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Ecu power requirements


vnm02

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Hi I have fitted several  G4 Storms into Honda jetskis, last week I had one of my units that has been in the same ski for nearly a year burn a hole through pistons number 2. It has had the same tune in it for that long roughly 70 hours.

One thing that did happen, was the weekend before the piston failed the skis battery was dead flat, it would not even power up the gauge cluster. Even after hours of riding the battery did not charge up at all. The ski was jump stated every time it was stopped.

The question is does 12 volts low have much impact ont the injectors or fuel system enough to lean out the fuel table?

The next weekend the ski was ridden hard at 17 psi boost and it failed at the end of the day. When the engine was stripped 1  3 and 4 cylinders look perfect in actual fact a tad bit rich, but number 2 had the crown melted away at the edge of the piston which appears to have leaned out. The far that the ski was tuned to was set at 11.7 to 1 and up till now has been fine.

There is no room to fit get sensors to each cylinder as the ex manifold is water jacketed, so it is not possible to know if each cylinder needs trimming applied, however I have just had 4 injectors flow tested and they are within 1% flow of each other.the only other thing I can think of is possibly a faulty or blocked injector. I can post pics of the plugs and pistons if needed.

Thanks Bruce 

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By the way the ski only has a 26amp charging circuit, so.I am thinking that if the battery had a bad cell there might not have been sufficient voltage to run the rest of the electrical system as the main fuse fuse for the electrical system is rated at 30amps?

I have not pulled any logs yet as the USB cable was not on hand to see if there was any low voltage.

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Hi Bruce,

So long as your deadtime values are set in the ECU to match the injectors, the lower voltage would taken into consideration in the fuel calculation. The injector deadtime table spans 6 to 15 volts.

One possibility is that if the jetski was jump started incorrectly, damage could have been done to the ECU. Normally if this were to happen the injector driver would be fully on or fully off though. If you have access to the ECU it would be worth testing the injector output #2.

Another possibility, as you mentioned, is that a fuel system component failed.

Let me know if you are able to recover the log from the ECU, it could certainly help diagnose what went wrong.

Kind regards,

Scott

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Dont forget, the coils also need good power to provide spark, and the fuel pump needs power to provide fuel

 

All the injector dead time in the world wont cope with a fuel pump with no power, and 2v is a huge difference for a pump. If indeed the engine even had 12v when running and no method of charging.

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That piston has deinitly been hot!  Looks like it has been molten!  I can only think of a couple of causes:  It went lean and got hot or it started seizing and got hot!  Doesn't look like damage due to detonation.  The stuff on the spark plug is melted piston.

Very unlikely the ECU decided to run a cylinder lean.  It is also very unlikely one injector driver has been damaged.  More likely lack of fuel due to low fuel pressure (low pump voltage) or an injector not properly opening due to low voltage (pretty unlikely).  The answer to if it is a voltage problem is in the log files.  If it was lean enough to do that it should of been surging and mucking around as if it was fuel pressure related all cylinders should have been suffering.  

Any chance it picked up water or air in the fuel and just happened to be feeding that cylinder a water/fuel mix?  Pretty unlikely though.  It points to a blocked injector but that is rare and the driver should have noticed.

The other possibility is that it was always tuned a little too lean and advanced and has been running hot on that cylinder the whole time.  Might of just had enough.

Best install some safety sensors (fuel pressure etc...).  Can you put pyros into the exhaust by going through the flange rather than the middle of the pipes?

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Hi Ashley, just got the injectors back from cleaning and testing all are fine, they were a little dirty but nothing too serious.

I will have the ecu tonight to check logs, I don't think this tune is lean as checking plugs and log files all showv good figures when I have the ngk afx 02 sensor connected. 

I will check the logs and let you know

Thanks

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HI Guys,

 

I finally have the ecu in hand and have pulled the last logs from it. (Please note these logs are not of the low voltage problem the ski had. These are the last moments of this engine life.

 

I have also attached the PCL file for you to look at and see if anything jumps out at you.

I also had a good look at the rest of the cylinders and the pistons they are perfect no pitting around any of the crowns and no lean burn either.

I also tested the injector outputs from this ecu in my ski, all 4 cylinders fire perfectly.

 

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It still looks like a rich failure to me. The lack of pitting confirms this really. Pitting would show on lean detonation, but pre-ignition from being too rich would only show as melted edge. The theory behind it is that an overly rich mixture causes carbon buildup under the ring, which then lifts or pinches and causes oil to get by. this then massively lowers the octane rating of the fuel in that cylinder and then you end up with pistons like that. Ive got a honda engine (2.0) in my workshop now, that someone else tuned (lots of timing, lots of fuel) which looks exactly the same. ZERO pitting, even on the affected piston. just a melted edge, 1/4 of the way round and melted rings in the affected area. there was no shortage of fuel here either.

Obviously it depends a lot on fuel used and compression ratio etc etc, but that log looks to me to be quite a lot of timing for what must be a small bore engine at moderate revs (correct me if im wrong, but im guessing its a bike engine or similar and not race fuel/meth). And the high iats wont have helped much. Also, why does the boost pressure fluctuate without any change in revs/tps?

I think it may be that it was just pushed too far for too long, and no single component was to blame.

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Hi tony, would this only be evident on one cylinder?

The afr at full boost 200 kpa is around 11.5-11.7 I would not call that too rich, yes there is about of timing but we are suffering no knock from this and the high oat is caused by ambient temp being around 25 degrees with 80% humidity. The turbo is only very small on this ski it is a ihi built for Honda. We have fitted a larger intercooler but it still might need to go larger but there is also little room in the ski. There is very little air flow in the hull as it needs to be as watertight as possible.

The map pressure bounces around due to the ski coming in and out of the water all of the time, these engines get loaded and unloaded lots of times as the jet unhooks.

The ski has also never consumed oil and it only runs 98 octane fuel.

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So for the double up on posts bloody iPad makes it hard to edit post.

I have ran theses engine on a land and sea dyno, at 15.5 psi they make 260hp at 6700rpm. The std engine produces 200 hp at 10 psi, if the tune was too rich to cause a failure there is certainly no performance issue with being too rich. Also ther is no lagging of the engine it is clean right through the rev range.

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That makes sense about it coming out of the water, I never thought of that!

No, I wouldn't call 11.5 too rich either (maybe a little) but i do like to tune a little leaner than most but with less timing. it makes similar power but with more room for error if something goes a bit wrong. But no, 11.5 isnt too rich really.

But maybe something happened to cause it to go over rich?

Looking at your map i notice there is no adjustment for iat's. I always like to pull timing after about 40degC on boost but it depends a lot on the setup, but with your temps varying by over 20deg on boost it would have been good to have some adjustment. Im sure you're aware that a hotter charge is less dense and therefore requires (theoretically) less fuel. this could have caused a rich condition out on the water, when compared with it on a dyno with possibly lower iats. It would only need to dip into the 10's before i would get concerned about the amount of fuel, and thats not too far from where you were. its difficult to say without more data tho obviously. Theres a few random peaks and troughs on that map though.

It still seems like a lot of timing to me but then ive always been very conservative with that. but espescially with the 98 octane (RON?). but you're right, that should have showed as knock or deposition on the plugs and should have left pitting.

I doubt it was anything to do with the charging issue, ive had these ecu's on cars with batteries that have gone flat many times, and just jumped them off or charged them and had no issues. I even put the charger on backwards once in the dark and got lots of sparks! no issues though, still runs fine. I did once fry an injector chip in a g4, down to a peice of electrical tape coming unstuck due to having been contaminated with petol causing a short circuit (should have used heatshrink!). This was instant and permanant though, the injector stuck open, it ran on three cylinders and dumped fuel in the exhaust for a few seconds while it was restarted. But the nice people at link were kind enough to point me in the right direction to find a replacement chip and its fine now. Since you have tested the ecu since the failure I doubt that it failed.

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