Engine disaster without a known cause.

[Daltech]

I friend had his engine go down on the pto cylinder. The damages to the pistion and cylinder is unlike anything I have seen before.
Rear transfer ports on both sides is broken pieces of.
The sled has a mntk kit turbo kit installed, and was ran on av fuel@6,5 psi on 2500ft. There is no sign of detonation, and he was actually logging with the bullydog when this happend. Logging was to get baseline data before boost was to be increased.
I have seen my share of seisures over the years, but nothing like this. Piston top was dry, exhaust port was dry, but there was oil on the parts of piston skirts that was undamaged. So I dont think it is lack of oil.
Anyone have a clue on this one?`

 

[mt.sledder]

Looks like possibly a detonation issue. 6.5 psi is a fair bit of boost at 2500’. Maybe the fuel wasn’t fresh, fuel filter getting plugged or your boost was spiking higher. Should check with mntk to verify that their tune supports that boost at 2500’.

 

[Daltech]

Was logging data from the ecu when this happed, and there was no sign of detonation. Have full data of knock sensor, ignition and ign retard, but zero signs of detonation registered from the ecu.
Was also just doing very short pulls, with max 2 sec WOT pulls. This sled has been ran at pump gas on this boost level prior to this, without any problems with that.
So I am confident it is not related to detonation.

 

[Sheetmetalfab]

Ring locator pin backed out and ring spun and caught the port.

Use 15 pro pistons on reassembly to avoid that in future.

 

[kiliki]

Ring locator pin backed out and ring spun and caught the port.

Use 15 pro pistons on reassembly to avoid that in future.

^^ this. Look at the line in the jug

 

[tdorval]

Agreed on the ring locator pin. Looks like it from the pics at least.

 

[Daltech]

Valid point, I did not check if the pinlocator was still present. On the top ring it is still in place for sure, but uncertain about the bottom ring. I will check.
Regarding 2015 pistons, you talk about pistons from the older Pro ride engine? I was under the impression that there was a slight difference in pin locator indexing from the older proride engine to the axys engine?
Does people run pistons from the older proride engine in their axys with success?

 

[Sheetmetalfab]

Valid point, I did not check if the pinlocator was still present. On the top ring it is still in place for sure, but uncertain about the bottom ring. I will check.
Regarding 2015 pistons, you talk about pistons from the older Pro ride engine? I was under the impression that there was a slight difference in pin locator indexing from the older proride engine to the axys engine?
Does people run pistons from the older proride engine in their axys with success?

Yep.

Dimensionally they are the same.

The ring locator pins are more solidly held in place.

 

[Daltech]

Ring pin locator is still present in the piston.

 

[tuneman]

Your transfer ports were obviously damaged by the broken ring flying around. The ring broke because it fluttered from lack of support at the top, due to the missing piece of the piston at that location. The piston likely broke from detonation. The sled's det sensor won't pick up every det incident, especially if they are subtle.

 

[mt.sledder]

Was logging data from the ecu when this happed, and there was no sign of detonation. Have full data of knock sensor, ignition and ign retard, but zero signs of detonation registered from the ecu.
Was also just doing very short pulls, with max 2 sec WOT pulls. This sled has been ran at pump gas on this boost level prior to this, without any problems with that.
So I am confident it is not related to detonation.

If you were running that boost on pump gas previously you likely caused a fair amount of damage during that time and severely weakened the piston. Repetitive detonation events have a history of building up to a failure when you least expect it. A few weeks back one of my buddies ended up with a window in his turbo 800 etec crankcase on the trail down to the truck when he wasn't even giving her the business. The failure was determined to be caused from detonation and straight av gas that had been sitting around in an unsealed container for too long (2 seasons) and too much boost. When running boost you can't scrimp on fresh octane. Engines cost more than fuel!!!!!!!!

 

[whoisthatguy]

Is it possible that the air stream oil injector was plugged up on just one side? I had that happen to me once, but in a much older sled. Or that the mixture was too lean on just one side, due to a partially plugged injector? For reference purposes, could you please state the year and engine model number? Thanks

 

[Daltech]

This particular engine has not been ran on boost before. Last spring engine was opend after season, and pistons showed sign of detonation caused by to much boost/less octane. A second hand engine was installed ( the one that now is broken). This engine has only 1h run time on boost, and that is @6 psi on AV fuel.
The previous engine was ran on7-7,5 psi on pump fuel, and pistons took damage over time. It is another story why it was at that high boost level on pump fuel.
I am leaning towards that this second hand engine could have had some sort of damage, but it was not possible to see any sort of damage to it when it was checked prior to install.

The sled is a 2018 Pro rmk 800 .

I do not think it is lack of oil. There should have been alot more piston scuffing it was lack of lube.There is also a fair amount of oil on the piston skirt when teared down.