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June 11, 2009 10:52 p.m. ReverendDexter HalfDork

I have a buddy that likes to shift really aggressively to build up speed, then put the car in neutral and coast until he needs power again (or stops). This is his normal driving style, everywhere, all the time.

Everything in my gut tells me this is wrong and bad and evil, but for the life of me I can't remember the mechanical reason why.

I can't see it as a hypermiling technique, though it may be one, as putting the car in one gear higher and cruising at 2k in 4th to maintain speed shouldn't suck any more gas than letting the motor sit at idle. I've driven his car once, and he seemed very weirded out when I left it in gear to cruise.

Is this long-distance neutral-coasting actually bad, or am I just being overly critical?
June 11, 2009 11:00 p.m. Toyman01 Reader

I can't think of any reason it would be hard on the car. But I can't think of any reason you would drive like that either. Sounds like it wouldn't be fun to follow him on a two lane road.

I have a friend that drives like a wacko also, I just don't ride with him anymore. The older I get the more that stuff bothers me.
June 11, 2009 11:49 p.m. Trans_Maro Reader

"Granny shiftin', not double clutching like you should!"

Shawn
June 12, 2009 12:34 a.m. curtis73 Reader

If he's chasing efficiency, he's barking up the wrong throttle position. Any way you slice it, accelerating slowly saves more fuel than blasting to your target speed.

Not to mention, the aggresive shifting and acceleration are far more stressful to the engine than being "granny-like" and the constant shifting and clutch usage could dramatically reduce their life spans.

Punch your "friend" in the nuts and tell him to stop being an uneducated ricer.
June 12, 2009 5:37 a.m. foxtrapper SuperDork

I don't think it's particularly bad for the car, but it would make my tummy upset. That's almost as bad as the people with wiggly feet that are constantly on and off the gas. I need dramamine to ride with them.
June 12, 2009 8:36 a.m. dean1484 Dork

Hmmmm And how many other people drive like that normally? Putting max power through the drive line at every opportunity will shorten the life of the motor. Street cars are not designed to be driven like that. He needs to go to the track or something. What he is doing is not cool on the street. Maximum acceleration means minimum reaction time if say a kid steps off the corner, some one pulls out, one wheel hits sand. What he is doing is just stupid. Fun maybe but non the less it is by its very nature putting others at risk. I am assuming he is a young person?
June 12, 2009 9:12 a.m. 914Driver SuperDork

Coasting in neutral is illegal in any commercial vehicle. Now if you want to embarrass yourself is the Family Truckster....

My son's friend puts his Jetta in neutral to go around corners. Oy!
June 12, 2009 10:21 a.m. thedude New Reader

curtis73 wrote:

If he's chasing efficiency, he's barking up the wrong throttle position. Any way you slice it, accelerating slowly saves more fuel than blasting to your target speed.

Not to mention, the aggresive shifting and acceleration are far more stressful to the engine than being "granny-like" and the constant shifting and clutch usage could dramatically reduce their life spans.

Punch your "friend" in the nuts and tell him to stop being an uneducated ricer.

From what I understand there is a sweet spot somewhere in the speed of acceleration for optimum gas mileage. For some reason I remember something like 3/4 throttle and short shifting so that you attain your desired cruising speed quickly where you will be using least fuel and you avoid wasting time at lower speeds accelerating slowly.

Alternately, this dude is getting mega mpgs using hypermiling wizardry. http://www.metrompg.com/posts/pulse-and-glide.htm
June 12, 2009 10:28 a.m. aircooled SuperDork

He may be working off of some old assumptions. In "Oldy Tyme" days when cars had carburetors, a technique similar to that was considered efficient. The basic premise is that carburetors are rather inefficient in transition states (accelerating) and best when kept at a constant rpm. The technique was to accelerate somewhat quickly (obviously not full throttle) up to optimum cruising speed (which ideally would be around 35 mph) then cruise there. This gets you through the transition state as quickly as possible. Any coasting of course would be a bonus.

With modern time fuel injection / computer control etc. the technique is a bit silly. Coasting of course is still good (except being illegal and pissing people off of course) but I am not sure if running up to a speed and coasting with the engine on is any better than just cruising. If you can kill the engine, certainly, but that of course can be a very bad idea in modern cars.

I would guess the only advantage to accelerating at anything more than very light would be that you can get to your most efficient speed (35 I believe) quicker, put it in high gear, and stay there longer.
June 12, 2009 11:16 a.m. carguy123 Dork

The big issue of the whole technique isn't the banging thru the gears, it's the shifting to neutral and coasting up to stops, etc.

That leaves him totally unable to react in any kind of emergency situation.

You NEVER pull the car out of gear while driving, even at a light as you might as well paint a target on your side. You cannot move quickly regardless of what's happening outside your car!
June 12, 2009 11:47 a.m. laz New Reader

carguy123 wrote:

The big issue of the whole technique isn't the banging thru the gears, it's the shifting to neutral and coasting up to stops, etc.

That leaves him totally unable to react in any kind of emergency situation.

You NEVER pull the car out of gear while driving, even at a light as you might as well paint a target on your side. You cannot move quickly regardless of what's happening outside your car!

+1
June 12, 2009 2:59 p.m. Appleseed HalfDork
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Same applies to motorcycling.

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