Several setups use multitooth wheels with no missing tooth.
Some (mostly Japanese) engines like Nissan and Toyota's have
- primary trigger: 24 pulse on cam (or 12 on crank is effectively the same). We refer to it as 24+1
See [Fero's] config.txt and tables.txt (24+1 trigger used in a 6cyl supra with 1.1.12 firmware). Same trigger settings apply in later 1.1.xx firmware.
- number of teeth: 24 (tooth_wheel=18)
- tooth width is 30 deg (tooth_wheel_twidth1=78, tooth_wheel_twidth2=00)
- secondary trigger: 1 pulse on cam
The relevant part from Fero's 6cyl config:
<PRE>
primary_trigger=07
secondary_trigger=19
tooth_wheel=18
trigger_tooth=01
another_trigger_tooth=04
crank_minper=0D
tooth_wheel_twidth1=78
tooth_wheel_twidth2=00
cam_sync_r_edge_phase=33
cam_sync_f_edge_phase=46
reset_engphase_after=40
ign_tdcdelay=C2
...
h[1]=00 14 10 0C 08 04 00 00
</PRE>
A 4 cyl would be slightly different in the following:
<PRE>
another_trigger_tooth=06
...
h[1]=00 12 0C 06 00 00 00 00
</PRE>
Please note that N+1 where N<=11 requires 1.1.27 firmware (or newer). This is where tooth_width >=64 degrees, that is tooth_wheel_twidth2>0. Most notably relevant to
- 10+1 (5cyl engine with 5 pulses on crank, which happens to be the theoretical minimum number of bolts/slots to properly trigger a 5cyl engine)
- tooth_wheel_twidth1=20 , tooth_wheel_twidth2=01 (0x120=288 that is 72 deg)
- find config (full and partial extract) examples [here]
- 8+1
- tooth_wheel_twidth1=68, tooth_wheel_twidth2=01 (0x168=360 that is 90 deg)
- 4+1 (2 pulses on crank or 4 on cam)
- tooth_wheel_twidth1=D0 , tooth_wheel_twidth2=02 (0x2D0=720 that is 180 deg)
- TODO: test 4+1 setup. There is normally little point in this, as 4-1 is cheaper (no camsync) ... but camsync also has advantages (fuel timing for emissions, knock or misfire cylinder identification).
Pulse timing restriction
The campulse must always come between the exact same 2 crankpulse ("no race condition"). With HALL sensor, be careful to select the right edge (for both primary and secondary trigger) that satisfies this.
Since the cambelt sloppiness is usually well within +-12 crankdegrees, a 12 tooth crankwheel is practical (one tooth every 30 crankdegrees allows the sloppy campulse to be always between same two crankpulses).
How does this relate to auditrigger?
The InputTrigger/AudiTrigger (a.k.a. 270+1) is basically a very special case of multitooth-none-missing. The auditrigger hardware is special because of the 135 cranktooth, much more dense than 30 degrees (=12 cranktooth), so the crankhome-VR is needed, but a cam-HALL masking signal also needed.
The same software implementation (with appropriate config) could theoretically support either 24+1 and 270+1. But VEMS firmware uses slightly different, optimized implementation for each (that share some parts of course). Strangely the 270+1 was supported before the otherwise simpler 24+1 (10+1 and other related) trigger setup.
This N+1 style is supported in 1.0.x (since appr 1.0.36, early 2006), called InputTrigger/AudiTrigger setup, with 270+1 as the primary target (commonly found on 5 cylinder audi engines). 270+1 is when you have 135 tooth on crank. Unlike the 24+1, the 270+1 needs a hardware trick so the campulse always comes between same two crankpulses: it is a "pulse timed by crank, masked by cam" (nickname "cramhome"), that is the 3-input trigger system, see InputTrigger/AudiTrigger.
1.0.x Configuration example for 24+1
- tooth_wheel=87 (decimal 135 tooth, that is "auditrigger setup).
- another_trigger_tooth=06 (for 24+1 setup with 4 cylinders)
- trigger_tooth= with another_trigger_tooth=06, must be between 0..5
- alternate=13 # or 03 if no simultaneous injection is needed at startup
- ign_tdcdelay=.. # whatever the timing needs
- h[0]=according to injectors wiring
- h[2]=according to ign wiring, eg. 20 30 20 30 .. .. .. .. (beware of new sameantcis, see GenBoard/UnderDevelopment/FirmwareChanges )
- otherwise same as the old-style InputTrigger/AudiTrigger config, just another_trigger_tooth and trigger_tooth changed as indicated above (lower than decimal 54 and 27, of course)
- secondary_trigger=1D is standard rising edge, (camsync with filtering??)
- primary_trigger=FB # rising edge, coiltype (yes!), trigger filter disabled (bit2=0). Coiltype chosen. and primary trigger filter might work with 24+1 (but not with 270+1)
Note that in 1.0.x (only with auditrigger setup), trigger_tooth changes in the opposite direction than you got used to (with missing tooth wheel). That is, higher value will bring the spark earlier.
Important
- benchtest setup (firmware+config) with ElectronicDesign/TriggerSignalGenerator and LEDs before experimenting on real engine
- record both channels to see the timing restriction is satisfied
- firmware could log this somehow, in an advanced auditrigger-log format to ease verification
- you will need a TimingLight to adjust base timing on the engine
Please report your benchtest results with recent 1.0.x. There is some allowance for the campulse to come (eg. 1 pulse) ahead in some cases. This was desired for the original 270+1, and does not matter with a proper N+1, but with a bad camsync position (if the campulse sometimes comes slightly after crankpulse X, sometimes before), than 30 degrees retard you will feel for sure. The allowance should be configurable (like 0/1/2 tooth).
Beware: 1.1.x with auditrigger setup currently does not support N+1 if N < 270 (that is, below 135 tooth on crank)
Because with 135 or 142 tooth at appr 7000 RPM the engine lost power (retarded 1 tooth than cut spark, as a safety mechanism when firmware thought the input pulsecount was too low), there are some specializations in 1.1.x that currently do NOT allow arbitrary N+1, like 24+1. Work in progress, so 1.1.x will handle everything supported by 1.0.x (and more).