Digsy Posted February 7, 2007 Share Posted February 7, 2007 Ok, so fitting an underdrive kit without fitting the crank pulley won't actually underdrive the pulleys at all. The savings will be in lower inertia on the accessory drive, so the engine should be a little more snappy when blipping the throttle, plus a couple of kilos off static mass. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted February 7, 2007 Share Posted February 7, 2007 Ok, so fitting an underdrive kit without fitting the crank pulley won't actually underdrive the pulleys at all. The savings will be in lower inertia on the accessory drive, so the engine should be a little more snappy when blipping the throttle, plus a couple of kilos off static mass. Thats what id like to do Quote Link to comment Share on other sites More sharing options...
Scooter Posted February 7, 2007 Share Posted February 7, 2007 having read the crank pulley info on the link..............is it then possible that an all metal (even if a combination of two different alloys/types) can produce the same harmonic resonance/damping as a metal/rubber/metal stock type pulley? Quote Link to comment Share on other sites More sharing options...
Bob Posted February 7, 2007 Share Posted February 7, 2007 Ok, so fitting an underdrive kit without fitting the crank pulley won't actually underdrive the pulleys at all. The savings will be in lower inertia on the accessory drive, so the engine should be a little more snappy when blipping the throttle, plus a couple of kilos off static mass. Interesting. A few more blingy bits I can set my sights on now Quote Link to comment Share on other sites More sharing options...
Digsy Posted February 7, 2007 Share Posted February 7, 2007 having read the crank pulley info on the link..............is it then possible that an all metal (even if a combination of two different alloys/types) can produce the same harmonic resonance/damping as a metal/rubber/metal stock type pulley? The rubber is an integral part of the system. You might be able to do it with torsion springs. I think the BL pulley uses an arangement like this, but I'm not at all certain that it is specifically tuned in the same way that a stock TVD is. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 7, 2007 Share Posted February 7, 2007 having read the crank pulley info on the link..............is it then possible that an all metal (even if a combination of two different alloys/types) can produce the same harmonic resonance/damping as a metal/rubber/metal stock type pulley? No, an elastomeric pulley is designed to damp a fairly broad range of harmonics, and all metal one relies purely on its inertia (flywheel effect) and will do little broad spectrum damping. Toyota obviously thought long and hard about damping this long bendy crank, hence dual mass flywheel one end, big elastomeric puley the other. Quote Link to comment Share on other sites More sharing options...
Guest laz Posted February 7, 2007 Share Posted February 7, 2007 the pulleys are t6061 and machined to the same size as stock, just lighter.....the crank pulley is smaller, but thats not getting fitted....need to get more info on that.....when i first looked at the bottom pulley i thought it was seperate from the damper....good job that nut is tight!!.........and there is a noticeable difference , some where i read evey kg of spinning mass you take from the engine, is the same as removeing 25kg of weight from the car....does that sound about right??? Quote Link to comment Share on other sites More sharing options...
rick001 Posted February 8, 2007 Share Posted February 8, 2007 I still have all the stock ones if you want them, open to offers on it. Postage may be a little bit due to weight but not to much. Don't know what their worth. I'll post pictures when the camera is charged Hiya mate Really could do with the crank 1 mate please - price me up rick Quote Link to comment Share on other sites More sharing options...
Digsy Posted February 8, 2007 Share Posted February 8, 2007 the pulleys are t6061 and machined to the same size as stock, just lighter.....the crank pulley is smaller, but thats not getting fitted....need to get more info on that.....when i first looked at the bottom pulley i thought it was seperate from the damper....good job that nut is tight!!.........and there is a noticeable difference , some where i read evey kg of spinning mass you take from the engine, is the same as removeing 25kg of weight from the car....does that sound about right??? I don't think its as simple as that to quantify. In any case, the difference should only be noticable when the engine speed is changing. Making the pulleys lighter won't free up any more horsepower from your car (despite what the advertsing blurb says). What it will do is make it easier to accerate (or decelerate) from rest. Have a look at this link, which describes inertia - the property of a body that resists changes on rotational speed. With the necessary geometric info for the pulleys you could calculate the exact change in the pulleys inertia for the change from steel to ali, but that isn't really necessary. Inertia is directly proportional to mass, and therefore directly proportional to density. The density of ali is roughly 2.9 g/cc and steel is 7.86g/cc therefore, size for size, a steel pulley will have three times the inertia of an ali one. The torque required to accerate and rotating body directly proporational to its inertia, so for the same angular acceleration, the steel pulley will require three times as much torque as the ali one. Now, before you all go out and change your pulleys to ali to gove your car three times as much torque, the inertia you need to consider is the total rotational inertia of the engine: Pulleys, belt, timing drive, cranktrain rotating mass, flywheel, clutch or torque converter, geartrain, propshaft, diff, driveshafts, wheels and tyres. So in reality, its only the proportion that is represented by the pulleys that will reduce by a factor of three. Personally, I find it very hard to believe that this effect will even be noticable, yet people with ali pulleys do seem to notice it. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted February 8, 2007 Share Posted February 8, 2007 I find it very hard to believe that this effect will even be noticable, yet people with ali pulleys do seem to notice it. Placebo effect Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 8, 2007 Share Posted February 8, 2007 yet people with ali pulleys do seem to notice it. Oooh oooh I didn't! I didn't! I'm great -Ian Quote Link to comment Share on other sites More sharing options...
Gadget Posted February 8, 2007 Share Posted February 8, 2007 Please explain to me how putting a lighter crank pully on the supe will slow it down, as on all websites that sell these it states that it is spead up due to the fact they are lighter, I have been reading this thread for 3 days now and am very confused now. It is proven that if you lighten something it will go faster, so why if you change the crank will this make the drive system run slower??? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 8, 2007 Share Posted February 8, 2007 The original reason for underdrive pulleys was to slow down the engine driven ancillaries like the water pump and laternator, to stop cavitation and to run an alternator at its most efficient speed on a race engine running at high RPM's for the majority of its running time. Here's a post about inertia in race car drive shaft joints, which may help to illustrate inertia effects: MODERN DRIVESHAFT JOINTS VS. RUBBER DOUGHNUTS I am running a Historic Formula 2 March 712 in Europe. I am working hard to improve the handling. To make the car lighter, first I removed the heavy doughnut with heavy strong driveshafts and I saved a total of 7 Kg after the modification to modern CV joints. Can I expect a improvement on handling? I think the rubber doughnuts are likely working as a spring and are not so nice to drive on corner entry and exit and I am losing power on acceleration (and the polar moment is much higher; that means the acceleration is different.) Can you give me more information about that? Handling should be helped a little. The difference may be too small to feel or even measure, but anything that reduces weight should help handling, once the car is optimized for the new weight and weight distribution. In this case, roughly 50% of the mass in question is unsprung, and that improves the payoff, at least when there are any bumps. Rubber doughnut joints are compliant in torsion, and this can create surging: an oscillatory longitudinal acceleration of the car, caused by the joints wrapping up and unwrapping. Any jerky application, release, or reversal of torque can provoke this. This is not strictly a handling issue – more of a driveability issue. However, we do partly control the behavior of the chassis with the application of torque to the wheels, and anything that reduces our control of torque to the wheels inevitably hurts our ability to control the car. As for the addition to the wheel rate from the doughnuts, no doubt there is some. However, we need wheel rate; we aren't necessarily seeking to minimize it. We can compensate for any contribution from the joints by running slightly softer springs. We do want to know wheel rate as accurately as we can, and the addition from the joints complicates this a bit. If we are really fastidious, we can measure the joints' contribution fairly accurately by putting the car on the scales, removing the springs, jacking the sprung mass up and down, and noting changes in the scale readings. Probably the doughnuts have a somewhat different rate when everything is in motion, but measuring their rate statically should be at least as valid as measuring a tire's rate statically. Of course, all this is moot if the rubber doughnuts aren't there anymore. Regarding improved acceleration due to reduction of moment of inertia, that's also good, but I expect the effect here will also be small. It will be nowhere near as big as a similar moment reduction at the flywheel or clutch, because the drive shafts turn much slower. If the engine turns, say, four times as fast as the shafts, then any given saving at the flywheel is worth sixteen times as much as the same reduction at the shafts. The engine has to accelerate the flywheel four times as fast as the shafts, and any given inertia torque at the shafts looks only one-fourth as great to the engine because it is reduced through the gears. Still, even if the effect is small, it is surely helpful. Quote Link to comment Share on other sites More sharing options...
Gadget Posted February 8, 2007 Share Posted February 8, 2007 That cleared that up! Quote Link to comment Share on other sites More sharing options...
Digsy Posted February 8, 2007 Share Posted February 8, 2007 Please explain to me how putting a lighter crank pully on the supe will slow it down, as on all websites that sell these it states that it is spead up due to the fact they are lighter, I have been reading this thread for 3 days now and am very confused now. It is proven that if you lighten something it will go faster, so why if you change the crank will this make the drive system run slower??? Putting a light pulley on a Supra will not slow it down. You're mis-reading. Underdriving your front end accessories by fitting a smaller crank pulley will slow the rotation of those accessories down - hence the concern over the water pump. The reduction in inertia you get from fitting the lighter pulleys is supposed to give you a noticable benefit. Quote Link to comment Share on other sites More sharing options...
Guest RPM_PARTS Posted February 10, 2007 Share Posted February 10, 2007 Hi All, Very new to the forum so if i upset any one please tell me where to go.!!! i sell these light weight pulleys on ebay and off ebay and havent had any problems, there a nice bit of kit and fit perfect. If any one has not been put off, and whats some light weight bling for under the hood let me know. rpm_parts_store Quote Link to comment Share on other sites More sharing options...
Gamer Posted February 10, 2007 Share Posted February 10, 2007 Hi All, Very new to the forum so if i upset any one please tell me where to go.!!! i sell these light weight pulleys on ebay and off ebay and havent had any problems, there a nice bit of kit and fit perfect. If any one has not been put off, and whats some light weight bling for under the hood let me know. rpm_parts_store You might want to watch the unauthorised advertising for trade. Quote Link to comment Share on other sites More sharing options...
Branners Posted February 10, 2007 Share Posted February 10, 2007 Hi All, Very new to the forum so if i upset any one please tell me where to go.!!! i sell these light weight pulleys on ebay and off ebay and havent had any problems, there a nice bit of kit and fit perfect. If any one has not been put off, and whats some light weight bling for under the hood let me know. rpm_parts_store nothing like cheap pulleys from an unknown source. To advertise as a trader on this forum you need to become a reognised trader. Please do not advertise your wares on this forum again. JB Quote Link to comment Share on other sites More sharing options...
Vagnum Posted February 10, 2007 Share Posted February 10, 2007 So has anyone actually killed an engine or know anyone who has killed an engine due to fitting a solid alloy crank pulley or is it a case of believe what you read? Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted February 10, 2007 Share Posted February 10, 2007 So has anyone actually killed an engine or know anyone who has killed an engine due to fitting a solid alloy crank pulley Yes, but not on a Supra. I've worked on engine development (no more detail, so please don't ask). I've seen engines fcuked by incorrectly 'tuned' torsional vibration dampers (cam or crank pulleys). A solid damper in this situation I would class as incorrectly tuned (or to be more precise, untuned). Now, you may fit one and be lucky and find that the engine lasts forever. Maybe there are users out there with results that they'd like to share. Quote Link to comment Share on other sites More sharing options...
2JZ-GTE-IS200 Posted February 18, 2007 Share Posted February 18, 2007 from what i understand the damping part of the damper is between the hub and the outer drive ring for the accessories, so i cant really see how this has an overall effect on the crank damping, is it not that the rubber dampener material is to actually reduce shock loadings on the drive ring for the accessories???? as a thought im currently looking for a new pulley as mine has seperated, but as my car is a pure track car ive started thinking more along the single crank pulley route...and the more i look into it, the less i find about actual evidence, of ``what the need`` is for the damped pulley. i can understand maybe the need on a car that maybe covers many miles a year......... Quote Link to comment Share on other sites More sharing options...
Guest chrisflorey Posted February 18, 2007 Share Posted February 18, 2007 Removed Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 18, 2007 Share Posted February 18, 2007 You REALLY should keep a damped pulley, IMO, preferably the stock Toyota one. Quote Link to comment Share on other sites More sharing options...
Guest chrisflorey Posted February 18, 2007 Share Posted February 18, 2007 Hi Chris . Yes I do like the idea of the Boost Logic Supra pulley but not the cost ... If we could get a good order we can half that cost + save on shipping costs and import fee's . Who do I see about becoming a trader ? Cheers Quote Link to comment Share on other sites More sharing options...
flukey-lukey Posted February 18, 2007 Share Posted February 18, 2007 But for piece of mind we can insert a rubber / plastic part to do the same job or even make the pulley out of two parts! Please let me know if this is of any interest to anyone , Im here to answer any questions you may have, You want to set up a Group buy between yourselfs I can offer good price! So this would be an exact replica of the stock crank pully but made with alloy? I might be interested, but I think you should PM Mawby to get traders/hobbyist licence thing, or he might tell you off What are other peoples thought on these if they're made with rubber inbetween like the stock one? Mr Wilson? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.