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Old 05-07-2013, 06:19 AM   #1
the_jest OP
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Throttle sensitivity/engine braking?

I'm not sure exactly how to phrase this....

I'm a relatively new rider, and recently got a new Triumph Bonneville (no performance mods) that I've been riding a lot.

I recently borrowed a friend's standard-transmission car; I hadn't driven a stick in some time. And I was struck that in the car (a ten-year-old 3-series BMW), when I take my foot off the gas, I don't slow down all that much. I can't even engine-brake, really--downshifting alone isn't enough to slow the car to any notable amount, I have to use the brakes as well.

On the Bonnie, OTOH, I barely need to touch the brakes. Easing up on the throttle _significantly_ slows down the bike, to the extent that I can't relax my right hand at all without the bike unpleasantly slowing. This makes it very tiring, and annoying if I have a passenger, who then whomps into my back if I twitch my hand slightly.

I'm wondering if this level of throttle sensitivity (perhaps this is the wrong expression) is normal for motorcycles in general, or if it's the way my bike is adjusted, or if the car is especially light, or what.
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Old 05-07-2013, 07:30 AM   #2
Dan-M
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A twin cylinder engine will provide more engine braking than a multi of the same displacement. I don't know what RPM you cruise at but if you shift into a higher gear the braking won't be as severe. Also, make sure there is very little play in your throttle cable. A lot of slop at the throttle will make it harder to have precise control and make on / off throttle action more abrupt.
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Old 05-07-2013, 08:25 AM   #3
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In general fuel injected bikes like the modern Bonneville (love them fake carbs) will completely shut the fuel off to the engine when closing the throttle completely. The tough thing to do for the computer is to turn it back on when idle is needed to keep the engine running. That will give you a ton of jerkiness.

They have to do this for emissions and fuel economy.

You will get better at throttle control as you get used to it. There are some other methods to help, but break that bike in first and go to a Triumph forum for more information.
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Old 05-07-2013, 08:46 AM   #4
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Generally speaking something to keep in mind is the mass of the systems to the negative longitudinal force provided by engine braking.

F=ma, If the negative longitudinal force being provided by engine braking is held constant then one can see that as you increase the mass the negative acceleration (decel) must decrease in proportion to the mass. Hence why a car is not as largely affected by comparable engine braking.

This jerkiness you are feeling though can be caused by maladjustment of the following….

-Throttle cables (as stated earlier)
-Too much chain slack (check according to your owner manual)
-Your throttle hand (developed over time... practice, practice, practice)
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Old 05-07-2013, 08:57 AM   #5
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I ride a BMW 650 single and it has way more engine braking than any car that I've driven (I've mostly driven manual cars). However, I'm sure that the 3-series will engine brake quite a bit, you just have to shift into a lower gear more aggressively and not worry so much about the sounds that it makes (though be gentle on the clutch and/or blip the throttle).
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Old 05-07-2013, 10:43 AM   #6
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Don't forget there's a HUGE difference in weight between a car and a bike. So of course a bike will slow faster simply because of the difference in mass. On top of that, bikes are generally nowhere near as aerodynamic as a car, so the air resistance will also slow you much quicker than a car.
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Old 05-07-2013, 11:06 AM   #7
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One data point from the car perspective:

I have a 2005 Mustang V-6 that has the annoying feature of leaving the throttle open a bit when I let off of the gas completely. I can shift into neutral while coasting up to a red light and it will keep the RPMs somewhere between 1200 and 1800 until I come to a complete stop, then it finally drops down to 800 or so. It's a total throttle-by-wire system with no direct connection between the gas pedal and the throttle on the engine. This features is especially annoying when going down steep hills, because I don't get the engine braking that I want. At some point it will finally close the throttle and I'll get more engine braking, but I can't usually tell when it will finally "decide" to do that.

All of the bikes that I've owned recently have either been big V-twins or big singles, and they all have quite a bit of engine braking. If you don't want the engine to slow you down when you let off of the throttle, you can always pull in the clutch. I do that on occasion when I need to do something with my right hand besides hold the throttle at the right position.

When I used to ride two-stroke motorcycles, they had almost no engine braking at all. You just have to adapt to the behavior of a given motorcycle.
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Old 05-07-2013, 11:11 AM   #8
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Use the brakes to slow down. A riding school will teach you this.
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Old 05-07-2013, 11:29 AM   #9
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It's a Power:Weight ratio thing, (I THINK) The few standard cars I have driven have minimum Engine breaking effect, when compared to the KZ or Streetbob, BUT AGAIN, Think of the weight of the bikes, The aerodynamics and the Power:Weight,

Car= 3,247 Ibs / 1472kg 0.0868493994 P:W Ratio
247HP

Bonny= 451lbs/ 204kg 0.1441241685 P:W Ratio
65HP (?)
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Old 05-07-2013, 01:42 PM   #10
Neil E.
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Fuel injection sytems on cars are programmed all wrong if you are used to older vehicles. Older vehicles with carburetors generally had very good engine braking. The current systems are designed to prevent engine braking; the idea is that having no vacuum under the throttle plate reduces emissions. This pretty much eliminates one of the more useful things about having a manual transmission.

Engine braking is a good thing - it's nice that motorcycles still have it.
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Old 05-07-2013, 03:32 PM   #11
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Tell your buddy to do a compression check on his car.

Use the clutch on your bike more. I've never had a problem with snatchiness on a bike, even if it was FI. I work the friction zone of the clutch, or pull the clutch in altogether.

Ride in a taller gear.

Get a throttle lock if you want to be able to let go of the throttle grip without slowing. I use mine for momentary things all the time.
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Old 05-07-2013, 07:20 PM   #12
4TooMany
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Quote:
Originally Posted by Kommando View Post
Tell your buddy to do a compression check on his car.
Contrary to popular belief, compression is not what causes engine braking. It's vacuum. Ever ridden a two-stroke or driven a diesel? Lots of compression, but no engine braking.
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Old 05-07-2013, 11:26 PM   #13
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engine braking in cars started going away for all practical purposes, back in the late '60s and early '70s when emissions were first regulated, even with a carb, that was a vacuum operated stepper that kept throttle open slightly and released at a slower rate

to those who say to use brake, I say why, its idiotic if rolling off throttle slows you enuf, also, when you slow, you want to be in progressivly lower gears for quick acceleration in proper gear if necessary for safety

nothing like being in 4th gear as you slow to near a stop and seeing a cage approaching your rear view at a high rate of speed, no thank you, I'll be in 1st or 2nd at that point
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Old 05-08-2013, 09:45 AM   #14
Neil E.
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Quote:
Originally Posted by 4TooMany View Post
driven a diesel? Lots of compression, but no engine braking.
Not true. My previous vehicle (GMC 6.5TD) had very good engine braking. Superb drivability unlike the POS F250 gas 5.4 I have now (both with sticks).
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Old 05-08-2013, 09:49 AM   #15
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Quote:
Originally Posted by Neil E. View Post
Not true. My previous vehicle (GMC 6.5TD) had very good engine braking. Superb drivability unlike the POS F250 gas 5.4 I have now (both with sticks).
That's not from true engine braking. It's from systems they add to simulate engine braking. Do some research.

Here, scroll down to Diesel Engines: http://en.wikipedia.org/wiki/Engine_braking
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