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Ignition problem Link g4x


Greg1987
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Hello, I have a problem that I can't figure out. I have link g4x on lancer evolution 8. I started tuning the car and I have cut at around 6000-6500rpms. It is not a misfire it is cut like you hit the wall. I tried spark plugs, coils and still same problem. It is happening only on boost. First I was thinking it is my tune a problem but I was trying everything ( leaner, richer, less timing, more timing) and still same problem. I was able to catch that on the logger and look like whenever I have a cut my rpm read 0rpm. Bad camshaft or crankshaft sensor? I changed both of them couple weeks ago. Please help. I am including 2 loggers. Thank you!!!!

PC Datalog - 2022-07-29 11;12;00 pm.llgx PC Datalog - 2022-07-29 10;51;08 pm.llgx

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6 hours ago, aerace_fab said:

You're losing Trigger 1 according to the first log.

You are right. Look like trigger 1 reading no at that time. It is Crankshaft sensor right? Both sensors are couple weeks old. Where should I look for problem? Should I get new sensor or I have wiring issue? Thank you

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Im not sure if it would necessarily be a sensor problem.  Could be a bad connection, broken wire, loose crimp, electrical noise etc.  Does it do it every pull?  Only at high RPM, full boost?   Can you do a triggerscope around that RPM?

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1 hour ago, Adamw said:

Im not sure if it would necessarily be a sensor problem.  Could be a bad connection, broken wire, loose crimp, electrical noise etc.  Does it do it every pull?  Only at high RPM, full boost?   Can you do a triggerscope around that RPM?

I will triple check the wiring and connection. It is not doing it every pull but very often. I would say every 2nd pull and it is happening only at full throttle full boost in around 6500 rpm area. On light throttle runs perfectly fine. I will try my best to do triggerscope around that area

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Here is triggerscope but I am not sure if I catch it in the right moment. I can still try to do other trigger scopes. On this one I can see voltage on trigger 1 is around 3.20v but sometimes jumping to 2.90 and 4.10v and in couple places to 0.23 and 0.69V Is this how that should be?

TriggerScopeLog1.llgx

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Ok, guys something very strange is happening. To test it I change the car to the stock ecu and this stock ecu has been tuned with exactly same timing, same afr and same boost as link ecu. On oem ecu car has absolutely no cut at all. Runs perfect and smooth on full boost. I was driving the car for 2 hours non stop and car has never had any sign of cut or even a little misfire, runs perfect! So I came back to my garage and switched to link and first pull I did car had massive cut at 6500rmps. Can you guys please check what is going on?? Look like some trigger issue on link ecu. I am including another trigger scope that I hope I did in a right time of a cut. Thank you!!

TriggerScopeLog4.llgx

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There is nothing too unusual in either of those scopes, possibly a couple of spikes of noise but .  What does it have for an ignition system?  Are the spark plugs resistor type? 

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3 hours ago, Adamw said:

There is nothing too unusual in either of those scopes, possibly a couple of spikes of noise but .  What does it have for an ignition system?  Are the spark plugs resistor type? 

Maybe I got those scopes not in the right time. It is so hard to be on boost and click capture when car has cut. The cut is so massive that feels like I am hitting the wall.  Spark plugs I have are ngk br8es they are resistor type. Ignition system is coil on plug honda denso coils. Those coils are known to be great up to 800whp and high boost. On the logger trigger 1 is reading 0 rpm when cut happens. Any idea? Thanks

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Here is another logger from today. I spent some time today to look for a problem with no luck. I changed all ignition coils, spark plugs, I checked and tested wires also crank and cam wires. I added extra ground to the crank sensor and still cut at around 6000rpm. I lowered the car with boost to minimum still the same cut. When the cut happens my cluster rpm goes to 0 rpm and than back to 6000rpm. I checked my map again and still no luck. I put oem ecu again today and car run perfect with no cut or anything similar to the one on link so what link is using that oem doesn't to make that issue?. Please please help me guys I am retired of ideas what can make this problem and my only option would be to keep the car on stock ecu :(. There is nothing in the tune that can do this, Map limit is set to 450kpa where I am at 300kpa during boost. rpm limit is set to 8800 and cut is happening at 6000rpm. Thanks!!

PC Datalog - 2022-07-31 12;20;33 pm.llgx

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The RPM goes to zero when there is a trigger error.  The ECU cuts all fuel and spark when it loses crank position to prevent damage.  So this your problem, but we need to find the cause.  My best guess is noise from the ignition system since all previous logs have only shown it occur at high loads, but ignition energy should reduce when you lower boost so it is bit odd you have an issue at lower boost.  What is the minimum boost you can run?  

It really needs an experienced tuner with a standalone scope to diagnose.  

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The lowest boost I can run is 25 psi. How can I reduce noise from ignition? Is link ecu more sensitive for that kind of noises than oem ecu? I was running as high as 37-38 psi on oem ecu and did not had any of those problems. Maybe I should change camshaft and crankshaft sensors and try that first? They are couple weeks old but you never know maybe one of those sensors going bad??:wacko:

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1 hour ago, Greg1987 said:

Is link ecu more sensitive for that kind of noises than oem ecu?

The factory ECU was only ever designed to work with one specific engine and with only a 2 tooth crank wheel, so they can put a massive amount of filtering and other software tricks to mask any noise.  An aftermarket ecu on the other hand has to be flexible enough to work with almost any trigger system and the G4X can work with up to 200 teeth on the crank, so there are less options to mask noise.  Having said that, we rarely see an issue like this on any engine, and if I think about Evo's specifically there are some fairly serious Evo drag cars around running G4X successfully.   

It is however difficult to diagnose an issue like this on the road with little diagnostic gear.  An issue like this is much easier to solve when you can for example reproduce it in a controlled environment on a dyno with an oscilloscope connected to the triggers to see what the actual problem is.  At the moment I am really just guessing it is noise, but as you say it could be a failing sensor or something else.  Cam sensors are pretty prone to fail in the Evo's since they are close to the turbo heat, but Im pretty sure with G4X you can unplug the cam and it will still keep track using crank only (can you try unplugging cam sensor with engine idling to see if it keeps running) - in which case we could rule that out.  

Do the coil grounds connect to a good clean point on the cyl head?  Do you still have the factor supressor on the coil power supply (Im pretty sure evo's had them).

 

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1 hour ago, Adamw said:

The factory ECU was only ever designed to work with one specific engine and with only a 2 tooth crank wheel, so they can put a massive amount of filtering and other software tricks to mask any noise.  An aftermarket ecu on the other hand has to be flexible enough to work with almost any trigger system and the G4X can work with up to 200 teeth on the crank, so there are less options to mask noise.  Having said that, we rarely see an issue like this on any engine, and if I think about Evo's specifically there are some fairly serious Evo drag cars around running G4X successfully.   

It is however difficult to diagnose an issue like this on the road with little diagnostic gear.  An issue like this is much easier to solve when you can for example reproduce it in a controlled environment on a dyno with an oscilloscope connected to the triggers to see what the actual problem is.  At the moment I am really just guessing it is noise, but as you say it could be a failing sensor or something else.  Cam sensors are pretty prone to fail in the Evo's since they are close to the turbo heat, but Im pretty sure with G4X you can unplug the cam and it will still keep track using crank only (can you try unplugging cam sensor with engine idling to see if it keeps running) - in which case we could rule that out.  

Do the coil grounds connect to a good clean point on the cyl head?  Do you still have the factor supressor on the coil power supply (Im pretty sure evo's had them).

 

Thank you so much for explanation. Ok so I did unplugged cam sensor while engine was idling and the engine died immediately. So look like it does need cam sensor to run. To the supressor on the coil power supply I have no idea to be honest with you. I have coil on plug denso coils with the wiring that the coils came with (I purchased it as a kit). Since car need cam sensor to run and since they are prone to fail (even mine is couple weeks old) I will order new cam sensor first and if that will not help I will try new crank sensor and see the results!! Coil ground has good clean point on the cylinder head but I will also add extra ground straight from negative battery and see if there is any change.

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19 hours ago, Greg1987 said:

To the supressor on the coil power supply I have no idea to be honest with you.

I remember my evo 6 had one up on one of the cam cover bolts, but I looked at my evo 7 yesterday and couldnt see one so suspect yours never did.  

Yeah I agree it is worth changing that cam sensor.  I remember the older G4+ would keep running without the cam so you could use that as a test but G4X has more robust error checking and Im not sure if I have ever tried unplugging the cam with G4X.  

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