Hey guys, this is something I never do but I see it constantly. The scenario--someone is at the track (or street) and throws their car into neutral at the end of run. Example:

[media]http://www.youtube.com/watch?v=S5Dc98d_a38 [/media]

Notice the car is completely dropped out of gear at 110 mph, lol. Doesn't this confuse the heck out of the ECU since the motor is idling but the wheel speed is still high? Just thought this would maybe cause a rough idle over time or something? Can anyone provide a more technical explanation as to why this is bad for the car? Or maybe it's not bad at all?

I feel uneasy coasting at 20 mph out of gear let alone 100. I consider it safer to always be in a gear that's appropriate for your speed. Thoughts on this?

 

The problem is not the motor, it is the danger of shift locking the rear wheels putting the car back in gear without raisingthe RPMs back up. If someone sucks so badly at driving that they coast in neutral at any moving speed, chances are they don't rev match in all situations. People like this buck the car going slow but going 100mph that is asking for a spin if the wheels arent pointed straight. In fact drifters do this on purpose to modulate the rear wheels. I've heard Americans call it clutch kicking, to let the RPMs fall and lock the wheels by releasing the clutch to lock the rear wheels through the synchro process as the drivetrain gets back up to speed.

 

Stupid.

For safety, and engine health (vaccuum cooling principles, wont get into it here), and driving properly, LEAVE it in gear.

 

Thanks Billman250, I've often wondered this as well. Strictly thinking about the end of a 1/4 mile run after you cross the line, not driving stupid on the highway like this guy.

Also to consider are differences in oil flow characteristics between the two scenarios, particularly given the 4th cylinder scoring issue and lack of 4 hole oil jet bolts on many ap1s (like mine). I take it that the engine is probably better served by leaving it in gear at higher rpms and letting them settle down as speeds drop so you have higher levels of oil flow and pressure as compared to an idle rpm setting. Ive read a few posts of guys scoring cylinders at the end of a hard run, I'm thinking they had inadequate oil flow and cooling once they dropped the rpms to idle speeds, just a guess.

 

he thinks he is saving gas by letting it drop down to idle.

 

The engine doesn't "know" if you're going 200mph and you're coasting in neutral or 5mph coating in neutral. All your motor sees is engine speed & load.

If you're going 100mph and select the wrong gear you can easily loose control of the car.

 

If its about saving fuel you should leave it in gear.
Engine braking costs 0 (zero) fuel.
Idling uses fuel.

 

Neutral is only for a stopped car, or damn close to stopped. What do they think they're driving, a soap box car???

 

I don't think its that big of a problem? worst outcome I see is oil pressure drops/water pump speed drops, but the engine is already idling so the high oil pressure isnt really needed, correct me if I'm wrong?

I think keeping it in gear + letting it wind down from 9K is worse for the engine. If I were that guy I'd go through all my gears and put it into 6th and let it cruise down from there

 

Really?

So when you let off on the gas there is 0 fuel being injected into the cylinders, really???