Some details of the 2AZ-FE engine

Using only half a set of variable valve timing (VVT) saves money.

Some manufacturers use it on the intake side, some on the exhaust
side. If VVT is used on the exhaust side then the engine should have
NO EGR valve. The timing will allow the exhaust gas to be sucked back
into the cylinder. So that's one advantage for exhaust side VVT.

Of course, real luxury car engines would have VVT on both intake and
exhaust. Not only that, for instance, accelerator pedals on some newer
BMWs use CONTINUOUSLY VARIABLE VALVE LIFT to control acceleration!
(What throttle valve?) That's another reason why I say Toyota Lexus
isn't worth the money unless you like the dolled-up look, which really
is fine.

On Jul 14, 8:08 pm, Built_Well <Built_Well_Toy...@m> wrote:
> The VVT-i only works
> on the intake camshaft, not the exhaust camshaft.  It varies
> the timing of the intake valves.  There are two intake valves per
> cylinder and two exhaust valves per cylinder.  Having two of
> each increases the total port area, so more air can flow into
> and out of the combustion chamber.  As the manual's authors
> write, "Intake and exhaust efficiency has been increased due
> to the larger total port areas."

On Jul 15, 11:57 pm, johngd...@m wrote:
> Hee hee hee. 2AZFE "an advanced powerplant?" that's a good one.
> Checkout the Audi FSI 2.0T for an advanced design with a flat torque
> curve from 2000-5000 RPMs.
>
IIRC, The flat torque is because of the CVT transmission design and
not the engine. I could be wrong.
..

On Jul 16, 12:43 pm, EdV <systme...@m> wrote:
> On Jul 15, 11:57 pm, johngd...@m wrote:> Hee hee hee. 2AZFE "an advanced powerplant?" that's a good one.
> > Checkout the Audi FSI 2.0T for an advanced design with a flat torque
> > curve from 2000-5000 RPMs.
>
> IIRC, The flat torque is because of the CVT transmission design and
> not the engine. I could be wrong.
> .

The old 1.8T had an essentially flat torque curve over the same rev
range and was only available with conventional transmissions. I
wasn't aware that Audi had a CVT yet, although I have missed stuff
before. I thought their new high end transmission was the dual-clutch
deal?

nate

On Wed, 16 Jul 2008 09:43:13 -0700 (PDT), EdV <systmengr@m>
wrote:

>On Jul 15, 11:57 pm, johngd...@m wrote:
>> Hee hee hee. 2AZFE "an advanced powerplant?" that's a good one.
>> Checkout the Audi FSI 2.0T for an advanced design with a flat torque
>> curve from 2000-5000 RPMs.
>>
>IIRC, The flat torque is because of the CVT transmission design and
>not the engine. I could be wrong.
>.

A transmission has nothing to do with torque output of an engine.
A CVT is able to keep the rpms at max torque at all times while
accelerating.

RT wrote:
> On Wed, 16 Jul 2008 09:43:13 -0700 (PDT), EdV <systmengr@m>
> wrote:
>
>> On Jul 15, 11:57 pm, johngd...@m wrote:
>>> Hee hee hee. 2AZFE "an advanced powerplant?" that's a good one.
>>> Checkout the Audi FSI 2.0T for an advanced design with a flat torque
>>> curve from 2000-5000 RPMs.
>>>
>> IIRC, The flat torque is because of the CVT transmission design and
>> not the engine. I could be wrong.
>> .
>
> A transmission has nothing to do with torque output of an engine.
> A CVT is able to keep the rpms at max torque at all times while
> accelerating.
Max HP speed will give best acceleration.

On Jul 18, 11:05 am, "C. E. White" <cewhi...@remove>
wrote:
There is an injector in the combustion chamber
> instead of in the intake tract before the intake valves. Air is
> admitted into the combustion chamber by the valves. Fuel is injected
> directly into the combustion chamber, instead of being mixed with the
> air in the intake tract before the intake valves.

Ahh, so the intake valves is just for the AIR and the injector for the
FUEL. no pre-mixing involved. The mixing occurs directly inside the
combustion chamber. The fuel is pressurized and not the air like in a
turbo setup. Thanks!

Dyno wrote:

> Actually, the reason to go to mechanical lash is not for high speed
> valvetrain control but rather to reduce engine friction. The hydraulic
> lash adjusters exert a significant amount of force on the cam base
> circle, increasing mechanical friction. This IS both measureable and
> does contribute to fuel savings. If you examine the base circle of the
> came you can even see the lobe is narrower and flairs out to a wider
> surface (Ford Zetec).

That would be a lot more palatable explanation if not for two factors:

1) Lash adjusters (unlike hydraulic lifters) are generally located at
the valve-stem end of the follower. They're about the diameter of a
valve stem, not a lifter. Therefore, the plunger inside them is about
the diameter of a valve stem, not order-of 5/8 inch like a lifter.
Taking the oil pressure and multiplying it by the surface area of the
lash adjuster plunger produces a TINY number. When lift begins the
valves in the lash adjuster close and the entrained oil is
incompressible so they don't collapse, but the BASE CIRCLE pressure is
solely due to engine oil pressure multiplied by plunger area, and is
miniscule.

2) With roller followers cam followers, adding base circle pressure
doesn't increase friction much at all. That's one big reason they're
used- far far lower friction than flat lifters from base circle all the
way to full lift. And of course they can follow a lobe profile with a
much sharper ramp rate so that you can get long duration without
excessive overlap.

>
> With modern oils and their additive packages, the need for frequent lash
> adjustment is very rare. Most will make it thought the mandatory 100k
> emissions durability requirements with no adjustment.

No argument there, but I still think eliminating auto lash adjusters is
more cost-driven than engineering-driven. And I don't even disagree that
its a good idea to go ahead and save that money IF the engine can run
200k miles without opening the overhead, as we've come to expect from
cars with hydro lifters or hydro lash adjusters.

Leftie wrote:

>
> There are two problems with hydraulic lifters: they are more
> expensive to build and, more to the point for us, they tend to fail long
> before the rest of the engine. Who wants to have to spend $1k on new
> lifters on a car with 150k miles on it?

They FAIL before the rest of the engine? Hardly. Ask any mechanic how
many hydraulic lifters or lash adjusters he's had to replace because the
lifter or adjuster ITSELF was a root cause of a problem in the last 10
years and I'll bet you can count the average answer on 1 hand, and if
you probe further you'll find that those were typically in badly
neglected sludged-up engines.

Steve wrote:
> Leftie wrote:
>
>>
>> There are two problems with hydraulic lifters: they are more
>> expensive to build and, more to the point for us, they tend to fail long
>> before the rest of the engine. Who wants to have to spend $1k on new
>> lifters on a car with 150k miles on it?
>
>
> They FAIL before the rest of the engine? Hardly. Ask any mechanic how
> many hydraulic lifters or lash adjusters he's had to replace because the
> lifter or adjuster ITSELF was a root cause of a problem in the last 10
> years and I'll bet you can count the average answer on 1 hand, and if
> you probe further you'll find that those were typically in badly
> neglected sludged-up engines.

My engines were not "badly neglected". The motorcycle was given full
synthetic oil. The two Mazda engines may have had poorly designed oil
passages, but I've also heard from other people abut lifters failing.
Think of all the "stuck lifter" stories out there, and you may realize
that it isn't just bad maintainance causing it to happen.

>How may car owners ever use the automatic transmission dip stick?
>

All of them with half a brain.

How often do you actually add ENGINE oil? I never need to between
changes, but I still CHECK it weekly. Same with the transmission fluid.
The whole idea of maintenance is to CATCH a potential problem before it
becomes costly. Eliminating the transmission dipstick pretty much
guarantees a low-fluid failure will ultimately destroy the transmission,
be it at 10,000 miles or 200,000 miles.