direct injection on a desmodue?

[zooom]

sure, but Porsches don't have THAT much chamber pressure.

but they run the pump off of the cam and the system does require to be at a minimum of 1100psi IIRC...

[chris1044]

Chris, that's for direct injection, compression ignition motors right?  Wouldn't a direct injection spark ignition motor (like virtually all new cages and many sleds use) be considerably simpler? Also, JE will make a set of pistons to spec for a pretty reasonable cost. 

The Motus motorcycle is direct injection 

I know a bunch of two stroke sleds and skis are direct injection, I wonder if any of the four strokes have gone that route yet?  Many if not most cages are now directly injected (pretty much everything from Germany and Korea anyway and almost all of the smaller stuff from the U.S. and a hodge-podge from japan).

No, not just for HCCI (direct injection compression ignition otto cycle engines).  This holds very true for spark ignition motors as well.

The motus motorcycle is DI because that's what the engine was designed as.  Taking a non-DI engine and simply converting it isn't as simple as some are making it out to be on here.  So we're all on the same page, Direct injection is the technology that sprays the fuel directly into the cylinder, unlike port injection which sprays it onto the back of the intake valve. 

When an engine is designed, port or direct injection, the combustion chamber is designed to work with the fuel atomization that is going to occur because of the injector location/engine air flow/etc.  The cylinder swirl/tumble is something that is carefully designed into an engine and helps assist fuel atomization on port injection engines.  With direct injection you don't have that luxury, so the injector spray pattern becomes far more crucial.  This is part of the reason injection pressures are so high, but it's also the reason why the injector location/combustion chamber design becomes so crucial - to ensure you get the correct flame fromt propegation across the cylinder during a combustion event.

Additional issues arise when trying to adapt this to an air-cooled engine (assuming that's what the original post was intended for).  For starters, you're removing metal from the cylinder head, which acts as a crucial heat-sink for cylinder cooling.  Next, injector location may be ideal in a location that has oil flowing through it, or very close to a valve which can negate cooling of that valve.  There are all kinds of other things that should be considered with something like this....and again, IMO it's not worth the time unless you've got parts/$$ lying around to throw away, essentially.

[Drunken Monkey]

Both MotoGP and WSBK rules don't allow for DI (either through limits on fuel pressure, or actually saying 'no DI allowed') , so that's one problem.

The combustion chamber shape is another.

The final one is I don't think DI actually gets you much in the way of additional performance when you ignore emissions.

Basically it's great if you want a high perf engine that still passes emissions tests. But if you don't care about emissions (coughLikeMecough) you can get high power by simply tuning your engine to be 'dirtier'.

[Dirty Duc]

These guys will supply OEM systems (no sales to the public), using Siemens ECUs.  http://www.synerject.com/di.html

After looking at some other DI engines, I don't think that the Ducati combustion chamber is inappropriately shaped (Mazda is a pent-roof shape, Ducs are hemi-ish).  It might not be optimized, but it should work.

I do agree that on a naturally aspirated Otto-cycle engine, DI does not do much (if anything) for performance.  It should improve efficiency (mpg) and other changes then available could improve performance.

I didn't see in the SBK rules where DI was banned, nor did I see a maximum fuel pressure like in MotoGP 

[bikepilot]

Even a significant improvement in mpgs is a performance improvement in my book 'cause it means you can carry less fuel for the same range = less weight and more compact bike. Seems you might also be able to get some added protection from pre-ignition withing having to use crazy cams (not that I've anything against really pointy cams) or run high octane - for example the Hyndai at 11.3:1 compression runs on 87 octane and has fairly large bores and, I assume, very mild cams.

Maybe I'll do some research and write a short article on the topic or something - if anyone happens to nail down the superbike/moto gp rules as they apply to DI that'd be a great start   

[Dirty Duc]

MotoGP does limit fuel pressure to 150psi, and I guess for SBK it depends on interpretation of a couple of lines from the 2011 rule book (in bold in context):

2.4.8.1 Carburation Instruments / Fuel Injection System
2.4.8.1.2 Carburation Instruments
Carburation instruments refers to throttle bodies and variable length intake tract
devices.
• The original homologated carburation instruments must be used unmodified.
• The use of optional homologated carburation instruments is not
allowed.
• The fuel injectors must be stock and unaltered from the original
specification and manufacture.
• The carburation instruments intake insulators may be modified.
• Bell mouths (including their fixing points) may be altered or replaced.
• Vacuum slides may be fixed in the open position
• Secondary throttle valves and shafts may be removed or fixed in the
open position and the electronics may be disconnected or removed
• Air and air/fuel mixture can go to the combustion chamber exclusively
through the throttle body butterflies.
Only for motorcycles homologated after the 1st of January 2010
• Electronically controlled throttle valves, known as 'ride-by-wire'
systems, may be used exclusively if the homologated model is
equipped with this system. Software may be modified but all safety
systems and procedures designed by the original manufacturer must
be maintained.
2.4.8.1.3 Air restrictors for 1200cc 2 cylinders
Definition : An air restrictor is a metallic device with a tract of constant controlled
section and which is placed in the induction duct between the carburation
instrument (throttle body) and the cylinder head. The length of the controlled
tract must be at least 3 mm. No air and/or air-fuel mixture to the engine must bypass
the restrictor. No carburation part (injector, needle, slide, etc) must extend
through the restrictor.

SBK rules:

MotoGP rules: