Originally Posted by edub370 School yourself guys.. For those of u thinking external harmonic balancers reducing crank deflection is a myth, go do some researching on other forums. It won't
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01-20-2013, 03:55 PM | #1 (permalink) | |
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Andrew 2009 370Z Sport/Touring 6MT sold 2013 Honda Civic Si coupe D/D |
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01-20-2013, 08:00 PM | #3 (permalink) | |
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Wel maybe I'm off the mileage a bit, but you get the idea.
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01-20-2013, 08:16 PM | #5 (permalink) |
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Just to clarify for what that rubber ring is for, it's to balance the pulley it's self. I wouldn't doubt it's to assist N/V/H as well, but we all know our engine is not the silkiest around.
Kyle @ Stillen asked Nissan engineers about it on an old thread "This is a harmonic dampener of sorts, on that point you're exactly right. But it's not to balance the engine, it's to balance the pulley ITSELF."
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01-20-2013, 09:03 PM | #6 (permalink) |
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Just to add some more data into the debate, here is the US patent for a plastic hub torsional harmonic damper which has some good graphs that illustrate the effect on crankshaft twist in degrees vs engine RPM for various damper configurations including no damper.
Even if the engine is perfectly balanced there will always be torsional pulses which can and do form harmonic modes as a result of the discrete, not continuous combustion pulses (each cylinder firing in turn). Balancing the entire rotating assembly will not stop rotational twist of the shaft from the power pulse as each cylinder fires. It will stop out of axis oscillation. The pulley being made out of cast iron is also on purpose, cast iron has one of the highest dampening capacities (google cast iron damping) of any metal. If you don't want to read the whole document look at Figure 2 to see the effect on torrosional vibration via a typical damper (construction shown in Figure 1)
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2011 Nissan 370Z Touring/Sport, 6MT, KAD Last edited by Trilitheum; 01-20-2013 at 09:11 PM. |
01-20-2013, 09:18 PM | #7 (permalink) | |
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01-20-2013, 10:15 PM | #8 (permalink) | |||||||||||
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There's no question that the stock pulley gives the complete system a lower Q factor than any of the aftermarket pulleys available. Cast iron and rubber are unquestionably more efficient at translating vibration to thermal energy. Hysteresis loss is far higher in an iron/rubber assembly, vs an aluminum one. Quote:
I'd love to see a source for the bolded part. Quote:
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I'd be confused as to why a pulley needed a "harmonic dampener of sorts" Quote:
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I absolutely agree with the first statement here. Data is in the numbers. Would be fantastic if a pulley vendor gave us a graph of the frequency response of the crankshaft with each pulley installed. THAT would tell you something. Quote:
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01-21-2013, 02:07 PM | #9 (permalink) | |
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Every car company is going to say, leave your engine alone and it will be fine. Every aftermarket company that makes parts for said manufacturer is going to say, "Buy this and it will be even better" Who do you believe? Forums like this is feedback from everyone. I said it before, take everything you read in here with a grain of salt. Yes, even everything I say and argue about, which I admittedly do a lot sometimes. I'm not out to convince the World, but there are always two sides to the story. Obviously, it's difficult to go wrong with a stock crank pulley. I 100% agree. I also believe a well engineered aftermarket crank pulley can be safe to use. Some do not. People ask why, we say what we think, preferably have relevant source material to back our findings. Could I be wrong? Absolutely. Is the Bible indisputable fact? Do you believe every animal floated around Noah's ARK for months and the entire Earth flooded? I used the word mitigate because regardless of internal or external balancing, spin a motor fast enough and even the best motors can grenade to harmonics. If Nissan plans on spinning the VQ to 9-10,000 rpm or higher, I'm pretty sure we would see a different crank pulley, maybe to a true dampener. FYI, I never stated my finding's as absolute facts. I listed my arguments to the topic. Regarding my statement about external balancing not being necessary, it is absolutely true for some smaller displacement motors. I think the VQ fits in this category, but there is room for argument there. Lastly, and I'm repeating myself, DO YOUR OWN HOMEWORK AND COME UP WITH YOUR OWN CONCLUSION!!! I'm tired of people giving recommendations like it's fact and not letting them decide for themselves by only giving them one side of the argument.
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01-21-2013, 02:25 PM | #10 (permalink) | |||||||||||
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01-20-2013, 08:36 PM | #11 (permalink) |
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Okay so what you're saying is damaging harmonics and torsion don't affect the rotating assembly at all, and if it did then auto manufacturers have not developed a solution for it so therefore no need to worry.
And they balance a metal pulley with a rubber ring? This is what you're trying to convince us of? |
01-20-2013, 08:50 PM | #12 (permalink) | |
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The stock pulley is not a harmonic dampener to remove potential damaging frequencies. The stock pulley with the rubber dampening sandwiched between the cast iron pieces is for N/V/H and balancing of the pulley it's self. The pulley is also balanced afterward by tapping. Torsional effects are mitigated by balancing the entire rotating assembly and adding counterweights to the crank. No external balancing was necessary. Engineers that work on designing and manufacturing factory engines have advanced engineering to the point where in most cases, external balancing and/or harmonic dampeners aren't necessary. I don't take your quotes out of context, please award me the same.
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01-20-2013, 09:08 PM | #13 (permalink) |
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Love how everyone still skirts around the facts that these lightweight pullies to the crank...
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01-21-2013, 02:43 AM | #14 (permalink) | |
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