[premier]

I was just reading the latest issue of the Bike magazine and an article about MV agusta F4R 312. It said that they've toned down the motor braking by making one cylinder's "compression pressure" zero when rolling off the throttle. I have no idea what that means and I don't know how to translate these terms, but I guess some of you know better.

We have fairly good tools (tuneboy) to fiddle with these things. So could something similar be done with tuneboy? I'm thinking speedy could definitely use a little softer motor brake.

 

[dr_gallup]

I don't know what MV is doing but maybe they are keeping one cylinder's valves open so there is no compression. Not something we could do. You could try increasing your idle speed a little with the tuneboy. If you added some flywheel weight that would decrease engine braking but also slow acceleration so I wouldn't recommend that approach unless you plan on dirt tracking speedy.

BTW, I was searching for more info on this and the Cycle World test just says it has a slipper clutch.
http://www.cycleworld.com/article.asp?section_id=3&article_id=338

 

[premier]

It propably has both? I doubt they just made up something like that ;D

I know speedy has been programmed so that when you roll off the throttle it does so gradually to smoothen things up. How is this done? Is it in tuning or throttle mechanism? If one could adjust it, it might solve the "problem".

 

[HarriS]

I don't know if there is any such feature in the S3. The butterflies are with direct cable operation. When you shut the throttle, it is shut for good. There is no air bypass or anything. Tuning won't help engine braking if the engine doesn't get any air to burn any fuel.

It could somewhat be done with the idle stepper motor but that feature is not adjustable with tuneboy.

 

[premier]

I remember reading somewhere that speedy don't shut the throttle all the way right away... and I've always thought that's the way it is And I still think so ;D

It must be built in the ECU? Still not adjustable with tuneboy?

 

[HarriS]

At least tuneboy does not have such an adjustment. It would be pretty complicated. RPM, throttle position, gear, clutch etc...

 

[premier]

Why would it need clutch control? Basically the tune would just override the throttle position sensor? Even though the throttle is off it would seem to the ECU that it is rolled off slowly. Can this be done in any way?

 

[Martin_R]

I remember reading somewhere that speedy don't shut the throttle all the way right away... and I've always thought that's the way it is And I still think so ;D

I remember looking at the butterflies when my airbox was off and like HarriS said, they operate direct with the throttle cable. Once you pull the butterflies shut by closing throttle no air is going past them.

So if your theory is right, I would like to know the mechanism that you think is still feeding air into the cylinders? Did I miss some ECU operated bypass hose?

 

[StuckInKansas]

I really don't mean to sound like a smartass, but I just roll the throttle off slowly when I don't want the engine braking. I like the fact that the bike has strong engine braking, I just practice good throttle control while accelerating, and decelerating. I use engine braking to slow me before a corner, then roll into a neutral throttle as I lean in, then power out. I don't need a slipper clutch, 'cause I don't bang downshifts at high revs. My $0.02...

:blah: :blah: :blah:
:slap:

 

[premier]

I remember reading somewhere that speedy don't shut the throttle all the way right away... and I've always thought that's the way it is And I still think so ;D

I remember looking at the butterflies when my airbox was off and like HarriS said, they operate direct with the throttle cable. Once you pull the butterflies shut by closing throttle no air is going past them.

So if your theory is right, I would like to know the mechanism that you think is still feeding air into the cylinders? Did I miss some ECU operated bypass hose?

OK. Just didn't think of that. No need to be a smart ass :devil:

 

[HarriS]

I really don't mean to sound like a smartass, but I just roll the throttle off slowly when I don't want the engine braking. I like the fact that the bike has strong engine braking, I just practice good throttle control while accelerating, and decelerating. I use engine braking to slow me before a corner, then roll into a neutral throttle as I lean in, then power out. I don't need a slipper clutch, 'cause I don't bang downshifts at high revs. My $0.02...

:blah: :blah: :blah:
:slap:

Correct. I don't find the S3 engine braking overly severe. Control of the wrist is needed with a powerfull engine anyway instead of just wanking the throttle like there is no tomorrow.

The softening of the engine braking could be done by holding the butterflies open with the idle stepper motor. The clutch control is needed that the engine is not screming for mercy if you pull the clutch while coasting down.

 

[cheapbastard]

I agree with Stuck, I love the engine brake'n as is. When I want to ride a good smooth pace, that engine brake'n comes in handy. Sometimes I can hit every turn without even touch'n the mushy front brakes. :violent1: ;D

 

[premier]

I'm just saying slipper clutch type of thing could be useful. Loosing traction on the rear tire isn't necessarily a good thing and it happens fairly often with this bike.

 

[kartstar]

I think it'd be fun for one of us to adapt a slipper clutch to this bike...there were some times on the track I experienced some rear wheel hop on corner entry. Granted, it was usually from a clumsy or mis-timed downshift, but the diff. between smooth and not-so-smooth is measured in milliseconds at those speeds.

For everyday street riding, the engine braking on these engines is fairly minimal at lower revs, and wouldn't really benefit from a slipper clutch or the like...there's a great "how-to" on "blipping vs. slipping" on downshifts in the July Sport Rider which should keep the rear tire from ever breaking loose on downshifts.