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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
Ok so it seems the basics from thread No 1 have been accepted without challenge?? Somewhat begrudgingly I might say, but hey this is rec.boats if it were easy it would be too crowded:-) So now you've all thrown your various sexist hissy fits, none of which addressed any of the thread's issues:-) but were more about silencing me, which isn't going to happen:-) maybe this time you can either comment directly on the substance of the material of just stay quiet, very very quiet??? (please) Next, again at this stage lets not bother with Ficht per se; just see if we can get agreement on the basics of what is needed & "why". I have thought this might be covered in 3 or 4 threads but it seems the lack of understanding is even worse than even I imagined (not possible surely:-)). So I'll take it a bit slower & make sure we all agree in each step, if that's OK with you. There'll be plenty of later threads to address Ficht by name & yes spam man Bill don't panic; even E-Tech:-) (1) The design of petrol engines is dependent on the fuel burning within the closed combustion chamber in a consistently predicable way, with the accepted target in petrol engines to; (a) To have the fuel ignition instigated by the spark plug & only the spark plug (b) To have the flamefront propagate at a known speed/time, reliable throughout the charge, that speed varies with temp/pressure so it varies as the burn proceeds, starts slow then speeds up as the chamber temp /pressure rises. (c) So as the temp/pressure combo in the chamber rises, the extremities of the charge do not reach their autoignition temp, before the accelerating flamefront has arrived as intended. (c) To have the burn all but completed & the highest chamber pressure occur just at or just after the piston leaves TDC on the power stroke. The pursuit of this target over a variety of conditions involves juggling many variables, including; (2) the octane rating of the intended petrol including anything that may dilute/contaminate it (whole books exist just on this fuel/octane subject so this is very much in a nutshell, however comments are very much valued), (a) A lazy way to describe this is the higher the octane rating of the fuel the higher the temp it autoignites at & usually the slower the flamefront will propagate. Or the lower the octane rating the lower the autoignition temp will be & the faster the flamefront will propagate (flashover, remember the flamefront speed varies as the chamber's temp/pressure varies)). (b) Once properly vapourised, (so each drop of vapour has access to air/oxygen & is close by others) if fuel vapour is heated beyond it's autoignition temp then the burn/flamefront will auto commence propagating from that hottest point. This will happen no matter what, no matter if the spark plug has or hasn't fired nor if other parts of the charge have already ignited nor where the piston is. The design depends on the spark plug's spark being the only thing in the chamber that exceeds the fuel's autoigntion temp. & that nothing within nor any part of the chamber exceeding the autoignition temp till the burn/flamefront has arrives. (c) Old worn engines & new 2 stroke OBs allow lube oil into the combustion chamber, this has the effect of reducing the fuels octane rating, again the design has to be aware of & allow for this effect. Over years this has been recognised as a reliability issue in 2 stroke OBs, so some effort has gone into reducing the amounts of oil carried up into the chamber. (d) So for the burn to be predictable & consistently controlled over the full range of operating conditions the actual octane rating arriving within the chamber needs to be as close to the raw fuels rating as possible with as little oil dilution as possible. (3) Some side comments?? The DFIs you'd think have solved this octane dilution problem by not having oil mixed in the fuel?? not so, what they do do is; (a) inject really tiny amounts of raw oil into the crankcase & by design it has nowhere to go. (b) The DFI people seem to think this is good & market it by saying the DFI engines "use" no more oil than a 4 stroke does, however that ignores the fact that a 4 stroke hopefully never burns it, you drain it into a bucket. (c) This burning the oil & the way/when it's done are issues with the DFIs because over say a less than 50 hr season it burns a lot of oil, certainly much much more than any 4 stroke that is still in use:-) (d) The very small amounts of oil stay in the crankcase & get hotter & hotter & hotter, (e) At lower revs there isn't enough air flowing through the crankcase to carry any excess oil up the transfer ports & out the at low revs overlapping exhaust, this is a deliberate "must pass the EPA test" tactic & it works in stopping raw oil getting out at low revs. (f) So at low revs the DFI has virtually no oil getting into the chamber & the fuels octane rating (resistance to autoignition, flamefront speed(s))) is as placarded however, (g) When the engine is powered up any excess built up crankcase oil can escape, but by now the useful overlap between the transfer & exhaust ports is diminished (again as intended by the design) so the oil can get into the chamber & dilute the fuel's octane rating. (h) The thing to be considered is that at low revs the oil isn't being transfered & burnt at all, so at low to moderate revs the octane rating of the fuel is "safe", but as the revs rise oil definitely (what?? 1 ltr ever 12 hrs running??) does get burnt, but because it's no longer consistently mixed in fuel it goes up in fits & spirts, some not a risk, others definitely a big risk of severely dilluting the fuels octane rating. I hope this gets some genuine substantive review & thanks in advance to anyone who bothers. I'm sure lots will just say it's No 2's:-) with no actual rejoinders on the issues. K |
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#2
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
"K Smith" wrote in message ... Ok so it seems the basics from thread No 1 have been accepted without challenge?? Somewhat begrudgingly I might say, but hey this is rec.boats if it were easy it would be too crowded:-) So now you've all thrown your various sexist hissy fits, none of which addressed any of the thread's issues:-) but were more about silencing me, which isn't going to happen:-) maybe this time you can either comment directly on the substance of the material of just stay quiet, very very quiet??? (please) snip (1) The design of petrol engines is dependent on the fuel burning within the closed combustion chamber in a consistently predicable way, with the accepted target in petrol engines to; (a) To have the fuel ignition instigated by the spark plug & only the spark plug ok (b) To have the flamefront propagate at a known speed/time, reliable throughout the charge, that speed varies with temp/pressure so it varies as the burn proceeds, starts slow then speeds up as the chamber temp /pressure rises. This is just the way things are, right? (c) So as the temp/pressure combo in the chamber rises, the extremities of the charge do not reach their autoignition temp, before the accelerating flamefront has arrived as intended. no detonation. (c) To have the burn all but completed & the highest chamber pressure occur just at or just after the piston leaves TDC on the power stroke. I don't know about this one. It is for sure you don't want it before tdc. but I don't know that you want it too near after tdc either. The pursuit of this target over a variety of conditions involves juggling many variables, including; That's why the engine designers make the big bucks. (2) the octane rating of the intended petrol including anything that may dilute/contaminate it (whole books exist just on this fuel/octane subject so this is very much in a nutshell, however comments are very much valued), (a) A lazy way to describe this is the higher the octane rating of the fuel the higher the temp it autoignites at & usually the slower the flamefront will propagate. Or the lower the octane rating the lower the autoignition temp will be & the faster the flamefront will propagate (flashover, remember the flamefront speed varies as the chamber's temp/pressure varies)). yep, definition of octane snip (c) Old worn engines & new 2 stroke OBs allow lube oil into the combustion chamber, this has the effect of reducing the fuels octane rating, again the design has to be aware of & allow for this effect. Over years this has been recognised as a reliability issue in 2 stroke OBs, so some effort has gone into reducing the amounts of oil carried up into the chamber. (d) So for the burn to be predictable & consistently controlled over the full range of operating conditions the actual octane rating arriving within the chamber needs to be as close to the raw fuels rating as possible with as little oil dilution as possible. Or the engine has to be designed to cope with the known effects of oil in the gas. (3) Some side comments?? The DFIs you'd think have solved this octane dilution problem by not having oil mixed in the fuel?? not so, what they do do is; snip (d) The very small amounts of oil stay in the crankcase & get hotter & hotter & hotter, (e) At lower revs there isn't enough air flowing through the crankcase to carry any excess oil up the transfer ports & out the at low revs overlapping exhaust, this is a deliberate "must pass the EPA test" tactic & it works in stopping raw oil getting out at low revs. It is not clear it is an EPA thing, or just the way things are. I don't even know if it is really true. (f) So at low revs the DFI has virtually no oil getting into the chamber & the fuels octane rating (resistance to autoignition, flamefront speed(s))) is as placarded however, (g) When the engine is powered up any excess built up crankcase oil can escape, but by now the useful overlap between the transfer & exhaust ports is diminished (again as intended by the design) so the oil can get into the chamber & dilute the fuel's octane rating. (h) The thing to be considered is that at low revs the oil isn't being transfered & burnt at all, so at low to moderate revs the octane rating of the fuel is "safe", but as the revs rise oil definitely (what?? 1 ltr ever 12 hrs running??) does get burnt, but because it's no longer consistently mixed in fuel it goes up in fits & spirts, some not a risk, others definitely a big risk of severely dilluting the fuels octane rating. This is an interesting theory. You've abandoned the hot piston causes detonation theory? Or is this complimentary? I hope this gets some genuine substantive review & thanks in advance to anyone who bothers. I'm sure lots will just say it's No 2's:-) with no actual rejoinders on the issues. Substantive review? wrong kind of engineer K |
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#3
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
"K Smith" wrote in message ... Ok so it seems the basics from thread No 1 have been accepted without challenge?? The fact that virtually no one reads or comments upon the vomit you project here does not mean it is "accepted without challenge." It means that virtually no one reads or comments upon the vomit you project here or that virtually no one cares to get down in the muck with you because of your bizarre behavior in this newsgroup, or -most likely- no one gives a crap what you think you know. |
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#4
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
del cecchi wrote:
"K Smith" wrote in message ... Ok so it seems the basics from thread No 1 have been accepted without challenge?? Somewhat begrudgingly I might say, but hey this is rec.boats if it were easy it would be too crowded:-) So now you've all thrown your various sexist hissy fits, none of which addressed any of the thread's issues:-) but were more about silencing me, which isn't going to happen:-) maybe this time you can either comment directly on the substance of the material of just stay quiet, very very quiet??? (please) snip (1) The design of petrol engines is dependent on the fuel burning within the closed combustion chamber in a consistently predicable way, with the accepted target in petrol engines to; (a) To have the fuel ignition instigated by the spark plug & only the spark plug ok (b) To have the flamefront propagate at a known speed/time, reliable throughout the charge, that speed varies with temp/pressure so it varies as the burn proceeds, starts slow then speeds up as the chamber temp /pressure rises. This is just the way things are, right? Yes, mostly takes about half the burn time to establish the burn & consume 10% of the charge, this immediately starts to increase the chamber's pressure/temp, so the remaining 90% is consumed in the other 1/2. (c) So as the temp/pressure combo in the chamber rises, the extremities of the charge do not reach their autoignition temp, before the accelerating flamefront has arrived as intended. no detonation. A bit controversial really, that last bit of flamefront is oft termed flashover, because by that time the chamber pressure/heat is at autoignition temp anyway. As to "when" designed flashover effect becomes detonation?? hmmm. (c) To have the burn all but completed & the highest chamber pressure occur just at or just after the piston leaves TDC on the power stroke. I don't know about this one. It is for sure you don't want it before tdc. but I don't know that you want it too near after tdc either. Once the piston starts down the bore the pressure drops, so too the temp. This would & in old tech 2 strokes does result in a slower flamefront, such that over heating of the piston can occur. Years ago we had a NG fight about how the big 2 strokes tended to go out after a long period trolling?? then were suddenly spooled up & bang. This was because they slow the idle speed by using a very much retarded spark timing, which lengthens the time of the burn because by then the pistonb is retreating, so putting more heat into the piston. The pursuit of this target over a variety of conditions involves juggling many variables, including; That's why the engine designers make the big bucks. Well there seems to be lots of copying which makes you 'feel" for the original people, the Japanese started out just copying, but now they do have a fair bit of their own stuff as seen in the hondas & Yamahas. It's probably right that the situation is now the other way around. (2) the octane rating of the intended petrol including anything that may dilute/contaminate it (whole books exist just on this fuel/octane subject so this is very much in a nutshell, however comments are very much valued), (a) A lazy way to describe this is the higher the octane rating of the fuel the higher the temp it autoignites at & usually the slower the flamefront will propagate. Or the lower the octane rating the lower the autoignition temp will be & the faster the flamefront will propagate (flashover, remember the flamefront speed varies as the chamber's temp/pressure varies)). yep, definition of octane snip (c) Old worn engines & new 2 stroke OBs allow lube oil into the combustion chamber, this has the effect of reducing the fuels octane rating, again the design has to be aware of & allow for this effect. Over years this has been recognised as a reliability issue in 2 stroke OBs, so some effort has gone into reducing the amounts of oil carried up into the chamber. (d) So for the burn to be predictable & consistently controlled over the full range of operating conditions the actual octane rating arriving within the chamber needs to be as close to the raw fuels rating as possible with as little oil dilution as possible. Or the engine has to be designed to cope with the known effects of oil in the gas. Yes absolutely & the older oil mixed in the fuel engines could be, but the DFIs?? How?? they don't really know when the oil will arrive in the combustion chamber. (3) Some side comments?? The DFIs you'd think have solved this octane dilution problem by not having oil mixed in the fuel?? not so, what they do do is; snip (d) The very small amounts of oil stay in the crankcase & get hotter & hotter & hotter, (e) At lower revs there isn't enough air flowing through the crankcase to carry any excess oil up the transfer ports & out the at low revs overlapping exhaust, this is a deliberate "must pass the EPA test" tactic & it works in stopping raw oil getting out at low revs. It is not clear it is an EPA thing, or just the way things are. I don't even know if it is really true. The early Orbital designs tried to deal with it & the fix seems to have settled on just using tiny amounts of oil, particularly at low revs. (f) So at low revs the DFI has virtually no oil getting into the chamber & the fuels octane rating (resistance to autoignition, flamefront speed(s))) is as placarded however, (g) When the engine is powered up any excess built up crankcase oil can escape, but by now the useful overlap between the transfer & exhaust ports is diminished (again as intended by the design) so the oil can get into the chamber & dilute the fuel's octane rating. (h) The thing to be considered is that at low revs the oil isn't being transfered & burnt at all, so at low to moderate revs the octane rating of the fuel is "safe", but as the revs rise oil definitely (what?? 1 ltr ever 12 hrs running??) does get burnt, but because it's no longer consistently mixed in fuel it goes up in fits & spirts, some not a risk, others definitely a big risk of severely dilluting the fuels octane rating. This is an interesting theory. You've abandoned the hot piston causes detonation theory? Or is this complimentary? No we're still sticking with that being the "cause"; hot uncooled piston caused by lean mix & poor atomisation, but this is something which is "probably" an unpredictable wild card, as to it's occurrence & it's effects. The fact E-tech have so severely cut the oil supply back even further, is a thing worth noting. Given they're going for reliability first & foremost, given their priors:-) you'd think that would be the last thing they'd be doing if it was just to have the dealers spruik about lower oil costs, because even the old DFI's didn't use much oil compared to carbed or efi anyway. They have never been able to stop the oil baking the rings etc, tried new oils as you know etc & now seem to be trying to just have less there??? It's the heat every time, everything they do is saying it. I hope this gets some genuine substantive review & thanks in advance to anyone who bothers. I'm sure lots will just say it's No 2's:-) with no actual rejoinders on the issues. Substantive review? wrong kind of engineer Well thanks anyway as always:-) K K |
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#5
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
"K Smith" wrote in message ... This was because they slow the idle speed by using a very much retarded spark timing, Ok, Karen, give specifics, What is too much retarded spark at idle? List the top 3 makes of engines and what timing they idle at? Bill Grannis service manager |
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#6
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
Billgran wrote:
"K Smith" wrote in message ... This was because they slow the idle speed by using a very much retarded spark timing, Ok, Karen, give specifics, What is too much retarded spark at idle? List the top 3 makes of engines and what timing they idle at? Bill Grannis service manager Again you distract me from the Why Ficht failed threads & I'm busy enough, but you have asked a genuine question without abuse so I better respond, in kind:-) This is related to the basic problem of getting particularly bigger multi cyl 2 strokes to idle slowly & smoothly. The problems to be overcome are; (i) The exhaust is submerged & notwithstanding some bleed holes, at idle the exhaust sees quite some back pressure (e.g. see the water the bleeds spray) & that back pressure is "various" depending on how deep the leg is. (ii) Unlike a 4 stroke where they can just shut the butterflies & restrict the air/fuel going into the motor, the OBs can't because coupled with the exhaust back pressure they run the risk of back flowing or spitting at idle. (i.e. if they created a very high vacuum in the crankcase, with little air & fuel, as the transfer port uncovered the exhaust would flow back into the crankcase, rather than overcome the exhaust back pressure & go out there. It is likely to ignite the charge in the crankcase ) The fix is to keep a fair amount of air/fuel flowing through the engine even at slow idle. (iii) Because despite the throttles being against their stops, the butterflies themselves (or in some a bypass) still allow plenty of air into the engine which means it will have a very fast idle. (iv) The fix since very early on is to just keep retarding the spark timing at idle till a slow soft smooth idle is achieved. (v) A retarded spark timing has always been known to cause heat buildup, even in 4 strokes, however with an endless supply of cooling water & very low temp thermostats, the OBs have pretty much gotten away with it. Not so the motor cycles, they didn't have access to the sea water:-) so had to run much more normal spark timing at idle for fear of overheating & you could see it in there idle's performance, it was usually lumpy at best & terrible more likely. As a good starting point use anything later than 10 BEFORE TDC as being retarded enough to build heat. You have the manuals as I do, some like merc regularly give a number & it's invariably extremely retarded at idle e.g. a 200?? 12-15 degs AFTER TDC which is up to 25 degs later than it ought be, if heat buildup is to be avoided. Yamaha ?? The bigger Yamahas are around 5 degs AFTER TDC again well too late (15 degs) if piston heat at idle is to be avoided. OMC They don't tell, (that's why years ago you were so totally unaware that they even controlled idle speed almost exclusively with spark timing I still can't believe you didn't know that!!) However you can see how extreme the retarded timing is in the bigger OMC engines if you look at the pickup point timing, on some even that is still AFTER TDC or very close to it, now see how much further the system moves in the spark retard direct after the pickup point has been left??? I should thank you again for at least asking a real question so..... thanks, however again may I take it you still have no problem with the substance of the post itself?? if so I'll move on when I get a minute, busy busy busy, not fair:-) K. |
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#7
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
K Smith wrote:
Billgran wrote: "K Smith" wrote in message ... This was because they slow the idle speed by using a very much retarded spark timing, Ok, Karen, give specifics, What is too much retarded spark at idle? List the top 3 makes of engines and what timing they idle at? Bill Grannis service manager Again you distract me from the Why Ficht failed threads & I'm busy enough, but you have asked a genuine question without abuse so I better respond, in kind:-) Bill asked specific questions. Your answers were non-specific, especially in relation to his questions. Conclusion: You have no specific information, only what you can clip, rewrite and introduce errors to, and paste. -- Email sent to is never read. |
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#8
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
Harry Krause wrote in message ...
"K Smith" wrote in message ... Ok so it seems the basics from thread No 1 have been accepted without challenge?? The fact that virtually no one reads or comments upon the vomit you project here does not mean it is "accepted without challenge." It means that virtually no one reads or comments upon the vomit you project here or that virtually no one cares to get down in the muck with you because of your bizarre behavior in this newsgroup, or -most likely- no one gives a crap what you think you know. When I worked for GM, I specialized in Port Fuel Injection runability problems. Personally, I find K's posts, which btw are on topic, facinating. Everything she talks about brings back fond memories of studying chamber readings on the occilliscope, and comparing them with emissions readings... If you know what you are looking at, you can see that K is pretty much on the mark here with *MOST* of her theory. So go back to shilling the union threads Harry, hopefully most will ignore you there too... Scotty from SmallBoats.com |
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#9
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Why Ficht Failed No 2 (octane, propa speeds, oil dilution)
Backyard Renegade wrote:
Harry Krause wrote in message ... "K Smith" wrote in message ... Ok so it seems the basics from thread No 1 have been accepted without challenge?? The fact that virtually no one reads or comments upon the vomit you project here does not mean it is "accepted without challenge." It means that virtually no one reads or comments upon the vomit you project here or that virtually no one cares to get down in the muck with you because of your bizarre behavior in this newsgroup, or -most likely- no one gives a crap what you think you know. When I worked for GM, I specialized in Port Fuel Injection runability problems. Personally, I find K's posts, which btw are on topic, facinating. That's good. Frankly, I wouldn't trust you with a hammer, a screwdriver or a paint brush around my boats. -- Email sent to is never read. |
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