jc052685 Posted January 28, 2010 Share Posted January 28, 2010 Ok, This just jumped into my head. When having a custom cam ground why not change up the fireing order? Would there be any benifet? Obviously there would be a sound change as well. Has anyone heard or or even tried it on the L? Quote Link to comment Share on other sites More sharing options...
jasper Posted January 28, 2010 Share Posted January 28, 2010 :hs:http://www.familycar.com/Engine.htm Quote Link to comment Share on other sites More sharing options...
ktm Posted January 28, 2010 Share Posted January 28, 2010 The crank shaft sets the firing order, not the cam shaft. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted January 28, 2010 Author Share Posted January 28, 2010 The crank shaft sets the firing order, not the cam shaft. Wrong. Quote Link to comment Share on other sites More sharing options...
PurePontiacKid Posted January 28, 2010 Share Posted January 28, 2010 The crank shaft sets the firing order, not the cam shaft. made me lol. ever heard of the 4/7 swap cams for Small Blocks and other GM motors? Quote Link to comment Share on other sites More sharing options...
MAG58 Posted January 28, 2010 Share Posted January 28, 2010 sort of. 2 cylinders are at TDC at once, so technically you could invert those firing orders, but you cant exactly invert cylinders that aren't at tdc at the same time. You're both right! Yay. Quote Link to comment Share on other sites More sharing options...
jasper Posted January 28, 2010 Share Posted January 28, 2010 http://www.humanspeakers.com/audi/engine5.htm sort of. 2 cylinders are at TDC at once, so technically you could invert those firing orders, but you cant exactly invert cylinders that aren't at tdc at the same time. You're both right! Yay. Quote Link to comment Share on other sites More sharing options...
ktm Posted January 28, 2010 Share Posted January 28, 2010 Go ahead and set your firing order to whatever you want it to be, say, 1-2-3-4-5-6 and see how well your car runs, or 1-3-5-6-4-2, or any other combination that does not take into account the relative positions of the crankshaft journals. Read: http://www.hotrodders.com/forum/what-determines-engine-firing-order-103531.html Quote Link to comment Share on other sites More sharing options...
MAG58 Posted January 28, 2010 Share Posted January 28, 2010 http://www.humanspeakers.com/audi/engine5.htm We were talking about I6 L series, so that's what I was talking about. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted January 28, 2010 Author Share Posted January 28, 2010 Go ahead and set your firing order to whatever you want it to be, say, 1-2-3-4-5-6 and see how well your car runs, or 1-3-5-6-4-2, or any other combination that does not take into account the relative positions of the crankshaft journals. No reason to get an attitude. I am fully aware that the crank will have some say in what the fireing order can be BUT it does not set the fireing order. That is the cams job, period. Quote Link to comment Share on other sites More sharing options...
ktm Posted January 28, 2010 Share Posted January 28, 2010 No reason to get an attitude. I am fully aware that the crank will have some say in what the fireing order can be BUT it does not set the fireing order. That is the cams job, period. Did you read the link? It is not the cam shaft but the crank shaft. The cam is timed to the crank shaft, not the other way around. Read the first link I provided and this link as well: http://www.absoluteastronomy.com/topics/Firing_order No where is there talk about the cam shaft setting the firing order. The firing order is determined during the design of the crank to satisfy design criteria. Read #56 http://books.google.com/books?id=6V1VAAAAMAAJ&pg=PA60&lpg=PA60&dq=what+determines+engine+firing+order&source=bl&ots=dM2KTlr1Nd&sig=A1sWDFXuXuaaY55D8CdCWaJ4qx0&hl=en&ei=hxNhS6SeOczQ8QaOidDUDw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CA0Q6AEwAzgU#v=onepage&q=&f=false Again, no discussion regarding cam shafts. Here: http://en.allexperts.com/q/Classic-Antique-Car-2542/2009/7/1927-chevrolet-firing-order.htm Again, no discussion regarding cam shafts. Here is a thread where Paul is talking about flat plane cranks and has some great diagrams: http://forums.hybridz.org/showthread.php?t=139545 Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted January 28, 2010 Share Posted January 28, 2010 Just my two cents... I don't think custom "grinding" a cam would change the timing... Wouldn't you need a custom "stamped" cam or "forged" cam...Right? Custom grinds just change the lift and duration... so, how long and how big the valves open, but in order to change the timing the cam lobe would have to be moved on the cam shaft. But... I don't know what I'm talking about ... so feel free to put me in my place. I hope this was helpful. Matt- Quote Link to comment Share on other sites More sharing options...
jc052685 Posted January 28, 2010 Author Share Posted January 28, 2010 I have lost all intrest in this thread in all of an hour.... Quote Link to comment Share on other sites More sharing options...
PurePontiacKid Posted January 28, 2010 Share Posted January 28, 2010 mag58 is the only one 100% right in this thread... Quote Link to comment Share on other sites More sharing options...
MAG58 Posted January 28, 2010 Share Posted January 28, 2010 Before this thread gets locked because we're all acting like very big boys and girls, let's see why the firing order is 153624 on virtually all I6's. Split the engine in two since you've basically got two I3's mirrored in an I6 That means you have 123 on one half and 456 on the other, putting the firing order together gives you this 1 _5 3 _6 2 _4 meaning that all exhaust pulses are exactly 120 degrees apart. If you fire all three front cylinders and then all three rear cylinders, then you'd get some really funky in harmonics in the exhaust, meaning that anything but a 6-1 header wouldn't see even firing pulses. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted January 28, 2010 Administrators Share Posted January 28, 2010 (edited) Just my two cents... I don't think custom "grinding" a cam would change the timing... Wouldn't you need a custom "stamped" cam or "forged" cam...Right? Custom grinds just change the lift and duration... so, how long and how big the valves open, but in order to change the timing the cam lobe would have to be moved on the cam shaft. But... I don't know what I'm talking about ... so feel free to put me in my place. I hope this was helpful. Matt- One could feasibly have a custom cam manufactured with a different firing order. It would have to be billet stock as most cam blanks are typically manufactured with the rough shaped lobes already set in sequence, then final ground to a specific lobe profile. With the given crank throw configuration of the L-6 crankshaft, you will be limited to the combination of different firing orders allowed. Because 2 pistons in the L-6 arrive at TDC at the same time, 1-6, 2-5, 3-4, and with 2 complete crankshaft revolutions per cycle, that allows each piston 2 different opportunities to fire. You could have cylinders #1 & #6 swapped with each other, and/or cylinders #2 & #5 swapped with each other, and/or cylinders #3 & #4. Only those swaps or a combination of those swaps would work with the L-6 crankshaft. Now as to why anyone would do that? There are NO benefits to altering the firing of the inline 6 cylinder. It is already optimum with the least compromises. For a V-8, that is a different story. Altering the firing order trades one benefit for another which again does not hold true for the inline 6 cylinder. Edited January 28, 2010 by BRAAP Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted January 28, 2010 Share Posted January 28, 2010 Paul has spoken... And we all have learned. Thanks Paul! Matt- Quote Link to comment Share on other sites More sharing options...
jc052685 Posted January 28, 2010 Author Share Posted January 28, 2010 Before this thread gets locked because we're all acting like very big boys and girls, let's see why the firing order is 153624 on virtually all I6's. Split the engine in two since you've basically got two I3's mirrored in an I6 That means you have 123 on one half and 456 on the other, putting the firing order together gives you this 1 _5 3 _6 2 _4 meaning that all exhaust pulses are exactly 120 degrees apart. If you fire all three front cylinders and then all three rear cylinders, then you'd get some really funky in harmonics in the exhaust, meaning that anything but a 6-1 header wouldn't see even firing pulses. think its more like.... 1-- --2 -3- -4- --5 6-- I think thats right but I could be wrong. edit: ok, paul got to it before me so yeah, this is right^ Quote Link to comment Share on other sites More sharing options...
ktm Posted January 28, 2010 Share Posted January 28, 2010 No, you are correct. #1 and #5 are 120 degrees apart, #5 to #3 are 120, and #3 to #6 are 120 degrees, which puts #1 and #6 at TDC together. http://forums.hybridz.org/showthread.php?t=149540&highlight=gasket Look at the first picture and it confirms your statement. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted January 28, 2010 Share Posted January 28, 2010 In be for the lock down! I can agree that the cam could change firing order but all you would accomplish is reverse the intake and exhaust order and get a reverse order. No gain there........ just for snaps and giggles. Quote Link to comment Share on other sites More sharing options...
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