Crank Balancer snapped off (Whipple 2.9)

[engineermike]

I don't see how SC vs Turbo changes cylinder pressures or risk of ring damage if given the same band of pressures.

That's one problem with turbos.....too easy to turn up the boost.

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[80FoxCoupe]

Anyone on this forum who claims to know this particular answer is either flat wrong or basing it on the same sparse failure data that you and I already have access to. Like I said, there are very few people globally who really know how to answer this accurately.

When dealing in rotational harmonics, consider the following: The crankshaft has a torsional stiffness and a moment of inertia, as any spring-mass system does. If you were to hold one end steady, twist the other end, then let go, it will vibrate rotationally at some frequency. But in use, the first torsional resonance will be both ends moving opposite each other with some "node" in the middle that's turning at basically constant speed. I'm going to make 2 huge assumptions for simplification: 1) that they don't want it ever operating at resonance (this isn't always true but I suspect it is in this case) and 2) the first critical speed is the one we are trying to avoid.

The idea, then, would be that you want the maximum forcing function to be below the first torsional resonance by some margin. The forcing function is simple and possibly just 4 x running speed, or about 30k cpm (7500 rpm x 4 power strokes/cycle). Therefore, you need the rotational natural frequency to be something like 33k cpm or higher for a 10% separation (rule of thumb). You can see why Ford said years ago that increasing the rpm or power (forcing function frequency or amplitude) would increase failures. Torsional natural frequency of the crankshaft can be increased by reducing moment of inertia on either end (not to be confused with the damper's "inertia weight") or by stiffening the middle, which generally isn't an option. The damper contains either an elastomeric element or a viscous fluid, coupled to a mass. This changes the dynamics of the front of the crankshaft by basically attaching a spring-mass-damper to it, which of course must be selected (spring rate, mass, and damping coeffient) to effectively counter-act the motion and increase the natural frequency of the system. This is one reason that a lighter damper might be a bad thing; because the internal inertia-mass is probably better if heavier.

If the above were all there was to it, I might could figure it out myself given a couple of weeks. But the truth of the matter is I grossly oversimplified it in the above explanation. You'd have to figure in the rod big-end weight, rotational effects of the torque converter and even transmission input shaft and oil pump, consider amplitude of the forcing function, factor in the all the accessories (each one being a spring-mass-damper), factor in the 4 cams and chains (more spring-mass-dampers), consider multiple mode shapes (>1 nodes), consider running above the first resonance, oil damping in the bearings, and even consider temperature effects on the properties of the elastomer or viscous fluid in the damper. Then of course, run the model through a matrix of all possible engine speeds, power levels, and temperatures. I bet that there is a small engineering group at Ford that does this full-time for all the engines in development, and they have the software modelling and hardware testing capabilities that the aftermarket can only dream of.

Well said. Looks like we will never really know what would be beneficial in terms of effective harmonics dampening. Maybe the old school method is the best, get a stronger crankshaft haha.

 

[80FoxCoupe]

Are people snapping Boss cranks too?

Boss crank is same production coyote crank. Cross plane 5.2 crank is a different composition and is stronger than the coyote crank. According to Ford Performance.

 

[shogun32]

Maybe the old school method is the best, get a stronger crankshaft haha.

perhaps, but I would research replacing the bearings.

Boss crank is same production coyote crank. Cross plane 5.2 crank is a different composition and is stronger than the coyote crank. According to Ford Performance.

and it will have very different harmonics

 

[80FoxCoupe]

perhaps, but I would research replacing the bearings.
You lost me.

and it will have very different harmonics

Agreed, but we dont know if the harmonics will be better or worse.

 

[SolarFlare]

I don't see how SC vs Turbo changes cylinder pressures or risk of ring damage if given the same band of pressures.

you think I said turbos are many times more likely to break a ring land vs a supercharger. What I said is that the most likely failure is a ring land or bearing failure. But people sweating a 1/100 type failure like a snout.

 

[Black Dog]

Cant be that hard of a concept for some thick skulls to get it thru their head. Turbos with untouched balancers had had broken snouts. Even Aldo from Aldowelds who sees more turbos in coyotes than most in here combined has said this is a “normal” thing on coyotes, cracked or broken snouts.

Well hot rod.......how do you "Untouch the Balancer when doing OPGs and TG? Because the correct way to do these Coyotes when ramping up HP/TQ is well known the Coyote needs OPGs and TG.

 

[Black Dog]

People that buy turbos to avoid the potential chance of breaking the snout are too funny. Considering you’re many times more likely to experience a bearing or ring land failure.

Turbo really don't have to worry about snapping a snout. It is not common at all.
And blower boys seem to be having just as much if not more ring land failures.
I have been in both worlds. Have you ever had a turbo kit on you Mustang? Not talking about an Ecoboost.

 

[SolarFlare]

Uh oh lmao now turbos don’t even break ring lands….it’s like a different type of cyl pressure and heat lol

 

[Duece McCracken]

So.

I've been stalking this thread a bit. I like to keep this stuff in my mind for when I start ripping it apart.

To help prevent the rare occurance of snout breakage.

1. Proper balancer install. Clean surfaces, use installation tool, FULLY seat it. Torque properly

2. S/C belt tension. Too tight is bad, lol

Those seem the two big take aways. Unless you are running a 10 rib and over 1k hp? Then crank support is a good idea?

I will probably snag that ARP crank snout stud kit. That just seems like a very nice piece to keep that balancer nice and tight, and possible combat some of the flex on the snout.

My goal is a stage 2 whipple on E85, probably in the 750-800whp range.

So, just to be safe, opg, csg, ARP crank snout stud, and install balancer properly.

Am I missing anything?

 

[Black Dog]

So.

I've been stalking this thread a bit. I like to keep this stuff in my mind for when I start ripping it apart.

To help prevent the rare occurance of snout breakage.

1. Proper balancer install. Clean surfaces, use installation tool, FULLY seat it. Torque properly

2. S/C belt tension. Too tight is bad, lol

Those seem the two big take aways. Unless you are running a 10 rib and over 1k hp? Then crank support is a good idea?

I will probably snag that ARP crank snout stud kit. That just seems like a very nice piece to keep that balancer nice and tight, and possible combat some of the flex on the snout.

My goal is a stage 2 whipple on E85, probably in the 750-800whp range.

So, just to be safe, opg, csg, ARP crank snout stud, and install balancer properly.

Am I missing anything?

^^^ Bet money this is where most failures come in especially when using after market tensioners. And yes sir Too tight is bad.

 

[SolarFlare]

Nope. That’s a good plan

 

[80FoxCoupe]

Turbo really don't have to worry about snapping a snout. It is not common at all.
And blower boys seem to be having just as much if not more ring land failures.
I have been in both worlds. Have you ever had a turbo kit on you Mustang? Not talking about an Ecoboost.

So.

I've been stalking this thread a bit. I like to keep this stuff in my mind for when I start ripping it apart.

To help prevent the rare occurance of snout breakage.

1. Proper balancer install. Clean surfaces, use installation tool, FULLY seat it. Torque properly

2. S/C belt tension. Too tight is bad, lol

Those seem the two big take aways. Unless you are running a 10 rib and over 1k hp? Then crank support is a good idea?

I will probably snag that ARP crank snout stud kit. That just seems like a very nice piece to keep that balancer nice and tight, and possible combat some of the flex on the snout.

My goal is a stage 2 whipple on E85, probably in the 750-800whp range.

So, just to be safe, opg, csg, ARP crank snout stud, and install balancer properly.

Am I missing anything?

If a crank support is available for your combo, run it. There is no downside other than cost. But you are running a boosted s550, you have plenty of money to spend so no biggie.

 

[Duece McCracken]

^^^ Bet money this is where most failures come in especially when using after market tensioners. And yes sir Too tight is bad.

If a crank support is available for your combo, run it. There is no downside other than cost. But you are running a boosted s550, you have plenty of money to spend so no biggie.

I'll have to see the cost for a kit that'll work on my 19' Bullitt with a 6 rib Whipple 3.0 gen 5 .

If I blow this up, and build a new motor for sure. I'm not super worried about the crank snout currently, but I like to make cost effective choices while I have it torn apart for OPG and snout gear.

The balancer install, and issues people can have, has enlightened me for sure.

Thank you all for this!

 

[Veteran]

Anyone on this forum who claims to know this particular answer is either flat wrong or basing it on the same sparse failure data that you and I already have access to. Like I said, there are very few people globally who really know how to answer this accurately.

When dealing in rotational harmonics, consider the following: The crankshaft has a torsional stiffness and a moment of inertia, as any spring-mass system does. If you were to hold one end steady, twist the other end, then let go, it will vibrate rotationally at some frequency. But in use, the first torsional resonance will be both ends moving opposite each other with some "node" in the middle that's turning at basically constant speed. I'm going to make 2 huge assumptions for simplification: 1) that they don't want it ever operating at resonance (this isn't always true but I suspect it is in this case) and 2) the first critical speed is the one we are trying to avoid.

The idea, then, would be that you want the maximum forcing function to be below the first torsional resonance by some margin. The forcing function is simple and possibly just 4 x running speed, or about 30k cpm (7500 rpm x 4 power strokes/cycle). Therefore, you need the rotational natural frequency to be something like 33k cpm or higher for a 10% separation (rule of thumb). You can see why Ford said years ago that increasing the rpm or power (forcing function frequency or amplitude) would increase failures. Torsional natural frequency of the crankshaft can be increased by reducing moment of inertia on either end (not to be confused with the damper's "inertia weight") or by stiffening the middle, which generally isn't an option. The damper contains either an elastomeric element or a viscous fluid, coupled to a mass. This changes the dynamics of the front of the crankshaft by basically attaching a spring-mass-damper to it, which of course must be selected (spring rate, mass, and damping coeffient) to effectively counter-act the motion and increase the natural frequency of the system. This is one reason that a lighter damper might be a bad thing; because the internal inertia-mass is probably better if heavier.

If the above were all there was to it, I might could figure it out myself given a couple of weeks. But the truth of the matter is I grossly oversimplified it in the above explanation. You'd have to figure in the rod big-end weight, rotational effects of the torque converter and even transmission input shaft and oil pump, consider amplitude of the forcing function, factor in the all the accessories (each one being a spring-mass-damper), factor in the 4 cams and chains (more spring-mass-dampers), consider multiple mode shapes (>1 nodes), consider running above the first resonance, oil damping in the bearings, and even consider temperature effects on the properties of the elastomer or viscous fluid in the damper. Then of course, run the model through a matrix of all possible engine speeds, power levels, and temperatures. I bet that there is a small engineering group at Ford that does this full-time for all the engines in development, and they have the software modelling and hardware testing capabilities that the aftermarket can only dream of.

I was wondering if Ford approved the Roush SC , they must have run some harmonic tests with it. In this case there is some back door proof that a belt running a SC is possibly within acceptable Harmonic levels.
My question is, if the kinetic crank stud is a improvement, why wouldn’t they fit a similar fastner when doing a warranty approved Roush ? Could the kinetic change harmonics for the worst ?

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