Direct Injection or Fuel Injection?

I would suspect Fuel Injection - I'm still thinking about whether Direct Injection would be any advantage (or even possible??) with an Atkinson Cycle engine?

 

It'sregular multi-port fuel injection. While direct injection can be used in Atkinson cycle engines, i think Toyota didn't use it due to frequent stop starts of the gas engine. This could lead to intake port and valve deposits, as well as emission issues. Direct inject engines tend to produce lots of particulate matter in the form of soot. Hope this helps.

 

Lexus has it. Hyundai Iconiq has it.

 

Toyota uses multi-port fuel injection on the Prius. However, Toyota doesn't use Direct Injection only engines on any of their vehicles including Lexus. They use a system call D4-S which is a hybrid Port and Direct injection. A normal 6 cylinder engine like the one found in the revised 2017 Toyota Sienna would have 12 injector instead of the 6 found on the 2016 engine. 6 injectors would be low pressure port injector used during initial start-up and under low load conditions. The high pressure injectors are used under normal idle, low load and high load conditions. Under high load conditions only the direct injectors are used in order to cool the intake charge in the combustion chamber. Subaru uses the D4-S system in the engine found on the Subary BRZ/Toyota GT86 formerly Scion FRZ. This system has the added benefit of reducing carbon build up on the back of the intake valves since gasoline still passes through them when the low pressure injectors are in use.

 

An Atkinson engine pushes the fuel/air mixture up past the intake valve into the intake manifold, so doesn't it inherently prevents carbon buildup on the backside of the intake valve?

 

In theory it could, but it could also wait until the intake valves close before injecting fuel.

Earlier direct injection engines had build up issues, but control of injector pulse timing should reduce them. The real plus of port/direct injection is reduced particulates. When enforced, EU regulations would require DI to have exhaust filters like diesels. Some port injected engines have exceeded the particulate limits in the past.

 

My understanding is that the build up occurs on the backside of intake valves as a result of "dirty" (oil vapor rich) air resulting from PCV. Because there is no gasoline to clean up the valves. Not sure how injector pulse timing would reduce such deposits??

 

Early DI designs had serious deposits. Now they don't. It could be that the PCV system is better at reclaiming oil vapor for the crankcase, or just not letting as much out.

Guess I'll put an oil catch can on any non turbo DI get though. I've put such of port injected cars in the past, and they do catch a lot of oil.

 

Another thing that Mazda does is try to get the intake valves as hot as possible to burn off the deposits.

 

How do they do that? Usually higher temperature(s) accelerates the coking of petroleum distillates...

 

13:1 Compression and 40 mpg on 87 Octane fuel? Introducing Mazda’s Skyactiv Technology


Apparently they found that too low temperatures promoted deposits.

My guess is, the coking is happening at any reasonable temperature, but at sufficiently high temperatures, it doesn't stick.

 

Thanks - very interesting!!

 

I thought that high temperatures burns valves and causes preignition.

 

The expression 'high' is entirely relative. You need a baseline for it to have any real meaning.

 

Kind of amazing what they are doing with engines these days. Still, when are we going to go away from piston engines.

 

Perhaps when we develop something better that satisfies most needs. EVs, Fuel Cells, and others are not quite there yet for most families.

JeffD

 

TOYOTA have said that the new C-HR 1.2 litre Turbo has Direct Injection - with variable valve timing which has "the ability to switch to the fuel-saving Atkinson cycle". I'm not sure if this has any similarity to the valve timing arrangement on PRIUS, or something totally new.

< New C-HR engine offers more for less >

But it's still got pistons.

 

So, what the 8NR-FTS has is wide-authority variable valve timing. Basically, at times of light load, it retards the intake camshaft (makes it open and close later than normal) to push excess air back out of the cylinder into the intake manifold.

The Prius's engine does the same thing, except it does it all the time, not just at light load.