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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / October 2005wrist pin lubrication
How do modern auto engines lubricate the wrist pins? I seem to recall that many years ago the wrist pins got lubrticated by the sloshing effect as the fast-moving crankshaft dipped into the oil pool near the bottom of the oil pan. Soemone recently told me that modern engines pump oil directly to the pin itself, but he couldn't explain how. I can't figure out how this could be done. The wrist pins are moving up and down violently, and the idea of somehow pumping oil directly onto the pin (between the pin and the rod bushing) seems totally impractical. So, can I assume the modern method of getting oil between the rod bushing and the wrist pin is still just by sloshing the oil up there, as before? littlberry > How do modern auto engines lubricate the wrist pins? I seem to recall > that many years ago the wrist pins got lubrticated by the sloshing [quoted text clipped - 7 lines] > the rod bushing and the wrist pin is still just by sloshing the oil up > there, as before? littlberry I would assume drilled con rods. Just an extra mfg. step to drill a hole from the rod bearing saddle up to the wristpin bore. I would ASSume that any engine using this method would either use full-floating pins or preferably pins pressed into the pistons. There would be a hole in the rod bearing so that some of the oil being pumped into the rod bearing from the crank gets gets diverted up to the pin. nate An awful lot of wrist pins still use splash lub - but it's oil flung from the rod bearings, not actual splash from the oil pan. There is a lot of oil moving around in there, and wrist pins don't need much. There is an option of a direct feed from the rod bearing up the center of the rod, usually a very small hole EDM'd, not drilled. Not common, but available as an option on Carrillo's etc. Brian >> How do modern auto engines lubricate the wrist pins? I seem to recall >> that many years ago the wrist pins got lubrticated by the sloshing [quoted text clipped - 16 lines] > > nate > I would assume drilled con rods. Just an extra mfg. step to drill a > hole from the rod bearing saddle up to the wristpin bore. I would > ASSume that any engine using this method would either use full-floating > pins or preferably pins pressed into the pistons. There would be a > hole in the rod bearing so that some of the oil being pumped into the > rod bearing from the crank gets gets diverted up to the pin. I doubt you have ever owned an engine with a drilled con rod. It has been done, but isn't usually. A couple of things come into play. 1) oil is being splashed all over the inside of the engine and some is bound to work its way into the gap between the piston and the rod (I believe some designs add channels to facilitate this by directing oil to the gap). 2) compared to other bearings, the wrist pins don't move very much. They just oscillate maybe 25 degrees back and forth around the vertical. The pressure is high, but the movement is comparatively restricted and slow. Ed > > I would assume drilled con rods. Just an extra mfg. step to drill a > > hole from the rod bearing saddle up to the wristpin bore. I would [quoted text clipped - 13 lines] > > Ed I believe the VW 1.8T con rods are rifle drilled, as are the ones from the old G60 engine. So doubt all you want, but I'm fairly sure that I have :) I'm sure about the G60, as my fiancee has one, and I replaced the rod bearings on it a couple years ago (factory used some experimental bearing that didn't last on the early G60 engines) nate > I believe the VW 1.8T con rods are rifle drilled, as are the ones from > the old G60 engine. So doubt all you want, but I'm fairly sure that I [quoted text clipped - 3 lines] > bearings on it a couple years ago (factory used some experimental > bearing that didn't last on the early G60 engines) Look like a stuck my foot in my mouth. <sigh> VW does so many "special" things (and still manages to build crap) I usually discount them. But I am sure you are right. http://bildon.com/catalog/DetailsList.cfm?ID=053.105.401&Nav=6 says in the product description - "OEM 144mm Connecting rod. For all 1.8L Golf, Jetta and 2.0L Golf, Jetta with oil fed wrist pin bushing." Other "performance" VW rods do not appear to have the same sort of arrangement for feeding the wrist pin bushing - http://bildon.com/catalog/DetailsList.cfm?ID=ECR.198.159.EA21LW&Nav=6 - nothing at all http://bildon.com/catalog/DetailsList.cfm?ID=ECR.198.144.EALW&Nav=6 - a hole on top, maybe to let oil drip in? http://bildon.com/catalog/DetailsList.cfm?ID=ECR.198.159.EA20&Nav=6 - nothing at all It appears that the Subaru WRX engine also feeds oil under pressure to the wrist pin. And so do at least a few Nissan engiens. Sorry about the misinformation. I guess more engines that I know use drilled connectring rods. It also appears that some connecting rods include a hole in the center of the top to allow oil to enter the bearing from the top (not pressure fed). Ed > Look like a stuck my foot in my mouth. <sigh> VW does so many "special" > things (and still manages to build crap) I don't know if "crap" is the right word. Crap connotates being non-functional yet simple (what could be less complex than a turd, after all?). VW repeatedly builds stuff that manages to be LESS functional than "crap," yet more complicated than a space probe. Its like they're still trying to live down the fact that the Beetle was so simple... as if that were a bad thing. > > Look like a stuck my foot in my mouth. <sigh> VW does so many "special" > > things (and still manages to build crap) [quoted text clipped - 5 lines] > still trying to live down the fact that the Beetle was so simple... as > if that were a bad thing. I don't know what either one of you is on about. The 1.8T puts out over 180 HP (it's rated at 180, but I've seen dyno sheets of stock GTIs laying down 175+ real HP AT THE WHEELS) with everyday, no hassle reliability. All based on the original watercooled VW block, kind of the VW equivalent of the SBC. Tried, true, and bulletproof. Kind of hard to argue with that... Now they did have some supplier issues with the coil packs and the window regulators, but those were rectified and recalls issued. Other than that, there's not much not to like. The only downside to owning a VW is having to deal with VW dealers, but even a few of those are decent. nate >> I don't know what either one of you is on about. The 1.8T puts out > over 180 HP (it's rated at 180, but I've seen dyno sheets of stock GTIs [quoted text clipped - 8 lines] > VW is having to deal with VW dealers, but even a few of those are > decent. Well in my immediate family we have owned three VW products - 1981 Audi Coupe - 1986 VW Jetta - 1991 VW Passat Of the three, the Audi was the best. No major problems. However in less than 3 years the seats looked ragged and the plastic on the control levers and the dash was turning white. The Jetta was bad. Multiple in tank fuel pump failures, weird rear tire wear, power window failures, sun roof leaks, leaked oil everywhere, and the transmission finally failed (5 speed manual). Plus dealer maintenance was hideously expensive. And what is with the weird clutch release mechanism? But the Jetta was actually good compared to the Passat. Expensive motor mounts failed, three out of four power windows failed, passenger side exterior door handle fell off, power locks quit, timing belt tensioner jammed and wrecked the head (non-turbo 4), sun roof leaked, leaked oil like a sieve, paint faded in less than 10 years. This was my younger Sisters car. She had it maintained by the book at the dealer. Against my very muted advice, my SO just bought a 2005 Jetta for her daughter to drive (she was impressed by the safety ratings). So far it has been good except for some weird behavior of the instruments. Also recently a co-worker bought a new Passat Wagon, but after a month or so, he forced the dealer to take it back after a list of problems almost too long to imagine (left his pregnant wife stranded twice, oil pressure would suddenly drop to zero for no reason, gunk oozing out of the bottom of the doors, seat covers had to be replaced, water leaks, more). He was lucky, the same dealer sold both Hondas and VWs and took back the Passat and gave him a Honda at cost. So when I say VW's are crap, I am not just making a random accusation. At best it looks like you have less than a 50/50 chance of getting a good one. On the other hand, when they are right, they drive nicely and fit me a lot better than your average Japanese vehicle. >>>Look like a stuck my foot in my mouth. <sigh> VW does so many "special" >>>things (and still manages to build crap) [quoted text clipped - 7 lines] > > I don't know what either one of you is on about. Oh, things like pneumatic power door locks that have to have an air compressor to operate them, thermostat housings with no less than 8 rubber hoses that attach to direct coolant to various and sundry places, requirements to use proprietary coolant that's the same color as Toilet Duck (or maybe Vanish), etc. etc. Just general over-complication of ordinarily simple tasks. > How do modern auto engines lubricate the wrist pins? I seem to recall > that many years ago the wrist pins got lubrticated by the sloshing > effect as the fast-moving crankshaft dipped into the oil pool near the > bottom of the oil pan. Soemone recently told me that modern engines > pump oil directly to the pin itself, but he couldn't explain how. The whole crankshaft is filled with pressurized oil in an internal drilled passage (multiple passages that intersect and are plugged externally, since the crank isn't straight, actually) Oil is fed into the crank at each main bearing saddle from a hole in the upper half-bearing. The upper half-bearing also has a groove so that oil can flow from the saddle hole into a drilled hole in each bearing journal on the crank while that hole in the upper half of its rotation. Since the engine has several main bearings (5 in the case of a v8) its always getting oil from at least one of the main bearings at any given instant. Likewise, each connecting rod journal on the crank has a drilled hole that connects to the crankshaft internal oil passage. Oil flows out of this drilled hole and lubricates the connecting rod bearing. From there, it can get to the wrist pin one of two ways. Most engines have a hole somewhere on the outer rim of the connecting rod "big end" and through the rod bearing positioned such that when the crank oil hole lines up with it, it will be aimed up at the cylinder and piston above. Frequently this is at the parting line of the rod and cap, and the line-up happens when the rod is at its maximum tilt. So once per crank rotation, the cylinder, underside of the piston, and wrist pin are blasted by a shot of pressurized oil. Some engines have an internal passage in the connecting rod itself to lubricate the wrist pin, but that doesn't spray the underside of the piston and cylinder wall, so an alternate method has to be privded I didn't realize there would be enough pressure between the rod bearing saddle and the crankshaft throw to force oil up through a hole in the rod and then still have enough pressure to keep oil between the wristpin and the wristpin bore. There must be a whole system here that I need to read up on. Can either of you recommend a website? I am guessing now that there must be a way of pumping oil INTO the crankshaft (there must be a channel inside it, right?) which can emerge in between the surface of the throws and the rod bearing saddles. It sure seems to me like a very complicated and iffy concept - how long has this method (forced channeling of oit within the body of primary AND SECONDARY moving parts) been perfected. If must be perfected because today's engines last easily over 200k miles with regular oil changes. > I didn't realize there would be enough pressure between the rod bearing > saddle and the crankshaft throw to force oil up through a hole in the [quoted text clipped - 9 lines] > because today's engines last easily over 200k miles with regular oil > changes. The oil gets into the crank passages through holes in the main journals. The mains are fed from the oil galleries in the block. (as well as the cam bearings and the rocker shafts) nate  Signaturereplace "fly" with "com" to reply. http://home.comcast.net/~njnagel > I didn't realize there would be enough pressure between the rod bearing > saddle and the crankshaft throw to force oil up through a hole in the > rod and then still have enough pressure to keep oil between the > wristpin and the wristpin bore. Well, the oil pump generates betwwen 40 and 80 PSI (typically, depends on the engine) so there's PLENTY of pressure to do the job. Volume needs to be good too, because each bearing that the oil crosses (going into the crank through the mains, coming out of the crank through the rod bearings) loses some oil for its own lubrication and flings it back into the crankcase. > There must be a whole system here that > I need to read up on. Can either of you recommend a website? Hmmm.... Factory Service Manuals for various engines usually have full oiling path diagrams. Haven't looked for any on-line. In a nutshell, an oil pump (either interlocking-rotor or gear type) draws oil from the pan, passes it through a filter, and then directs pressurized oil into a whole system of passages in the block casting which lead to all the bearings, the lifters, and (in some designs like Chrysler v8s) the overhead rocker arm shaft to lubricate the rocker arms and valve stems. The crankshaft is internally drilled to carry oil from the mains to the rod bearings. At every bearing, some oil leaks out as it lubricates/cools the bearing, and returns to the oil pan. In cam-in-block v8s, the cam itself is flooded in oil that is draining back to the pan from the lifters and the overhead area. I am > guessing now that there must be a way of pumping oil INTO the > crankshaft (there must be a channel inside it, right?) which can emerge > in between the surface of the throws and the rod bearing saddles. It > sure seems to me like a very complicated and iffy concept - how long > has this method (forced channeling of oit within the body of primary > AND SECONDARY moving parts) been perfected. Its not "iffy" at all! Chrysler was one of the earliest mass-production manufacturers to go to full pressure oiling (all bearings, including cam bearings, plus valve lifters, plus conrod squirt holes to spray the cylinder walls), and did so in the late 1920s, with their full line of engines being so-equipped by the early 30s. High-end manufacturers like Duesenberg, Packard, Bentley, etc. were not really all that far ahead of that. Ch*vrolet stuck with a crappy splash lubrication system until 1955, though. > If must be perfected > because today's engines last easily over 200k miles with regular oil > changes. I know some 1940s engines that lasted that long, and I own a 1973 engine with > 400,000 miles. No big deal at all with quality oil and proper maintenance. IMO, modern engines actually have less margin for long life (weaker aluminum blocks and other lighter weaker parts, mainly) and the real reason that a bigger PERCENTAGE of them are lasting past 200k miles is because oils have gotten better by huge orders of magnitude since the 70s. |
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