question....accelerating with manual....

when getting on highway, is slow or quick acceleration to highway speed better in your opinion?

looking forward to responses...

Quick acceleration.

Have you ever been stuck behind an idiot who doesn't know how to merge? They putter along in the merge lane going half the speed of traffic, and then they run out of room and stop, potentially causing a massive pile-up and multiple deaths.

So I would say get up to highway speed quickly, and merge. You only have so much room to do it, and that basically dictates how fast you have to accelerate. Generally, the sooner you're up to highway speed, the more options you have in case something goes wrong. You can still slow down again to merge behind someone, which might be easier than speeding up even more if you had to do that.

Ironman11142 said:

when getting on highway, is slow or quick acceleration to highway speed better in your opinion?

looking forward to responses...

Click to expand...

Mike_04GolfTDI said:

Quick acceleration.

Have you ever been stuck behind an idiot who doesn't know how to merge? They putter along in the merge lane going half the speed of traffic, and then they run out of room and stop, potentially causing a massive pile-up and multiple deaths.

So I would say get up to highway speed quickly, and merge. You only have so much room to do it, and that basically dictates how fast you have to accelerate. Generally, the sooner you're up to highway speed, the more options you have in case something goes wrong. You can still slow down again to merge behind someone, which might be easier than speeding up even more if you had to do that.

Click to expand...

Yup. Get up to the speed of traffic or a bit faster, find the hole, and merge.

Research "Pulse and Glide" and you may find the answer you were looking for.

Quick is the way to go. It exercises the engine and the engine is more efficient (more fuel converted to power) under load. Plus, you aren't "that guy" dawdling along in the merge/acceleration lane.

Guess it depends on your version and/or opinion of "better".
Better for what?
Quick is better for traffic, if there is any (usually none where I'm at typically). Also perhaps better for the occasional exercising of the turbo and engine. From an efficient analysis a engine under load is "better".
It will not net you "better" fuel mileage.

quicker and progressive shifting. As you get into higher gears, drop your shift rpm.

in my opinion.

yes...F/E

heard various theories about slow and fast acceleration vs. fuel economy

just wanted to hear some real world opinions....

personally, I like to get up tp highway speed ASAP so that engine can get to fuel sipping range quicker

Jettawreck, I don't agree. If it only takes 4-5L/100km to stay at speed, accelerating to that speed quickly (assuming no traffic lights, jams, etc. ahead) so I can cruise sooner nets a better average overall. Accelerating, even slowly, is usually 12-20 instant L/100km, so the momentary time spent at very high consumption is more than offset by reducing to steady cruise consumption sooner. As an added benefit, you prevent traffic buildup behind you by not impeding traffic that's already up to speed. It seems nobody around town knows what the tall skinny pedal is for anymore...

nkgagne said:

Jettawreck, I don't agree. If it only takes 4-5L/100km to stay at speed, accelerating to that speed quickly (assuming no traffic lights, jams, etc. ahead) so I can cruise sooner nets a better average overall. Accelerating, even slowly, is usually 12-20 instant L/100km, so the momentary time spent at very high consumption is more than offset by reducing to steady cruise consumption sooner. As an added benefit, you prevent traffic buildup behind you by not impeding traffic that's already up to speed. It seems nobody around town knows what the tall skinny pedal is for anymore...

Click to expand...

It's ok not to agree.
Years ago on this forum there was a guy that spent a lot of time logging and improving his fuel consumption. He did some tests doing calculated runs at varying rates getting up to speed with his TDI NB manual tranny. The end results were the slower runs up to speed were using less fuel over the total length of the runs.
Doesn't matter that much, drive the way you want. You won't find me getting in anybody's way.

Ironman11142 said:

heard various theories about slow and fast acceleration vs. fuel economy



just wanted to hear some real world opinions....



personally, I like to get up tp highway speed ASAP so that engine can get to fuel sipping range quicker

Click to expand...

Then you have your answer! Nail it.

I had a fuel injected motorcycle with an oem trip computer and it kept very accurate mpg I double checked frequently on paper. One of the available displays was an instant mpg readout. Years and 150k plus miles of watching the computer and I beieve a rapid acceleration anytime you want to increase speed is best for mpg. EVERY time you accelerated at ANY rate of change and the mpg took a big hit. It led me to believe that the best way to gain mpg's is to change speed rapidly and resume your desired speed.

Lots of variables. Depends on what you value most, and what the conditions are.

In Arizona, the entries to highways are like a mile long, and are typically two lanes (yes, two-lane entries) - so you can accelerate slowly without causing any problems.

Most other places - certainly on the East Coast - shorter (and single lane) entries dictate fast acceleration.

Strictly from a fuel efficiency stand-point: this is hotly debated. Again, lots of variables. Its not just a question of how rapidly to accelerate, but at what RPM's to shift.

Most will say fast acceleration is best for fuel efficiency. I remain a skeptic. Practically speaking, fast acceleration will generally entail shifting at high RPM's (above 2,500), hurting efficiency. Also, ever seen puffs of dark exhaust under heavy acceleration? That's either oil or unburnt fuel.

Very tough to gauge accurately, but I seem to end up with better MPG's when I accelerate slowly.

Floor it. It's the time to clean the plumbing... a good 3rd gear pull... check your mirrors, pick a spot, and merge in at a proper hwy speed. Then hit cruise.

CourierGuy said:

Floor it. It's the time to clean the plumbing... a good 3rd gear pull... check your mirrors, pick a spot, and merge in at a proper hwy speed. Then hit cruise.

Click to expand...

Thank you!

The faster you drive the poorer your fuel economy. It take more power to drive fast and the kinetic energy of the car increases as a square function of speed. The energy came from somewhere and it came from the fuel. You can recover some of the spent energy in acceleration if you look ahead to slow down by putting it in neutral and coasting down to a lower speed. The more you use your brakes the more energy (originally from the fuel) is wasted and the lower your mpg.

The difference is in the terminology.
Maximum economy and maximum efficiency.
Old topic, but interesting.
Low rpm, high engine load will apparently burn the least fuel getting up to "speed".
http://forums.tdiclub.com/showthread.php?t=151740&highlight=Acceleration&page=6
This is not the thread about the many tests that Ernie did that I mentioned earlier. I haven't had time to search much.

Fuel mileage. ..whatever. efficiency..WHATEVER. engine load blah blah blah. Studies. ..tests...schmests.

You're merging on a hwy!

Get up to speed. BLEND in...then pick your/a cruising speed.

CourierGuy said:

Fuel mileage. ..whatever. efficiency..WHATEVER. engine load blah blah blah. Studies. ..tests...schmests.

You're merging on a hwy!

Get up to speed. BLEND in...then pick your/a cruising speed.

Click to expand...

That's probably the best advice, if you spend most of your time at speed. Get going and settle in.
But, someone asked....

CourierGuy said:

Fuel mileage. ..whatever. efficiency..WHATEVER. engine load blah blah blah. Studies. ..tests...schmests.

You're merging on a hwy!

Get up to speed. BLEND in...then pick your/a cruising speed.

Click to expand...

I like you more every day!

You sound like my mechanic/tuner lol

JohnWilder said:

T...... You can recover some of the spent energy in acceleration if you look ahead to slow down by putting it in neutral and coasting down to a lower speed. The more you use your brakes the more energy (originally from the fuel) is wasted and the lower your mpg.

Click to expand...

I thought the trick (pulse and glide) was to coast down in gear. As long as the rpm is above idle it will use no fuel. If in neutral some fuel is used to maintain idle rpm. I am just breaking myself of the habit of putting it in neutral when coasting down to a stop.

Lol... Me too. Just started doing that on current fill up.

3turboz said:

I thought the trick (pulse and glide) was to coast down in gear. As long as the rpm is above idle it will use no fuel. If in neutral some fuel is used to maintain idle rpm. I am just breaking myself of the habit of putting it in neutral when coasting down to a stop.

Click to expand...

It sort of depends on what you are trying to do. Slow down instead of using brakes or (coast in gear) or maximize the coasting distance (neutral).
The amount of fuel used in a typical coasting/idle situation very minimal either way. Sort of like the way you choose to up to speed.
The main thing is to coast instead of burning off energy with the brakes. Anticipate conditions/traffic situations ahead of time.

"I thought the trick (pulse and glide) was to coast down in gear."

I'm not sure I understand why this is always brought up. Yes, if you coast in nuetral the engine will idle and use a LITTLE fuel. If you coast in gear the engine will use NO fuel until around the thousand rpm mark depending on the car. So, most people compare LITTLE to NO and make the leap that you''ll save fuel by using NO fuel coasting in gear. EXCEPT, coasting in gear means you can't go nearly as far which means you'd have to use the throttle to make up the difference or start coasting later. It's math, there's no way around it.

To confirm, do this. Find a modest hill with no traffic. Find a known starting point like a sign. Approach this sign at 50 MPH and take your foot off the throttle. Place something on the road at the point you have to put the clutch in. Now, return to the starting point and conduct test two. This time as you approach the starting point again at 50 MPH, slip the transmission into neutral and continue to coast down the hill. When you approach the beer bottle you set out as a marker, see if your kid brother can pick it up at that speed. Try pushing him out and see what he does. That's way more fun than this test anyway. See how much more distance you can go traveling in neutral? That's free distance minus the neglible fuel usage at idle. You determine for yourself. There's no comparison. Now, if the light turns red as you're coasting, you may as well put it in gear because now you're going to stop anyway so you might as well reduce fuel use to zero. OTOH, if you have the right set of rolling hills, you might travel 10 miles in neutral without touching the fuel but commuters to your rear may not like that.

mohawk69 said:

"I thought the trick (pulse and glide) was to coast down in gear."

I'm not sure I understand why this is always brought up. Yes, if you coast in nuetral the engine will idle and use a LITTLE fuel. If you coast in gear the engine will use NO fuel until around the thousand rpm mark depending on the car. So, most people compare LITTLE to NO and make the leap that you''ll save fuel by using NO fuel coasting in gear. EXCEPT, coasting in gear means you can't go nearly as far which means you'd have to use the throttle to make up the difference or start coasting later. It's math, there's no way around it.

Click to expand...

It's a little more Physics than just crunching numbers with mathematics.

"you'd have to use the throttle to make up for the difference" is not a catch-all. Every situation is unique, you can either:

A)Conserve momentum and coast in neutral, idling.

If you are on the highway, going downhill and expecting to go up another hill right after, this is usually the better option. You are conserving the forward momentum you worked for going up that hill you are going down. If you end up increasing speed when in neutral, you are also increasing the force of Drag [Fd], which could slow you down quicker than a combination of A and B, depending on the hill.

B)Decelerate via compression braking via coast in gear using no fuel.

If you are anticipating a stop, slow down ahead, etc in-gear will net better fuel economy results. Instead of generating [as much] heat/wasting energy via braking, you can use the engine and not burn any fuel in trade.

There may be some OEMs using that strategy now, but future iterations of Predictive [GPS-based] Cruise Control will have some of this logic and decision-making built into it on automatic/DSG models.

A lot of variables come into play, but in general I think what's going to give the best mpg is the lowest number of total engine revolutions in that distance.

You all should read this thread and watch the videos. Very interesting stuff: http://forums.tdiclub.com/showthread.php?t=335035

OP, you answered your own question correctly
The sooner you can get to sipping fuel the better, within reason.
On P@G:
If you have very few hills, it is not as much fun or profitable. If you do have some grades and bumps it is both fun and profitable. When I worked up on Mt. Rainier, I had epic coasts on the way home. I know, a bit of an extreme example