1320Turbo Posted February 28, 2008 Report Share Posted February 28, 2008 http://cgi.ebay.com/ebaymotors/PEUGEOT-2-0...sspagenameZWDVW anyone try these? I'm thinking horsepower and rebuilding the stock engine and attempting to beefen it up a little. Matt Quote Link to comment Share on other sites More sharing options...
Bean Posted February 28, 2008 Report Share Posted February 28, 2008 Wrong engine - that's for the XN series of cam in block engines like Rob's (NorCal) car. They don't make for good boosted engines either due to the floating cylinder liners. (Be great for a NA build up for the engine though!) Seems odd that they have them - but maybe somebody there owns a Peugeot and they did up an extra set while they were at it... Although heavy - the connecting rods and crank in the N9TE are forged - so with some balancing and some lightening they'll still be decent for modest power increases. Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted February 28, 2008 Report Share Posted February 28, 2008 Funny that they say that shot-peening relieves stress, when it's quite the opposite. (But in a good way ) Here's what a N9Txx-rod (I think they are all alike) looks like and some of the stuff I'll be using when I lighten/balance them. As you can see it weighs about 880g. I was wondering one thing, I've seen that sometimes people grind away the forging-ridge visible in the second photo. It is removed because it acts as a stress-riser (and weight) but often/always it is stated that you need to shot-peen the rod afterwards. And now to my question, what is best: A. Remove the ridge and not shot-peen the rod. B. Leave the ridge as it is. Sorry for hijacking your thread but I thought you might think this is interesting. Quote Link to comment Share on other sites More sharing options...
1320Turbo Posted February 29, 2008 Author Report Share Posted February 29, 2008 hijacking is ok, i wasnt going to buy them, i just wanted to find out about them. I have all the world to work on the 505 while i drive my 3000gt so I want to make it as fun as i can on a budget Quote Link to comment Share on other sites More sharing options...
Bean Posted February 29, 2008 Report Share Posted February 29, 2008 And now to my question, what is best: A. Remove the ridge and not shot-peen the rod. B. Leave the ridge as it is. Sorry for hijacking your thread but I thought you might think this is interesting. I think it's best to remove the stress risers that would be a place for material stress spike starting a fracture or that would instigate a bending moment. If it's polished smooth and shot peened the forces that act on the beam will be able to be evenly distributed on the surface. So I'd smooth the edges and look for places to remove material in less critical places, but I thing smooth is safer than lightening, so do it sparingly to just balance the rods to a minimum weight... That's what I'd do anyway... Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted February 29, 2008 Report Share Posted February 29, 2008 You people have a strange way of polishing things , to me polishing is like when you take a rag and some compound and rub the thing you want to polish. What I was talking about grinding, I ment what you refer to as polishing. I'm not sure what you mean when you say that a stress riser could instigate a bending moment? I don't feel that I got a clear answear to my question, do you think it's better to polish away that ridge and not shot-peen it or just leave the rod as it is. (but balance it of course.) If I were to remove that ridge, it wouldn't be mainly because of the weight. To remove some weight, I was thinking more in line of this: Quote Link to comment Share on other sites More sharing options...
Bean Posted March 1, 2008 Report Share Posted March 1, 2008 You're right Johnny - but I think the term polish is similar to porting and polishing head ports. Engine slang maybe? As for my comment about bending, I was just referring to one of the failures of rods is when they bend under load. Similar to an I beam - most of the strength in these rods is in that outter edge - so the smoother it is the more even the stresses are across the surface. I've seen guys that have made the entire rod as smooth as possible. With any grinding it can cause uneven hardness levels from the heat and action of the grinding, so shot peening it should even it all out. Stress relieving it would be another option - and cryo treating is also a possibility. I watched that video as well and it does make sense where they took off material - tried to find the video he mentions at the end of "end" balancing the rods which would also be a good thing to do. Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted March 1, 2008 Report Share Posted March 1, 2008 Hehe, I know that shot-peening etc. is good. However, that was not my question. do you think it's better to polish away that ridge and NOT shot-peen it or just leave the rod as it is. (but balance it of course.) I'm not convinced that all the tenison would be in the outer edges of the rod since IMHO there is basicly only compressing/pulling tenison in the rod. I think the phenomenon of the rod bending is not from bending moment, but from buckling. Quote Link to comment Share on other sites More sharing options...
Bean Posted March 1, 2008 Report Share Posted March 1, 2008 I'm not convinced that all the tenison would be in the outer edges of the rod since IMHO there is basicly only compressing/pulling tenison in the rod. I think the phenomenon of the rod bending is not from bending moment, but from buckling. Sorry - I was thinking about making the rod stronger as well as lighter - if you're just worried about weight I wouldn't bother touching it. There are probably other areas that are easier to remove weight from without any worries. To clarify my "bending moment" phrasing - (that's how I remember my prof referring to it.) The forces acting on the rod are indeed push pull - but when it reaches a critical point and is about to buckle from the forces acting on it, what will trigger where it bends is the weakest part of the rod - and that trigger is usually some sort of surface irregularity that causes stresses to spike at that point. (since it's bending about a point I think of it as a moment.) Once that weakness fails - the rod bends. What I was getting at (but not your question) was that by eliminating the surface irregularities - the forces are then spread over the whole surface making it as strong as possible. Granted it can still fail - but you'll buy yourself a certain amount of additional strength that could possibly avoid damage. Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted March 1, 2008 Report Share Posted March 1, 2008 Then we are on the same page. But basicly it should be risk-free to remove that ridge because when the rod buckles, it will always buckle in the other way. And it contributes very little to the cross sectional area. I imagine that the rod can only fail in two ways, buckling or breaking in two pieces. Buckling would occur when the pressure in the combustion-chamber is to big, and breaking in two pieces would occor when over-revving. Correct? Quote Link to comment Share on other sites More sharing options...
Bean Posted March 1, 2008 Report Share Posted March 1, 2008 Yep - looks like we're on the same page. As for buckling though - I've seen a nasty collection of rods at the machinists bent all sorts of ways - so I don't think you can predict how it fails... As for breaking - over revving is likely the best bet for that too. Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted March 1, 2008 Report Share Posted March 1, 2008 As far as I know, a rod always buckles to the direction where it's weakest. I've only seen pictures like this: Hmm, maybe I could ask my teacher about this. I'm studying Mechanical engineering right now, so my teacher should know. (I hope ) Btw, What is the machinists? Quote Link to comment Share on other sites More sharing options...
Bean Posted March 2, 2008 Report Share Posted March 2, 2008 I've actually seen them folded in half almost - 90 degree bends - but then again I have no idea what the mode of failure was since there's so many possibilities. (Piston breaks and jams in block? hydrolocked? crank snaps, etc etc) I've even heard that they can stretch enough to hit the head! Machinists work in "machine shops" - this is where they bore the blocks, resize rods, plane heads etc etc. Same as an engine builder - but here they often do a number of other jobs on top of just engine building... Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted March 2, 2008 Report Share Posted March 2, 2008 Hehe, I know what a machinist is, I thought you ment some place called "the machinists". Quote Link to comment Share on other sites More sharing options...
Trevor Posted March 3, 2008 Report Share Posted March 3, 2008 As far as I know, a rod always buckles to the direction where it's weakest. I've only seen pictures like this: Hmm, maybe I could ask my teacher about this. I'm studying Mechanical engineering right now, so my teacher should know. (I hope ) Btw, What is the machinists? A rod is just a pinned I-beam, so yes it will tend to buckle in that direction under concentric loading. But that's assuming your ends are still ideally pinned. Dont assume this is always the case... as bean mentioned, it really depends on the failure mode. a jammed up engine component can create all sorts of eccentric loadings on that rod and deform it in just about any way you can think of. And remember this isn't a statics problem and the loadings aren't totally concentric. A 6k rpm engine has considerable dynamic loadings... There is a large bending moment applied to those rods, hence their I-beam shape. And yes all the stress related to that bending moment is concentrated in the material farthest away from the neautral axis of your rod... So it's important to have a nice finish on the outside of those rods. Go ahead and grind them, but make sure you dont leave them too rough along those edges... polish it up fairly well so cracks dont want to propogate. And lastly... if you're really considering creating enough power with a 505 to have any problems with your rods... i think you'll find problems elsewhere first... :-) remember to draw your free body diagrams. :-) Quote Link to comment Share on other sites More sharing options...
Johnny Posted March 3, 2008 Report Share Posted March 3, 2008 A rod is just a pinned I-beam, so yes it will tend to buckle in that direction under concentric loading (normal operation). But that's assuming your ends are still ideally pinned. Dont assume this is always the case... as bean mentioned, it really depends on the failure mode. a jammed up engine component can create all sorts of eccentric loadings on that rod and deform it in just about any way you can think of. The disussion was basicly about how removing the forging-ridge from the rods will affect their performance. And in the case of another engine component being jammed up, it doesn't matter if you have CrMo H-beam rods. Your engine would still be toast. Therefore I made the assumtion that the rod would be perfectly pinned. Quote Link to comment Share on other sites More sharing options...
1320Turbo Posted March 3, 2008 Author Report Share Posted March 3, 2008 remember to draw your free body diagrams. :-) Vector A - Vector B - Vector.......Physics class is attacking me online Quote Link to comment Share on other sites More sharing options...
Bean Posted March 3, 2008 Report Share Posted March 3, 2008 I should mention that my mechanical engineering classes were over 15 years ago... Holy crap I hate putting date stamps on stuff now! I'm in the IT field now so I don't even use any of it anymore except for how it applies to cars, racing, and making more power. So my apologies if my phrasing is off - but the basics are sound. Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted March 3, 2008 Report Share Posted March 3, 2008 And remember this isn't a statics problem and the loadings aren't totally concentric. A 6k rpm engine has considerable dynamic loadings... There is a large bending moment applied to those rods, hence their I-beam shape. And yes all the stress related to that bending moment is concentrated in the material farthest away from the neautral axis of your rod... So it's important to have a nice finish on the outside of those rods. Go ahead and grind them, but make sure you dont leave them too rough along those edges... polish it up fairly well so cracks dont want to propogate. And lastly... if you're really considering creating enough power with a 505 to have any problems with your rods... i think you'll find problems elsewhere first... :-) remember to draw your free body diagrams. :-) The problem being static or dynamic is not an issue, since we're not calculating anything and don't need to determine the loads. I really don't understand how you can say that there is a large bending moment when there are no perpendicular forces. IMHO, the only bending moment that will be present is due to the big and small-end holes not being perfectly parallell. My guesstimate is that the rod will buckle before the bending moment will become so great that the rod will deform. Feel free to drop in a free body diagram yourself :-) You're probably right about having problems elsewhere before developing so much power that the rods break. I'm not fully clear on what you mean by "the loadings aren't totally concentric" though, my (technical) english is far from perfect. Quote Link to comment Share on other sites More sharing options...
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