DerFahrer Posted January 9, 2007 Share Posted January 9, 2007 They were right guys. I meant 360º, not 180º Quote Link to comment Share on other sites More sharing options...
frag Posted January 9, 2007 Share Posted January 9, 2007 In 4-cycle engines, the crank completes two full revolutions for each single turn of the camshaft(s) (4 cycles requires 2 full up-down strokes). Therefore, one revolution of the crank corresponds with half of one for a camshaft. But you knew that. Of course. But that's beside the point. The point is crank mark up cam marks down will or will not set correct timing ? I dont think it will because of the triggering tabs on the driver's side cam sproket, those that trigger the cam prosition sensor wich in turn - in synch with the crank position sensor - triggers the spark AND the injectors. That will not be at the right place at the right time. The ecu will see a discrepancy between both position sensors and the car will not start. I presume... Can some expert here (nipper ?) give a credible verdict? Quote Link to comment Share on other sites More sharing options...
OB99W Posted January 9, 2007 Share Posted January 9, 2007 They were right guys. I meant 360º, not 180º You may have meant 180 deg, but that doesn't change the validity of what I said above (post #24) in this thread. Quote Link to comment Share on other sites More sharing options...
avk Posted January 9, 2007 Share Posted January 9, 2007 In those terms, the marks are at the right place every other revolution of the crankshaft, anyhow, but not every single revolution. Quote Link to comment Share on other sites More sharing options...
OB99W Posted January 9, 2007 Share Posted January 9, 2007 Of course. But that's beside the point. The point is crank mark up cam marks down will or will not set correct timing ? I dont think it will because of the triggering tabs on the driver's side cam sproket, those that trigger the cam prosition sensor wich in turn - in synch with the crank position sensor - triggers the spark AND the injectors. That will not be at the right place at the right time. The ecu will see a discrepancy between both position sensors and the car will not start.I presume... Can some expert here (nipper ?) give a credible verdict? Sorry if you don't think I'm credible. We can let Nipper play referee, if he wants to... However, what I said is not "beside the point". The crank goes through 720 degrees (twice around) during the time the cams turn once (360 degrees). Let's assume that we start off with the crank and cam marks all up. Now rotate the crank through 360 degrees; the crank mark of course will again be up, but the cams will have only gone through 180 degrees, and their marks will be down, but still correctly timed. Rotate the crank through another 360 degrees, and the cams will rotate another 180 (360 total), and their marks will again be up. Here's the point: The crank sensor doesn't know the difference between one time that the crank completes a revolution (when the cam marks are up) and another time (when the cam marks are down). It only detects the passing of particular points, which happen each revolution. It's the pulses from the cam sensor that allows the ECU to determine the definitive position of things. This should help; see page 5 of: http://endwrench.com/images/pdfs/DirectIgnition.pdf Note that the cam reluctor causes there to be 1, 2, or 3 sensor pulses, depending on which 90 degree position the cam is in. The crank sensor's output allows the ECU to determine piston position, but the cam sensor output lets the ECU figure out how that relates to the cylinder cycles. Quote Link to comment Share on other sites More sharing options...
frag Posted January 10, 2007 Share Posted January 10, 2007 Sorry if you don't think I'm credible. We can let Nipper play referee, if he wants to... However, what I said is not "beside the point". The crank goes through 720 degrees (twice around) during the time the cams turn once (360 degrees). Let's assume that we start off with the crank and cam marks all up. Now rotate the crank through 360 degrees; the crank mark of course will again be up, but the cams will have only gone through 180 degrees, and their marks will be down, but still correctly timed. Rotate the crank through another 360 degrees, and the cams will rotate another 180 (360 total), and their marks will again be up. Here's the point: The crank sensor doesn't know the difference between one time that the crank completes a revolution (when the cam marks are up) and another time (when the cam marks are down). It only detects the passing of particular points, which happen each revolution. It's the pulses from the cam sensor that allows the ECU to determine the definitive position of things. This should help; see page 5 of: http://endwrench.com/images/pdfs/DirectIgnition.pdf Note that the cam reluctor causes there to be 1, 2, or 3 sensor pulses, depending on which 90 degree position the cam is in. The crank sensor's output allows the ECU to determine piston position, but the cam sensor output lets the ECU figure out how that relates to the cylinder cycles. Sorry OB99W, I did'nt want to imply that you were not credible, just that a few members here are more credible, have more experience and mechanical knowledge than you and me (but I'm talking for myself cause I dont know you.) As for the rest, I think I will get back at it tomorrow and see if you've succeeded or not in convincing me. Have a good night! P.-S.: One thing I am absolutely certain of, cause I tried it last time I replaced my belt, is that the three marks do not go back together at 12 O'clock every second revolution of the crank. So that's a part of your theory that does'nt work. Quote Link to comment Share on other sites More sharing options...
avk Posted January 10, 2007 Share Posted January 10, 2007 The belt marks obviously do not line up every other revolutiuon, but sprocket marks do. Suppose the belt isn't marked and timing is done by tooth count. What matters is that the three sprockets come back to the same relative position. Quote Link to comment Share on other sites More sharing options...
OB99W Posted January 10, 2007 Share Posted January 10, 2007 Sorry OB99W, I did'nt want to imply that you were not credible, just that a few members here are more credible, have more experience and mechanical knowledge than you and me (but I'm talking for myself cause I dont know you.)No problem, I'm not offended. It's true that you don't know me or my credentials, because I've never mentioned them on this forum, and I don't see a need to do so now. I've never claimed to be infallible, but I do try to be credible . As for the rest, I think I will get back at it tomorrow and see if you've succeeded or not in convincing me.Have a good night! Thanks; you, too. P.-S.: One thing I am absolutely certain of, cause I tried it last time I replaced my belt, is that the three marks do not go back together at 12 O'clock every second revolution of the crank. So that's a part of your theory that does'nt work.What definitely won't align every second revolution of the crank is the marks on the t-belt. However, the cams should come back to the same position after two crank turns, or the engine isn't staying in time. Quote Link to comment Share on other sites More sharing options...
frag Posted January 10, 2007 Share Posted January 10, 2007 No problem, I'm not offended. It's true that you don't know me or my credentials, because I've never mentioned them on this forum, and I don't see a need to do so now. I've never claimed to be infallible, but I do try to be credible . Thanks; you, too. What definitely won't align every second revolution of the crank is the marks on the t-belt. However, the cams should come back to the same position after two crank turns, or the engine isn't staying in time. Ya, you're right, I meant the marks on the belt wont coincide with those on the crank and cams which is irrelevant to our disscussion. So, I think the bottom line is you're right and I'm worng : installing the belt with crank mark up and both cam marks down (6 o'clok) would work (as far as I can figure). Which brings my credibility one notch (at least) down. Well there is always tomorrow... Quote Link to comment Share on other sites More sharing options...
OB99W Posted January 10, 2007 Share Posted January 10, 2007 Ya, you're right, I meant the marks on the belt wont coincide with those on the crank and cams which is irrelevant to our disscussion.So, I think the bottom line is you're right and I'm worng : installing the belt with crank mark up and both cam marks down (6 o'clok) would work (as far as I can figure). Which brings my credibility one notch (at least) down. Well there is always tomorrow... Frag, don't beat yourself up -- nobody here is infallible (as I've said, including me ), and sometimes it takes time to wrap one's head around a concept. By the way, there's some more good info on how the crank and cam sensors work (among other "stuff") in this (see especially page 15): http://endwrench.com/images/pdfs/Fuel.pdf By the way, I'm not suggesting that doing a t-belt change with the alternative positioning is the best approach. Following "the book" seems to work just fine and is basically straightforward. Quote Link to comment Share on other sites More sharing options...
uniberp Posted January 10, 2007 Share Posted January 10, 2007 Did anybody mention that the belt may be mismarked? I would hate to open my timing covers and see that. What brand belt? I used a Cloyes. It lined up fine. Trying to hang the timing belt (Subaru OEM) on my '95 Legacy 2.2. Lined up the crank and both cam sprockets properly with their apppropriate marks. Slid the belt on and its marks line up perfectly with the crank sprocket and the right (passenger side) cam sprocket. But no way in heck will it line up with the left (driver side) sprocket mark. It appears that the left sprocket mark is midway between a "tooth" and a "valley!" Seems to me it should be dead center on a "valley" to line up with the printed mark on the belt, which is centered over the 41st tooth from the crank sprocket mark. Anyway I matched marks as closely as possible, took the slack out and this (the photo) is where it ended up--about 3/16" beyond the notch on the tb cover. The tensioner is still pinned and mounted in its right-most position. So what does anyone think. Is it right or is it off by a tooth?[ATTACH]4549[/ATTACH] Quote Link to comment Share on other sites More sharing options...
Olnick Posted January 14, 2007 Author Share Posted January 14, 2007 Update, Question and Confession . . . ! UPDATE: I feel like I have a new engine! New timing belt, toothed idler, water pump/thermostat/hoses, crank and cam seals, 0-ring in left cam holder, resealed oil pump, plugs/wires, pcv valve and fresh coolant. Oddly enough, I wasn't too impressed the first day I drove it to work. Engine ran smoothly but didn't have anymore spunk than it did before. Now it's getting better each day (I think the ECU is relearning my driving since I had the battery out for a few days.) QUESTION: How poorly would the engine run if one cam was off by a single tooth? Would it be really obvious--rough-running--missing? Really would appreciate any informed input on this since my original question is still gnawing away at me! CONFESSION: Last Monday I was busy buttoning up the front end so I could kick back and enjoy the BCS football game (Yes, "It's great to be a Florida Gator!"), which was to kick off at 3:30 our time. Had the belt covers and crank pulley back on by noon and was looking for a large screwdriver to wedge the alternator into place. "Screwdriver" rang a bell in my head--then it hit me, I had forgotten to wedge the tensioner to the left and torque it down before pulling the pin!!! What a sinking feeling. So it was back to square one and start all over again. Positioning the belt (for the umpteenth time) I thought maybe I was sent back in for a reason. This time I lined up the marks and let the belt fall where it may--which means the left cam sprocket is one tooth counter-clockwise from its position in the original photograph. And as I said, it seems to be running beautifully. To quote Tex, "I dunno!" FINALLY: Mahalo nui loa to all you Keiki o ka Makali'i. I couldn't have done it without you. I wouldn't have even tried. Aloha. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.