It's a typographic error(but I like your description much better).:rofl: BTW, how is your scrotum these days?:zlove:
Aye, so what, only get one that goes on a newly rebuilt / balanced engine? Makes a lot more sense in this regards.
Chesutiko, is your Zed aus spec? If so, and you have log books then it's fair to assume they're correct in the milege. if yours is a Jap spec, then 99% guaranteed it has done way more than 77,000k's as they're almost always clocked back before coming over here. But in saying that, most of our Zeds here are J-spec and happily run UDP's. So in answer to that, it doesn't matter what K's the car has done, it is purely to do with the condition of the engine and how balanced it is already. Best thing to do (as you've already said) is to whack it in, and see how it feels. If you feel instant vibration, then you know it's most likely caused from the UDP. If no vibrations are there, then it should be sweet.
Folks, we are confusing 2 separate things - a UDP has as its sole function an increase in diameter to reduce the speed of the belts. These are commonly used on full-race engines that spend >80% of their life at 0.8 vmax rpm and more. An alternator which the OEM designs to run at a regular engine speed of (say) 2500rpm with occasional bursts to red-line will sh1t itself rapidly when run at 6000rpm and above for extended periods of time. Standard pulleys are fine for track-days. An Impreza STi I used to own did 42 track days over the course of 6 years and it never had a water pump, alternator, power steering pump or air-con pump problem So, most race engine builders will spec either oversized ancilliary pulleys to slow their rotational speed, or an underdrive crank pulley (UDP) for the same effect. Now, the purpose of a "crankshaft damper" is to permit the damping of vibrations/harmonics in the crankshaft that arise as a consequence of the CIEE cycle in the engine. Most race engines are fully balanced internally, but this is not usually the case for an OEM engine. Even so, there will still be torsional vibrations and harmonics that require damping in a race engine - V8 Supercar, F1 boat and so on all have dampers fitted - albeit they can be of smaller diameter to reduce rotational inertia. Some confusion comes with an OEM setup that combines these two functions - lots of OEM crank pulleys fulfill both functions (and the damping is performed by the rubber ring between the piece attached to the crank and the bit that forms the pulley to drive the belts. Because the VG30 engine is so short, the incidence of torsional vibration/harmonics is lower than with (say) an RB30 engine where the propensity for harmful harmonics is an order of maginitude higher. However, IT STILL EXISTS. If you want to justify fitting a UDP - do so on the basis of BLING only .... and accept that if you rev the pickhandles off the thing all the time, then eventually, you will see harmonic related engine damage. This can be: stuffed bearings, rod bolt failure, cracked bearing caps, rod/piston failure and even valve train failure can be anticipated -harmonics in an engine are a true devil child and to be avoided if you have the choice. Whether this damage actually occurs is dependent on engine condition, age and drvier behaviour of course. Some modern engines run a two-piece flywheel with a damper integral in the flywheel and therefore will not run a damper on the nose of the crank. I personally do not run a damper in my full race engine (4.98 litre aluminium V8, quad-Weber 45DCOE, carillo rods, steel crank, blah/blah), BUT it is rebuilt with new rings/bearings/valve springs/valve-train retainers and rod/main cap bolts etc EVERY season (after about 20 hours competition running), with everything being crack-tested before re-assembly. Pistons are junked after every 3rd rebuild and rods after every 4th rebuild. Crank life is currently 100 hours, but these are carved from steel billet. All I can say is that there is a lot of misinformation in this thread .... good as it is, the VG30 will still suffer harmonics eventually. That said, if you want to run a UDP, don;t expect it to drop your ET by half a second, nor improve you laptimes by half-a-second - it is just for bling in a roadie, and only one small part of the spec of a ful competition engine, significant only as a part of a complete package .... because its sole purpose is to slow the drive belts for a hi-rpm engine and with a reduction in mass, will give you less rotational inertia so it will rev a little quicker. A manufacturer who tells you different is "advertising". FPUO RB
Good write up mate its what I have heard previously and pretty much agree 100%, hence why even my engine is currently being rebuild and balanced I'm still not going to get one
Yes the "Driving" pulley would have to be smaller in diameter to reduce actual belt speed. The "Driven" pulleys however would have to be increased in diameter to slow their rotation
D'oh ... increase ancilliary pulley dia and inverse on crank ... blame it on 60-yo brian .. having a senior's moment
Who is this "60 year old Brian" you want us to blame(or is that just another trip & fall)?:rofl::rofl::zlove::zlove:
I think i'll still put it on anyway. Kind of over coming up with a good reason anymore, besides that I bought it... and that Benny C has one. I'll see what happens then make a decision from that, as I've said many times. All this technical talk of harmonics and such seems good and all, though I honestly don't think it will cause catastrophic damage based on these harmonics. Hell... a rough piece of road probably makes more flippin' harmonics thorugh the whole car than a UDP.. or maybe even ridiculously oversized sound systems..... The engine I have was in a head on car crash.. front of the car is mutilated. Engine still run's beautifully regardless of the massive shock that it probably felt from the head on.
Ah, someone who understands engine dynamics/harmonics/torsional vibration.. The VG does have a short crank, and does experience vibration issues at higher RPM's. Some testing with ATI years ago proved this. Ever wondered why guys break the oil pumps in the RB26's with big hp/rpm's. TORSIONAL VIBRATION shatters the gears. Underdriving the pulleys, for a gain of about 5kw's (on a 400kw engine, that's only 1.25%!!!) is beyond reality .. You'll get more power loss from an intercooler that's heating up or cylinder head temp changes OR TYRE SLIP ON THE ROLLERS. 4'c intake temp change is around a 1% poer gain loss - humidity staying constant with the delta temprature. Stu
UDP resurrection . Even though I understood the damage of harmonics I still used a alloy UDP , (to squeeze out more power,chasing response). But after having snapped a cam I have to surrender to the fact that they are an unneccesary evil. Was my damage directly related? yes ..maybe ..no.. who knows Most wont have a problem with one but if you are truly a hard driver that constantly kills their engine ,you will find out the hard way (taking it to redline every now and then is not hard driving) not worth the risk . Next engine super light chromo flywheel with ross dampner.(its not a balancer) and greddy oversized accessory pulleys http://www.atiracing.com/products/dampers/damper_dinan.htm
Holy thread dig Batman lol, Yeah i'm another who long ago swapped the GFB UDP for a Ross one, Peace of mind with the amount of track work i do.
