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jetape

Hard time starting

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I'm having a hard time starting my Rotax 4tec motor, I've been trying all kinds of crank enrichment values but can't seem to pin point the issue.  This is a jetski so there aren't exactly coldddd starts, 20C / 70F is basically as cold as it gets.  If I connect stock ECU it starts up very nicely and very quickly.  With link it's a struggle. 

From logging it seems to takes a bit of time for RPM to register after the start button is pressed.  I also see trigger errors.  Sometimes there's a weird high spike even though that didn't happen in reality. I tried everything from 0 crank enrichment to 60/70 and everything in between.  Doesn't seem like there's a pattern where it seems to be getting better going either direction.

Attached is my map and couple logs of start attempts.  (lambda is not logged since I had my controller on another battery to see values during cranking)

 

Thanks :)

30.1.1.pclr dw - Log 2019-08-10 5;51;06 pm.llg dw2 - Log 2019-08-10 5;51;06 pm.llg

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I did some trigger scope readings while cranking.  Honestly I have no idea how to interpret the results.

Attached is also a regular log while I was doing the scope captures.

s1.jpg

Trigger Scope Log 2019-08-11 12;12;51 pm.llg Trigger Scope Log 2019-08-11 12;15;10 pm.llg Trigger Scope Log 2019-08-11 12;16;25 pm.llg Trigger Scope Log 2019-08-11 12;17;22 pm.llg dw - Log 2019-08-11 12;17;43 pm.llg

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I've been doing a bit more research on this and with my current Trig 2 set to Falling the falling edge of Trig 2 might be too close to the tooth of Trig 1.  Any issues with changing Trig 2 to Raising to move it further away?

 

s3.png

 

 

Looks like I'm dealing with the same thing as 

 

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What a tease, I switched to Rising and the first attempt to start was perfect, it fired up instantly with zero trigger errors.  I'm like wow no way ...tried another start and it's back to garbage :(

Tried changing trigger voltages to various levels, different filtering, nope nothing.  Once in a blue moon it will fire up perfectly as if a lottery wheel turned and it was just lined up that one time.  Next attempt will be trash.

This is so rough on the starter and the starter gear on the flywheel on these motors.

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Here are logs of back to back start attempts on a "cold" engine that was sitting for 24h.  Exact same settings, the good start happened on first attempt, second attempt was 30 seconds after the first attempt.

 

start1.PNG

start2.PNG

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It will be best if you send an email to tech@linkecu.com.  The ecu seems to have trouble reliably detecting the missing tooth when cranking on these engines.  I know it was on the todo list for the engineers to investigate when I was there but the more people that report the issue the higher the priority it will get.

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I have fought this kind of cranking issue with single and 2 cylinder motors.  The compression on cranking really messes with the ecu's ability to accurately read the triggers, clearly.  I have always remedied this with very low if not negative timing in the 0-250 rpm and low TP area of the ignition map.  It would be nice if link could add a cranking timing setting in the main ignition settings but considering that is not there, you have to do it in the main table.  As Race Jase in the other thread said, he damaged starters and Bendixes due to kick back.  The low to negative timing values fixed that for me as i even sheared teeth off the flywheel as well.

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4 hours ago, Adamw said:

It will be best if you send an email to tech@linkecu.com.  The ecu seems to have trouble reliably detecting the missing tooth when cranking on these engines.  I know it was on the todo list for the engineers to investigate when I was there but the more people that report the issue the higher the priority it will get.

OK I just emailed them giving a short explanation and pointing to the two threads on the issue.

 

2 hours ago, Brad Burnett said:

I have fought this kind of cranking issue with single and 2 cylinder motors.  The compression on cranking really messes with the ecu's ability to accurately read the triggers, clearly.  I have always remedied this with very low if not negative timing in the 0-250 rpm and low TP area of the ignition map.  It would be nice if link could add a cranking timing setting in the main ignition settings but considering that is not there, you have to do it in the main table.  As Race Jase in the other thread said, he damaged starters and Bendixes due to kick back.  The low to negative timing values fixed that for me as i even sheared teeth off the flywheel as well.

Interesting, I'll give that a try, at this point I'd just like to start the motor without grinding the gears, it's nasty.  Will most likely pull the motor over winter to inspect things from all these kick backs.

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the kick back is from the combustion event happening while the piston is still on the way up the bore.  with the negative timing it will happen after it passes tdc so the combustion event will help push the piston down the bore.

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I emailed tech support and they opened a ticket, not sure what that means exactly.

Did some experimenting with the timing at cranking RPM, it lessened the nasty sounds but I think there's build in logic that disengages the start status when RPM crosses it.  With the ECU seeing garbage RPM spikes to 4k during cranking it's causing the starter to disengage and engage even though the start is held.

Here is a pic how cranking looks, no steady RPM detected by the ecu and all those spikes are causing starter cycle, rough stuff.

Still not sure how last season it seemed to start a lot better.  Now it doesn't even see a steady cranking RPM, I could blame a bad sensor but the stock ECU starts just fine.

 

 

 

start3.PNG

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go to starter control in the chassis and body tab.

change starter switch mode to normal and deactivation to 4500rpm

The starter button or switch should then act like a normal system where you have to hold it till it starts.

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Bit of a hack job, but with a start switch config, and no other use for secondary ignition table, you can set up dual ignition table, and set the table 2 trigger to be DI2 (your start button). Then set ign table 2 to be a single value -2*. This means as long as you keep the start button pressed, its going to fire at -2 degrees regardless of what RPM it thinks it is seeing. It wont stop the starter kicking on and off, but it will stop it getting kickback as described by Brad if it sees 3k rpm because of trigger errors and jumps up to a "real" load point on the ign1 table.

Speeding up the rotation speed during cranking process like this (by firing on the down stroke) may help prevent the trigger issues that cause the RPM spikes in the first place too.

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8 hours ago, cj said:

Bit of a hack job, but with a start switch config, and no other use for secondary ignition table, you can set up dual ignition table, and set the table 2 trigger to be DI2 (your start button). Then set ign table 2 to be a single value -2*. This means as long as you keep the start button pressed, its going to fire at -2 degrees regardless of what RPM it thinks it is seeing. It wont stop the starter kicking on and off, but it will stop it getting kickback as described by Brad if it sees 3k rpm because of trigger errors and jumps up to a "real" load point on the ign1 table.

Speeding up the rotation speed during cranking process like this (by firing on the down stroke) may help prevent the trigger issues that cause the RPM spikes in the first place too.

didnt even think about that.  But that is perfect.

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All good ideas, but my feeling is they won’t help.  If the ecu has dectected the missing teeth in the wrong place then it doesn’t know where tdc is.  So no matter what you do with ignition trims or tables it is still going to be firing at the wrong time.  The cranking trigger scope looks just as bad on these things whether the spark is enabled or not.

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Yeah it makes cranking not as rough but the ECU is just not picking up a steady crank rpm.

Looks like it's back to stock ECU flashing for me. Hopefully tech people will look at my ticket and build a trigger preset for these motors into the firmware.

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What's weird is that it's gotten worse over time. Can these sensors lose performance but not totally fail? Stock ECU would not start if they're were broken but it does and Link has taken a massive turn for the worse.

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18 hours ago, jetape said:

What's weird is that it's gotten worse over time. Can these sensors lose performance but not totally fail?

More likely the cranking speed has gotten less even.  Possibly the starter clutch slipping a bit more due to it having a hard life or possibly electric related like battery putting out a little less cranking amps.

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