3000 +/- rpm at 70+ in sixth is my typical range