Why is the engine braking so modest?
Grand HDF Member
Joined: May 2008
Posts: 4,624
Likes: 189
From: Newcastle, Ca.
After installing cams and a 2n1, "compression braking" increased and works very well when descending when riding in the hills, mountains and, if necessary, prior to entering turns. This surprised me, in a good way. Very useful.
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Stellar HDF Member
Joined: Feb 2014
Posts: 2,710
Likes: 528
From: Lethbridge, Alberta Canada
Jim G
Tourer
Joined: Apr 2014
Posts: 288
Likes: 3
From: UK
Things that affect engine braking for the same engine size.
1) compression ratio (lower compression less braking)
2) gear ratios (taller gears men less braking)
3) idle speed (higher idle speed less braking)
4) bike weight (heavier bike, more momentum less braking)
1) compression ratio (lower compression less braking)
2) gear ratios (taller gears men less braking)
3) idle speed (higher idle speed less braking)
4) bike weight (heavier bike, more momentum less braking)
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Stellar HDF Member
Joined: Feb 2014
Posts: 2,710
Likes: 528
From: Lethbridge, Alberta Canada
- Compression ratio on my Stage 4 103 Breakout is higher (the difference is so great that it was actually RECOMMENDED that the VTX be run on 89 octane fuel)
- gearing IS taller on my Breakout
- Idle speed is virtually identical (1000 on Breakout versus 950 on VTX)
- The Breakout is lighter in weight by over 75 lb (100 lb if both bikes were stock, but the VTX had been lightened by about 25 lb)
So, the Breakout has:
- 1 factor that reduces engine braking (taller gearing)
- 1 factor that is neutral (idle speed)
- 2 factors that would predict MORE engine braking (higher compression, lighter weight)
And, here is a final zinger: The flywheel assembly on the VTX is the heaviest one that Honda has ever put in a motorcycle.
Intriguing, isn't it?
Jim G
Stellar HDF Member
Joined: Jan 2013
Posts: 3,466
Likes: 425
From: Illinois
That flywheel weight may be your answer-the rear tire has to
'push" that flywheel against it's own inertia,and the Harley wheel is much lighter.Easier to push.
'push" that flywheel against it's own inertia,and the Harley wheel is much lighter.Easier to push.
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Stellar HDF Member
Joined: Feb 2014
Posts: 2,710
Likes: 528
From: Lethbridge, Alberta Canada
On the other hand, my rear wheel is undoubtedly heavier than the one on the Honda. I have the HD chrome Turbine wheel set, and that Turbine wheel even LOOKS heavy! The heavier rear wheel would make the Breakout more resistant to changing engine rpm with the throttle closed.
Jim G
Last edited by JimGnitecki; Jun 17, 2014 at 11:44 AM.
