piston failure on M8T

Antsa · Jan 15, 2016

Hey.

Anyone seen this

Is that due detonation like I suspect?
I think my fuel pressure drops for some reason on 7000rpm starts puking and bogging and sputtering when I really got in to boost. Got one capture done from the boondocker box and it said rpm to be 10970, is that even possible?
The most annoying thing is that it run pretty nicely last winter. https://www.youtube.com/watch?v=96S_zwep69c

This one is perfectly running motor before piston change. MAG side No damage to cylinders

This is from 50km after piston change. Cylinder failure on PTO side.

Ideas what to check:
Sensors?
Stator?
Fuel pump voltage?
Injectors?
Cabling?
Air leaks?

I have fresh set of cylinders and pistons. But just want to be sure that I don't do more damage.

My setup is:
- Boondocker racegas kit, low pressure actuator on wastegate.
- Boost tee 9 psi of boost, running on neste 98e5 fuel
- Intercooler
- greddy bov
- 2 degree advance key on crank
- 3 degree e-key to retard
- 800 2008 stock motor
- Walbro high cap fuel pump
- bdx external fuel regulator set to about 35-38psi on high idle
- innovate lambda gauge
- koso fast egt probes
- about 89grams of weight on MDS turbo weights. yellow/white spring on clutch
- 38/44 cpc helix with green white spring, in that video there was totally original 2011 m8 snopro driven on place
- 2008 original gearing on diamond drive

kiliki · Jan 15, 2016

have the tps checked, funny i have one on the bench just like it from a tm1. i would move your fuel oct up.

Antsa · Jan 15, 2016

was it detonation ? or how did you end up breaking the piston ring land?

Bacon · Jan 15, 2016

Was this first ride? Did you have old gas in sled? Sure looks like detonation to me. If it ran good last year, something changed. I'm assuming you are running at low elevation? At 9 lbs you should be running plenty of octane. I would say 110.

Polarisrocks · Jan 15, 2016

That is definitely detonation, heavy. If you google it it say tooo much heat, too low of octain, or too advanced timing. It sucks, Poobrew on here has done this a few times. Ususally takes out the turbo turbine fins when the pieces go through it..

Hardass · Jan 16, 2016

What is 98e5 fuel? what elevation are you riding at just curious about your set up 89 grams and 38/44 are pretty big for a 800 it seems just curious

Antsa · Jan 16, 2016

Driving at sea level.
98e5 is neste oil fuel that we can get here in Finland https://www.neste.fi/tuotteet_tuotelistaus.aspx?path=2589,2655,2698,2699,2702#

Polarisrocks · Jan 16, 2016

Whats your shelf life on that fuel? Did you drain that tank from the previous season and start with fresh fuel? Do you run it straight? Do you Av gas for small airplanes? A lot of guys here in the states run av gas, cheap and at most little airports. What is the MON octain of that fuel?

Antsa · Jan 17, 2016

RON 98
MON 87
Ethanol content 5 vol.-%

and those are minimum numbers.

I had about half tank of old fuel from last season, straight after piston change I went to fuel station and filled up with fresh 98. And also put some 2t oil to the tank.

Don't know the shelf life, but there might be reason for the failure, did not really think it could do that.

Also it did not give me the octn code with the e-key, even if it was detonation like a rockstar. But when I took the e-key out it gave the code in the first wot moment.

Might be little bit wiser when I get to the sled next weekend.

fastgas · Jan 17, 2016

Antsa said:
Hey.

Got one capture done from the boondocker box and it said rpm to be 10970, is that even possible?

You likely have a bad connection somewhere that is causing this. The box determines rpms from the injector signal from the ECU. A bad ground will cause the box to reset - you can determine this by pressing the Sel button after startup to go to main or stats screen, if the box ever goes back to the startup screen (before shutting off seld) then you probably have a bad ground or power connection (power comes from the injector voltage supply). High rpms likely means you have a bad connection to one of the injectors going to the ECU.
Be sure to fix this before riding on boost for very long since the box likely won't be fueling right if it's getting a bad signal. A less likely cause might be a bad voltage regulator (which can cause exhaust valves to not work), or other intermittent short on the sled, but you'd probably be seeing fault codes (have you removed/unplugged headlights recently - this can cause issues).

Polarisrocks · Jan 17, 2016

Most fuel has a 6 month shelf life, then is starts loosing octain pretty fast. So with that 87 mon fuel you are basically a pump gas set up, 5- 6 lbs. If you stay at 9 you will need more octane to keep that motor alive at sea level. So you know now you need to drain that tank before your next ride, Pull that turbine housing off the turbo off and check the side fins on that turbine wheel.

Do you have small airports locally?

\

Antsa · Jan 17, 2016

fastgas said:
You likely have a bad connection somewhere that is causing this. The box determines rpms from the injector signal from the ECU. A bad ground will cause the box to reset - you can determine this by pressing the Sel button after startup to go to main or stats screen, if the box ever goes back to the startup screen (before shutting off seld) then you probably have a bad ground or power connection (power comes from the injector voltage supply). High rpms likely means you have a bad connection to one of the injectors going to the ECU.
Be sure to fix this before riding on boost for very long since the box likely won't be fueling right if it's getting a bad signal. A less likely cause might be a bad voltage regulator (which can cause exhaust valves to not work), or other intermittent short on the sled, but you'd probably be seeing fault codes (have you removed/unplugged headlights recently - this can cause issues).

Taken out the right side plugs from the headlights. What does this cause?

My idea was to take out some load from the stator, since I have the boondocker intercooler fan, larger capacity fuel pump, AFr gauge, turbo oil pump etc.

I think I had similar problems last season when I installed the kit, put can't really recall what was the actual fix.

Might as well solder up all the connections that are currently done with abikos. And use dielectric grease on the originals.

Polarisrocks said:
Most fuel has a 6 month shelf life, then is starts loosing octain pretty fast. So with that 87 mon fuel you are basically a pump gas set up, 5- 6 lbs. If you stay at 9 you will need more octane to keep that motor alive at sea level. So you know now you need to drain that tank before your next ride, Pull that turbine housing off the turbo off and check the side fins on that turbine wheel.

Do you have small airports locally?

Did you check that video? is it detonating in that one?

Polarisrocks · Jan 17, 2016

I watched the video, cant hear much other than too much wind noise. Go out a take a hammer to that piston and see how hard you have to hit it get a different part of that piston ring land to break out. The damage happened probably on the trail down by the truck. It only take a 1 tenth of a second to cause that detonation. Do a google search, read up on detonation and what causes ring land failure..

Antsa · Jan 17, 2016

Did not mean to be disrespectful, but what I meant was that it worked out just fine last year, the motor being exactly the same.

I think the first piston that has the broken ring land, damaged in the early phase of the last season when I has similar issue with the detonation, I think it was either bad connection multi wire connector in the boondocker harness that I have near the fuel pump. Or in the tps.

Polarisrocks · Jan 21, 2016

No worries man, its hard to wrap your head around how harsh det can be. Hope you get it figured out.

Antsa · Jan 21, 2016

Does detonation on snowmobile do this:

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piston failure on M8T

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