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techtalk:evo:carb04 [2019/03/22 02:16] ixl2relax [Exhaust Pipes & Cams - Power or Reversion] |
techtalk:evo:carb04 [2021/03/31 23:19] ixl2relax [Gaskets] |
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| ===== Gaskets ===== | ===== Gaskets ===== | ||
| - | |Cometic (bottom) versus HD (top) exhaust gasket comparison ((photo by Hippysmack))| | + | The Exhaust Port Gasket is a crushable gasket intended to seal the opening between the cylinder head exhaust port and the upper end of the exhaust pipe. In most cases, it is best to install it into the exhaust port and then align the pipe to it. Tighten the exhaust pipe flange nuts in alternating steps so that the pipe draws to the head evenly. |
| - | |{{:techtalk:evo:carb:cometic_vs_hd_exhaust_gasket_by_hippysmack.jpg?direct&400|}}| | + | |
| + | There are a number of XLForum threads regarding installing the Exhaust Port Gaskets.\\ | ||
| + | http://xlforum.net/forums/showthread.php?t=44022\\ | ||
| + | http://xlforum.net/forums/showthread.php?t=143646\\ | ||
| + | http://xlforum.net/forums/showthread.php?t=204486\\ | ||
| + | http://xlforum.net/forums/showthread.php?t=856566\\ | ||
| + | http://xlforum.net/forums/showthread.php?t=1597528\\ | ||
| + | http://xlforum.net/forums/showthread.php?t=1779860\\ | ||
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| - | ===== Exhaust Pipes & Cams - Power or Reversion ===== | + | Here are some comments from this thread: (http://xlforum.net/forums/showthread.php?t=558421) |
| + | "The SE ones are preferred by almost every engine builder I've ever spoken to.. More so then any of the aftermarket versions.. They are generally much better at sealing and last longer then the stock ones." | ||
| + | "The Factory seals are a total Nightmare ! I have been struggling with this for months. The Standard seals are IMPOSSIBLE to get into the head, And the Manual says to put them on the pipe first." (Note: It is better to install in the heads rather than on the pipe.) | ||
| + | "I changed to the SE seals and there is not much material in them compared to the stockers." | ||
| - | **Quoting Aaron Wilson from the XLForum (aswracing):**((xlforum.net/vbportal/forums/showthread.php?t=1028905 - Post#12)) | + | "I used copper crush gaskets, they are difficult to line up but once good they seal tight." |
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| + | "I don't get it, I have swapped back and forth from SE to stock depending on pipes for years and never had an issue intalling the stock gaskets. Yes they are more difficult than the SE but you just work them in one edge slightly in then in a circle pattern until just the edge is in all the way around then keep pushing them in in the same manner until they are seated. Then I take and run my thumb all the way around the inside to make sure they are completely smooth. When installing the exhaust you do so CAREFULLY. Leave the clamp out of the way and pull the heat shields if you can't see up there perfectly. Center the pipe in the gasket and hold tight, slide up the clamp, install the nuts and tighten them evenly. Then again the SE ones work good too and are easier to install. I think if the stock head pipes are on it and you can get the stock seals installed and done correctly that they will last longer, but hey to each is his own." | ||
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| + | There is a Jims (#788) Exhaust Seal Installation Tool: ([[techtalk:ref:tools167#jims_788_exhaust_seal_installation_tool|Sportsterpedia Tool Section for Jims #788]]) | ||
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| + | | Stock HD Exhaust Port Gasket (65324-83B)\\ \\ Notice that the gasket is tapered.\\ Tapered side should face out toward pipes. | {{:techtalk:evo:carb:exhaust-gasket-hd-65324-83b.jpg?direct&300|}} | | ||
| + | | Cometic (bottom) versus HD (top) exhaust gasket comparison. ((photo by Hippysmack)) | {{:techtalk:evo:carb:exhaust-gasket-cometic_vs_hd_by_hippysmack.jpg?direct&300|}} | | ||
| + | | Scremin Eagle Exhaust Port Gasket (17048-98)\\ \\ Notice that the gasket is squared off. | {{:techtalk:evo:carb:exhaust-gasket-se-17048-98.jpg?direct&300|}} | | ||
| + | | Aftermarket Copper Ring Exhaust Port Gasket\\ \\ Essentially an o-ring shape. | {{:techtalk:evo:carb:exhaust-gasket-alt-copper.jpg?direct&300|}} | | ||
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| + | ====== Exhaust Pipes & Cams - Power or Reversion ====== | ||
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| + | All exhaust systems have harmonic pressure waves passing down and up the pipes. These waves are initiated by the operation of the exhaust valves. The waves move back and forth, with new waves combining or competing with the existing waves in the exhaust system, to either help move the exhausted mixture out of the pipes or back toward the cylinder. In a complicated way, the rpm of the engine is creating a certain frequency of new waves while the length and shape of the exhaust system is reflecting those waves at its own frequency. | ||
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| + | This complex combination of frequencies causes each exhaust system design to have it's own characteristics of helping the combustion cycle at certain rpms (making more power) and hindering that cycle operation at other rpms (creating reversion and less power). The trick is to match the right exhaust system and cams so they are working together to efficienctly create the most power. | ||
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| + | In the following quotations, of an XLForum discussion about stock 'D' cams versus Andrews 'N4' cams, Aaron Wilson provides a very good explanation: | ||
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| + | **Quoting Aaron Wilson from the XLForum (aswracing):**((http://xlforum.net/vbportal/forums/showthread.php?t=1028905 - Post#12)) | ||
| Well, contrary to what you might hear, the N4's are quite capable of delivering more bottom end than the stock D cams. The reason is that they have overlap, where the "D" cams have very little. | Well, contrary to what you might hear, the N4's are quite capable of delivering more bottom end than the stock D cams. The reason is that they have overlap, where the "D" cams have very little. | ||
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| Overlap is the period in time when the exhaust valve is almost closed and the intake valve starts to open. There's a window of time when both valves are open. The piston passes through TDC during this window, finishing it's exhaust stroke and starting it's intake stroke. | Overlap is the period in time when the exhaust valve is almost closed and the intake valve starts to open. There's a window of time when both valves are open. The piston passes through TDC during this window, finishing it's exhaust stroke and starting it's intake stroke. | ||
| - | Imagine what's going on right then. A whole bunch of hot, high pressure exhaust has just left the cylinder. Sitting in the intake tract is a fresh, relatively cool, air/fuel charge sitting at low pressure. Both valves are open.\\ \\ The piston starts down, and starts pulling. Where is it going to pull from? The answer is that it wants to pull from the exhaust. That's where all that hot, high pressure is sitting. | + | Imagine what's going on right then. A whole bunch of hot, high pressure exhaust has just left the cylinder. Sitting in the intake tract is a fresh, relatively cool, air/fuel charge sitting at low pressure. Both valves are open. |
| - | So what makes it pull from the intake instead?\\ \\ It's extremely critical that the exhaust system creates a suction wave right then. If it does, the suction wave will actually pull on the intake tract (remember, both valves are open) and get that fresh charge moving before the piston even starts pulling on it. If the exhaust system does this, it greatly helps cylinder fill. | + | The piston starts down, and starts pulling. Where is it going to pull from? The answer is that it wants to pull from the exhaust. That's where all that hot, high pressure is sitting. |
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| + | So what makes it pull from the intake instead? | ||
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| + | It's extremely critical that the exhaust system creates a suction wave right then. If it does, the suction wave will actually pull on the intake tract (remember, both valves are open) and get that fresh charge moving before the piston even starts pulling on it. If the exhaust system does this, it greatly helps cylinder fill. | ||
| On the other hand, if the exhaust has high pressure right then, it'll actually push the intake charge back out the intake tract, really screwing up the cylinder fill. What's more, the intake charge will go back out the carb. Then when the piston goes down and the exhaust valve closes, the piston will pull on the intake again. The intake charge ends up passing through the carb three times: in, out, and back in again, picking up fuel each time. | On the other hand, if the exhaust has high pressure right then, it'll actually push the intake charge back out the intake tract, really screwing up the cylinder fill. What's more, the intake charge will go back out the carb. Then when the piston goes down and the exhaust valve closes, the piston will pull on the intake again. The intake charge ends up passing through the carb three times: in, out, and back in again, picking up fuel each time. | ||
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| The shape of the torque curve tells the story. It's a map of cylinder pressure, which for all intents and purposes is a map of cylinder fill. A perfect torque curve is table flat. Where it comes up from that tends to be where the pipe is working. Where it drops from that tends to be where the pipe is pushing back. When it's pushing back, the afr also tends to go rich.\\ | The shape of the torque curve tells the story. It's a map of cylinder pressure, which for all intents and purposes is a map of cylinder fill. A perfect torque curve is table flat. Where it comes up from that tends to be where the pipe is working. Where it drops from that tends to be where the pipe is pushing back. When it's pushing back, the afr also tends to go rich.\\ | ||
| (end quote) | (end quote) | ||
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