No "balance-shafts" - Engineered 4G63 crankshaft.........??
Originally Posted by jerchi
They're not the same product but I would assume that the forged stuff is a lot better. Forging usually aligns the grains of the material along the direction of the stress. So the material has greater strength along one direction (hopefully the direction it's designed to take loads in) than other directions. In most cases the CNC time is the biggest factor in cost unless you had a special blank made and/or it's a special material (ie a 3' by 3' by 3' piece of titanium). And sure the coating and other stuff matters too but from the description alone the Magnus stuff is expensive because of the CNC time not because it is really better. ...
If it were not better, it would have no market value, particularly at the several times multiple it has over the Eagle or factory forged cranks. Let's first identify the market -- someone making over 700HP from a 2.0 or stroker Evo motor. That narrows it down to the serious players, who really need more than the stock crank can provide without substantial modifications.
For a serious motor build, you'll need to consider the following machining operations on your stock (or Eagle) crank: clean, magnaflux, X-ray or similar for cracks, knife-edge counterweights, lighten, balance, shotpeen for stress relief, nitride it, check for straightness and straighten if needed, regrind, repolish, cryo if you wish, etc. When you're done, you still started with a stock metalurgy crankshaft, still limited by what you could do with the configuration the factory chose to produce. It still has the strength limitations inherent in the stock design, just some improvements that machine work can accomplish.
Any idea on cost for these procedures? $750 for the new crank, for starters, then at least that much (if you skip some of the above steps) in machine work and balancing. There was recently a Pauter modified stock crank on the for sale list that noted that it cost $2200+ when the modifications were calculated into the cost...
By way of comparison, a billet crank starts with a much more capable base than the stock or Eagle crank. (1) better materials and quality control (2) machined and shaped counterweights with better windage shapes and harmonics (factory does not machine counterweights, they're stamped in the forging process like a cookie cutter); (3) many additional processes after CNC is done -- shotpeening for strength and stress relief, hardening, nitriding hard case finish, finish grinding with oversize fillets, balancing, etc.
Many serious racers rebuild their bottom end and replace stock cranks every 30-40 passes. Why? They're already cracking from the much higher stresses caused by high HP builds. In 2.4 strokers in DSMs, breakage at the #4 journal is commonly reported on factory cranks. Break a crank and you may have a much higher repair bill than just the crank.
It's overkill if you don't have a need for it. If you do, it may be the most economical route for you to go when you factor in all the costs for the alternatives... Please don't suggest that they're anywhere close in comparison, though...
Sure tuning for resonance frequencies is a more elegant solution than a balance shaft but at what cost? The cost benefit ratio and lack of reliability probably doesn't justify removing the balance shaft. It's like kids on this forum getting carbon fiber mud flaps and other dumb **** and claim it's for weight reduction. I like carbon as much as anybody else but it's worthless in terms of performance gains. Ferraris are flat plane v8 (no balance shafts ) and while they sound awesome and rev fast as hell they are also unreliable and expensive.
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From: Birmingham, AL
Originally Posted by CO_VR4
Actually, balance shafts do not "rob" oil pressure. The main reasons that balance shafts are removed are (1) to eliminate the very common breakage of the balance shaft belt, which would cause the timing belt to jump time and destroy the valvetrain, and (2) eliminate about 9 lbs of driven rotating weight.
It has to do with resonance harmonics, which are a function of both the crankshaft design and manufacture and other rotating parts. The balance shafts rotated in counterweight to the crankshaft (and to each other) to cancel out the inherent harmonics of the crankshaft and rotating pistons/rods. You can balance the crankshaft perfectly, but every crank will still have an inherent harmonic, just like every bell will ring when you strike it. If the crankshaft is not balanced, it will also have vibrations caused by the imbalance, IN ADDITION to the natural resonance vibrations and torsional vibrations. The Mitsu factory crank has natural resonance too; the balance shafts simply cause the driver to feel it less.
Balance shaft removal had nothing to do with crankwalk.
Evos are not known for crankwalking (like the 2g DSMs),
Last edited by GPTourer; Aug 7, 2006 at 06:54 PM.
"If it were not better, it would have no market value..."
That statement if obviously untrue for many reasons. Many things that are more expensive are not better. They are expensive because people will pay for it. A carbon hood isn't better because it's $800. The performance to price ratio isn't always in favor of the more expensive car or part (Carrera GT vs electric Ariel Atom). If you don't understand why that is then please stop reading.
If the Magnus cranks are better it's not because of the nature of a billet stock but the pre and post treatment. Why you think billet stock provides a "more capable base" than a forged stock is beyond me. Please read the Wikipedia entry on forging (http://en.wikipedia.org/wiki/Forge). Also if billet was more capable then why are connecting rods, piston blanks, valve blanks, wheels (more expensive ones), etc. all forged?
Anyway, it's not really the inherent strength of the parts here that's important. It's the reduction in the vibratory amplitude and the tuning of the resonance frequencies away from your operating range. Vibrations are big concerns in terms of reliability and drivetrain behavior that you either isolate, damp, or move it (diesel trucks, jet engines, race cars, everything that moves). I have seen torque spike amplitudes around 300 ft-lb on a helicopter drivetrain (main rotor back driving the drivetrain from aerodynamic forces). Check out www.fluidampr.com . For the same reason that power upgrades come with dyno sheets these "balanced" crankshafts should come with bode plots or something that shows their effetiveness. If people are considering removing their balance shaft for the sake of reduced complexity then they should also consider installing a viscous damper for reliability.
That statement if obviously untrue for many reasons. Many things that are more expensive are not better. They are expensive because people will pay for it. A carbon hood isn't better because it's $800. The performance to price ratio isn't always in favor of the more expensive car or part (Carrera GT vs electric Ariel Atom). If you don't understand why that is then please stop reading.
If the Magnus cranks are better it's not because of the nature of a billet stock but the pre and post treatment. Why you think billet stock provides a "more capable base" than a forged stock is beyond me. Please read the Wikipedia entry on forging (http://en.wikipedia.org/wiki/Forge). Also if billet was more capable then why are connecting rods, piston blanks, valve blanks, wheels (more expensive ones), etc. all forged?
Anyway, it's not really the inherent strength of the parts here that's important. It's the reduction in the vibratory amplitude and the tuning of the resonance frequencies away from your operating range. Vibrations are big concerns in terms of reliability and drivetrain behavior that you either isolate, damp, or move it (diesel trucks, jet engines, race cars, everything that moves). I have seen torque spike amplitudes around 300 ft-lb on a helicopter drivetrain (main rotor back driving the drivetrain from aerodynamic forces). Check out www.fluidampr.com . For the same reason that power upgrades come with dyno sheets these "balanced" crankshafts should come with bode plots or something that shows their effetiveness. If people are considering removing their balance shaft for the sake of reduced complexity then they should also consider installing a viscous damper for reliability.
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Joined: Jun 2006
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From: Grand Island, NE
In any book on engines you will read that you can't balance a four cylinder engine.
I entered the DSM scene in 1992 and the initial reason for DSM owners removing balance shafts was balance shaft bearing failure (usually a spun bearing). Balance shaft belt failure wasn't uncommon either. This combination of problems relating to the balance shaft system caused it to be one of the more troublesome components of the engine. Once burned you were happy to have the balance shafts gone.
By the time the Evo came to America it appears the Mitsu engineers had solved the balance shaft problems.
I entered the DSM scene in 1992 and the initial reason for DSM owners removing balance shafts was balance shaft bearing failure (usually a spun bearing). Balance shaft belt failure wasn't uncommon either. This combination of problems relating to the balance shaft system caused it to be one of the more troublesome components of the engine. Once burned you were happy to have the balance shafts gone.
By the time the Evo came to America it appears the Mitsu engineers had solved the balance shaft problems.
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Ok, I have to ask. Where have you read about these "many people." I havent seen it. On top of that, do you mean bearing failure? I find it hard to believe a simple counter weighted roatating shaft will "fail." Bearing failure, thats a bit more reasonable.
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Joined: Feb 2007
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Oil pump shaft bearing failure and balance shaft belt failures, causing the cam timing belt to shred itself against the pick up wheel.
Do some research
Balance shafts serve a purpose. Removing them is definately noticable. Whoever says a good balance job eliminates the need for balance shafts has no idea what he is talking about. The harmonics a straight four makes can only be countered with balance shafts. I leave them in all my motors. I eliminate them on drag cars. When the balance shaft fails is is always from detonation. Detonation beats on the rod bearings. Small particles of bearing material enter the oil. These particles do not pass through tight bearing clearances easily. The balance shaft bearing is the easiest to hurt and destroy.
