Drafting, it puts me beside myself with laughter

[NoCO2]

So yesterday and today were my first real treks on the freeway, being fuel conscious. So the first thing I did was set cruise control to 60mph, great, no one gets mad at me for going to slow and I can keep the RPMs down pretty low. Next step, lets try seeing what sort of hill I need to maintain this speed while in Neutral, sweet I don't need that much of a grade and I start to actually accelerate just a little.

The next step is what put me almost in tears with laughter. I decided to try getting behind a semi-truck and playing with a little drafting. Ok, so 100 ft behind the semi. Seems ok, but there is a little turbulence so lets try moving up as bit. Ok, now we're at 50 ft, cruising at about 65 mph and the RPMs are the same...hm, I wonder why that is, must be the minimum speed for the engine at 65 while still in gear...we can fix this. Put the car in neutral, o ok, this works, I'm not slowing down, must not have any wind resistance at this distance....wait...what the heck, I'm accelerating , but I'm in neutral, how does that work...yea, road is flat...hehehe, there goes mile number 2 in neutral behind truck...and mile 3...awww shucks the truck is pulling off the freeway...but wow, I just cruised 3 miles in neutral at 65-70 mph, actually having to tap the brakes occasionally because I was apparently being sucked into the truck

Now, just for the record, I know that being that close to a semi is not very safe, however there wasn't any traffic so I felt confident there wouldn't be any sudden changes in driving behaviour from the driver since I had observed him for a bit at 100ft and he seemed pretty steady. BUT I DON'T RECOMMEND ANYONE TRY THIS. But I have to say, it was really very strange and very very entertaining to say the least...

I now have 420 miles on my trip odometer and still 1/4 of a tank to go. I'm usually out of fuel by 380-400...sweet.

[Frank Lee]

You'll reduce your FE with two in the car!

[brucepick]

Good going.
Man, I wish my box on wheels that I call a car would coast like that.

[trebuchet03]

Ok, now we're at 50 ft, cruising at about 65 mph and the RPMs are the same...hm, I wonder why that is,

Because drafting is not the same as changing your transmission gearing Drafting reduces aero load

[3lr]

Originally Posted by NoCO2

I was apparently being sucked into the truck

Hello NoCO2,

my Jetta weighs in around 1900 lbs, tires are filled with 40 psi and i hug them rigs MUCH closer that you do
yet i still have to motor!
were talking on the flats between 60 and 70mph
What is your your secret???

that really sucks

[max_frontal_area]

Originally Posted by NoCO2

So yesterday and today were my first real treks on the freeway, being fuel conscious. So the first thing I did was set cruise control to 60mph, great, no one gets mad at me for going to slow and I can keep the RPMs down pretty low. Next step, lets try seeing what sort of hill I need to maintain this speed while in Neutral, sweet I don't need that much of a grade and I start to actually accelerate just a little.

The next step is what put me almost in tears with laughter. I decided to try getting behind a semi-truck and playing with a little drafting. Ok, so 100 ft behind the semi. Seems ok, but there is a little turbulence so lets try moving up as bit. Ok, now we're at 50 ft, cruising at about 65 mph and the RPMs are the same...hm, I wonder why that is, must be the minimum speed for the engine at 65 while still in gear...we can fix this. Put the car in neutral, o ok, this works, I'm not slowing down, must not have any wind resistance at this distance....wait...what the heck, I'm accelerating , but I'm in neutral, how does that work...yea, road is flat...hehehe, there goes mile number 2 in neutral behind truck...and mile 3...awww shucks the truck is pulling off the freeway...but wow, I just cruised 3 miles in neutral at 65-70 mph, actually having to tap the brakes occasionally because I was apparently being sucked into the truck

Now, just for the record, I know that being that close to a semi is not very safe, however there wasn't any traffic so I felt confident there wouldn't be any sudden changes in driving behaviour from the driver since I had observed him for a bit at 100ft and he seemed pretty steady. BUT I DON'T RECOMMEND ANYONE TRY THIS. But I have to say, it was really very strange and very very entertaining to say the least...

I now have 420 miles on my trip odometer and still 1/4 of a tank to go. I'm usually out of fuel by 380-400...sweet.

which vehicle did this happen in? any mods done to it?

[kach22i]

Originally Posted by NoCO2

Put the car in neutral, o ok, this works, I'm not slowing down, must not have any wind resistance at this distance....wait...what the heck, I'm accelerating , but I'm in neutral

You list three cars, which one were you in?

Not to call you a liar, but I smell fish.

You need to video this if you can ever get these same circumstances again.

I'm still scratching my head.

[Old Mechanic]

The OP is from 2-12-2008! 3.5 years ago, LOL. If you get the right conditions it takes very little grade to maintain speed if you are in the perfect draft. I know my Altima will coast and accelerate on the downhill parts of the Interstate here at 65-70 MPH. The CVT goes into neutral and the mileage goes through the roof. Shifting back into drive at 70 is no problem. Revs stay low until you give it some gas and when everything matches the torque converter locks up and you can accelerate smoothly.

Divide your speed by 16 and the mulitply it by 60 and you have your MPG. Example 64MPH divided by 16 is 4, times 60 is 240 MPG coasting at 64 MPH with no AC.

regards
Mech

[kach22i]

Originally Posted by Old Mechanic

The OP is from 2-12-2008! 3.5 years ago, LOL.

I wonder why Full_Frontal_Area dug this one up?

I'll try a PM to the original poster, maybe we can get some more good stories. I want to believe it's true, just need some documentation.

[max_frontal_area]

indeed, oooooooold post. i thought it was BS, a myth. drafting without motoring, cause i know i HAVE tried. 2000# car with skinny tires on HOT days drafting behind semis real close, close enough actually that i could roll down the window reach out and grab the trailers bumper. perhaps i shoulda just done that and quit trying so hard?!

regardless, this summer i did it. totally by accident. a truly surreal experience.
3000# car, not so skinny tires with the engine idling. a bit of traffic that day,
i had to motor 3x because the Ryder box van which i was rolling behind had stepped
on the brakes. Correspondigly i had to react which rapidly increased distance between us.
And lemme tell you this was a gig i did not want to loose - considering having chased
after this elusive or should i say allusive "connection" for such a long time.

mind you there was a flatbed trailer between the truck and my vehicle, making for a less than perfect draft especially comparing to my than standard, highly vaseline reliant, shall i say hookups?!

High desert <3000' hot-n-dry (100*F+) late afternoon midsummer day.
flat road except for a slight 1/4 mile downhill at the beginning of the run.
very slight tailwind <5mph.

the journey lasted for FOUR MILES, its endurance was spent in disbelief