Changes by last author:
Changed:
| I know I could get away with wasted spark & paired injectors... I just don't want to for various reasons. I will be keeping the crank trigger (as discussed above) as this has worked perfectly from day 1 and I'm happy with it. So I need a cam trigger to provide engine phase information. |
| VEMS has a really good set of individual cylinder features now, so let's use them! Step 1 is a working cam trigger. |
| If I understand things correctly, I have all the piston position information I need from the crank trigger, but I need to create a "reset" pulse at approximately 70 crankdegrees BTDC for cyl 1 (or 20 crankdegrees ATDC for cylinder 2) so the engine phase can be established. I understand the cam pulse can't overlap with any activities... |
| Building the cam trigger - new better version! |
| Building the "cam" trigger |
| Looking at the timing cover on my engine during the rebuild, I noticed it was cast to take a cam trigger sensor, but it was never fitted because my cam pulley didn't have trigger teeth. |
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Since the cam is difficult to get at, I thought I'd use the (now redundant) distributor body and a hall sensor instead of the camshaft wheel. They both turn at the same speed (more or less) so I see no problems.
Some spare dizzy parts have generously been donated to the cause. They are for an older Rover V8, so need some modification to fit... |
| "But how hard can it be to add them?" I asked... |
Spare Dizzy parts. Note the original on the top was different to the donated one until it was attacked in the workshop... |
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The answer would appear to be "Not very". I sketched a cam trigger in a CAD tool and had it water jet cut:
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With no vac advance needed, the middle plate can be used to mount the hall sensor to look at the remaining spring retainer pin from the remains of the mech. advance mechanism, so I get one pulse every 720 crank degrees.
First camsync trial. Hall sensor is G-clamped to the case! |
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Then bolted it on to the engine and fitted a sensor so I get a single pulse per cam rotation.
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| Unfortunately, this didn't work reliably when tested - I think there was too much ferrous metal spinning round - , so my new idea was to remove the plate completely and make a thin tapered blade with a M6 bolt in the end to fit on the dizzy shaft. This was much more successful and worked well on the test bed. (bench power supply, volt meter and pull-up resistor) |
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Configuration |
| It's actually better balanced than the old distributor was. (Tested unscientifically by spinning it with a drill) |
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The ECU config is here:
https://dl.dropboxusercontent.com/u/8968424/vems/v3.3_u004371-A-2014.07.04-09.26.05.vemscfg |
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| Note that the config is for a zero mile engine that has run for a grand total of 3 minutes and 45 seconds, so all of the calibration parameters are all over the place and mostly wrong. However the trigger settings should be right. (I know it's still using dual-out ignition - I wanted it to run first time...) |
| It's back in the engine now, and I just need to align it and do the config. |
| Trigger log |
| The nice thing about using the dizzy is that the camsync pulse can be positioned anywhere in the cycle to suit both hardware and firmware. |
| I made a trigger log using the ECU in the above configuration. I think I see cam trigger pulses where I expect to, but would be very pleased to get a second pair of eyes on it because the trigger logging bit of VEMStune is new to me. |
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Configuration |
| https://dl.dropboxusercontent.com/u/8968424/vems/v3.3_u004371-2014-07-04-19.18.03.triggerlog |
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Primary trigger
* 36-1 multitooth as above ** I[Marcell?] have to check if some changes are needed, camsync was only used with coil-type primary trigger, and 60-2 multitooth, not with 36-1 multitooth. |
| I hope I have interpreted the trigger log correctly... This chart shows the primary trigger tooth count and the secondary pulse reliably appearing just after tooth #24 on the primary trigger. Not ideally placed - would be better sitting after cyl 2 TDC, but should be OK if I rotate the firing orders to suit. |
| Secondary Trigger Settings: |
| I assume I configure the firing order to be 4-3-6-5-7-2-1-8 so that the cam trigger resets the cycle at the end? |
| Currently using the following config. Shout if there's something wrong... |
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||Active:||Enabled||
||Edge:||Falling|| ||Edge while cranking:||single|| ||Filtering:||enabled|| ||Type:||coil type|| ||Use:||Camsync|| |
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Back to MembersPage/DavidBlades |
| Cam sync, engine phase at next primary trigger |
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||Rising Edge (cam_sync_r_edge_phase):||212||
||Falling Edge (cam_sync_f_edge_phase):||212|| |
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---- Building the "cam" trigger - OLD VERSION |
| These refer to the position of secondary pulse edges; range 0..215 (with 216 funny degrees) So for my case of having the cam trigger at approximately 70 degrees BTDC cyl 1, the cam pulse occurs 7.5 'real' degrees before the trigger tooth. Since everything works on degrees after the trigger (I hope!) this needs to be converted: 360 - 7.5 = 352.5 degrees. This then gets converted to 'funny' degrees: 216 * (352.5/360) = 212 (rounded up) |
| Since the cam is difficult to get at, I thought I'd use the (now redundant) distributor body and a hall sensor instead of the camshaft wheel. They both turn at the same speed (more or less) so I see no problems. |
| Q: Is there a trigger logging command like mde40 for the cam trigger? Even better - can you log the crank and cam triggers together to test them? |
| Some spare dizzy parts have generously been donated to the cause. They are for an older Rover V8, so need some modification to fit... |
| Timing lamps are difficult since there's an exhaust and bits of chassis in the way of the crank pulley. |
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Spare Dizzy parts. Note the original on the top was different to the donated one until it was attacked in the workshop... |
| Nearly finished!! |
| With no vac advance needed, the middle plate can be used to mount the hall sensor to look at the remaining spring retainer pin from the remains of the mech. advance mechanism, so I get one pulse every 720 crank degrees. |
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Believe it or not, this is the last job to do on the current engine. After this, it's time for tuning, refinement and trials...
(And sorting out the paintwork) |
First camsync trial. Hall sensor is G-clamped to the case! |
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Old things |
| Unfortunately, this didn't work reliably when tested - I think there was too much ferrous metal spinning round - , so my new idea was to remove the plate completely and make a thin tapered blade with a M6 bolt in the end to fit on the dizzy shaft. This was much more successful and worked well on the test bed. (bench power supply, volt meter and pull-up resistor) |
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How to know cam-pulse angle ?
* speculation ** from mechanical measurements and voltage levels * scope * soundcard ** beware of the polarity ! * we were thinking to "cheat-configure" as auditrigger and take mdd0c log (this won't start the car, you can even leave the fuelpump off) but rethinking it, this is unlikely to help even if the primary was a 60-2 or 36-1 multitooth ** maybe mixing the primary and secondary signal (not easy with VR and HALL) and InputTrigger/TriggerLog would help, but than the scope/soundcard seems more appealing ---- |
| It's actually better balanced than the old distributor was. (Tested unscientifically by spinning it with a drill) |
| Back to MembersPage/DavidBlades |
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| It's back in the engine now, and I just need to align it and do the config. |
| The nice thing about using the dizzy is that the camsync pulse can be positioned anywhere in the cycle to suit both hardware and firmware. |