johnc Posted March 13, 2003 Share Posted March 13, 2003 I'll keep it simple. Solid pulley = Good (all pulleys are solid and are bolted/attached to the damper). Solid Damper = Bad. Any type of through bolt/pin/stud that affects the rotational differences between the two parts of the damper bonded together by rubber = Bad. How's that? Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted March 13, 2003 Author Share Posted March 13, 2003 Looks like I solved my problem without affecting what it's ment to do. Great! , now, what about a ballance issue? Like I said, the Tec wheel was put on the backside before by a shop, chough, TopEnd, cough, and I don't think it was ballanced. And everytime I changed dampers, I didn't either.... is this a no no?? thanks for the info... joel Quote Link to comment Share on other sites More sharing options...
TimZ Posted March 13, 2003 Share Posted March 13, 2003 I would take it to a reputable shop and have it balanced. Just bear in mind that this is a seperate issue from the damping issue. Damping has nothing to do with balance. To elaborate on John's statement, the mod that you did probably effected the damping characteristics to some degree. How much is hard to say. I would have to guess that it is still better than no damper, so long as you left enough clearance around the pin to allow it to move sufficiently to damp the crank vibrations. Trouble is that I can't tell you exactly how much movement that is. I would recommend leaving clearance of at least the thickness of the rubber all the way around the pin. We are hesitating to recommend this mod simply because of all the "if"s in the abouve statement. IF you do all that stuff (stuff that I don't know exactly how much to tell you to do) correctly, and IF the mod didn't remove enough material to drastically effect the damping characteristics (which I also don't know what to tell you as to how much is acceptable), THEN the mod should probably be okay. If any of those things are not right, then worst case is that it's the same as a solid pulley, which is bad. Quote Link to comment Share on other sites More sharing options...
jeffp Posted March 13, 2003 Share Posted March 13, 2003 I understand your situation and I have taken steps to fix the problem, and believe me I have been working on it for some time now. You have spent a good amount of money on your car, turbo header, TWM's and all that jazz and you a scrimping on a critical part in my opinion. The fact is that these engines need a good damper, and tha modification you have done in my opinion is defeating the purpose of the part. You may get some dampening affect, but not to the extent that may be needed. Myself, I haven't driven my car for some time until I get this issue solved. You mentioned you did not understand all that was going on with the part. well in a nut shell the story is that what ever you want to choose for a material. All materials have a resonate frequency (you can look it up in the dictionary if you like to understand better) but this is the frequency that will basically make the material start to oscillate, it is that oscillation that will make the part, break, crumble, and destroy itself. Every material has this resonate frequency, even for example sheet rock, you get the resonate frequency of the sheet rock and you will break it by projecting that frequency at the wall at the correct level, it will simply start to oscillate at that frequency and then berak. That is what is happening in your engine. That is why a damper was made. The fact of the matter is that the stock part was NEVER designed to spin at 7000 rpm levels and if it did it was for a very short time in relation to all of the other rpm ranges the average engine would see, and it was NEVER designed to spin to 7300 rpm, you would never see that on the street in a stock application. you may want to do a search on the net and see what kind of hits you get on dampener for cars. hopethat clears it up. Jeff Quote Link to comment Share on other sites More sharing options...
jeffp Posted March 13, 2003 Share Posted March 13, 2003 Harmonic Balancer (Vibration Damper) The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both. When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel. This keeps the crankshaft operation calm. Quote Link to comment Share on other sites More sharing options...
David K Posted March 14, 2003 Share Posted March 14, 2003 When does the twisting/vibration reach its peak? Quote Link to comment Share on other sites More sharing options...
katman Posted March 14, 2003 Share Posted March 14, 2003 Good question. Don Potter always told me there was a resonance at about 6800 rpm in an L24 with stock balancing (i.e. no heavy metal) but our dyno runs always had a buzz in the floor at about 4000 rpm (lots of different engines, same buzz). I could never confirm the 6800 rpm thing, but never instrumented for it either. The floor buzz at Sunbelt could be a function of the natural frequency of the dyno stand and not the engines. We've put a lot of race miles on junkyard OEM dampers and never had a failure or any sign of impending doom. I suspect folks who have recurring problems with dampers don't have a damper problem, they have a balance or straightness problem. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted March 14, 2003 Author Share Posted March 14, 2003 I suspect folks who have recurring problems with dampers don't have a damper problem, they have a balance or straightness problem. hmm... I suspect folks with the damper/trigger wheel set up like mine, (almost 3/16" of metal taken off the backside so that the wheel will not contact the timing cover) are having or going to face the same fate as mine, because by removing that much material off the damper, I belive it's no longer ballanced, and more importantly, not as much rubber/metal is left to hold these peices together as when un-cut. Quote Link to comment Share on other sites More sharing options...
jeffp Posted March 14, 2003 Share Posted March 14, 2003 My engine is new, and it was built by Robello racing, and balanced. I have only had the one dampener go bad on my engine. I did some calling around and found out this does happen frequently. The rpm ranges, well there again, nobody has taken the time to really look into the situation scientifically at least that I was able to find. I do know that the L28 engines and their dampeners are all sertup at the same frequency, so that much I know for a fact. The parts were frequency tested and that verified the tuning. One thing I was reading argarding the L24 engines and I thought it was curious was that they were also doing the same thing, but in this case it was at the flywheel and pressure plate. You can read the article in the new sport magazine, the crank was redesigned and it seemed to take car of the problem for the most part. They had to add the counter balances on the crank and it smoothed out the crank and vibration. BAE (I think is the company) was having a bad problem with it on their race cars. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 14, 2003 Share Posted March 14, 2003 You can read the article in the new sport magazine, the crank was redesigned and it seemed to take car of the problem for the most part. They had to add the counter balances on the crank and it smoothed out the crank and vibration. BAE (I think is the company) was having a bad problem with it on their race cars. The company was BRE, Brock Racing Enterprises. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted March 14, 2003 Author Share Posted March 14, 2003 Well I'm game for a better fix. Please post the info where to buy a damper to solve this problem, please... I'd buy it in a split second.. Quote Link to comment Share on other sites More sharing options...
David K Posted March 14, 2003 Share Posted March 14, 2003 Now guys im thinking of a new fix. Im going to find out where it would be most ballanced to drill holes in the pulley. Im looking for some rubber plugs in the shape of studs. Im going to take the rubber plug, drill a smaller hole in it, and then add some kind of metal stud within the rubber. I am then going to put the rubber/metal plug in the hole i drilled in the pulley. Im guessing this would give the pulley some strength but also keep the damping effect. What do you all think? Quote Link to comment Share on other sites More sharing options...
David K Posted March 14, 2003 Share Posted March 14, 2003 Here is some great reading. I stand corrected on running a solid pulley. http://www.dinanbmw.com/html/danger_of_power_pulleys.htm Quote Link to comment Share on other sites More sharing options...
clint78z Posted March 14, 2003 Share Posted March 14, 2003 There are some pretty sharp minds here, but they would all be guessing if this would work or not. Any form of messing with the rubber piece or pulley itself is going to affect the dampening propeties as well as the balance of the pulley. How long you could sneak away with this is unknown. Go down to a junkyard and find a 240z and get a flashlite and find one with non cracked rubber. A nismo or OEM pulley might be a better option since the rubber will be new. The only way I would recomend you do anything to this dampener is if you had experience with engine harmonics, did destructive test on the crank itself. Any form of reducing the effectiveness is not a good option. I am quite surpised that as much as the L6 is raced a fluid damper has not been designed. Quote Link to comment Share on other sites More sharing options...
David K Posted March 14, 2003 Share Posted March 14, 2003 Us guys with power steering cant simply go down to the junkyard and pull a pulley off a 240z. We need a pulley with the 6 10 mm bolt holes for the extra power steering pulley to be added at the end. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted March 14, 2003 Author Share Posted March 14, 2003 Another thing I wonder, is has everyone that has the Tec2 wheel on their damper, had it ballanced? This dosen't get brought up to much in this discussion Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted March 14, 2003 Author Share Posted March 14, 2003 Us guys with power steering cant simply go down to the junkyard and pull a pulley off a 240z. We need a pulley with the 6 10 mm bolt holes for the extra power steering pulley to be added at the end. I drill four holes and tap them for the wheel, so I would think it could be done for the pully add on.... Quote Link to comment Share on other sites More sharing options...
David K Posted March 14, 2003 Share Posted March 14, 2003 Us guys with power steering cant simply go down to the junkyard and pull a pulley off a 240z. We need a pulley with the 6 10 mm bolt holes for the extra power steering pulley to be added at the end. I drill four holes and tap them for the wheel, so I would think it could be done for the pully add on.... But again, how ballanced it this? Quote Link to comment Share on other sites More sharing options...
TimZ Posted March 14, 2003 Share Posted March 14, 2003 Another thing I wonder' date=' is has everyone that has the Tec2 wheel on their damper, had it ballanced?This dosen't get brought up to much in this discussion [/quote'] Yes I did have mine balanced. With respect to a couple other recent posts, I'll say this one more time... While all of the reciprocating parts should be balanced, the damper is not correcting for imbalances in the crankshaft, or for vibrations caused by imbalances in the crankshaft. Again, this is why I don't like the term 'harmonic balancer' - it is inaccurate. As Jeff has already said about three times, the resonant vibrations are a completely seperate issue - they are there due to the material properties of the crank, and will still exist in a perfectly balanced crank. This cannot be avoided. The damper is there to damp those vibrations - like throwing a rubber matt over a ringing bell. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted March 14, 2003 Author Share Posted March 14, 2003 The damper is there to damp those vibrations - like throwing a rubber matt over a ringing bell. I guess that would be like when you get a brake drum turned, they put that big rubber band around it . Boy does that make a diffrence, now I get the picture... Quote Link to comment Share on other sites More sharing options...
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