[QUOTE=PWRMKR,Jul 26 2010, 04:13 AM] 2001 S2000 Owner's Manual Recommended Shift Points
Drive in the highest gear that lets the engine run and accelerate smoothly. This will give you the best fuel economy and effective emissions control.
The following shift points are recommended:

 

Worth repeating, I guess:
"Normal Acceleration" is NOT the same thing as "Cruise".

 

i dunno how i get 25 mpg city cruising 35mph in 3rd (with a tp) while I know people who do the same thing in 4th-6th and get worse mpg than me. I do what works for me, it as simple as that.

 

THIS!!!

You can be in 6th gear at 35 mph if you are on a flat road surface or going down a hill and you will be getting the best MPG. If you are going up a hill in 6th gear at 40 mph you are wasting fuel!



Can you guys who keep claiming that a wider throttle opening at lower RPM's is going to increase my fuel economy...please find a legit article on this. I would like to read up on this from a reputable source.

The problem with having a wide throttle opening is that this allows more air into the intake which in turn causes the injectors to pump more fuel and the car accelerates.

So if in theory lugging our engines around at 2,500 rpms with 1/2 throttle should give us better gas mileage than 3,500 rpms at 1/4 throttle. In practice driving like this is no fun, the car has no power even if you floor it and you would have to downshift 2-3 gears to accelerate with the quickness if you needed to.

I accelerate slowly in normal driving and engine brake when coming to a stop with ZERO throttle and I always get 26-29 MPG around town, through stop lights, stop signs, etc. I shift at 4K in each gear with light throttle and keep RPMS at 3,000 +/1 when cruising in a gear at steady speed.

 

I found that on a level road driving at 35 in 4th gear requires slightly more pedal pressure than in 3rd gear.

My experiment consisted of these highly accurate scientifically designed steps:

Drive on level road in 3rd gear at 35 mph.
Shift to 4th gear without lifting or depressing the accelerator.
Notice speed in 4th gear is now 33 mph with some slight (possibly imagined) lugging.

Obviously I'm no expert on the subject, but I'm assuming that since 4th gear requires more throttle than 3rd gear to go 35mph on level ground, it's more fuel efficient to drive in 3rd gear.

 

35 mph = 5th for me if I'm just cruising.

 

^yup. but i usually shift around 3500rpms or less 1st through 4th gear while driving normally. i'll upshift 1 gear higher if i'll be cruising.

 

While the throttle plate position makes a difference for efficiency, I've often wondered about "sweet spots" in terms of engine rpms as well for engine efficiency (due to port sizes/shapes/etc). There are obviously more dynamics at play in engines than just pumping losses, or we'd all run 4" exhausts and make more power. This is why I think the notion of running an engine at as low an rpm as possible to "save fuel" isn't necessarily correct. Since the s2000 has relatively large intake/exhaust ports, lugging it at low rpms is probably hurting efficiency (or so I think at least).

Don't remember if I saw this mentioned, but another thing to keep in mind when accelerating is load. An old friend of mine used to drive his car by shifting religiously at 2krpm (a domestic). I think he thought he was saving gas by doing this, but it's important to remember that if you're at WOT and shifting at 2krpm, you're putting more stress on the motor, and the ecu will run the engine richer, which will likely result in worse gas mileage than partial throttle.

 

[QUOTE=JLUDE,Jul 28 2010, 12:54 PM]Can you guys who keep claiming that a wider throttle opening at lower RPM's is going to increase my fuel economy...please find a legit article on this.

 

SlowTeg, the article I've linked above has graphs showing sweet spots for a few different engines.