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techtalk:ref:engctl01 [2020/01/10 17:12] ixl2relax [Daytona Twin Tec TC88A] |
techtalk:ref:engctl01 [2020/01/12 00:55] ixl2relax [Too Much Advance Timing?] |
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| + | ===== Too Much Advance Timing? ===== | ||
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| + | Quoting XLForum member, **ASWRacing**:((http://xlforum.net/forums/showthread.php?t=1650461 Post#12))\\ | ||
| + | **A Perspective by Aaron Wilson of Hammer Performance. (June 2013)**\\ | ||
| + | | I've dyno'ed thousands of bikes over a long period of time, and on many many of them I've dialed in the timing during the process. Advanced it until the power dropped off, retarded it until the power dropped off, and then centered it in between those two locations. I've also played with curves a lot.\\ \\ **I'm here to tell you that too much timing most definitely costs power, and on the vast majority of bikes, the optimum timing is well below the threshold of ping. Running more timing than optimum makes your motor run hotter and puts the pistons at risk and the threshold of ping is a terrible place to put the timing on most bikes!**\\ \\ Most of these bikes, when they have reasonable compression and chamber turbulence (i.e. a squish band), will want their ignition timing set for about 28-30 degrees max advance at WOT. Going past that starts hurting power and making the motors run hot.\\ \\ When you do a performance build, you really should get an aftermarket ignition, because not only can you turn down the timing, you can bring the timing in more slowly. You almost always find power when you do that on a higher compression build! Most of the motors like it so slow that it's not all-in until 4500-5000rpm. On many ignitions, I've found the best power on the softest curve available. For example, the Dyna 2000 curve 4 almost always works the best if the bike under test has 10:1 compression or more. **On a Twin Tec TC88A I literally found the best power on my 04 883/1250 on initial 2 / slope 0.** That's the softest curve and almost the least amount of timing the module can give.\\ \\ Getting this notion out of people's heads that more timing = more power has always been a huge challenge in this business. When you're talking about a performance build, the exact opposite is almost always true. We have a vested interest in seeing our customers get this right, because we don't want complaints of scuffed or broken pistons, and that's exactly what will happen if you run the timing too high, sooner or later. | | ||
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| ===== Manifold Absolute Pressure -vs- Vacuum Reading ===== | ===== Manifold Absolute Pressure -vs- Vacuum Reading ===== | ||
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| Quoting XLForum member, **RacerWill**:((http://xlforum.net/forums/showthread.php?t=1422868 Post#27))\\ | Quoting XLForum member, **RacerWill**:((http://xlforum.net/forums/showthread.php?t=1422868 Post#27))\\ | ||
| | Just a quick note on MAP(Manifold Absolute Pressure). First, the word "absolute" refers to where zero is placed on the scale. In PSI Absolute, 0 psi is a perfect vacuum and atmospheric pressure is 14.696 psi approx. In PSIg (gauge) atmospheric pressure is zero and a perfect vacuum is -14.696PSIg (equal to 30 inches of mercury, InHg). Kilopascals is the metric version of the absolute measure where a perfect vacuum is zero and atmospheric pressure is 101.325 kPa.\\ \\ The MAP value represents engine load - a higher number represents higher load (more open throttle compared to RPM).\\ \\ For example:\\ Cruising along at 3000rpm on a slight down grade has very low engine load and a lower MAP (kPa) number. If that slight downgrade turns into a steep uphill, you open the throttle to maintain 3000 rpm and the same speed. The MAP (kPa) number starts to climb towards atmospheric pressure 30 InHg (101.3 kPa).\\ \\ Engines require more advance under load at a given rpm and also need more advance as rpm increases at a given load. | | | Just a quick note on MAP(Manifold Absolute Pressure). First, the word "absolute" refers to where zero is placed on the scale. In PSI Absolute, 0 psi is a perfect vacuum and atmospheric pressure is 14.696 psi approx. In PSIg (gauge) atmospheric pressure is zero and a perfect vacuum is -14.696PSIg (equal to 30 inches of mercury, InHg). Kilopascals is the metric version of the absolute measure where a perfect vacuum is zero and atmospheric pressure is 101.325 kPa.\\ \\ The MAP value represents engine load - a higher number represents higher load (more open throttle compared to RPM).\\ \\ For example:\\ Cruising along at 3000rpm on a slight down grade has very low engine load and a lower MAP (kPa) number. If that slight downgrade turns into a steep uphill, you open the throttle to maintain 3000 rpm and the same speed. The MAP (kPa) number starts to climb towards atmospheric pressure 30 InHg (101.3 kPa).\\ \\ Engines require more advance under load at a given rpm and also need more advance as rpm increases at a given load. | | ||
| - | (I wonder if that should be 'less advance under load at a given rpm'??) | + | (I think that should be 'less advance under load at a given rpm'??) |
| Here's another good reference to understand that the vacuum gauge value and the Manifold Absolute Pressure value are readings taken from opposite ends of the atmospheric pressure range:\\ | Here's another good reference to understand that the vacuum gauge value and the Manifold Absolute Pressure value are readings taken from opposite ends of the atmospheric pressure range:\\ | ||
