Dies after Idling after a few seconds (Phazer)

[slobra96]

Hey guys, Im back with another problem. So now that we have rpms and can get our engine started, we are now having problems with the engine idling for around 15-30 seconds and then randomly shutting off. I have attached our megatune file and a datalog of it idling for a good 15-30 seconds. We are leaning towards a problem with ignition because the air fuel ratio remains relatively constant as does the fuel pressure. We can't seem to find anything wrong with our datalog and are running out of ideas to try.

Some specs about our engine, if it helps, is its a 499cc two cylinder engine out of a 2007 yamaha phazer. It is turbocharged with an intake restrictor after the throttlebody because it is for fsae competition. We are running 100 octane gasoline.

Thanks

[24c]

I had a quick look, and it looks like your MAP signal is jumping up & down, which is causing the RPMs and PWs to fluctuate, despite your TPS being constant.

I wonder if you restrict the MAP sensor vacuum feed, whether you'll get better results or at the very least more stable rpms. Does your throttle body have an idle bypass air screw? Can you reduce the butterfly opening, ie the TPS value and still get a stable idle?

[slobra96]

Hey 24c, our throttlebody does have the idle set screw. We had to open it up some for it to idle. I can try and play around with it some more. When it does idle and shut off, its not like the rpms slowly drop and then it shuts off, its a sudden shut off after a few seconds. It wont start right back up then, it needs about a minute to do whatever and then it will start back up. Its almost like something goes off sync or over heats and causes it to shut off (I could be totally wrong) and then it needs to rest or cool down for a minute in order for it to restart.

If it is because of the map, would playing with the ve tables and afr tables help to try and get a more constant map?

Im sure I will be playing around with it some more tomorrow and will have some more updates.

Thanks

[Matt Cramer]

The MAP sensor bouncing is one contributor, but the real problem is the unsteady signal is triggering your acceleration enrichment, making the engine very difficult to tune. Try increasing the thresholds to keep them from false triggering.

[slobra96]

Hey guys, sorry if I have not been adding enough information and if I've been too short, it has been a busy and stressful couple of weeks. So today I went to try and start our engine and I could get it running for about 15 seconds at most and then it died. I then pulled the spark plugs, and one plug was all black from carbon while the other plug looked brand new . This lead me to think that one of the cylinders is not sparking at the correct time, and it was pretty much running on one cylinder, which caused it to shut off. Now the injectors both have power running to them. Both of the Coils spark. We tried swapping the coils and injectors to see if the same cylinder would get all carboned up and the same cylinder indeed got all carboned up, while the other cylinders plug look spotless. So this showed that it was not a problem with a faulty injector or coil.

I am not sure what to do now, our settings are correct. I read on another thread in which the person was using the same engine as me that a "bias" was wired into the vr sensor which caused the signal to not stay at a consistent zero. (sorry if the terminolgy is not correct, I am not an EE) We do not have anything wired into the vr sensor, just a 100k resistor wired into the cam sensor. Should we try and do this?

Does anybody have any idea what could fix it? I can post anything that would be helpful in order to troubleshoot whats wrong (scopes of vr and halls effect, tachref, datalogs, megatune files, etc...)

The MAP sensor bouncing is one contributor, but the real problem is the unsteady signal is triggering your acceleration enrichment, making the engine very difficult to tune. Try increasing the thresholds to keep them from false triggering.

Would this help with our problem? if so what are the thresholds? sorry Im all new to this microsquirt and megatune

[grippo]

You have found the problem - one cylinder is not sparking and its not the coil or plug. That leaves 2 possibilities - one of the ignition drivers is bad or the odd angle/ cylinder offset is incorrect. Your msq is showing an odd-fire angle of +180 deg, which says that cylinder 2 fires 180 deg earlier than it would if it were an even-fire engine. Is your engine an odd-fire and is the second cylinder offset 180 deg early or is is it the reverse - late ? Can you put a timing light on each cylinder and see if they are firing where you want them to ? When you test, just crank the engine with the injectors unplugged - makes it easier on the engine. The other thing you can do is check the ignition drivers and see if one of them gets hotter than the other or even if both are very hot. Maybe first verify there is spark to both cylinders by removing the plug cables and letting them spark to the block.

The really good news is that you are not losing synch - your vr sensor and wiring is fine - please don't change it.

You also definitely need to boost up the acceleration enrichment threshold. Do this by setting the map threshold from 35 to 200, or set the weighting proportion to 100% tps. But if this were the only problem, you would not see one cylinder rich and the other normal.

[slobra96]

You have found the problem - one cylinder is not sparking and its not the coil or plug. That leaves 2 possibilities - one of the ignition drivers is bad or the odd angle/ cylinder offset is incorrect. Your msq is showing an odd-fire angle of +180 deg, which says that cylinder 2 fires 180 deg earlier than it would if it were an even-fire engine. Is your engine an odd-fire and is the second cylinder offset 180 deg early or is is it the reverse - late ? Can you put a timing light on each cylinder and see if they are firing where you want them to ? When you test, just crank the engine with the injectors unplugged - makes it easier on the engine. The other thing you can do is check the ignition drivers and see if one of them gets hotter than the other or even if both are very hot. Maybe first verify there is spark to both cylinders by removing the plug cables and letting them spark to the block.

The really good news is that you are not losing synch - your vr sensor and wiring is fine - please don't change it.

You also definitely need to boost up the acceleration enrichment threshold. Do this by setting the map threshold from 35 to 200, or set the weighting proportion to 100% tps. But if this were the only problem, you would not see one cylinder rich and the other normal.

Thanks for answering grippo, I just checked to see if there is spark from the coils and there indeed is spark from both coils. Our engine is an oddfiring engine. We checked that setting on geoffct's msq and another fsae teams msq to make sure ours was the same as theres and it is. (we are using the same engine as both of them)

I did not do the timing light yet, I will have to see if we have one. Do you have any suggestions on how to test to make sure they are firing when we want them too by using the timing light? Also, are the ignition drivers inside the microsquirt? What happens if one of those is bad? Is there a way to prevent that from happening?

Thanks

[slobra96]

Hey Guys,

We checked the ignition drivers today, and they do not get hot. Both coils are producing spark when we take them out of the head. We put brand new plugs in, and after two trials of 30 seconds runs at round 2000rpm the cylinder one plug was black and the cylinder 2 plug was clean which smelled like fuel. ( I attached a picture of the spark plugs below)

We also changed the odd fire angle to -180 degrees now, because it did not seem like it wanted to started when it was at +180 degrees.

We are at a loss right now on what is our problem. We have pretty much just been playing around with setting and seeing if anything helps, no luck yet.

What could be our problem? Could the drivers still be bad if we are getting spark out of both? Please help

Thanks again

[slobra96]

Sorry heres the picture

[slobra96]

I forgot to mention this before, but our engine is odd firing in which cylinder two fires 180 degrees after cylinder one.