How To: Accelerate?

[96CX]

After converting minutes to seconds so that my units match....

Revving it up to 35mph in 2nd uses 131.25 revolutions, while slogging it out only uses 90.

[Occasionally6]

You also need engine load in there somewhere. The total engine revolutions isn't much of the story.

[96CX]

I'm pretty sure I'm close to a 80-90% load in both scenarios. Accelerating as fast as the engine will allow, without overrichening the A/F mix by too much throttle. Then again, all this is seat of my pants, since I have no gauges...

[PaleMelanesian]

The real magic comes in the glide. Any reasonable acceleration method will get you 90+% of the way there. By reasonable I mean not actually flooring it and not revving past 3000 or so. Focus on "no brakes" and coasting all the time. What I mean is, my standard driving mode is neutral EOC, only starting the engine and engaging the gears when I need more speed and then I'm back to coasting.

[ever_green]

it doesn't matter how you accelerate as long as its followed by a good period of coasting.

Usually the harder I accelerate the longer I coast after. I have found no significant difference from using say 60% engine load to accelerate to cruising speed on highway than 80-90%.

in your case, if the parking lot is fairly short and you have to come to a stop early on again, I would use as little throttle as possible. But if you are accelerating on a long open road with no stops any time soon use as much throttle without inducing open loop enrichment (this varies with cars).

[TheManVan]

So driving like a grandma is not always the most fuel efficient? So with a standard tranny its ok to pull hard up to 2500-3500 rpm depending on the Fuel enrichment mapping on you car? In other words rpms kill mpg not engine load?
sorry for all the questions, but I am a newbie at this stuff :P

[BV1]

Had to chime in, sorry for my first post being in mid thread, but as a instructor and a tuner this is something I get asked alot.

The short an simple answer is that disregarding air resistance or losses due to great average speed, the ideal eco-acceleration should be the maximum acceleration available prior to entering open loop, or pulling ignition timing due to knock, in the highest gear possible.

I tend to accelerate under heavy load in 5th gear (as soon as its reasonable to take), but reduce the acceleration enough to stay in closed loop.

This minimizes frictional losses in the engine by using the piston stroke, valve duration and pumping losses to their maximum ability and since rotational losses are not load dependent the greater power output increases the efficiency of each engine power stroke by reducing the loss %.

Its the same idea as having to withdraw $400 from a ATM, would you do it all in one hit or in 10 little hits? Your gonna get dinged $1.00 for each transaction so might as well minimize the number of transactions by maximizing the available amount in each one.

Its the same reason why the same engine in a turbo diesel variation can get better mileage then in that engine in non turbo diesel variation. The extra RPM needed in the non turbo causes unnecessary frictional losses.

Hope that helps,

Steve

[TheManVan]

ok cool !

[PaleMelanesian]

I concur, but with a clarification. High throttle is good for acceleration, but as BV1 stated, low rpm. Higher rpm will cost you more. I usually limit my rpm to about 2200 max, except when I need the extra power (freeway merge or something like that). Even then, I'll push it to 3000 but not much more.

... except when my speed forces me to rev higher thanks to Honda's poorly chosen gear ratios. Limiting myself to 2200 rpm requires keeping my speed below 48 mph. Faster than that and the revs just keep climbing.

[user removed]

At higher speeds I learned that you can accelerate very gradually with practically no loss in mileage, then glide and your mileage skyrockets. I'm not so sure it would work well on perfectly flat roads but if there is any elevation change then you can use the technique to climb the upslope and then greatly extend your glide on the downslope.

To the east of my home the greatest grades are overpasses, but even those grades that are less than half of an overpass offer opportunities to stay close to the same speed while pulse and gliding. I also look for drafting opportunities when traffic is so heavy that you have no choice, like it is regularly around here.

I'll stay in the right lane and if there is traffic entering the Interstate, in most cases I stay in the right lane and coast, even up the overpass to allow the traffic to merge safely. I might move over, but in heavy traffic here those in the left lane like to speed up to block you from being courteous and allowing those entering to merge safely, which is absolutely stupid and causes most accidents. On the Fort Eustis Interstate cloverleaf, there is one section of guardrail that is replaced almost every month due to idiots who exit at too high a speed, and those who try to move from the left lane to the exit ramp at much too high a speed, too late. You have to watch for those Morons all the time if you stay in the right lane and they don't know what a turn signal is, in many cases when I turn on miy signal the car in the lane I am trying to get into will rapidly accelerate to block me from safely changing lanes.

That may not be the case for many here, but I suspect "lane blocking" is common in higher traffic areas.

regards
Mech