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this crack is from twisting. It is a diagonal fracture. And the damper is on the other end of crank, so that wouldn't help much. What will help is a softer sprung clutch (which is similar to a damper itself). If you have unsprung or puck clutch with a heavy rotational mass, you're asking for this oil port to crack. I'm not discounting that damper on other end wouldn't help since it can reduce some of the harmonics when the biggest stress hits that oil port area.
BS will help with the vertical vibrations getting to the flywheel. The frequency will be double the RPM, so what ever your normal driving RPM is, your exposing 2x the RPM in vertical vibrations.
They can hold big power. I believe English racing quoted upwards of 1000whp. They just mentioned that the billet cranks are lighter and thus running them makes your whole rotating assembly lighter.
thinking is free. I just don't want to spend a bunch of money and a bunch of time in an engine to find it fail. It may still fail, but I'll know I've tried my best to build it right.
They can hold big power. I believe English racing quoted upwards of 1000whp. They just mentioned that the billet cranks are lighter and thus running them makes your whole rotating assembly lighter.
Thought more about the rod/crank forces. Red is force from rod during power stroke. Blue is the tranny resisting rotation (when transferring power to wheels). Imagine crank rotating to where oil hole is exposed to the rod force. Right before the hole (missing support), that's where the load is focused. Over time, it starts cracking there. Once there is a crack, that part can't resist the rod load and continues the cracking until it reaches the corner. Then you get the crack that we see.
Last edited by 2006EvoIXer; May 3, 2018 at 10:37 PM.
I think I just realized why firing order isn't 1-2-3-4. Any guesses?
Spoiler
They could have made the firing order 1-2-3-4, but the stress is too much and could crack the crank. Power strokes 1-2-3-4 should be fine as each increases crank power going to clutch. Problem is when it goes 4-1. There is too much distance and when 1 fires again, we'll likely see similar crank failure except at rod #1.
So why 1-3-4-2? Because this pattern starts the stress at inside cylider (3) and then outside (4), which is then transferred to tranny. But look at next pattern: inside (2); and followed by outside (1) before going to damper and pulleys. This firing order helps minimize twisting motion within the crank.
Last edited by 2006EvoIXer; May 4, 2018 at 12:34 AM.
It uses that firing order to minimize vibrations, attempting to keep NVH to a minimum. It's the main reason engines have a firing order in the first place. You're definitely overthinking this.
It uses that firing order to minimize vibrations, attempting to keep NVH to a minimum. It's the main reason engines have a firing order in the first place. You're definitely overthinking this.
I just thought it was cool that the inner cylinder fires to pre stress the crank before firing the outter cylinder to transfer the energy to accessories. The physics of the engine dynamics was well thought out.
The only things I can think of to minimize the chance of cracking crank at #4 rod is to:
- put highest flowing injector in #4
- port 1-3 intake/exhaust/runners more
- keep tires stock (no slicks or sticky street)
Injector placement has nothing to do with it, neither does manifold porting. The power difference from the bit of extra air is negligible. The #4 web sees the pulses from all the other cylinders to transfer the torque to the flywheel, so it see's the most abuse. Simple as that.
What this really is a good example of is why you shouldn't run a 100mm crank. Too much flex.
The reality of it is that we are asking a lot out of a 2.0-2.3L engine. Shoving (usually) more than 2 extra atmospheres into it and asking for >150hp/cylinder. Not per liter, per cylinder. It's simply not going to last 200k miles, or even 100k miles, if you drive like you should be driving a built car.
Also, OEM cranks mean the business. The ER drag X, and Jeff Bush's DQ run OEM cranks. Both over 1200whp.
