Quote:
Originally Posted by wheelspeed
To someone ignorant on boxer engines (me), this is interesting. It seems that a dip may be inherent to boxers that isn't there in inline 4s. You don't see this on the Miata engine and I don't think there was one on my old Mazda 3 2.3L (though I didn't scrutinize any dyno charts in 2009). Anyway, I'm thinking maybe trade-off to the boxer layout to have a torque dip somewhere, but you get the lower CoG of the boxer layout?
Anyway, I'm trying to save judgement until I drive one. I was perfectly happy with my Mazda 3's 150hp/150tq engine because, despite low numbers, it felt "willing and happy" and was fun to row through the gears. I was just sick of it being FWD. As long as the new 2.4 boxer engine feels willing and happy, I'll be happy with it.
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There are definitely plenty of cars out there with a torque dip. I have done dyno searches before for various sports cars and big power naturally aspirated beasts. In the big powered ones, it is often quite small looking, as 20-40 lb-ft of a dip in a 400 lb-ft car doesn't look like much.
IMO, I believe the reason is more related to shooting for as much power as you can get out of an engine. In order to do that, the engine design has to be quite good and the tune has to be extremely on point. This is where emissions comes in to bust it. Because it is the tune that can't be brought to a maximum these days due to emissions. Just as removing the front cat and getting a proper tune removes the torque dip completely.
Even the MX-5 has a small dip of about 5-10 lb-ft. But I don't think this engine was built and tuned up to the same extreme the FA20 was. Again, this is just my theory, but if they were to tune the power up a bit more all around, I bet that torque dip would remain more or less in the same place, making it larger.
My guess would be that most cars in general (that aren't sports cars or very high powered monsters) are not tuned up to maximize power, obviously, and therefore avoid having a torque dip. This is not always the case of course, as even ordinary cars have a dip sometimes, and again I believe this is thanks to modern emissions. I am sure companies that heavily support better emissions (like Subaru with their PZEV) experience this more with their vehicles.