So as near as I can tell, efficiency when it comes to fuel consumption is just plain different in a rotary from other cars (or am I just flat wrong?). Here's my 2 scenarios (assume the car is in perfect condition):


Scenario 1:

Cruising along a flat stretch of road at 60mph, I can reasonably be in 3rd, 4th, 5th or 6th, with RPM's ranging from 3k in 6th to 5k in 3rd. Maintaining a steady speed, which gear is using more gas? Anectdotally, I've noticed no difference in throttle position between 4th, 5th and 6th, however it might be so minute that I just didn't notice.

Scenario 2:

Cruising along at 60mph, on I-5 North, the speed limit goes up to 70 just outside of Seattle. So, to go from 60-70 I can: Shift into 3rd, Shift into 4th, Shift into 5th, or stay in 6th. In 3rd it might take 1 second to make the difference and then I'm back into 6th cruising while in 6th it will take more time with less throttle. Which is actually going to use more gas?


I'm actually really tempted to break out my AP and datalog these 2 scenarios to find out after I change my oil later this week/early next week, but if you actually know the answer, post! Please don't respond with "One time I was...". I mean, in theory I could just draft off a Semi the whole time and get 35mpg but that's not the point, I'm interested in the actual efficiency of the engine.

 

Great questions, I would be very interested in some well-researched theories as well...
Also prompts the question I've been askin for a while: why are all new car manufacturers (or the EPA during testing) not required to generate a velocity vs. MPG chart (for gear as well, if possible) along with EPA mileage numbers? Or at the very least, the most fuel-efficient cruising speed (and gear, although I'm assuming this will be the "top" gear). Common experience indicates maximally efficient speed is somewhere around 45 mph in 6th gear, but some actual data would be nice, even if just in unrealistic experimental conditions that could be used to at least relatively maximize efficiency.

That all sounded really geeky....can you tell I'm german? hah

 

Makes sense to me, but then that indicates what I am.

I would also be interested in some true thorough testing of the 8, as well as a metric from manufacturers that posts the maximum efficiency possible and the speed/gear to do that in.

MPG isn't an issue for me, never has been, but it is still a mathematical study in dynamics and efficiency, and that interests me from a mental standpoint. Most people assume that 6th is the most efficient. "It has to be". But is it actually? From my understanding, the higher the gear, the more fuel you have to dump in per injection to keep the same speed, but the less individual injections you need. 2 different metrics that work in opposite directions could actually cross, and I believe that they do. Maybe they don't cross within the normal driving range, but plotting data points is really what is needed.

Someone else did a Speed vs Load chart and MPG, but while accurate, I don't think it really presents a complete picture, and isn't something that the new-owner can use.

Say the AP value for MPG in 5mph increments for each gear?
I wish I had the money for an AP to do it myself. I would enjoy logging that.

 

well I have noticed that cruising around 3k rpms i get the best mileage u must remember that at 3750 RPM's another set of injectors are on and supposedly cruising above that drops the mileage down about 2mpg...also another set at 6500 which will just wreck mileage.

https://www.rx8club.com/rx-8-discussion-3/gas-mileage-findings-147154/

thisis some "logging" I did (on paper) on my move to FL mind u those are keeping the RPM's about 3600 or so to keep below the 2nd set....

 

i get about 15-17 MPG