Crank scraper....discuss! More specifically, teflon edged crank scrapers. Good, bad or indifferent? Since a thread is officially useless without pics...here are pics:
I have seen some made of just metal plaque being really close to the crank and rods Yes good as it avoid the oil to stick on the crank and rods Make it kind of lighter Some engine builder claim 5bhp gain and a good addition of a windage tray Now if your one is touching the actual moving part not so good And must be really noisy Fair enough it s teflon but still
Not touching...but close. You mark the teflon with Engineering Blue, turn the crank and then trim off the teflon where it rubs to leave an interference fit. Even turning by hand takes the teflon off...so you can get very close in a short time. Fit to block, do 50 miles or so to let the teflon bed into the crank/rods...and dump the oil along with any small bits of teflon. You should then end up with a 'run in' telflon blade as close to the rotating parts as it's possible to get.
Call me old fashioned but is this not a little overkill? I mean there are jets squirting oil onto the bottom of the pistons and rods anyway. I suspect centrifugal force will see that most of the oil is thrown off the crank. I use this fine German example to demonstrate, and bare in mind the rotational speeds involved are far higher in an engine. [YOUTUBE]cQApDp5GXuQ[/YOUTUBE]
Some day Ill setup the lathe and rig up a very dangerous demo involving an engine block, and some perspex, the crank whisks up some oil from sump and creates a mini oil hurricane around the crank. The scraper stops the oil pick up whisking hurricane thing. This oil actually slows crank as it hits it/whisks it. This is why you bullnose the crank leading edges, and knife edge the trailing edges, makes the counters more aero, and cuts down on case turbulence. They do work, and are worth it and should be fitted more I feel. Everylittle counts and they cost damn all. I hope that makes sense as Ive been spraying 2 pack paint the last hour. Dan, that video is hilarious, nearing epic proportions.
But the diesel windage plate sump gasket is going to do a fairly good job at keeping the oil in the sump and away from the rotating crank. I would have thought there would be more frictional losses caused by having to rotate a second cam and compress the springs on the extra 8 badly positioned valves myself.
So how much does the windage cloud actually slow a 30lb set of rods and crank spinning at 8k rpm? Bearing in mind there's 4 oil squirters pointing up at the under side of the pistons squirting a jet of oil and not a mist, which then falls onto the top of the crank/rod combo. As good as these may be at 18k I feel they maybe lost on an 8k vw engine. Also, the scrapper is close to the counterweight to 'scrap' oilmist but miles away on the big ends. So, in effect isn't the std VW windage tray doing just as good a job if not better due to the sump being more enclosed? Not knocking the idea but it seems the std windage tray would stop more windage cloud whilst still allowing oil to drain back.
18k engines use dry sump I feel they benefit enough for someone to go out and buy one. Be it a diesel one, or a fancy dan bling item. If its worth 1 hp its worth its in my opinion,
I am concerned with the pumping losses too. That flat crank scraper plate has sharp edges, hardly conducive for allowing the air under the cylinders to pass back and forth as they reciprocate with each crank revolution. In fact it is concerning me soooo much I am going to have another beer and lie down till the stress dissipates.
I would take a steer from the wet-sump rally engines. There was a carbon windage tray fitted to the Mk3 Kit Car AFAIK, but I'm not aware of a scraper.
I got my wording a bit messed up there so I do apologise. A scraper is to 'clean' crank of oil, and breakup the cloud around it that results from the oil falling on crank from up top, be it squirters, or journals/etc. A windage tray stops crank whipping oil from sump at times of cornering, braking etc. I guess if you had no squirters, then the scraper could be done away with, But the windage tray will always be an advantage no matter what.
If it's anything like my bike engine, there are virtually no counterweights on the crank...and the crank itself is tiny...as is the block...so maybe not the same turbulence?
I have had my stress nap. Ok, there are bound to be more effective ways at reducing parasitic losses than the crank scraper plate I would imagine. Alternator, power steering, water pump, air con, and idlers are going to have to be taken into account. Never mind the fact that the OP has a lardy mk3!!
