It has been established that the Maserati V6 engines are odd fire.
- exact angle of the trigger pulses is still unknown
- Be sure to describe when you get to know
An hopefully easy to understand example in engine degrees:
0 +90
90 +150
240 +90
330 +150
480 +90
570 +150
720
If we remove 360deg from all values >= 360 we get:
090
240
330
120
210
0If we interlace them and apply the 90/150 degree rule to the table:
0
90 (90-90=0)
120 ignore
210 ignore
240 (240-150=90)
330 (330-90=240)
0 ignore
90 ignore
120 (360+120-150=330)
210 (210-120=90)
240 ignore
330 ignore
0 (360+0-150=210)
90 (90-90=0)
120 ignore
210 ignore
240 (240-150=90)
330 (330-90=240)
0 ignore
90 ignore
120 (360+120-150=330)
210 (210-120=90)
240 ignore
330 ignore
0 (360+0-150=210)
90 (90-90=0)
We find that we want to ignore two triggs and then act on two triggs. We also see the 30/90 pattern in the triggerwheel that can be used to update rpm. This definitely can be done without stabilizing the trunk code, applying some code in multitooth.c.
Some thinking also show how the Buick odd fire engine can be run with wastefire! As usual with waste fire grouping we take the Buick fire order:
1-6-5-4-3-2, write on two rows:
1-6-5
4-3-2
The columns are grouped on each wastespark coil. Adding 90+150+90give us 330 degrees betweeen #1 and #4 TDC's and that means that #4 is 30 deg BTDC in it's exhaust stroke when #1 is in compression TDC. That should be ok. Counting the other way around starting from #4 compression TDC give 150+90+150=390 which would indicate that #1 is 30 degrees into it's intake stroke when #4 is at compression TDC. I get a feeling that late timing might be bad as if we were to fire at TDC the #1 cylinder would start to fill up with fresh mixture!
- IF COIL ON PLUG IGNITION is used you can even trigg it with only a multitooth crank trigger!
- is cam-trigger not available ? Yes, 2 spaced appx. 75 degrees (making it 150 crank-degrees)
- If waste fire was to be used the cylinder that has an early twin would be fired at the right time and 60 degrees too early!
- For odd-fire V6, I never heard of pairing cylinders using 3 transformers in wasted-spark configuration. Even if we cannot find such references, it doesn't mean that it cannot be done. However, there are too many uncertainties with it: if possible, cam+crank+COP would be the straightforward way to go.
Here is a link to a place showing the engine, also sliced (scroll down). The indexer pins on the pulley can be seen clearly. It corresponds with my estimate that the 1st of the 2 pins are almost at the same angle as the frontmost crank throw. The pickup is straight below the pulley.
http://www.maserati-alfieri.co.uk/alfieri134.htm
Einar (Spamcheck-AT) Sjaavik (Spamcheck-DOT) com