Changes by last author:
Changed:
| For the Nissan CAS trigger (360 pulses) 3 possible solutions (one working, one being implemented and one hard/dropped) |
| Nissan CAS trigger (360 pulses) |
| Current solution is a 24+1 slot trigger wheel as described here: VehicleFitment/Nissan |
| Old solution was a 24+1 slot trigger wheel as described here: VehicleFitment/Nissan ... plenty of cars are running on these trigger disks. Still a good option, especially above 1.6 million pulses per minute (above 9000 RPM). |
| We have a number of cars running on these trigger disks. |
| Leaving the 360 impulse disk - we are finalizing implementation after someone writes exact pattern info here (in place of the "..." below, relative to TDC) - from a reliable source or measurement. |
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Leaving the 360 impulse disk - implementation works well (slightly above 10000 RPM on bench)
* the 4 (or 6) window pulse connected to primary-trigger HALL input * the 360 pulse signal connected to sectrig HALL input (without any hardware divider !) ** lower filtering capacitor must be used of course, so mention "sectrig=HALL,Nissan360pulse" in the order comment * See "Nissan special settings" in [VemsTune Help] on how to measure the length of the longest primary trigger window (if you don't know, or want to verify) ---- Note: everything below is for GEEK / Developers ---- We'll adjust the TDC-delay (or is it close to 60 crankdegrees which makes most sense ?) in the userfriendly "1-click" triggersetup configuration (bottom of primary trigger dialog) * after someone writes exact pattern info here (in place of the "..." below, relative to TDC) - from a reliable source or measurement. |
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A hardware divby4 divider can help. We have divby4 / 8 implemented with HCF4024 circuit (under PCB manufacturing, originally for high toothcount ABS wheels). Since this circuit has (active-high) reset input, this can be useful to make a precise 180, 90 or 45 pulsetrain from the 360 tooth.
* Please help to find this out so our stimulated pattern is exact, and we can recommend good ignition trimming values if necessary ! - Gunni : Please find the patent information for the nissan trigger here (http://www.freepatentsonline.com/RE34257.pdf) It explains the syncing methods used by nissan, hope it helps. |
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We thought to use a hardware divby4 divider, but when we implemented in v3 firmware, we found that the 360 pulse works perfectly, while the divby4 is not as reliable
* which might be surprising, but is actually the case, no mistake * so HW divider is not needed (actually divider is not supported) ! * [nissan trigger patent information] explains the syncing methods used by nissan |
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** is the sync pulse falling edge not racing with (the rising or falling edge of) one of the 360 pulses ? (I assume not, because that would be very stupid. This would make a counter-type implementation impossible, but a helper "assistant CPU" could still help)
** configuring sectrig input=both edges and firmware modification is necessary with the 4-window sync pulsetrain ** by blocking 3 of the 4 windows, (and using a HW divider) firmware mod would not be needed (good for experiments, but this should not be needed finally) * TODO: actually try the resettable divby4 counter (on bench, and on engine) ** with divby4 (360 => 90 pulses).firmware could (should) be configured to divby3 or even divby15 (via divby-ANY setting) ** divby8 (360 => 45 pulses) for 4 cyl engines requires a small trick of 4 crankdegrees ignition trimming (because delaying by 23 teeth is not exactly the same as the required 22.5 teeth) ** according to MembersPage/JannoKusman/NissanTrigger both sectrig edges must be sensed because of the 4 slot syncpulse Besides any necessary HW, suitable config will be provided (configlet to be able to upload to suitable firmware with 1 click). ---- Alternative solution would be (without HW divider) a software divide by the main processor. The processor is definitely capable (up to at least 17000 RPM). But unfortunately we have some tasks in interrupt that would need to be rewritten. (not the trigger input capture interrupt, but other interrupts that could interfere). From auditrigger bench experiments that worked at 11000 RPM (pulse=2.66 crankdeg), we know that 8300 RPM (pulse=2 crankdeg) is possible without major rewrite. Going above the "all pulse always sensed" threshold could delay ignition by 1 tooth (2 crankdeg) or more (not advance that could blow engine). We speculated that without HW divider going above 9300 RPM could be too much work that would delay other developments unacceptably. So we will only implement fw mod that works well with HW divider. * we think >9300 RPM is minimum reasonable goal to say that some trigger is supported (even though much lower than the 11k RPM of 135 tooth auditrigger with sufficient divbyANY config or 25k RPM of lower toothcount wheels) |
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* according to MembersPage/JannoKusman/NissanTrigger both edges of the 4-window (or 6-window) signal must be sensed...
** yes, the implementation works that way. |