Highest RPM for a 696?

[thurmanjr7]

Can anyone tell me what is the highest RPM possible on a M696 without causing valve float? The 9000 limit is killing me. I would love to tune it to rev to 11-12000 for the potential power increase and just the sound of a 12000 RPM twin makes me randy. Anyone who has done this and can tell me what their results were?

[Drunken Monkey]

Valve float isn't the problem, it's *a* problem.

Bigger issues will be getting it to breathe at that RPM and the crank flying apart.

I'm also pulling this out into it's own thread, as this doesn't belong in Closed Loop ECU mods (except tangentially)

[Drunken Monkey]

This chart doesn't do a great job of showing it, but I'm guessing torque is going to take an even bigger nose dive past redline. And this chart does show that you're well past the point of peak HP.

So why rev that high unless you have a way to get it to breathe well at that RPM. And with a 2-valve motor, it's going to be pretty hard to accomplish that...

[ducej]

Valve float THE speciality of our Ducs was desmo I thought. Forced opening and closing... I agree with drunken monkey, you need air, don't worry about your valves, they will not float with higher rpm's.

[Speeddog]

A 749R has a stroke ~3mm shorter than a 696, and they redline at about 11k.
The peak power is at about 10k.

Your 696 doesn't have sufficient cylinder head airflow to make power at anywhere near that high an rpm, and likely would suffer consistent valve train failures if it did rev that high.

I see many more broken half rings on the small motors, even with the existing rev limits.

[Raux]

There is a limit based on the rods. I spoke to a well known Ducati race engine builder and we discussed this extensively.

The theoretical rpm limit to the 696 is 13375 rpm.
The 796 is 11591 rpm.
This is based on the stock rods strength.

If you get Ti rods you can go higher.

To get more air into the cylinder at those higher RPMs you'll have to open up the throttle bodies, work the cam and a get more volume in the airbox.

The valves themselves are the largest they can be for the cylinder size, anything larger will actually hurt.

[Goat_Herder]

I don't know much about all the technical stuff and RPM.  But if you are looking to rev higher to get more HP out of the bike, you might just have the wrong bike to start with.  You need a bigger bike (796/1100) or a different bike (Inline 4s).

[thought]

I don't know much about all the technical stuff and RPM.  But if you are looking to rev higher to get more HP out of the bike, you might just have the wrong bike to start with.  You need a bigger bike (796/1100) or a different bike (Inline 4s).

or a 4v duc...  but yeah, from what i understand... anything over 9k on a 2v duc basically just burns gas and makes a lot of noise with no real other effect.

i know some people raise the rev limiter so it's not such a hard cut off for track use, but again, it's not for power.

[ChrisH]

Agreed with the group. You'd need to find cams that made power that high, you'd likely be looking at porting and polishing, and then you'd be dealing with tuning. Is it possible? Sure. Is there a solution that is ready made to get you there? hell no.

[thurmanjr7]

I appreciate all the helpful information, it would be fun to do something no one has apparently done before. Head work, a cam, bigger injectors and throttle bodies seems like a small price to pay for a one of a kind duc. I feel 12000 is a bit optimistic but even 10500 would be cool. I need to do more research on 2 valve motors for how much they can handle.

[thurmanjr7]

or a 4v duc...  but yeah, from what i understand... anything over 9k on a 2v duc basically just burns gas and makes a lot of noise with no real other effect.

i know some people raise the rev limiter so it's not such a hard cut off for track use, but again, it's not for power.

I would be ok if it just maintained peak power for longer. If you get the torque curve falloff to match the increase in rpm that would be ideal.

[Raux]

I would be ok if it just maintained peak power for longer. If you get the torque curve falloff to match the increase in rpm that would be ideal.

i think if you were to really open up the throttle bodies and airbox you would get the high rpm but might lose some of that low tq. but it's a 696. it's all after 6k anyway. put a lightweight flywheel and spin it faster to that high rpm hit.

[Speeddog]

696 has 45mm diameter throttle bodies.

Same as many other Duc motors, like my S4, for example.
It's 30% bigger motor, and makes ~100HP at 9000rpm.

Throttle body isn't holding that 696 back.

[thurmanjr7]

i think if you were to really open up the throttle bodies and airbox you would get the high rpm but might lose some of that low tq. but it's a 696. it's all after 6k anyway. put a lightweight flywheel and spin it faster to that high rpm hit.

Haha so true, I never have my bike under 4k and if I am running it's never under 6k. That's why I wish there was more than 3k  to play with.

[thurmanjr7]

696 has 45mm diameter throttle bodies.

Same as many other Duc motors, like my S4, for example.
It's 30% bigger motor, and makes ~100HP at 9000rpm.

Throttle body isn't holding that 696 back.

The only thing a larger Throttle body is gonna do is allow more air for my high rpm desires, 45 is plenty for my 9000 rpm motor but I might need to step to a 54mm ish to obtain any power from the deal.