advanced engine technics

[silver343124]

Many car engine manufactorers have many different approach to increase engine efficiency and maintain or even raise performance.
The main goals is to achieve the most perfect burning invironment, the least engine friction and the best possible termal efficiency.

The future is at piezo direct injection, solenoid intake and exhaust valves (rather than camshat), laser ignition (rather then spark plug) and of course electronic engine control.

Well piezo direct injection is allready the reality, laser ignition and solenoid valves will be reality from 5-8 years.

But at these point I will like to discuss about present technics.
VAG has FSI, which is solenoid/piezo direct injection engine with EGR and special intake plate so engine can operate under wery lean mixture at partial load.
BMW has valvetronic, whic is throttless engine, instead of it it has variabile camshaft timing and lift electronic control. The engine aslo comes with solenoid direct or manifold injection type.
Toyota, Honda uses VVTi, whic is also direct injection engine with variabile valve timing and lift electronic control.

There are also many more manufactorers with different tehnics.

But what is the essence of variabile valve timing and lift electronic control?
In simplification it is desire for valves to open later and shallower at low RPMs and sooner and deeper at high RPMs.

There are also some technics used to prevent swirling of the intake air in the intake system. If I am correct at low RPMs air travels at the longer tube that at high RPMs.

Turbos...
Many manufacorers proceed to small supercharged engines, because small engines use less fuel. These kind of engines have biturbo system - smaller for low RPMs and higher for high RPMs, so there are no turbo lag.

EGR..
this technic was used in the past only for diesels, but now all gasoline direct injection engines have it.
It is a bypass from exhaust manifold to intake manifold with electronic controled EGR valve and EGR cooler.
Engines before that used variabile valve timig and lift control to achiev EGR - exhaust valve didn't left all the exhaust gases out of the cylinder.

So do gasoline engines have all of these technics or just some of them?
(VAG's FSI for instance don't have variabile valve timing and lift control)
Why diesel engines don't have variabile valve timing and lift control?

[GreyGoose006]

diesels dont have valve timing controls because they do not have throttles, and are running at full throttle all the time.
they vary the power output by increasing or decreasing directly the ammount of fuel that enters the engine.

diesels also have direct injection, so that is another reason they are more efficient/ better.

i dont really get your questions though,
not all engines can have all the things you talk about.
besides, it is very expensive to produce those devices, so if every engine had them, there would hardly be any cars that you could buy for less than 40K

[KiwiBacon]

To my knowledge toyota and honda don't have direct injection.
Nissan does, they call it "Neo".

Exhaust gas recirculation is used to lower peak cylinder temperatures and reduce NOx formation.
I understand that the old method was to take it from the exhaust, and feed it to the intake. But the preferred method is to control the valve timing to the extent of retaining exhaust inside the cylinder when needed.

This requires very clever valve control, like the solenoids you mentioned (but I'm sure this isn't the only way).

Diesels don't need variable valve timing as much because their rev ranges are smaller and they don't have the rough idle problems that petrol engines suffer from with a more aggressive cam.

Intake manifold lengths are tuned to pulse charge cylinders (force more air in through natural resonance). Intake manifolds with variable lengths can make this happen through the rev range, rather than at specific points.

[Moppie]

Originally Posted by KiwiBacon

To my knowledge toyota and honda don't have direct injection.
Nissan does, they call it "Neo".

Honda do have a direct injection engine, used with VTEC in the new Logo/Jazz.
Although its Mitsubishi who have the edge with the technology, having had in use in cars for well over 10 years now.

[KiwiBacon]

Originally Posted by Moppie

Honda do have a direct injection engine, used with VTEC in the new Logo/Jazz.
Although its Mitsubishi who have the edge with the technology, having had in use in cars for well over 10 years now.

How new are we talking? My grandmothers jazz isn't even Vtec. It's a 2004 I think.

[Moppie]

Originally Posted by KiwiBacon

How new are we talking? My grandmothers jazz isn't even Vtec. It's a 2004 I think.

Since at least then, but of course its not in all of them.
I know there was a JDM version that used a super high efficiency engine, where Direct Injection was only one its many features. How many other markets the engine was released in I don't know, and I have no idea how many were sold in Japan along side less advanced models.
I would be willing to bet your grandmothers Jazz is VTEC, Honda haven't sold a non-VTEC car since the late 90s. They just don't always advertise it, and by 2004 its so advanced and subtle you don't notice its there.

[KiwiBacon]

Originally Posted by Moppie

Since at least then, but of course its not in all of them.
I know there was a JDM version that used a super high efficiency engine, where Direct Injection was only one its many features. How many other markets the engine was released in I don't know, and I have no idea how many were sold in Japan along side less advanced models.
I would be willing to bet your grandmothers Jazz is VTEC, Honda haven't sold a non-VTEC car since the late 90s. They just don't always advertise it, and by 2004 its so advanced and subtle you don't notice its there.

Found it, the DSI engines, NZ new it's a 1.3litre.
I'd also bet that the grandmothers jazz has variable valve timing. But for differing goals than the usual ricer VTEC, hence the lack of branding.

Even my 98 Nissan with a QG18DE has variable valve timing.

[drunken monkey]

Honda also have different types of v-tec, differentiated by an i or e suffix if i recall. Might've changed since then though.

[silver343124]

Originally Posted by GreyGoose006

diesels dont have valve timing controls because they do not have throttles, and are running at full throttle all the time.
they vary the power output by increasing or decreasing directly the ammount of fuel that enters the engine.

you must be a very smart person to figure that out

Originally Posted by GreyGoose006

diesels also have direct injection, so that is another reason they are more efficient/ better.

diesel engines are more efficient because diesel fuel have more energy density, because pistons have longer stroke (better thermal efficiency), and because they run almost intire time at excess air and air is a good thermal isolator, so less heat is lost through cylinder walls. that's rougly it.

Originally Posted by KiwiBacon

To my knowledge toyota and honda don't have direct injection.

of course they do!

Originally Posted by KiwiBacon

Exhaust gas recirculation is used to lower peak cylinder temperatures and reduce NOx formation.

correct, but in gasoline engines it also enables the engine to operate at extra lean mixture when at idle or partial load.

Originally Posted by KiwiBacon

I understand that the old method was to take it from the exhaust, and feed it to the intake. But the preferred method is to control the valve timing to the extent of retaining exhaust inside the cylinder when needed.

As I know diesel have bypass and control valve/plate as aslo the EGR cooler.
as for gasoline engines, only the small amount of EGR can be applied with valve timing and lift as internal temperature has to stayed low if we want to prevent fuel self-ignition.

Originally Posted by KiwiBacon

This requires very clever valve control, like the solenoids you mentioned (but I'm sure this isn't the only way).

solenoid intake/exhaust valves are not yet in the use, they will be in the future

Originally Posted by KiwiBacon

Diesels don't need variable valve timing as much because their rev ranges are smaller and they don't have the rough idle problems that petrol engines suffer from with a more aggressive cam.

as far as I understand the meaning of valve timing it can be explain with fluid dynamics. At low RPS we want the intake valve to open at the begining of the intake stroke, but at high RPS we want the intake valve to open sooner, because the air has its inertial resistance. so I don't really get the point why diesel engines won't have variabile valve timing control as it is the fact that more air than we forced into the cylinder more fuel we can apply. and at full load also the diesel engine runs at lambda<1 and that is the reason we see black smoke from the exhaust pipe.

Originally Posted by KiwiBacon

Intake manifold lengths are tuned to pulse charge cylinders (force more air in through natural resonance). Intake manifolds with variable lengths can make
this happen through the rev range, rather than at specific points.

yes, and why don't engines have vaiable manifolds lengths as it is the cheapest technik to boost engines power.

and there are also more technics to boost internal engine efficiency...
mazda uses miller cylce engine (honda uses for its hybrid versions of cars), saab uses variable compression (SVC) in its 1.6 turbo gasoline engine.

[KiwiBacon]

Originally Posted by silver343124

diesel engines are more efficient because diesel fuel have more energy density, because pistons have longer stroke (better thermal efficiency), and because they run almost intire time at excess air and air is a good thermal isolator, so less heat is lost through cylinder walls. that's rougly it.

This is very wrong.
The energy density does not influence an engines efficiency, only it's fuel economy.
The two main reasons a diesel has better efficiency is the higher compression ratio (roughly double a petrol engine) which gives higher thermal efficiency and lack of a throttle plate which reduces pumping losses.

Originally Posted by silver343124

correct, but in gasoline engines it also enables the engine to operate at extra lean mixture when at idle or partial load.

EGR doesn't change the oxygen/fuel ratio, it simply dilutes the oxygen with inert, burnt gases. It does not make the engine run lean, although many engines with EGR also feature lean burn.

Originally Posted by silver343124

as far as I understand the meaning of valve timing it can be explain with fluid dynamics. At low RPS we want the intake valve to open at the begining of the intake stroke, but at high RPS we want the intake valve to open sooner, because the air has its inertial resistance. so I don't really get the point why diesel engines won't have variabile valve timing control as it is the fact that more air than we forced into the cylinder more fuel we can apply. and at full load also the diesel engine runs at lambda<1 and that is the reason we see black smoke from the exhaust pipe.

Variable valve timing is primarily a benefit on naturuall aspirated engines.
Some diesels do feature variable valve timing. But when you've got a turbo feeding up to 45psi into the inlet manifold, the benefits of variable vale timing are limited.
Diesel engines never run rich (greater than lamba 1), even at a smoke limit they are running lean.

Many production petrol engines do have variable length inlet manifolds, it's a mature technology.
But again it's only really useful on a naturally aspirated engine. The changes in density and temperature of the charge in a turbocharged engine alter the resonant frequencies too much and too often.

[beef_bourito]

another reason you won't see vvt on many diesel engines is because the benefits of having more air in the cylender is much less because most of the diesels you see on the market aren't meant for performance so they won't want to burn extra fuel. the extra air in the cylender might give a very small increase in fuel economy at best.

[KiwiBacon]

Originally Posted by beef_bourito

another reason you won't see vvt on many diesel engines is because the benefits of having more air in the cylender is much less because most of the diesels you see on the market aren't meant for performance so they won't want to burn extra fuel. the extra air in the cylender might give a very small increase in fuel economy at best.

Only in America dude. The whole rest of the world is full of high performance diesels.

[beef_bourito]

USA AND canada

anyways in those performance diesels how lean are they running?

we're finally starting to see some "sporty" diesels here, well we're finally starting to see ONE sporty diesel. the volkswagen 2.0TDI is apparently pretty fun to drive, i don't think there are many other diesel cars here with any kind of performance to them.

[KiwiBacon]

Originally Posted by beef_bourito

USA AND canada

anyways in those performance diesels how lean are they running?

we're finally starting to see some "sporty" diesels here, well we're finally starting to see ONE sporty diesel. the volkswagen 2.0TDI is apparently pretty fun to drive, i don't think there are many other diesel cars here with any kind of performance to them.

The modern diesels run from as lean as required to idle, up to just below the smoke limit. Modern diesels don't smoke.

Some of them are running serious boost, BMW's 3.0l diesel was running 42psi boost about 3 years ago. They've pushed power and torque up considerably since then.
Compound turbos are stock on several engines from Ford/PSA, mercedes and others.

[2.2 Straight six]

i believe BMW are venturing into compound turbocharging too with a new (or at least updated) 3-litre diesel.