From a different thread First up can you explain how an UD pulley results in less torque down low? The answer is NO. This is I find it hard to explain what torque is. TORQUE The concept of torque in physics also called moment or couple originated with the work of Archimedes on levers. Informally, torque can be thought of as "rotational force". The rotational analogues of force, mass and acceleration are torque, moment of inertia and angular acceleration. The force applied to a lever, multiplied by its distance from the lever's, is the torque. For example, a force of three Newtons applied two metres from the fulcrum exerts the same torque as one newton applied six. Don't get mixed up between torque and power they are related but not the same. Just accept it on face value that the torque from a 6 kg pulley is a hell of a lot more than a 1.5 kg UD one. The amount of horsepower used to drive and store energy in the standard pulley is worth while as you transfer the energy to the very heavy torque convertor and flywheel. The second thing is this part of what you said You got to change the way you think about a motor to comprehend how a motor works and the potential horsepower it can produce. Also forget about hotter gases part that is very wrong and counterproductive, {if you want me to go into that I will let me know}. A motor can only produce so much horsepower that's the very top of the mountain. Now it's been a long time since I quoted these figures so I might be out but you will get the general idea. Motor producing max horsepower 100% Then take away the energy lost to noise made due to combustion 50%, heat 30%, fiction 30%, motor ancillaries {e.g. cams, valve train, alternator} 25%, gearbox 30%, drive shaft 5%, diff 10%, drag from brake 5%, wheels and tyres up to 10% and tyre noise up to 5 percent So for 3 liters of motor the energy produced at roughly 6 times 2 hundred of a second is over 2800 horsepower divided by 6 in the combustion chamber. Imagine only 20% of all power made is transmitted to the conrods. Quickly off topic a bit look up a thread on indexing spark plugs. Considering that the burn time in the combustion chamber is quiet slow at over 1.5 -2 hundreds of a second. Imagine just lining up the park plug tip[ to give you a 90 percent burn time in under 0.8 hundredths of a second and that wound increase you horse power { we should call it kilowatts BTW or joules} by 40 or more horse power. One word HUGE comes to mind, when it comes to heat noise and vibration losses this is the killer when it comes to making power. I went into this in the other thread so I won't go into detail here as much. There is no right or wrong way. However there is better ways. My reason is "if your are going to lose 30 percent of horsepower through a auto transmission why not use the torque effect of the standard under drive pulley to your advantage and use it as a multiplier for the torque convertor to give you more newton meters at the diff. However if you going for the manual transmission that loses less than 15 percent of power go for the under drive pulley and let the engine save it losses of power being sapped bye a 6 kg pulley. The CAS runs off the passenger side exhaust cam and is belt driven. Don't bring crank twist into it as that is a totally different problem that you should not see till your motor produces a crap load of horsepower. Check the online manual at page em13. anyone one else with something to add? shadow
Yep, you seem to be making a case for a 50kg OD pulley on autos :LOL: (Sorry - the devil made me do it) Cheers:zlove: Barry
.... okay, happily corrected on this, but still not convinced that belt will not transmit vibrations. however, as i keep saying, i agree with you in that i don't think these effects are important for a stock or semi-stock vg30. but i reiterated that you can't simply state that the pulley has nothing to do with timing. it does play a role, sometimes important, sometimes not so important. there are many companies selling harmonic dampers with proven results (well... proven by them ), more so for v8s etc, some of which are belt driven engines. yes, i have an understanding of torque and power (though admittedly it has some holes in it). think what you're trying to say is that a 6kg pulley has a higher moment of inertia than a 1.5kg pulley if both spinning at the same rpm. but the engine is what must supply the energy to the pulley, so for a stock pulley more power goes to accelerating the pulley yes? as you say, there is then more energy stored in the spinning pulley (higher moment of inertia). so it still isn't clear to me why it is better to store this energy in the pulley, instead of transferring it directly to the torque converter. this is another part of my understanding that could do with some work (stupid thermodynamics!). so if you feel like going on a rant, i'm listening. and i'm not exactly sure of the relevance of the rest of that paragraph about efficiencies etc.
man, ive never heard so much crap in my life.. give me figures on a dyno showing loss of torque down low when an UD pulley is installed, stored inertia in a big cheap pulley is not the same as torque yes.. aids mummy an daddy to get the car rolling from a start easier.. but then you must accelerate a 6KG pulley to 6000 rpm.. thats robbing power(and torque).. not adding it man.. which is why cars have big heavy flywheels.. the big pulley is steel for nissans bottom line i'm not even going to waste my breath on the rest of the crap you said (motor producing max HP of 100% then remove 200% and you will have a very fast car in reverse?? maybe honda did get it right with spinning their engine backwards.. haha) have you ever heard 300HP of noise?? my exhaust aint that good ok.. wasted some breath (why do we HPC coat turbo manifolds and put little beanies on our turbine housings if hot gasses are counterproductive?? they're much faster)
