Accelerating for good fuel consumption.

[PaleMelanesian]

I like somewhere around 12 for accelerating. The only thing is to watch the LOOP gauge and make sure it stays closed. Once it goes full throttle "open loop", the fuel mix goes rich.

You're right though. Accelerating is the smaller part of the puzzle. Getting all the energy back on the coasting end is where the magic happens. If I come to a stop at > 20 mph and use the brakes, I've made a mistake.

[JockoT]

Thanks. I'll stick to <12 and Closed Loop.

[JockoT]

Had a good run today and put the MAP technique to the test, and it seemed to work great. Sometimes I had to exceed 12 (such as accelerating from stopped and up a brae) but I kept it from going into open loop.
I find driving with load difficult, if I try to maintain instantaneous fuel consumption. My wee car does 50 mpg on the level, drops to 40 as soon as I reach the slightest incline, then drops very quickly to 30 as the incline increases. If I lift off to try and maintain 40 it just runs out of steam and I have to change down.
Using MAP, I just try and keep as near to 12 as I can, and it tootles on fine. I just disregard the mpg indicator in that instance.

[PaleMelanesian]

The engine actually produces more power-per-litre-of-fuel when you're using medium-to-high power. It's using more fuel in the moment, but fuel used to get up to speed is actually less. Then you cruise along with the lightest touch you can, or pulse-and-glide so it's always either running in the efficient heavy-load mode or just ticking over while coasting.

[JockoT]

Originally Posted by PaleMelanesian

Then you cruise along with the lightest touch you can, or pulse-and-glide so it's always either running in the efficient heavy-load mode or just ticking over while coasting.

I found good results by doing something similar.
http://ecomodder.com/forum/showthrea...ide-35486.html

[David Philips]

In years past when cars were carbureted the trick was to accelerate as fast as possible without getting into low intake manifold vacuum where you would trip power jet enrichment. This was typically around 8 inches of mercury or higher. With a manual transmission you would also shift as early as possible to get smooth running in the successive gear.

The discussions I'm reading here have you revving much too high for optimum mileage just to get to the optimum part of the torque curve.

I used to have an injected Ford 302 V-8 with a 4 speed auto and it would downshift on hill when the vacuum dropped to 8 inches to avoid power enrichment I'm guessing.

I use a Scan Gauge but it does not have a reading that is a good proxy for throttle opening and modern car with drive by wire systems do funny things with throttle openings that are not linear in response to throttle travel.

This is a a good question to explore. My inclination is to install a vacuum gauge, use the 8 inches of mercury floor for maximum throttle and shift as early as possible. Accelerate in this way until you reach your desired cruise speed.

[JockoT]

Originally Posted by David Philips

I use a Scan Gauge but it does not have a reading that is a good proxy for throttle opening

My ScanGauge E shows both Throttle Position Sensor information and Manifold Absolute Pressure. Is the MAP not just another form of Vacuum readout?

[ecocruze]

I have been going strictly by vacuum gauge lately. For my 55 mph zone. I have been running it up to 62 mph on the slight downgrades. Then down as low as 52 usually due to the next incline. Vacuum I do my best to keep right at 5 during acceleration. Started trying this out due to some cooler weather bringing down this routes mpg. Trying this bumped me back up to 52.6mpg vs 50-51 that I was consistently getting with weather under 50°. Vacuum is good lol