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Discussion Starter · #1 ·
For all you veteran riders / engineers out there...

I've only ridden a couple different bikes, so I don't have a whole lot of experience to judge.

I understand the bit about slowing a bike down with downshifting. But I find that even if I let off the throttle without shifting, the bike slows down quite a bit on its own. Is this pretty standard? I've seen some comments that the R3 has particularly strong engine braking.

So engine braking just comes from the cylinders trying to work against a closed air intake? Is the level of braking something that can be adjusted? Or I imagine it's a pretty integral part of the engine design?

What is it about motorcycle engines that make them so much different than car engines? Is it just engine volume relative to the weight of the vehicle? On my stick shift car, laying off the throttle just lets me cruise easily, without any feeling of engine braking.
 

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The engine is just an air pump when you take fuel out of the equation - At closed throttle,you have created, for purposes of this discussion, a blocked inlet to the air pump. During the intake stroke, the piston is now pulling against a greater vaccum that it would if throttle plate were open, slowing the engine much faster than mechanical friction alone would. All internal combustion engines will 'brake' to some extent. Commonly called "jake brake" on a semi-.

For bikes, engine braking depends on the engine design itself (big twins tend to have more than an I4, but big twins usually have more displacement, too), compression ratio, how good the rings are, whether or not the bike has a slipper clutch, ECU capabilities, etc. Some of the electronics packages out there include the ability to adjust level of engine braking, but not on the R3 that I am aware of. My untested theory is that it's more noticeable on a bike because you have less inertia to overcome than you would in the family truckster.
 

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I wouldn't call the R3's engine breaking out of line as far as motorcycles are concerned. To me if feels about the same as the ninja 250 I had before it. I used to have a VTX1300 and like Stirz mentioned being a big v twin it's engine breaking was much more pronounced.
 

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Interesting, I also thought that this bike had a lot of engine brake. I've got a few miles on a harley fatboy but it didn't feel as pronounced as the R3. Just a few days ago I went from 3rd gear to 2nd gear and my back tire started going to the front right before I was going to turn. It seems to be harsh when I release the clutch sometimes to a lower gear. Any explanation as to why my back tire suddenly wants to become my front tire?
 

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Sounds like your not matching the engine revs to your speed,blip the throttle between gears when changing down.
 

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Sounds like your not matching the engine revs to your speed,blip the throttle between gears when changing down.
That or slowly releasing the clutch will prevent the rear from locking up. Also make sure you aren't down shifting into a lower gear at too high of a speed for that gear.
 

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Sounds like your not matching the engine revs to your speed,blip the throttle between gears when changing down.
I was going to say that, I agree with Tal.
That or slowly releasing the clutch will prevent the rear from locking up. Also make sure you aren't down shifting into a lower gear at too high of a speed for that gear.
This too!
Engine braking? Try riding a Ninja 650 and that thumping Twin and you will never say the R3 has bad engine braking. This motor is pretty smooth all around.
Right? I owned a 650 and that thing engine brakes like no other lol. Actually I have heard from one other 650 owner and he said the only other bike he has owned that engine brakes worse than the 650 is a Ducati he owned.

As far as locking up the rear, its really easy to control on the R3. On the 650 however is another story lol.
 

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Discussion Starter · #9 ·
Thanks everyone for the great explanations, especially Stirz for all your good guidance along the way.

Now to get into the weeds of engine design...

So on the R3 or (fuel injected) motorcycles in general, when you lay off the throttle not only does the fuel injector stop, but the air intake gets closed off completely?
And this is why engine braking is so pronounced on a motorcycle, along with the engine displacement / motorcycle weight ratio?

As best as I understand my carbuerated Ford V8, all it's got is a choke plate. Once that is open, there's nothing to regulate incoming air flow. Power to the engine is therefore determined only by how much gas is squirted in by the throttle cable, or drawn into the cylinders by the venturi effect. So no closure of the air intake, and thus less engine braking?

Half the fun of cars or bikes is understanding the mechanics, at least for me.
 

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Thanks everyone for the great explanations, especially Stirz for all your good guidance along the way.

Now to get into the weeds of engine design...

So on the R3 or (fuel injected) motorcycles in general, when you lay off the throttle not only does the fuel injector stop, but the air intake gets closed off completely?
And this is why engine braking is so pronounced on a motorcycle, along with the engine displacement / motorcycle weight ratio?

As best as I understand my carbuerated Ford V8, all it's got is a choke plate. Once that is open, there's nothing to regulate incoming air flow. Power to the engine is therefore determined only by how much gas is squirted in by the throttle cable, or drawn into the cylinders by the venturi effect. So no closure of the air intake, and thus less engine braking?

Half the fun of cars or bikes is understanding the mechanics, at least for me.
Your Ford engine has a throttle plate the same as your bike. All common automotive gas engines regulate the engine via a throttle plate as well by metering the fuel. Now a Diesel engine works differently. It runs unthrottled for the most part being controlled by the amount of fuel injected. You might enjoy reading more about how engines work by doing a Google search. There are tons of interesting articles explaining the basics of engines.

Marc
 

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I realize you look real cool slamming the gear shift backwards at 10,000 RPM but remember, Brake pads are a lot cheaper than clutches and the labor to install them... as well as other components ?
 

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Engine design surely plays a big part in engine braking but I think it's the gearing that makes the most difference. My 1400 cc L4 will take low speed corners smoothly in either 1st or second. My 1098 Ducati V twin likes second. The r3 likes the same corner in 3rd.
 

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Coming from relatively high compression cars, the engine braking isn't too much of a surprise. I had a E83 X3 and currently am "borrowing" a E90 325i which have 10,5 and 10,7 respectively and especially the latter, it slows right down if you close the throttle.

Under normal riding, I let the engine braking do its work in its "current" gear, gently tap the brake so the car behind knows I'm slowing, change down/rev-match to 3rd @ 50-55 km/h, let it drag further down to ca. 20-25km/h, and then clutch in and stop. Basically I still consider brakes the main source of deceleration, but take advantage of the engine braking as reasonable.
 

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I don't have my Ninja 250 for a while now, but I think the R3 engine breaking might be a little stronger, but it's just fine, dare I say perfect. I had a vehicle once with minimal engine breaking, and honestly it's really annoying to have to touch the breaks all the time.

DFCO (dynamic fuel cut-off) plays a role too. My inline-6 Z4 has mean engine braking until a certain minimum rpm where it starts feeding fuel in again (lest you press the clutch and the engine dies -- the classic Ninja 300 issue which was eventually resolved with new ECU programming). The switch-over is quite obvious on the Z4. Suspicion is that dfco is actually disabled on the N300 now.
 
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