I've been reading about "hypermiling," the practice of trying to get the best mileage. It's often stated that fuel economy is best in the 55 mph range. But I'm sure that's for piston engines.

Have there been any studies on the speed that yields the best fuel economy for a rotary? I've been trying to cruise at 55 mph when feasible, but it struck me that this might not apply.

 

I kinda doubt 55 mph is best for fuel economy. I saw a test of a vehicle the other day, and they made quite a bit more miles at 35 mph than 55. But mpg quickly dropped at 65 ad 75

 

I think i remember seeing on here a LONG time ago that it was slightly faster for a rotary's optimum mileage

Your best bet is to find a big hill to park on top of, then give it a push and coast to where you're going

 

just install a scangauge2 and watch the mpg reading.

 

I tested on half a tank at each of these speeds, but it takes allot of Patience. With these results...I have scan gauge2, This is actually what I got on my 04 with A/T.
55mph.....29.5mpg
65mph.....27mpg
75mph.....23mpg

 

I've seen other vehicles tested and the results all seemed to fall somewhere between 40-50 mph. It's in there somewhere. Since I started taking a different route to work where I can pretty much hold 45 mph for a long time, my mileage has gone up. That's to be expected though as I don't have as many stop and the main route hits 70 mph in spots. The intersting thing is that over my 27 mile trip there is less than 5 minutes difference in drive time and that can vary depending on traffic conditions.

 

Best mileage - 6th and RPMs below 3500.
Best mileage without feeling the need to kill yourself or someone else - 6th and 4800 RPM.

Of course, with the advent of the AccessPORT, it is possible to tweak your cruise range (calcload of 38 or less and, say, 4500 RPM) to as lean as 17:1 on some cars.
Most seem to surge at 16:1, though. Even 15:1 makes a huge difference - especially over the 11:1 that Mazda wants to see there.

 

hypermiling makes me want to kick a baby.

 

aerodynamics helps our cars a lot apparently.

I'd like to see an aerodynamic comparison of some sort (ie drag coefficient numbers or something along those lines). I keep hearing how awesome the aerodynamics of the rx8 is but haven't seen solid proof other then i've never driven a car that seemed to go so fast with so little effort.

 

rx8 isn't too great on the aerodynamic side. It's .31, and .30 on the new 2009.

 

Really? Are you sure you weren't in a Ford Taurus?

 

here's a nice list of drag coefficients:

http://en.wikipedia.org/wiki/Automob...g_coefficients

Rx-7 was .29

 

interesting while the numbers are comparable to a mclaren f1 or diablo... all electric or hybrid cars seem to be designed more aerodynamically.. yay prius and insight!

maybe we should buy hideous nose cones for our cars.

 

Boy I could go for an ice cream cone right now.

 

Interesting. I'm not surprised it drops off after 55 mph. Slowing down 10 mph from 75 always nets you a lot better mileage no matter what vehicle you're in.

 

I know it's hard to believe and I don't know if I'd have the discipline to do it now. I did have a '86 Merc-Sable-V6 which was comfy on long trips. That was great on gas, It got 30mpg on the hwy, but it was a piece of crap had to sell it with only 51K miles on it.

 

If that's true I am impressed!

 

Speeding up from 65 to 80 adds almost 10% to my mileage.

 

I have been wondering about this lately. My AFR with the Int-X is 15:1 in 6th at cruise (load<30) at anything below 72mph/3600rpm/21"vac. My AFR is closer to 16:1 in 6th at anything above 72mph/3600rpm/21"vac. When should I be concerned that it is running too lean at cruise?

 

i believe i read that mazda stated 42mph in 6th gear was the most economical.

i've seen 24.5mpg, highway, at 65mph.

that was a looooooooonnggg 60 mile trip. even the truckers were swerving around me and i was in the right lane...

 

I think it meant that Old Rotor got 29.5mpg while cruising at 55 mph. Braking, stopping and accelerating would lower that figure.

 

Isn't the maximum MPG for any car the highest gear and lowest speed in that gear without lugging it?

 

Usually around there. The RX-8 owner's manual gives some recommended shift speeds which we usually deride as way too soon, but I'd expect those to give the best mileage.

We should all be carful about hypermiling stunts. Some - like coasting in neutral - are illegal and can be dangerous. Letting your speed run up downhill and come down uphill will save you gas, but if there's traffic around that has to react, that's likely to screw up everyone else's mileage. And tempers. Same with the ignorant technique of idling away from traffic lights.

Hypermilers have resurrected the old "drive in your socks" thing to help minimize jiggling of the accelerator. Good technique back in the days of carburetors and accelerator pumps, but I'd be surprised if it did a whole lot today.

My solution to gas prices is to just suck it up and pay, at least looking for the stations with lower (or less high) prices. As for driving technique - I didn't buy a sports car so I could avoid jackrabbit starts and coast down hills.

Ken

 

When it starts bucking.

No. The best fuel efficiency is at the torque peak, at the lowest possible throttle setting in the highest gear.

 

I did notice that when I had ignition problems and I was forced to drive under 65 for a few days I got an extra two days of driving (50 or 60 miles) out of the tank. I am making a long trip tonight, I will see what happens when I stay under 65.