I have a Mercedes m104 engine with 60-2 tooth flywheel and single tooth cam trigger. it is fully sequential but starts on wasted spark.
It has to use “inverted phase” firing order setting.
if I use “cam sync tooth window” I assume I have to use the value 18 (+/-2) as only up to 60 teeth available in the setting. Software mostly reports it running on tooth 78 or 401 degrees. is this correct?
I notice in the latest v3 software, sometimes cam sync trigger tooth mostly is reported as 78 but sometimes 18 or on occasion 0
I did try the latest “sync with cam level” but it didn’t really help.
The engine has (as fitted by Mercedes) a VR cam sensor, but later m104 engines have a Hall sensor, I am tempted to change to Hall. Scope shows ok, low filter applied.
I am chasing a (very first cold start of the day) issue which is sync related. other than that (starts second turn of the key) it starts fine and every subsequent start for the rest of the day. Runs great starts hot or cold, great idle etc.
Any advice please?
If the engine have a problem to start the very first time it looks like it is fuel related.
Try to make bigger prime pulse and eventualy increase fuel dose in first revolution.
Cam sync tooth window is to detect missing tooth or addition tool in high compression engines. It works on revolution basis not a cycle so once you have 18 and once 78.
If I look at the logs, the times it “locks on to” tooth 78 straight away it starts perfectly, cold or otherwise. I have logs where it is idling on tooth 18 and tooth 0. Sometimes on failed first starts, it shows tooth in excess of 120 (its a 60 tooth flywheel)?
When its running on tooth 0 or 18, is it still running in wasted spark mode? (it is set up to start up in it)
If you start in wasted spark, it can start before cam syncronisation so the cam tooth will be 0.
In your case it looks like a fueling issue. If the engine is cold, the combustion chamber is cold and there is no residual fuel in intake manifold.
So try to increase prime pulse, a liitle more fuel in first cycle of cranking and eventually afterstart enrichment
Finally got a perfect stone cold start !
I found good results from reducing the IACV duty cycle (quite dramatically) below 20 deg c. I already had nearly max prime pulse at that temp and and around 500 - 400 for the first couple of cranking cycles.
Second and all subsequent starts (throughout the day) have always been reliable and consistent.
I changed to Hall cam sensor, which appears to give more reliable results, but I did see an error on yesterdays “stone cold start”
This year, I went from 36 -1 to 60 - 2 flywheel with the introduction of a new gearbox, I don’t think that helped cam sync issues. I never noticed any deviation (while driving) of tooth on the old setup. I have on the odd occasion seen it on the new 60 tooth setup. I will check timing chain and tensioner.
I guess some cam sync errors are a symptom of a non start rather than the cause?
Thank you for your patience in helping me and others, I have enjoyed learning to date and look forward to learning more and fine tuning.