Quote:
Originally Posted by knucklesplitter
I think the very serpentinish serpentine belt configuration has more to do with the fact that it is single belt driving everything, the water pump is now driven by it, and the overall tighter packaging of accessories on the front of the new engine.
The whole motor is not all about lower resistance though. If that were the case they would have stuck with a timing belt instead of dual chains driving the cams. That was obviously a compromise to eliminate the need to replace the timing belt (up to twice) during the engine's lifespan. In general a timing belt is more efficient and more accurate than a chain. Whereas chains are generally cheaper and lower in maintenance than timing belts.
An interesting change is that the injectors are now in the head instead on the intake manifold. Maybe this is a step toward direct injection?
Also the tighter valve configuration may result in a smaller combustion chamber. This combined with the smaller bore would result in lower minimum best timing. This would be a good thing for turbo engines, as it reduces the tendency to knock.
The rocker arms in place of cam "buckets" are also interesting. It looks like they may be going for ECU-adjustable active valve lift with this configuration.
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Yeah, I don't know how a longer belt, plus additional idler pulleys would result in lower resistance.
An article I read explicitly said this motor appears to be a step towards DI. And I think there appear to be solenoids or something on the non-valve side of those roller(?) rockers, which would create variable lift.
I bet the STi version of this motor will be turbo, DI, variable timing, variable lift, and probably put out 350hp. Which is really needed, ever since the WRX got 265.