My2cents
ArboristSite Operative
Any descent shop that rebores that cylinder will pressure test before they bother to work on it. You will see. Your problem is not a typical text book seize.
anatomy of a burndown
- Thread starter bwalker
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The motor was already leakdown tested as previously stated. This damage was caused by detonation. Had coolant leaked in the chamber(have had it happen) it does not seize. Just runs like crap.BTW this engine does not use head gaskets. It uses rubber o rings. All the o rings where in good shape and not leaking.
Doug, Its a single. I forgot the distance I mounted the single pyro from the cylinder, but it was in accordance to my engine guys directions. I believe the warning light on my racepak comes on at 1350. I have run it over that hillclimbing a few times with no negative results. This setup has been stone reliable for many years.Previous to this I have only had to replace wear items like slides, wearbars, belts, plugs and a silencer can that blew apart.
My2cents
ArboristSite Operative
A very small crack does not leak coolant into the cylinder, in fact sometimes the leak shows up only under full load hot conditions.
Most of the suttle bad heads/cylinders I have seen never leaked coolant into the cylinder. Are you going to rebuild this assembly?
Most of the suttle bad heads/cylinders I have seen never leaked coolant into the cylinder. Are you going to rebuild this assembly?
Yes, I drove it up to my engine builder today. AS I said before it wasnt a coolant leak. The engine has been leak down tested. If it did have aleak it would not melt the piston like that. This type of thing is caused by air leaks, lean jets, misadjusted timing and bad fuel. I have narrowed it down to bad fuel as everything checks out ok.
Kneejerk Bombas
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All I know is I ain't using none of that synthetic oil!
THIS IS NOT OIL RELATED. To say otherwise is plain stupid.
Yes it would, but my egt gauge would have picked it up. In retrospec I should have noticed that the egt's where lower than usual prior to the failure. The reason for this is the piston is absorbing all the heat, leaving less to be exhausted once the exhaust port opens.
Crofter
Addicted to ArboristSite
Ben I'm going to crank you here. It seems you are going to great lengths to support what you feel MUST be the problem. A detonation event doesn't take long. How often do you monitor your egt. A stacking up of a few of the things suggested along with the extremely cold weather and a marginally lean condition to start with could well account for it. I'm not saying it was not the wrong gas but I dont think the evidence to that effect is so conclusive.
Frank
Frank
Kneejerk Bombas
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So Crofter thinks it was the oil too...
Could you explain exactly what makes a gas bad? More precisely, what was bad about the gas you got?
Could you explain exactly what makes a gas bad? More precisely, what was bad about the gas you got?
Tony Snyder
Addicted to ArboristSite
Is this a two cylinder engine, and if so did damage occure to the other piston?
Crofter
Addicted to ArboristSite
Yes Tony , 2 cyl. No I dont blame oil. I see detonation, but many things can lead to detonation. It does not have to be just one cause especially in an engine with that high an octane demand. When you are working close to the edge it doesn't need many sseconds. Low octane fuel certainly would account for it but without analysing the fuel, I don't think that it rules out some other things that could also lead to the same results. We are just being picky here, but I think it helps focus on what all different things can lead to a bad day. It sometimes is very hard after the fact to establish what conditions existed immediately before. What do you think Ben; if you were suing someone would the evidence you have hold up in court. You know, beyond the shadow of a doubt. Im just stirring the pot here, but I,m not making light of what happened to your sled.
Frank
Frank
Itwasnt cold(25 f) and the sled is jetted down to minus 20.
.
I t never got hot or the warning light on my guage would have tripped.
Mike, When I say bad gas. I mean I think I got a tank of 87 or worse. In a stock saw this might not make much of a differance, but in a engine that is built to run on premium as a minimum it is a issue.as aside note the area I got the last tank of gas in is one the most remote areas of MI. It was bought at a po dunk, no brand station. My friend a few years ago filled up at the only other station in the area and got a load of diesel in his sled. Talk about fouled plugs.
Tony read earlier in the post to explain why only one cylinder fried. The is quit common in multi cylinder motors.
QUOTE]What do you think Ben; if you were suing someone would the evidence you have hold up in court. You know, beyond the shadow of a doubt.[/QUOTE]
Crofter, If I wasnt sure it was fuel related I woudnt say so. I have the most interst in corecting whatever condition caused this as I do not want it to happen again(IE $). I have eliminated all the possible cause of such a event, but fuel. I can say with reasonable confidance that it was fuel related. One thing I forgot to mention early on is the fact that it puked within about five miles after the fillup. It was the first long straight section after I had filled up when it went.
Crofter, If I wasnt sure it was fuel related I woudnt say so. I have the most interst in corecting whatever condition caused this as I do not want it to happen again(IE $). I have eliminated all the possible cause of such a event, but fuel. I can say with reasonable confidance that it was fuel related. One thing I forgot to mention early on is the fact that it puked within about five miles after the fillup. It was the first long straight section after I had filled up when it went.
carhartted
ArboristSite Member
A tank of 87 octane run in an engine designed for 92 octane or so will definitly do some damage. In addition to the predetonation problems of regular, there are more BTU's per pound of regular than premium. This wold cause the engine to run hotter.
Another problem is the way in which the octane numbers are calculated. The feds require octane ratings to be measure by the (R+M)/2 method. The problem with this is the possible difference between the R and M.
The R stands for ROM or Reasearch Ocatne Number, and is calculated to give a rating for engine knock at low speeds and engine run on. This number is typically 8-10 numbers higher than the M.
The M stands for MON or Motor Octane Number, and is calculated at high engine speeds. If this number is too low engine knock may occur during power acceleration.
Some engines may need more R and less M or vice versa.
In example. A 87 octane gasoline typically has a MON of 82 and a RON of 92.
In this meltdown situation a higher MON is needed, it could be that the opposite was true at the po dunk gas station out in the sticks.
One other thing to consider. If the fuel had Oxygenates added it could explain the lean running and meltdown. Arctic Cat suggests going up one jet size if using Oxy fuel to make up for the loss of BTUs. This is due to the MTBE or other additive that makes Oxy fuel Oxy fuel. MTBE only has 97,000 btu/lb while Winter grade gasoline has between 113,000 and 117,000 BTU/lb.
Hope I didn't muddy the waters too much.
Jonathan
Another problem is the way in which the octane numbers are calculated. The feds require octane ratings to be measure by the (R+M)/2 method. The problem with this is the possible difference between the R and M.
The R stands for ROM or Reasearch Ocatne Number, and is calculated to give a rating for engine knock at low speeds and engine run on. This number is typically 8-10 numbers higher than the M.
The M stands for MON or Motor Octane Number, and is calculated at high engine speeds. If this number is too low engine knock may occur during power acceleration.
Some engines may need more R and less M or vice versa.
In example. A 87 octane gasoline typically has a MON of 82 and a RON of 92.
In this meltdown situation a higher MON is needed, it could be that the opposite was true at the po dunk gas station out in the sticks.
One other thing to consider. If the fuel had Oxygenates added it could explain the lean running and meltdown. Arctic Cat suggests going up one jet size if using Oxy fuel to make up for the loss of BTUs. This is due to the MTBE or other additive that makes Oxy fuel Oxy fuel. MTBE only has 97,000 btu/lb while Winter grade gasoline has between 113,000 and 117,000 BTU/lb.
Hope I didn't muddy the waters too much.
Jonathan
First of all there is no such thing as predetonation. There are preigntiion and detonation. They are radicaly differant. Second of all 87 doesnt have any more btu in it than 93. It also doesnt burn hotter unless detonation is present. MI does not have oxy gas so that isnt a issue.
Beginer, The things you mentioned would cause preignition, not detonation. Go to www.mavdizzy.com and look up detonation and preigniton. They are vastly differant.
carhartted
ArboristSite Member
I knew something didn't seem quite right. There is no such thing as predetination sorry. I do know the difference between preignition and detonation.
My point of the post was to suggest that the difference betwen the RON and MON might have been the culprit.
My point of the post was to suggest that the difference betwen the RON and MON might have been the culprit.
Crofter
Addicted to ArboristSite
Ben, it is my impression that early ignition, by whatever reason, will lead to detonation in an engine with high octane demand. preignition is ignition by a source other than the intended spark. It doesnt really matter what sets it off, if it is 10 or so degrees early you will have subsequent detonation in a high octane demand engine. There is a list of things that could lead to preignition including brken ring, metal wisker, plug problem etc. all of which evidence would have been destroyed by the ensuing terminal detonation and seizure destruction. It is hard to know by the wreckage exactly what was occurring immediately before the ship hit the sand.
Frank
Frank
Fish
Tree Freak
What is really not right is the hoax that is beginner.
He has haunted many other forums, and has made a mark here.
I have rooted him out on other forums, but have let him run here,
so it is my fault I didn't step in earlier. Read his threads on this
forum, and look at his last post, and realize we have all been duped. Look on the Garden web, do a search under the name metheme and zmoz, and you will see our friend. He is also
trying to infect Lawnsite now.
You all know I am usually joking around, but not now. This
person is a fraud and it is time to end it.
Fish
He has haunted many other forums, and has made a mark here.
I have rooted him out on other forums, but have let him run here,
so it is my fault I didn't step in earlier. Read his threads on this
forum, and look at his last post, and realize we have all been duped. Look on the Garden web, do a search under the name metheme and zmoz, and you will see our friend. He is also
trying to infect Lawnsite now.
You all know I am usually joking around, but not now. This
person is a fraud and it is time to end it.
Fish
This is not the case at all. Many engines will preignite or ping ocasionaly with out every detonating. Preignition can lead to detonation, but doesnt always. Conversly detonation doesnt nee to have preignition present to start.
Since the motor wasnt running hot I would tend to think that preignition never occured in this case. I wish it had as that would have been a warning that something was wrong.
here are some links for that will help beginner and others understand what is going on here. http://www.motorcycle.com/mo/mcnuts/fuelron.html
http://www.motorcycle.com/mo/mcrob/rt-fuel2.html
http://www.streetrodstuff.com/Articles/September_2000/Engine_Basics_I.php
