Another stupid question - engine braking

[boomer]

I love engine breaking!. Compression locking changing from 3rd to 2nd at high rpm locks up the rear wheel nicely and gives a good wiggle before throwing it in to the corner.

Im the same although i fear one day that wiggle won't be a wiggle, it's very addictive

I find that i'm staying high in the revs all the time and only use engine braking, unless i have to come to a sudden halt. This is a worry sometimes when i've got someone following and they dont see my tail light also i'm wondering if it adds greater strain to the engine?

[Motu]

Na, Bike g/box's are constant mesh. This is bike talk for sequential. As in the gearboxes that touring car drivers rave about. Bikes have had em for years.
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Just about every gearbox...bike,car or truck has been constant mesh since atleast the 30s.The sliding dog on a car gearbox has the syncromesh as well.A truck gearbox is more similar to a bike 'box,using toothed sliding dogs.Sequental is just the shifting mechanism,bikes use a drum or plate and have to go through each gear in order,rather slow...but an ''H'' pattern is hard to use on a bike.

[Lazy7]

yeap. its not hard changing gear clutchless on a car...

infact my master cylinder went on an old mini i had, drove it around for about a week before i buggered the gearbox with all the starting from stopped gave it too much of a hard time.

have yet to try it on a bike though

[terbang]

Brakes are primarily for braking and engines are primarily for accelerating.
Approaching a corner I use the brakes to slow down whilst shifting down to arrange my RPM correctly to maintain and eventually power me out of the corner at the appropriate time with as much grunt as required.
Too higher gear and you open the tap and it wont accelerate out (everyone else just sails past or runs up yer ass) and too lower gear and it just revvs the shit out of it, makes a lot of noise (and you are now alone on the road) so the skill on down shifting into a corner is based around an eventual power application. The advantage (or byproduct) of shifting down is that you can also use some engine braking advantage and this can be a nice bonus. On a lot of bikes this can be an excessive amount that will give you a rear wheel lock up, hence the slipper clutches that are fitted to such types. On a Sprot bike its your front wheel that does all the retarding in a straight line and the back brake and engine braking augments it on a lightening (as in getting light on the road) rear wheel. However it is a common technique to use the braking effect (brake and/or engine) on the rear wheel to assist with stability and directional control during high speed turn entries or, in some cases, patching up an over-cooked turn whilst retaining a suitable lean angle as the front brake will tend to stand you up. Tricky stuff using any sort of a brake whilst leaned over in a turn and often ends in tears..So I gues the moral of the story, or the safest option is to get it all done (or at least the majority of it) before you roll into the corner. Somewhere around this site I see a Signature (can't remember where) that says something like "Enter the corners slow and exit fast" which makes good sound sense to a person that rides on the public roads. As always the application of any sort of rear wheel braking needs to be treated with respect as it has similar effect to that of pulling only the handbrake on your car and if mishandled the rear wheel will loose grip (skidding wheels have less friction) and eventually attempt to overtake the front.

[Zed]

I engine brake too, sometimes in conjunction with the brakes to slow down extra quick, the bike can certainly handle it. I'm of the opinion that every bike/car should be given stick from time to time, it's good for them, so accelerate & decelerate as much as you like, just keep it well maintained! :spudguita

[terbang]

I find that i'm staying high in the revs all the time and only use engine braking, also i'm wondering if it adds greater strain to the engine?

I think that our engines are robust enough to take a fair bit of a hammering on engine braking and that we can't be doing too much harm though I do tend to think that they were designed to be engines (to drive) rather than compressors (to be driven). The only arguement I have ever heard against engine braking was a few years back, in a totally different life, when I was being taught aerobatics in a non supercharged piston engine aircraft (CT4 airtrainer) we were taught to avoid diving at high speed with the throttle closed for engine considerations. The first being that the aircooled engines rapidly cooled with the high air flow and the cylinder heads cracked and the second was that being normally aspirated we would end up with internal damage due to the propellor now driving the engine rather than the other way around. It was explained like this: The intake butterflys are closed with a closed throttle and as a piston moves down the cylinder being driven by the propellor (or rear wheel) on an induction stroke it was creating a very low pressure area in the cylinder due to the limited amount of air allowed to enter through the intake. The induction process is now lagging behind the machinery and when the piston reciprocates and is being driven back up the cylinder on the compression stroke, initially unimpeded in a partial vacuum (for want of a better word), it then slamms into a partial charge mid stroke thus creating excessive, outside of design, loads on the piston and crank assembly (all at the wrong place) thus leading to possible damage. Quite different technology between Aero engines and Motorcycle engines I am sure though basic piston engine principles remain. All this aside I havn't heard of any bike engines failing during overrun or engine braking. Does anyone know anything about those engine brakes on trucks and how they work?

[Aiolos]

http://or.essortment.com/jakebraketruck_raio.htm

diesels control fuel flow, not air, so they dont create the low pressure terbang mentioned. thats what the engine brake does.



my keyboard is busted. on screen keyboards suck.

[Blairos]

As a rider of a V-twin, I have discovered the engine braking capabilities are quite pronounced - from what I read here I am tending towards a technique "tweak" by combining both the engine braking and a good moderate application of Front (with a lesser rear input too)

I guess the only way for me to discover, is to get out there and try it on a decent ride (away from too much traffic lol)

[Motu]

Does anyone know anything about those engine brakes on trucks and how they work?

There are 2 types of ''engine brake'' for diesels.Basic OE engine brakes are just a butterfly or gate valve in the exhaust pipe,the engine just works against the pressure,pretty useless,but does help a little bit.

The one you hear on the big rigs is the Jacobs Brake.On the overrun the piston comes up on the force of compression and is slowed down...unfortunatly this is negated as the piston goes over TDC and the force is released,pushing the piston down the cyl again.What the ''Jake Brake'' does is lift the exhaust valve just before TDC,so the piston is slowed by the effect of coming up on compression,but doesn't get bounced over down the otherside.

They are very powerful,and on an unladen tractor unit can lock the wheels and stall the engine (We were told never to use the brake in that condition,but it needed to be proved eh?) They have throttle and clutch switches - you can hear a driver double clutching sometimes with the Jake Brake on,this acts like a clutch brake and slows the engine quicker on shifts.

[pritch]

(We were told never to use the brake in that condition,but it needed to be proved eh?)

Bling for spelling "eh" right and not using one of the many strange variations seen around KB.

I thought I might try a little positive reinforcement.

[TLDV8]

ahhh got to love the high compression and rev limeter, will just lock the rear and save the engine

Good luck with relying on that theory...no rev limiter will stop the exhaust valves floating risking the pistons hitting them with excessive revs on downshifting... You might want to fit a US$1800 slipper clutch ASAP.

*
Anyone locking the rear wheel on a regular basis might want to practise clutch control otherwise it will only be a matter of time before being caught out in the wet (imho) (fwiw)..... i base that off riding a 13.7/1 comp V-Twin with a 120 rear tyre and conventional clutch.I think most people will be more than aware of what happens if the rear tyre locks and you are not straight in the wet.Chattering the rear in the dry can also be amusing come time to turn in.

[Motu]

i base that off riding a 13.7/1 comp V-Twin with a 120 rear tyre and conventional clutch.:

Apart from the comp,that was my XLV750,and with shaft drive too.With my chop it down and toss it in riding style I got some serious step out on corner entry.With better tyres and an awareness of what it was doing the tyres showed extreme braking wear on the side knobs...you've got to get back on the gas early with these bikes.