Unlike its well-known 1MZ-FE ancestor, the new 3MZ-FE (3.3L V-6) is an interference design. Now, I haven't seen that on an official Toyota document, but I have seen it several places on the net. Woe to the poor fool who lets his timing belt go. . .
Originally posted by SolaraTRD I first heard about them on Nissan's.
what are the benefits of chain though? besides being all strong and no slipping wear. (The obvious)
They're much more durable than the belts. As a result, they don't abruptly break like belts can. A broken belt in an interference engine probably means the whole engine is destroyed, as the pistons take turns slamming into open valves. Ouch. Bad. Chains are lubricated by the engine's oil system, and are designed so that they should last as long or longer than the rest of the engine. Years ago, the main drawback of the chains was that they were noisier. That's now been largely designed out of them. Ironically, I find the VQ35 V-6 in my G35 is more "mechanical" sounding than the 1MZ in the Camry I had before, but none of the mechanical sounds seem to be from the chain.
Originally posted by Ukrainian102 Sorry for asking but what does interference and non-interference mean. Is it chain- and belt-drive?
No problem. In an interference design, the valves open deeply enough into the combustion chamber that they actually occupy space that the climbing piston will reach a few microseconds after the valve starts pulling back. These engines absolutely depend upon the proper operation of the mechanical timing system to ensure that the two don't try to be in the same place at the same time. Hence the disadvantage this type of design has when a timing belt, which is responsible for positioning the valves, breaks suddenly. This is generally a bad, bad thing.
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