Where does the precat go?

[Anonymous]

Just a quick Q?

My garage told me that if the pre cat started to fail the bits would just come out the rear pipe?

So could some one confirm where the pre cat is and where the bits go to cause damage

Thanks

[Ernie Ball]

The bits would go two places: 1) clogging the main cat.  They would not go out the exhaust because the main cat is in the way.  2) into the engine where they will do damage.  It seems counterintuitive but apparently it does happen.

[Ernie Ball]

Oh and I'd say you need a new garage.

[roger]

So could some one confirm where the pre cat is Thanks

The Pre-cat is (or should it be pre-cats are?) inside the exhaust manifold, so they either go one way or the other as Steve said.

[heathstimpson]

Just a quick Q?

My garage told me that if the pre cat started to fail the bits would just come out the rear pipe?

So could some one confirm where the pre cat is and where the bits go to cause damage

Thanks

Your garage should know better  s:? :? s:?

[Anonymous]

Most garages won't believe you when you tell them that precat gets in the engine, so be ready to tell them how:

1) precat becomes brittle, breaks away from manifold and clogs the main cat. This causes backpressure towards the engine.

2) As the Mr2 engine has VVTi, this means the exhaust valves are open at the same time as the inlet valve (i.e. when the piston for a particular cylinder is drawing fuel / air into it). This is known as "Valave overlap" as both valves are open momentarily at the same time. Basically, the suction is what draws the particles into your engines cylinders.

3) The particles of precat are very hard and scrape up and down the cylinder walls with the piston. This puts scores into the cylinder walls and allows oil to pass the piston rings. For this reason, your engine starts to burn oil excessively and therefore buggers up everything else, even more.



Anybody who has any other theories to this, please feel free to offer them instead of this....

cheers,

Richie

[dreambackup]

this is the theory I gave to my Toyota garage told me "those engines use a lot of oil, it's normal"  s:lol: :lol: s:lol:  (mine used no oil between services until now: 49000km)...

I am still under warranty so I does it means a free new engine soon?  s:twisted: :twisted: s:twisted:

[heathstimpson]

this is the theory I gave to my Toyota garage told me "those engines use a lot of oil, it's normal"  s:lol: :lol: s:lol:  (mine used no oil between services until now: 49000km)...

I am still under warranty so I does it means a free new engine soon?  s:twisted: :twisted: s:twisted:

Mine has never used a drop of oil in 21000 miles   s:wink: :wink: s:wink:

[markiii]

Most garages won't believe you when you tell them that precat gets in the engine, so be ready to tell them how:

1) precat becomes brittle, breaks away from manifold and clogs the main cat. This causes backpressure towards the engine.

2) As the Mr2 engine has VVTi, this means the exhaust valves are open at the same time as the inlet valve (i.e. when the piston for a particular cylinder is drawing fuel / air into it). This is known as "Valave overlap" as both valves are open momentarily at the same time. Basically, the suction is what draws the particles into your engines cylinders.

3) The particles of precat are very hard and scrape up and down the cylinder walls with the piston. This puts scores into the cylinder walls and allows oil to pass the piston rings. For this reason, your engine starts to burn oil excessively and therefore buggers up everything else, even more.



Anybody who has any other theories to this, please feel free to offer them instead of this....

cheers,

Richie

minor point, but valve overlap is not a function of VVTI. other than that pretty much spot on.