Running injectors above 80% duty cycle is not great. At 110% for long periods of time will cause injector to fail. You would have more motor meltdowns. I really don't think this is the problem.....
I respectfully disagree. I read once somewhere that the hp limit of these injectors is 80 hp per cylinder so at 155 ish hp the 800 E-Tec twin is at or very near the limit. And as far as meltdowns go I heard if the injectors fail they fail rich. A mechanic that works on E-Tec outboards told me this.
The injectors will continue to improve. When they first came out on the outboards there was no way they could handle the 8K rpms of a snowmobilie engine, even a 600 and now look where they are...
Fuel injectors don't have a "duty cycle". There are two design parameters that they work under: delivery volume and duration.An engineer calculates the amount of fuel required that the engine will need to run at maximum load and heaviest condions and coldest temps.ie: theoretical 10 mile pull in heavy snow with maximum weight on the machine at high speed and bitter cold.The injector has to be able to deliver this plus a comfortable safety margin more. The rail pressure determines the pressure of the spray, and the size of the body and pintle,plus the duration determine how much.The timing and duration is determined by the ecu, which calculates from the many inputs- throttle position, rpm, intake air temp,ambient air temp,exhaust temp and 02 in the stream,manifold pressure, barometric pressure,coolant temperature,vehicle speed, etc.Some or all of these may be used. The "map' is calculated so that the ecu controls the desired air fuel ratio under all conditions with the volume and duration of the injector "spray". And then there's the EPA!
I have to add something to my last post about fuel injection. I'm a newbie and ran out of room!lol I think I've got it figured out now. The injectors I was talking about are "port" injectors. As you all know,the etec uses the same principals, but rail pressure could not come close to being able to spray into the enormous heat and pressure of the combustion chamber.Nor could the standard elctromagnetic coil work fast enough to move the pintle, hence the "voice coil" technology of the etec direct injection. But someone posted that the injector will fail "rich". Never heard of this. As far as i know, a failure would not deliver fuel. If someone knows anything about this, could you please explain. Also, I've been watching the discussion about etec 800 piston failures vs the practically non existent 600 rate.I think its the heavier weight of the 800 piston. All snowmobile 2 strokes are running at maximum piston speed now and have been for quite awhile.Being as how they are practically slightly detuned race engines,they have an amazing reliability rate.They can't make the piston lighter, with the need for heat removal by the crown and ring lands. And the heavier piston has more reciprocating mass to change direction.The bigger bore piston has a larger diameter of squish,farther from the ignition source and slower flame propogation because of this,which means you have to ignite it sooner,which raises the possibility of detonation.All engines with smaller pistons have better volumetric effiency. But we don't want the added weight of more cylinders anymore. I actually am very impressed that BRP and the other manufacturers can get 150-160hp out of a 50lb chunk of aluminum with a single expansion chamber that doesn't need new pistons every weekend!And take the beating they doo in terrible conditions for thousands of miles with very little maintenance.And really,they get better fuel mileage than some road vehicles!It's a great time to be a snowmobiler! I'm sure glad Walter Kaden defected from East Germany 50 years ago!
Lots of wrong info above.
I'll try and keep this simple and brief
E-tec injectors don't operate anything like conventional fuel injectors. There are no "duty cycle" problems, and nothing ever made can run above 100% duty cycle anyway.
FWIW:
A duty cycle is the time that an entity spends in an active state as a fraction of the total time under consideration. The term is often used pertaining to electrical devices, e.g., switching power supplies.
On a conventional efi system this is when the injector is open spraying fuel. 100% duty cycle would be always open (or open 100% of the time)
E-tec injectors use a voice coil and work like a speaker, but instead of pushing a cone that moves air to make sound, they push a piston that moves fuel.
When a etec injector fails, it goes lean. If you're lucky it completely fails and doesn't move any fuel. This makes the engine run like crap, but doesn't melt a piston.
From what I've seen with the outboards a majority of the time they fail, they go lean, burn a piston, I call brp and they send a powerhead assy. I have replaced a couple injectors that where noisy, or just lean enough to cause a miss at idle.
