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integrale8v

trigger issue Rotax 4-tec

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I have a problem with a 3 cylinder Rotax 4-tec engine in a Skidoo snowmobile.  The trigger wheel/sensor is inductive 36-2. Stock wheel and trigger

  When I turn over the engine without plugs installed I get a clean signal, and stable RPM.   Also get stable RPM with 1 and 2 plugs installed.

 But with all 3 plugs installed the RPM fluctuate all over the place, the signal is also not consistent on the trigger scope.  Have tried trigger filter up/down, trigger arming.  But no luck..

Seems like the trigger wheel accelerate/deaccelerates and this disturbs the trigger,

The engine turns over quite fast with 3 plugs installed also, maybe around 180-200rpm.

 

Any suggestions?

 

The map is just a base map.

 

0 plug.jpg

1 plug.jpg

2 plug.jpg

3 plug.jpg

3.jpg

2.pclr

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Yep it is going to be the speeding up and slowing down of the engine on compression that is causing the issue.

As you have a cam sync, one option would be to modify the crank trigger to a 36 none missing then the ECU only counts teeth with out having to find a gap.

 

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Integrale8V,  One suggestion is to try your trigger 2 on rising edge since its falling edge clashes with the gap on trigger 1.  Also, I know you have already stated that you tried playing with arming voltages, but im curious if you tried something like the screen shot below;

Capture2.png

 

The reason I ask is I think with the way you have the arming voltage set up now @ 0.2V, that little hump that you have in the middle of the "gap" looks like it is high enough to potentially arm and cause a false tooth.  Maybe a long shot, but worth trying just to eliminate that.

Capture.png

 

Expanding on Simon's comments,  why is the cranking speed so variable on this engine - is it highly modified or perhaps bad battery/starter/wiring?  This engine I am not familiar with but some similar jetskis I have played with crank much higher - like 300RPM.  I have found 36-2 is usually quite immune to cranking issues so I would have thought it should work ok with the right settings.

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Is this the 900 Ace engine?

Im not sure why but in the days of the vipec we had this running our engines with out issue, when the vipec was discontinued and we changed to link we started getting kick back issues that i couldnt get rid of (trigger problems) .

On our 4 tec engines we cant change the style of crank trigger (36-2) with out major costs and a engine out and strip to do this.

I have also tried changing trigger voltages, changing rising to falling , falling to rising with out any joy ,but on the vipec i am running a trigger arming of 0.2,0.5,0.8,1.5,2.5,3,3.5,3.5" with trigger 1 filtering of 3 and a trigger 2 filtering of 2 and it starts and runs perfect everytime.

Jase

 

 

 

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Integrale8V,  One suggestion is to try your trigger 2 on rising edge since its falling edge clashes with the gap on trigger 1.  Also, I know you have already stated that you tried playing with arming voltages, but im curious if you tried something like the screen shot below;

 

The reason I ask is I think with the way you have the arming voltage set up now @ 0.2V, that little hump that you have in the middle of the "gap" looks like it is high enough to potentially arm and cause a false tooth.  Maybe a long shot, but worth trying just to eliminate that.

 

 

Expanding on Simon's comments,  why is the cranking speed so variable on this engine - is it highly modified or perhaps bad battery/starter/wiring?  This engine I am not familiar with but some similar jetskis I have played with crank much higher - like 300RPM.  I have found 36-2 is usually quite immune to cranking issues so I would have thought it should work ok with the right settings.

 

Adamw:  Have tried in steps up to 2v (also 1v) arming but no luck.  Also tried with rising edge on trigger 2 - no change.

Most of my testing has been without sync on trigger 2. (no fuel connected).  Want stable trigger 1 before adding the sync.

 

Without plugs this engine cranks like240rpm.  The starter sounds okay, and doesent look that old, but maybe you are correct that the cranking rpm should have been higher.  I will do some measuring on voltage drop too the starter. 

The owner has not given me the complete spec list yet but, it is a turbo engine so not very high compression ratio.

Is this the 900 Ace engine?

Im not sure why but in the days of the vipec we had this running our engines with out issue, when the vipec was discontinued and we changed to link we started getting kick back issues that i couldnt get rid of (trigger problems) .

On our 4 tec engines we cant change the style of crank trigger (36-2) with out major costs and a engine out and strip to do this.

I have also tried changing trigger voltages, changing rising to falling , falling to rising with out any joy ,but on the vipec i am running a trigger arming of 0.2,0.5,0.8,1.5,2.5,3,3.5,3.5" with trigger 1 filtering of 3 and a trigger 2 filtering of 2 and it starts and runs perfect everytime.

Jase

 

 

 

It is a 1170cc engine.  

And like you say it is not an easy task to change/modify the trigger wheel.  I have a Vipec V88 lying around, will try with that.

 

Eivind

Edited by integrale8v

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I have tried several different trigger wheels on the ski-doo 1200. (Stock, and 2 different applications witout missing tooth, and 1 with bigger tooths). It dont seems to be any better. But problem is always during cranking.

When engine first starts, there has never been a trigger miscount. Running normally around 9.000 rpm. (with rev.limiter on 9.500,-)

I belive the problem is low crank speed combined with low voltage during cranking.

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Possibly bigger battery cables, bigger battery or a LiFE battery might help?

If spare trigger wheels/flywheels were available and not too expensive, another thing I would try would be grinding off an extra 1 or 2 teeth to make it 36-3 or 36-4.  My logic here is with a bigger differentiation between the normal teeth and the gap it should help the ECU detect the gap.

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Possibly bigger battery cables, bigger battery or a LiFE battery might help?

If spare trigger wheels/flywheels were available and not too expensive, another thing I would try would be grinding off an extra 1 or 2 teeth to make it 36-3 or 36-4.  My logic here is with a bigger differentiation between the normal teeth and the gap it should help the ECU detect the gap.

The problem here Adamw is on some of these engines it can be a engine out and strip to just get access to the trigger wheel at a cost of  between $1000-1600.00 min so its not cheap

There has to be some way in the software or settings to help with this , Link still make a vipec unit for another aftermarket parts company that plugs into the seadoo factory harness that does not have these starting issues so there has to be a difference in how the triggers are picked up between the link and vipec units.

Jase

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Hi Jase

The Vi-pec and Link units are identical no differences in firmware there are hardware differences on the plugins but that is just to make it a plugin, No differences in the trigger circuits or decoding.

I would expect if you did a back to back the results should be identical.

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Hi Jase

The Vi-pec and Link units are identical no differences in firmware there are hardware differences on the plugins but that is just to make it a plugin, No differences in the trigger circuits or decoding.

I would expect if you did a back to back the results should be identical.

Hi Simon,

Yes i know what your saying and have discussed with you these issues in detail previously,

I have actually unplugged a V44 unit and with the same harness plugged it into the storm using the exact same map i had issues with the storm that i didnt have with the vipec.

Now i have also tried a complete vipec plug in map on a storm and atom with the same kick back (trigger) issues.

I am in the process of making a new plug and play harness for a customer that we will be using on a rotax 900 engine and extreme ecu, shit i really hope i can figure these trigger issues out as pulling the engine in this off road buggy is not a option.

Any thoughts or suggestions are welcome

Jase

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Did you get anywhere with the ACE 900 and Extreme triggering? Jase?

looking for an ecu for transplant 

Not yet Christmas got in the way but will get back to this over the next few weeks and will post my findings.

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For the SkiDoo 1200, 3 cylinder Rotax 4-tec engine, maybe a user changeable trigger arming threshold table would help ?

During cranking, I get less trigger miscounts when I set the volt as high as possible. (close to the peak voltage)

But when it is cold, engine is harder to turn over, and less battery voltage, -> the starter cranks slower, and actual trigger voltage is lower.

So i need to set the voltage a bit too low. The arming threshold increase is fixed to every 1000 rpm. Given the crank speed is around 180 to 200 rpm, I would like to have 0 rpm, 180 rpm, 200 rpm, 1000 rpm, 2000 rpm, .....

Not sure if this is a solution, but maybe this is a easy fix, and useful for other engines as well

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With the arming voltages they are to help eliminate the possibility of background noise causing issues.

In theory there should be no background noise so the arming voltages can be very low. However this is often not the case.

The existing zone steps blend so that as you approach the next cell it start to impact the arming voltage its not like it does a big jump as you go into the next cell.

 

 

 

 

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I still has the same trigger problem during cranking.

I have not spent more time solving this. Works great while engine is running, just need to crank a lot before engine starts..

Also, it messes up the statistics, as ecu thinks it has oscillating 200 /10.000/2.000 rpm during cranking (cause of the cranking trigger issues).

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This should be adressed in the trigger code  for low inertia engines and can be easily solved using the cam sync pulse.

Remove all ignition plugs and watch the trigger scope where the cam sync pulse occurs in relation to the crank missing tooth. You can then figure out how many degrees (and number of crank trigger teeth) before TDC cyl 1, a timing light while cranking  if you want to be accurate. It would help a lot if that information was available during cranking.

In the case of the Rotax ACE 900 with a 36-2 crank trigger wheel and cam sync, it would be a 34+1 trigger until it starts (exceeds rpm threshold) and only then be treated like a 36-2+1 trigger. Basically at low cranking rpm the code should care less about the missing teeth and calculate ignition timing based on cam sync pulse instead.

This is typically also a problem with Suzuki motorcycle engines, GSX-R with 24-1 and later ones have a bit easier larger missing teeth 24-2.

I've also seen this problem on huge engines (27 litre V12, trigger 24-1 no camsync) where the first few pistons will accelerate the rpm quickly and the missing teeth are lost.

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On 23.1.2018 at 10:06 PM, Mattias Sandgren said:

Integrale8v, race jase: Did you ever get this issue sorted ?

I modified the trigger,  so it had 6 teeth on the crank and cam sensor.

Works okay, but not perfect when starting.

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Unfortunately on the rotax engine platform ive had to use another ecu as the bad starting and kick back issues i had with the link was damaging starters and bendix's ,in saying that i use link for most other customers and have no issues and love to use/tune them.

Cheers

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So it seems that the problem is the ecu is looking for a rate of change in the crank signal to calculate the missing teeth and it is misinterpreting that as the engine slows during during a compression stroke. I am having the same problem with my 900 rotax engine in my Can am X3. RPM skyrockets/erratic during cranking and tosses trigger errors in 1/2/4 trig error increments, which seems to correlate to the longest space between non missing teeth and the actual missing teeth. 

I want to make this a pnp option for the X3 community so modifying triggers is out of the question at the current moment. My machine is pretty much brand new with a new battery and cranking is very reasonable. 

Im curious which ecu you chose Race Jase.

 

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On 12/13/2016 at 10:46 PM, integrale8v said:

3.jpg

Does anyone have this sort of wave saved as a log file?

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Since I'm not getting any bite in my own thread I'm bumping this one.

Any chance of a firmware based "fix" for the Rotax 4tec cranking trigger issues?  I'm experiencing the same issue with kickbacks and very poor and inconsistent starts.

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