30 mpg

[te72]

We should have small diesel cars in na. But as a whole we are fat pigs and don't want a smaller, louder car.

When I hear that similarly equipped VW Rabbits, Polos, and the like (as far as small commuter cars go) in England are getting over 60mpg easily because of a small turbo diesel engine, it makes me a little sad that we don't get them over here. Not that I'd really want to drive one, and would be horrified to try getting on a freeway in one, but it's nice to have options.

Exactly....

Look at the 2011 Ford Fiesta vs the Mazda 2. Basically the same chassis (different engines though, oddly), but Ford managed to stick an extra 200 to 300 pounds of crap onto the car (depending on trim level). With a car that small... where do they even find a place to stick that much extra weight?

Probably in the 12 airbags, stability control sensors, traction control sensors (hah!), electronic nanny sensors, and 100lbs of sound deadening I'd imagine...

 

[RazoE]

Would be curious to know what that does for things, please update when you can? I usually cruise around town in 3rd, but we have ~35mph limits most places around here.

That said, raise your hand if you bought your car for the mileage...

Here's the update...

4/11/2011 – 191,652.1 miles

12.88 gallons $55.63 -$4.319 per gallon


5/5/2011 – 191,847 miles - travelled 194.9 = 14.01 mpg

13.191 gallons $58.29 – $4.418 per gallon


5/16/2011 – 192,047 miles – travelled 200.2 = 15.79 mpg*

12.633 gallons $55.32 – $4.379 per gallon

*Included driving to TORC about 16.7 miles each way, so 33.4 miles on freeway in 5th, around 80mph, romping it to keep up with an 87 turbo BPU and 350Z


So I improved 1.78 mpg by changing my tires from 245/45/16 back to 225/50/16, and driving in 5th instead of 4th @40mph, and no engine braking..

I’m sure there’s more I can do, as I’m due for an oil change, new shocks, new filter, new spark plugs, and I use my heater on full blast in medium the entire time I drive (love the heat)…



p.s. all 3 fill-ups were 91 octane, at the same gas station at the same time, the first two were from the same pump, 3rd fill-up was from the pump directly in front.

 

[te72]

Interesting, I think I'll stick with 3rd gear around town (lower speed limits I'm sure), I don't think I've ever seen worse than 17mpg in my car. Then again my odometer has been broken for a while now so I haven't been keeping track of mileage...

Your comment about engine braking makes me wonder though. Under deceleration, an engine doesn't use fuel, right?

 

[Nick M]

Don't drive in too tall of a gear. Lugging the engine isn't good for it or effeciency. If you have a 5 speed, upshift at 3000 rpm.

 

[Devin LeBlanc]

Just got back from Northern Cali, Put a Total of 1600 miles on my car.. With an average of 24mpg.. Automatic, 4.30 rear end, Original GE engine NA-T. Not bad Doing 80mph RPM was at 3400. Thats what I cruised at the whole time

 

[D.J.T.]

Don't drive in too tall of a gear. Lugging the engine isn't good for it or effeciency. If you have a 5 speed, upshift at 3000 rpm.

so your saying, id have better gas mileage if i drive all my gears under 3000 rpm & shift at 3000 rpm?

 

[dubsupra209]

Just got back from Northern Cali, Put a Total of 1600 miles on my car.. With an average of 24mpg.. Automatic, 4.30 rear end, Original GE engine NA-T. Not bad Doing 80mph RPM was at 3400. Thats what I cruised at the whole time

should of stopped by

 

[Nick M]

so your saying, id have better gas mileage if i drive all my gears under 3000 rpm & shift at 3000 rpm?

Injection duration is based primarily on engine speed. (and airflow). More engine speed, more fuel. I was refering to acceleration, not steady cruise.

 

[te72]

I always tend to shift right at the point when it's about to start boosting under partial throttle. Friend of mine thinks I'm the biggest tease there is haha...

 

[Nick M]

You should not be approaching load to go into boost if you are trying to save fuel. I know those of you in large metro areas have to accelerate to merge with traffic. Sell the Supra and go with a C5.

 

[IJ.]

One observation I can add is gentle long acceleration to cruise speed uses more fuel than a quick medium throttle run up to cruise as you're not in the ACCEL part of the ECU for as long.
i.e.
caaaaaaaaaaaccccccccccccccc
cAAAccccccccccccccccccccccccc

c= 14.7:1
a= 13.8:1
A= 12.8:1

it all comes down to "time" in each.

 

[kneedragger85]

I used to get 19mpg highway with a Lex/550 and stock CT26. The old Holset and Maft-Pro tuned with a wideband gave me 29mpg highway hitting between 14.7-15.1 AFR's.

 

[TurboStreetCar]

...Under deceleration, an engine doesn't use fuel, right?

Above decel fuel cut it does not with closed throttle.

 

[te72]

You should not be approaching load to go into boost if you are trying to save fuel. I know those of you in large metro areas have to accelerate to merge with traffic. Sell the Supra and go with a C5.

I'm one of the crowd driving a Supra for the fun of it, not the mileage, otherwise I would have kept my old Miata. But a C5 would make a nice daily, not much to dislike with those, except for maybe the side mirrors being worthless. The torque is nice for cruising around town though.

One observation I can add is gentle long acceleration to cruise speed uses more fuel than a quick medium throttle run up to cruise as you're not in the ACCEL part of the ECU for as long.
i.e.
caaaaaaaaaaaccccccccccccccc
cAAAccccccccccccccccccccccccc

c= 14.7:1
a= 13.8:1
A= 12.8:1

it all comes down to "time" in each.

Makes sense, get up and going, then get off the throttle as quick as you can... has worked for me with some cars.

Above decel fuel cut it does not with closed throttle.

How come then my car goes to ~21.0:1 AFR's whenever I let off the throttle in gear? Just pulling air through the engine, no fuel, correct?