Why do rotarys blow up?
09-04-01, 02:57 AM
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Why do rotarys blow up?
A lot of times I see that when rotarys throw an apex seal the apex seals that weren't damaged from the broken seal are in good shape and people say that a lot of times they are still in tolerance. Well if this is the case then the apex seal that went must have had equal wear right? Then why did it throw it? This would be in a situation where the engine was not run low on oil and was not overheated.
If apex seals can just go at random for no real reason what is stopping a brand new rebuild from throwing an apex seal?
Am I overlooking something here?
Thanks fellas
If apex seals can just go at random for no real reason what is stopping a brand new rebuild from throwing an apex seal?
Am I overlooking something here?
Thanks fellas
09-04-01, 06:55 AM
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Apex seals dont just break out of the blue. A perfectly maintained/tuned engine should not break an apex seal (unless, of course, the engine has extremely high mileage, in which case the seals can simply "wear out").
Barring some strange manufacturing defect, the seals will only break if something engine related has gone awry. Common examples include: Aggressive timing, improper air/fuel mixture, too much boost, too little or too much oil, too much restriction in the exhaust system, overeving, overheating etc etc.
Barring some strange manufacturing defect, the seals will only break if something engine related has gone awry. Common examples include: Aggressive timing, improper air/fuel mixture, too much boost, too little or too much oil, too much restriction in the exhaust system, overeving, overheating etc etc.
09-04-01, 10:26 AM
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From my understanding the apex seals need a chance to seat, or wear into the rotor housings. This is part of the break in procedure.
Another variable is the quality of the replacement seals as well as the quality of the rebuild.
Did you blow up a new rebuild?
Another variable is the quality of the replacement seals as well as the quality of the rebuild.
Did you blow up a new rebuild?
09-05-01, 02:18 AM
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No, I didn't blow up a rebuild but I have blown 2 rotarys extremely fast. The first one lasted me about 4 - 6 hours. The second lasted about 2 weeks. The first had 170k miles on it so I understood why it went but the second was in my se. I bought it with 74k on it and it was about 2 quarts low on oil when I got it and it didn't seem to be very well maintained but I got it running good and I ran it pretty hard alot but I really never took it over 7500rpm at max. Well one day the dam thing lost compression in the front rotor so I pulled the headers and looked up in the exhaust holes with a mirror and flashlight and I saw that one of the apex seals was missing a half inch section right in the middle of the seal but the other 2 were good and the rotor faces looked nice. And I did have good compression on one of the 3 faces. So I figured that it must have had a crack in the apex seal and it must have just spit a cracked section out the exhaust. Once I got the se I maintained the hell out of it. I checked the oil mostly everyday and if it was even an 8th of a quart low I filled it up. I used MMO in the oil change and in the fill ups. So I guess I'm just paranoid now. I need some positive reinforcement. Ha Ha.
09-05-01, 08:36 AM
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There's an oil commercial that I find hysterical...
Don't remember the brand (or even if it is oil, or just some addititive), but a group of white lab-coat wearing "doctors" wake this guy up, slap electrodes on him, and throw his sleepy *** on a tread-mill. They switch it on full bore, and switch it off again, several times. The guy's barely able to keep upright, untill he crashes backwards, having flown off the tread mill.
The phrase is something like, "This is what you expect from your engine..." (About stop-n-go driving.)
Point? Well, I think that the next worse thing to simply overheating an engine, is not GENTLY getting it to temperature. You simply cannot crank it over, and speed off, hitting high RPMs untill it's up to temp, and expect it to be happy. You have several different components close together that are made from VERY different metals- The aluminum housing right next to a cast iron one, iron seals on the rotors...these things expand at different rates.
Two other factors I can think of... #1, one seal might have a tiny bit more carbon built up around it than another, causing it to make contact in a different mannor than the others, or to absorb heat at a different rate.
And #2, often upon start-up, I find my metering pump lines are not yet full of oil. (I've asked others, and it is common). This means that the oil (usually in one line) has seeped back down to the pump as perhaps the engine was shut off when the pump piston was partially open.
So the engine should have a few minutes of gental, low RPMs to ensure that the oil gets up there to the carb (12A) or manifold (13B). Even when you can visably see the oil has filled the length of the line, you can still count on a few seconds for it to find its way into the chamber.
This is probably all set by the time the engine is warm, and during this time, I never exceed 2,500 RPM w/ no load (sitting in the driveway.)
These are the little things that I believe are often overlooked, but very crucial to engine longevity.
Then there's just plain "It cracked...simple-as-that!".
Cast iron has a pretty weak granular structure to it. Mixing iron with other ingredients found in a variety of marketed steels yeild a "matrix"...kind of like haphazard random shards of different material mixed in with the base, creating anti-cracking properties. Unfortunately, these disolve into the granular structure of the metal at high temperature (which as far as molten metal temperatures, is relatively low...in some cases this happens at only a few hundred degrees F), where cast iron does'nt do that sort of thing. When the metal cools, the matrix reforms at random, and depending on the speed of the cooling, warping happens. (This is my GUESS why they use such a basic metal as cast iron).
A simple "brushing" of the basics of metalurgy (which is about the extent of my knowledge) can really help to understand what happens with heat and metal in your engine.
As you could maybe see, a detonation a year ago could've weakened a seal, but you did'nt know it. For whatever reason, it let go when it did.
I read on sites people praising the "bullet-proof" quality of their 12A engine. Then I read about guys like you who've gone through 1, or 2. Usually not having babied the engine, though.
It is entirely possible that you simply have had bad luck. But if it happens again, I would have to say you must be overlooking something.
All of what I've written is purely my opinion; a conclusion derived only from what I've read on sites like this, just so you know.
Don't remember the brand (or even if it is oil, or just some addititive), but a group of white lab-coat wearing "doctors" wake this guy up, slap electrodes on him, and throw his sleepy *** on a tread-mill. They switch it on full bore, and switch it off again, several times. The guy's barely able to keep upright, untill he crashes backwards, having flown off the tread mill.
The phrase is something like, "This is what you expect from your engine..." (About stop-n-go driving.)
Point? Well, I think that the next worse thing to simply overheating an engine, is not GENTLY getting it to temperature. You simply cannot crank it over, and speed off, hitting high RPMs untill it's up to temp, and expect it to be happy. You have several different components close together that are made from VERY different metals- The aluminum housing right next to a cast iron one, iron seals on the rotors...these things expand at different rates.
Two other factors I can think of... #1, one seal might have a tiny bit more carbon built up around it than another, causing it to make contact in a different mannor than the others, or to absorb heat at a different rate.
And #2, often upon start-up, I find my metering pump lines are not yet full of oil. (I've asked others, and it is common). This means that the oil (usually in one line) has seeped back down to the pump as perhaps the engine was shut off when the pump piston was partially open.
So the engine should have a few minutes of gental, low RPMs to ensure that the oil gets up there to the carb (12A) or manifold (13B). Even when you can visably see the oil has filled the length of the line, you can still count on a few seconds for it to find its way into the chamber.
This is probably all set by the time the engine is warm, and during this time, I never exceed 2,500 RPM w/ no load (sitting in the driveway.)
These are the little things that I believe are often overlooked, but very crucial to engine longevity.
Then there's just plain "It cracked...simple-as-that!".
Cast iron has a pretty weak granular structure to it. Mixing iron with other ingredients found in a variety of marketed steels yeild a "matrix"...kind of like haphazard random shards of different material mixed in with the base, creating anti-cracking properties. Unfortunately, these disolve into the granular structure of the metal at high temperature (which as far as molten metal temperatures, is relatively low...in some cases this happens at only a few hundred degrees F), where cast iron does'nt do that sort of thing. When the metal cools, the matrix reforms at random, and depending on the speed of the cooling, warping happens. (This is my GUESS why they use such a basic metal as cast iron).
A simple "brushing" of the basics of metalurgy (which is about the extent of my knowledge) can really help to understand what happens with heat and metal in your engine.
As you could maybe see, a detonation a year ago could've weakened a seal, but you did'nt know it. For whatever reason, it let go when it did.
I read on sites people praising the "bullet-proof" quality of their 12A engine. Then I read about guys like you who've gone through 1, or 2. Usually not having babied the engine, though.
It is entirely possible that you simply have had bad luck. But if it happens again, I would have to say you must be overlooking something.
All of what I've written is purely my opinion; a conclusion derived only from what I've read on sites like this, just so you know.
09-05-01, 09:06 AM
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Originally posted by Sterling
There's an oil commercial that I find hysterical...
Don't remember the brand (or even if it is oil, or just some addititive), but a group of white lab-coat wearing "doctors" wake this guy up, slap electrodes on him, and throw his sleepy *** on a tread-mill. They switch it on full bore, and switch it off again, several times. The guy's barely able to keep upright, untill he crashes backwards, having flown off the tread mill.
The phrase is something like, "This is what you expect from your engine..." (About stop-n-go driving.)
There's an oil commercial that I find hysterical...
Don't remember the brand (or even if it is oil, or just some addititive), but a group of white lab-coat wearing "doctors" wake this guy up, slap electrodes on him, and throw his sleepy *** on a tread-mill. They switch it on full bore, and switch it off again, several times. The guy's barely able to keep upright, untill he crashes backwards, having flown off the tread mill.
The phrase is something like, "This is what you expect from your engine..." (About stop-n-go driving.)
Gotta love that corperate brainwashing.
09-05-01, 09:37 AM
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Sterling, that was a great explanation!
I also peeked back at Audio Science’s second post and notice the following statement, “I ran it pretty hard allot but I really never took it over 7500rpm at max”. Wonder if the hard driving “allot” part may have played into the failures?
No one has mentioned it yet, but these are not new cars. They are between 22 and 16 years old now. Nothing lasts forever………………
I also peeked back at Audio Science’s second post and notice the following statement, “I ran it pretty hard allot but I really never took it over 7500rpm at max”. Wonder if the hard driving “allot” part may have played into the failures?
No one has mentioned it yet, but these are not new cars. They are between 22 and 16 years old now. Nothing lasts forever………………
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09-05-01, 02:58 PM
#8
Super Newbie
Stop ******* the **** out of engines that have been sitting forever, immediately after you get them running. Then they won't blow up.
My RX-2 was parked for 5 years, and it runs fine after I got it started a month ago. I've taken it easy on it to get it back in shape.
Sterling is absolutely right about the warm up procedure. Rag on a cold motor every day and watch it smoke like crazy before it gets to 80k.
My RX-2 was parked for 5 years, and it runs fine after I got it started a month ago. I've taken it easy on it to get it back in shape.
Sterling is absolutely right about the warm up procedure. Rag on a cold motor every day and watch it smoke like crazy before it gets to 80k.
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