curious about engine breaking 1

[rwelk]

I don't know if anyone can answer this question. But I was just curious if engine braking a car (manual transmission) has any negative effect on the motor, or gearbox?

 

[ivymike]

while decelerating. ...sure, during a short-duration braking event, but the question was about coasting (presumably for a while), not rapid decel.
* If you're going down a hill, and plan on going up the next one, then coasting in neutral will let you store energy in the vehicle on the way down to use on the way up.
* If you're going to drive up to a light and stop, you'll get better fuel economy if you idle the engine and coast a long way to the light (gradually decel) instead of running under power until the last 50 feet and engine braking + pedal braking to stop (rapid decel)...

 

[NickE]

Right mike, however if I just leave it in gear and let the momentum decay (and I can balance it with distance by gear choice) until I just have to use the brakes slightly I'll use less fuel.

(Note this isnt how I drive, just an extremely stretched rubber band of an example. Kind of like a 30profile 22" spinner.)

 

[tripleZ]

I tend to think most guys out there racing sportbikes are using a combination of engine braking and standard braking to scrub off speed. At least I do on my 600cc bike. The comment made earlier about getting off the throttle for front dip-in works. Although you shouldn't really be on the throttle until you're ready to crack it and commit to your cornering line. For those interested, books by Keith Code and Nick Ienatsch will cover this for sportriding.

As the 600's are geared lower than the literbikes, I'm generally dropping down a gear before entering the corner so that I can get the engine rev'ing higher in the sweet spot (usually 10K RPM or so). A small throttle blip is used to allow for the rev's to match. Basically you blip it high a learn to anticipate when to drop the clutch so the rev's match. I'm not fast enough or confident enough to brake right up to the apex, so I'm usually off them a bit before that. But if I'm moving in hot, I'm using both my engine (from the downshift), the front brakes, and the tires to scrub off speed. From there it's just a quick countersteer, cracking the throttle, and then rolling it on through the turn...hopefully with a knee scraping pavement. =)

For the question on over-revving, sportbikes and racers are leaning towards the slipper clutches to limit revs and avoid damage to the gearboxes. Is this what you were referring to?

I've never tried racing one of the vintage deals. That might be a fun restoration project too. Any recommended sites for info?