Not this engine, the balance shafts are up high, about halfway up the block. There's a somewhat strange chain and gear arrangement to drive them, strange in that the driver's side (I think) sprocket is NOT a 1:1 or 2:1 ratio, the rest of the difference is made up with a geardrive to reverse the shaft's direction. Lining everything up can catch you out if you aren't paying attention as you can have the chain sprocket's dots lined up with the balance shaft in the wrong place.chimpvalet wrote:Re: the Mitsu 2.6 as I recall the balance shafts are positioned in the block well above the sump. The Audi is configured like the 2.5 Nissan I've been driving, now well clear of 100k miles with no engine issues, carrying the shafts immersed down in the sump.
The interesting thing is the driver's side balance shaft pokes out the block just before the bellhousing, and a little toothed belt drives the water pump off of that end. The drive pulley just sits on a taper, with a taper seat reverse-thread bolt holding it in. Doing it this way allowed Audi to shorten the engine so much that the balance shaft chain actually sits "under" the water jacketing around #1 cylinder. The cam chain mounts more normally other than the cam being supported on both sides of the timing chain, which I ascribe to simple overthinking
All of that pales in weirdness compared to the variable valve lift mechanism. Honda has high and low lift lobes and they lock the high lobe rocker to the other rockers when they want high lift. Audi has only the two rockers but they move the cam lobes back and forth under the rockers when they want to go from low lift to high lift. Believe it or not the system looks pretty fault tolerant too.
