Are you ready to get nerdy about crankshafts? Let's go!
The waterboxer is a horizontally-opposed, 4-cylinder, 4-cycle engine just like its older Type 1 and Type 4 siblings—except it is water-cooled instead of air-cooled. What is interesting about the VW design is that the crankshaft has only three main journals. If you were to look down at one of these engines while it was running (and you had X-ray vision), you would see the forward two pistons (#1 forward right and #3 forward left) and the two rearward pistons (#2 rear right and #4 rear left) reciprocating back and forth away and toward each other, but slightly off-set from each other front to back. It's actually like two 2-cylinder engines joined by one crankshaft, or like two BMW motorcycle boxer engines bolted together.
Like any flat-four, 4-cycle engine, the front two and rear two opposing pistons get to top dead center (TDC) at the same time. One of them is just about to fire (compression/power stroke), and the other is exhausting (exhaust/intake stroke or "overlap"). When the two front pistons (1 and 3) are at TDC, the other two (rear) pistons (2 and 4) are at bottom dead center (BDC). Every time a spark plug ignites and an explosion takes place above the piston, the force is transmitted down the connecting rod to the crankshaft rod journal, causing a "racking" or twisting force around the vertical axis, over and over, again and again, billions of times over the life of the crankshaft. Since there are only three main bearings, all of these twisting forces pass right through the center main bearing. It is for this reason that the crankshaft on all VW flat-four engines would eventually crack right through the center main bearing journal, usually at about a 45-degree angle. Fun interesting fact: Since the break occurred at an angle, a VW flat four engine would often continue to run for some time even with a crankshaft broken clean in half!
The other place the crank would break—albeit, less commonly—is at the #1 journal where the flywheel bolts on, because that is the next weakest point. The Type 4 engine design (1.7, 1.8, and 2.0 liter) improved the #1 journal strength problem by making that journal significantly larger than the earlier Type 1 engines—switching from one flywheel bolt, plus four dowels, to five bolts and thus eliminating the failures at that location. The center main journal failure persisted, however.
By contrast, the crankshaft in the waterboxer is not known to fail at the center main journal. As a matter of fact, we have never seen a waterboxer crankshaft break at the center main journal. It is a superb design that is way more sophisticated than the crankshafts used in the two earlier VW horizontally-opposed engines, the Type 1, 2, 3, and Type 4. The waterboxer crankshaft design overcomes the twisting problem by implementing two massive “mini flywheel” sections, one between each pair of opposing rod journals, that are not present in either earlier design. These two hunks of mass act kinematically to absorb the momentary impact of the ignition process, thereby alleviating the stresses to the center main bearing. The waterboxer crankshaft also employs the identical #1 main journal design that VW figured out worked well on the Type 4. These improvements are examples of how VW drew on its many decades of knowledge, which culminated in the waterboxer design.
We go one step further with our GoWesty-design crankshafts by adding counterweights. Counterweights are not added to horizontally-opposed engines to make them more "balanced" or "smoother." Horizontally-opposed engines are already harmonically balanced due to their physical layout. The counterweights are added to reduce dynamic stresses even further, thereby extending the engine's lifespan.
The reason we counterweight our crankshafts is to decrease dynamic stresses even further than the mini-flywheels do and thereby increase longevity.
Our GoWesty crankshafts are offered in larger strokes than the original cranks. This (as well as the size of our pistons) is to increase the total displacement of the engine.
Here are the stroke and bore sizes of the original engines and our GoWesty engines and engine kits:
- VW 1900cc 69mm stroke 94mm piston
- VW 2100cc 76mm stroke 94mm piston
- GW 2200cc 76mm stroke 96mm piston
- GW 2300cc 79.5mm stroke 96mm piston
- GW 2450cc 84.5mm stroke 96mm piston
- GW 2700cc 84.5mm stroke 100.75mm piston
These larger displacement variants of the waterboxer are undoubtedly the direction Volkswagen would have pursued had they continued to produce the waterboxer. They didn't, but GoWesty did.
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