Re: Timing Belt Change Intervals

"y_p_w" <y_p_w@hotmail.com> wrote:
[color=blue]
>Gord Beaman wrote:[color=green]
>> y_p_w <y_p_w@hotmail.com> wrote:
>>[color=darkred]
>> >
>> >
>> >Gord Beaman wrote:
>> >
>> >> "jor" <jor@jor.com> wrote:
>> >>
>> >>
>> >>>My 2000 Avalon book calls for it at 90,000. Not sure what an[/color][/color]
>interference[color=green][color=darkred]
>> >>>engine is?
>> >>>jor
>> >>
>> >>
>> >> An interference engine is one in which, if the timing belt/chain
>> >> breaks, the pistons will hit the valves as the engine 'runs down
>> >> to a stop' causing much damage to the engine. I understand from
>> >> the Toyota experts here that in modern Toyota engines, if they
>> >> have a 'timing belt' then they have a non-interference engine and
>> >> if they have a 'timing chain' then they have an interference
>> >> engine...Mind you, I'm NOT an expert in these engines but that's
>> >> what I gather here. YMMV. :)
>> >
>> >Isn't there the one-in-a-trillion chance that if the timing
>> >mechanism breaks, the pistons and valves miraculously move at
>> >the same exact rate and never slam into each other? ;-)[/color]
>>
>> No, the valves STOP and the pistons DON'T... (big difference in
>> their inertia) :)[/color]
>
>Whoops. Forgot the whole thing about valves being attached to
>springs. I was thinking of the whole "Give a bunch of chimpanzees
>some typewriters and enough time, and they'll produce the complete
>works of Shakespeare" cliche.[/color]

Well, actually the springs play no part in the damage at
all...all they do is 'close' the valve as the tappet/push
rod/hydraulic lifter and cam allow them to. So when the piston
contacts the valve head it's a 'rock and a hard place' kind of
contact...the kind that costs big bux...and yes, I know where
you're coming from but I'd think that there's no chance of that
happening because of the large difference in inertia between the
cam shaft(s) on one hand and the rest of the engine on the other.
I'd think that the camshafts would stop almost instantly and the
rest of the engine wouldn't...
--

-Gord.
(use gordon in email)

Gord Beaman wrote:[color=blue]
>
> "y_p_w" <y_p_w@hotmail.com> wrote:
>[color=green]
> >Gord Beaman wrote:[color=darkred]
> >> y_p_w <y_p_w@hotmail.com> wrote:
> >> >
> >> >Isn't there the one-in-a-trillion chance that if the timing
> >> >mechanism breaks, the pistons and valves miraculously move at
> >> >the same exact rate and never slam into each other? ;-)
> >>
> >> No, the valves STOP and the pistons DON'T... (big difference in
> >> their inertia) :)[/color]
> >
> >Whoops. Forgot the whole thing about valves being attached to
> >springs. I was thinking of the whole "Give a bunch of chimpanzees
> >some typewriters and enough time, and they'll produce the complete
> >works of Shakespeare" cliche.[/color]
>
> Well, actually the springs play no part in the damage at
> all...all they do is 'close' the valve as the tappet/push
> rod/hydraulic lifter and cam allow them to. So when the piston
> contacts the valve head it's a 'rock and a hard place' kind of
> contact...the kind that costs big bux...and yes, I know where
> you're coming from but I'd think that there's no chance of that
> happening because of the large difference in inertia between the
> cam shaft(s) on one hand and the rest of the engine on the other.
> I'd think that the camshafts would stop almost instantly and the
> rest of the engine wouldn't...
> --[/color]

Yes, Gordon, I completely agree with you. Just on the basis of inertia
within the engine, the valve train is going to stop long before the
pistons do, as long as neither is, er... /influencing/ the other. :)

In addition, I note (to everyone) that if the belt fails, it will
probably fail during driving, not idling. In this case, the crankshaft
will be driven through the transmission, driveshaft (if any), axles, and
wheels by the entire linear inertia (forward momentum) of the car. The
rotational inertia of all these parts will also contribute to driving
the crankshaft. If the timing belt or chain in a non-interference
engine breaks at substantial speed (say 30 MPH), and if the transmission
remains engaged (and the brakes not), the difference in time between
when the valve train stops and when the pistons stop will be multiple
seconds.

Therefore, in an interference engine, the time difference will be
noticeably shorter. :)

Stephen

Gord Beaman wrote:[color=blue]
> y_p_w <y_p_w@hotmail.com> wrote:
>[color=green]
> >
> >
> >Gord Beaman wrote:
> >[color=darkred]
> >> "jor" <jor@jor.com> wrote:
> >>
> >>
> >>>My 2000 Avalon book calls for it at 90,000. Not sure what an[/color][/color][/color]
interference[color=blue][color=green][color=darkred]
> >>>engine is?
> >>>jor
> >>
> >>
> >> An interference engine is one in which, if the timing belt/chain
> >> breaks, the pistons will hit the valves as the engine 'runs down
> >> to a stop' causing much damage to the engine. I understand from
> >> the Toyota experts here that in modern Toyota engines, if they
> >> have a 'timing belt' then they have a non-interference engine and
> >> if they have a 'timing chain' then they have an interference
> >> engine...Mind you, I'm NOT an expert in these engines but that's
> >> what I gather here. YMMV. :)[/color]
> >
> >Isn't there the one-in-a-trillion chance that if the timing
> >mechanism breaks, the pistons and valves miraculously move at
> >the same exact rate and never slam into each other? ;-)[/color]
>
> No, the valves STOP and the pistons DON'T... (big difference in
> their inertia) :)[/color]

Whoops. Forgot the whole thing about valves being attached to
springs. I was thinking of the whole "Give a bunch of chimpanzees
some typewriters and enough time, and they'll produce the complete
works of Shakespeare" cliche.

"y_p_w" <y_p_w@hotmail.com> wrote:
[color=blue]
>Gord Beaman wrote:[color=green]
>> y_p_w <y_p_w@hotmail.com> wrote:
>>[color=darkred]
>> >
>> >
>> >Gord Beaman wrote:
>> >
>> >> "jor" <jor@jor.com> wrote:
>> >>
>> >>
>> >>>My 2000 Avalon book calls for it at 90,000. Not sure what an[/color][/color]
>interference[color=green][color=darkred]
>> >>>engine is?
>> >>>jor
>> >>
>> >>
>> >> An interference engine is one in which, if the timing belt/chain
>> >> breaks, the pistons will hit the valves as the engine 'runs down
>> >> to a stop' causing much damage to the engine. I understand from
>> >> the Toyota experts here that in modern Toyota engines, if they
>> >> have a 'timing belt' then they have a non-interference engine and
>> >> if they have a 'timing chain' then they have an interference
>> >> engine...Mind you, I'm NOT an expert in these engines but that's
>> >> what I gather here. YMMV. :)
>> >
>> >Isn't there the one-in-a-trillion chance that if the timing
>> >mechanism breaks, the pistons and valves miraculously move at
>> >the same exact rate and never slam into each other? ;-)[/color]
>>
>> No, the valves STOP and the pistons DON'T... (big difference in
>> their inertia) :)[/color]
>
>Whoops. Forgot the whole thing about valves being attached to
>springs. I was thinking of the whole "Give a bunch of chimpanzees
>some typewriters and enough time, and they'll produce the complete
>works of Shakespeare" cliche.[/color]

Well, actually the springs play no part in the damage at
all...all they do is 'close' the valve as the tappet/push
rod/hydraulic lifter and cam allow them to. So when the piston
contacts the valve head it's a 'rock and a hard place' kind of
contact...the kind that costs big bux...and yes, I know where
you're coming from but I'd think that there's no chance of that
happening because of the large difference in inertia between the
cam shaft(s) on one hand and the rest of the engine on the other.
I'd think that the camshafts would stop almost instantly and the
rest of the engine wouldn't...
--

-Gord.
(use gordon in email)

Gord Beaman wrote:[color=blue]
>
> "y_p_w" <y_p_w@hotmail.com> wrote:
>[color=green]
> >Gord Beaman wrote:[color=darkred]
> >> y_p_w <y_p_w@hotmail.com> wrote:
> >> >
> >> >Isn't there the one-in-a-trillion chance that if the timing
> >> >mechanism breaks, the pistons and valves miraculously move at
> >> >the same exact rate and never slam into each other? ;-)
> >>
> >> No, the valves STOP and the pistons DON'T... (big difference in
> >> their inertia) :)[/color]
> >
> >Whoops. Forgot the whole thing about valves being attached to
> >springs. I was thinking of the whole "Give a bunch of chimpanzees
> >some typewriters and enough time, and they'll produce the complete
> >works of Shakespeare" cliche.[/color]
>
> Well, actually the springs play no part in the damage at
> all...all they do is 'close' the valve as the tappet/push
> rod/hydraulic lifter and cam allow them to. So when the piston
> contacts the valve head it's a 'rock and a hard place' kind of
> contact...the kind that costs big bux...and yes, I know where
> you're coming from but I'd think that there's no chance of that
> happening because of the large difference in inertia between the
> cam shaft(s) on one hand and the rest of the engine on the other.
> I'd think that the camshafts would stop almost instantly and the
> rest of the engine wouldn't...
> --[/color]

Yes, Gordon, I completely agree with you. Just on the basis of inertia
within the engine, the valve train is going to stop long before the
pistons do, as long as neither is, er... /influencing/ the other. :)

In addition, I note (to everyone) that if the belt fails, it will
probably fail during driving, not idling. In this case, the crankshaft
will be driven through the transmission, driveshaft (if any), axles, and
wheels by the entire linear inertia (forward momentum) of the car. The
rotational inertia of all these parts will also contribute to driving
the crankshaft. If the timing belt or chain in a non-interference
engine breaks at substantial speed (say 30 MPH), and if the transmission
remains engaged (and the brakes not), the difference in time between
when the valve train stops and when the pistons stop will be multiple
seconds.

Therefore, in an interference engine, the time difference will be
noticeably shorter. :)

Stephen