You are oversimplifying the model, and I'm pretty sure it is leading you to the wrong answer. In almost every car, the best steady-state cruising efficiency is in the highest gear.

The way to get around this problem is simply to do a test. There is a lot of apocryphal data to suggest that the answer is not the one you think it is. However, I haven't really seen many people trying to do controlled experiments.

I don't know which way the answer actually is going to fall out, but I do think you are wrong in your opinion that the efficiency maximum can't possibly be above 50-55 mph.

Since you don't even have an S2000 to test with, I'm almost tempted to say you are drifting into the realm of trolling this board.

 

Guys:

Look -- I've got a car that will cruise anywhere in the 85 to 100 mph range and deliver 30 mpg! Let me say it again. I don't care why! I'm just thankful that I stumbled into a performance car back in '01 that will deliver that kind of mileage at the highway speeds we REALLY drive out here in the middle of nowhere. Just try doing that in other high performance cars. I don't know of one that will come close.

So talk about it all you want. All I want is for my car to keep on doin' what she's doin'!

Thanks,
Richard

 

conclusion?

 

dyhppy:

The conclusion is simple. Mine is just the report of a very satisfied s2k owner, whose car has given him a high performance ride for almost six years and an unexpected plus ---GOOD ACTUAL GAS MILEAGE !

Thanks,
Richard

 

Ok doing test with this tank of gas, in which 90% of the time has been in highway driving and shifting between 4k-5k in the city and when getting onto the highway...

I have been going at about 67-72mph (~4500rpm's) and of course staying in fifth gear to do this...

So far, with half a tank ALMOST gone I have accumulated 120miles (and i normally get 100miles to half a tank, and it's not even at half yet)...

So I dont know if i will get 240-260miles to the tank this time (i usually get 200-210 before the light comes on)...

Hmmm might just get my 4.77 gears!

 

i get about 23 hwy and 20city both agressive driving.

Beats the 17hwy and 13city i was getting in my 05 RX8.

 

My argument is that the car is NOT more efficient at 85-90 than 55 mph. One argument that has been made by others to explain the anecdotal observations is that the fuel map is extraordinarily rich at lower RPMs on early AP1's. This may be true or not.

If it's true then you'd be better off going slower in a lower gear to keep the RPMs in the sweet spot. This would be a counter-intuitive way to drive, but I'll keep an open mind.

If it's not true, then the anecdotal evidence is just due to wind, elevation, measurement error and self-delusion. You'd still be better off MPG-wise at a lower gear at the same RPM than going 90mph, but you'd be better off still driving the traditional MPG enhancing way: slower, but in the highest gear that doesn't lug the engine.

Yep. I think you'd want an accurate fuel flow meter, rather than relying on the repeatability of service station fuel pumps.

I didn't say that's where the max efficiency was. It could be anywhere between 50 and 70 and it wouldn't surprise me much. I just know that 55 is better than 85-90.

I'm buying an AP2, so it probably wouldn't matter for this discussion. Physics apply to this car just like any other.

-b

 

Ok guys sorry for the late update, I have been sick all weekend (and up until today actually) with the flu and a stomach virus (double whammy FTW ) so I didn't get to test the theory however it seams like we may have actually reached an agreement already.

Assuming all other factors are the same (including the rpm of the engine, but not including the selected gear) all cars will get less mpg. Physics is physics after all and on that bvan is correct.

My reason for disagreement (even though I actually agreed the whole time) stems from the origination of this theory. When this theory was originally formed, at least from what I have read and discussed with long time owners, it was formed with the assumption that in either case you would be cruising on the highway in 6th gear. With this assumption ap1 owners would see higher gas mileage at higher speeds, but only when comparing speeds in 6th gear.

So yes, you can get better mpg at higher speeds in 6th, or as bvan has said, downshift. At least that should be the new theory until tested.

To mend my test, I will instead try keep 4k rpm in 4th 5th and 6th, which should give 58.62mph 70.09mph and 83.92mph respectively. (from http://www.fatboyraceworks.com/gears/index.php ) Same idea, round trip filling up each time.

 

what kind of gas milage will 4.56 and 4.77 gears give me on highway and in city?