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I think , and you are free to correct me if I am wrong, but you are confusing knock temps for two mixtures quite a bit richer than stoich (lambda 1.0) or part throttle or lean vs rich CHT, EGTs readings WITH stoch mixture induced detonation. And IF you are right, then we shouldnt even care about mixture, because running 14.7 , as most all racers "think" , doesnt cause high combustion temps or risk detonation ( in reality, EVERYONE, as always been talkinig about running "lean" as causing major engine destruction". some proof is found in Mark Andersons Road america engine. it leaned out, passed through 14.7:1 (stoich) and blew the head gasket, and knocked whichis caused by extreme cylinder pressures and heat. So, you are showing that knocking is achieved with a richer mixture at a higher timing advance... so what.. what does that have to do with the problem or my claim/ theory?
however with the simple graph below. you can see that operating at near max power ranges in the 14.7 (lambda 1.0) range, creats the highest CHT and EGT temps. do you not agree? your graph has two charts on one graph straddling the 14.7 lambda 1.0, range.... It doesnt show lamda 1.0..
So, by the way... your chart is showing lambda .79 Rich and .90 Lean............this is 11.5:1 AFR vs 13.2:1 AFR.. a far cry from 14.7:1 lambda 1.0.
the TESTS conducted by Mahle were comparing rich with not so rich... NOT lambda 1.0 or 14.7.. because if they did , they would destroy the engine.
Your graph is what the differnce in temp is at knock limits vs the two differnet mixtures of 11.5.:1 vs 13.2:1... yes, there are differences AND the temps at the knock limits are the same... BUT this is not the same as running at 14.7:1 where you might , in most cases be at knock limit, ........
so the real issue here and why your graph doesnt address the issue, is that both graphs show the same temps at a knock limit. BUT, if temps are higher in the combustion chamber you can get at the knock limit, regardless of the gas used, or the mixture used. my point is, stoich can reach knock limit where other ratios richer , may not hit the knock limit. make sense?
edit: another way to look at YOUR graph shown, is to understand that for a given level of spark advance, "near knock limit" will be much higher in temp for the leaner mixture.... again, running quite abit leaner in this case, would be for SURE in the knock range, and the temps would be quite a bit higher. does that makes sense ?
As long as combustion is regular and the peak cylinder pressure is at sensible crank angle, the mixture in the 0.8-1.0 lambda range has only minor impact on piston temperatures. You might as well accept this, as it's the result that Mahle got from various ways of measuring the piston temperatures of running engines. (Cylinder head temperature and exhaust gas temperature are different from piston temperature.) Furthermore, when you adjust the ignition such that the gasoline engine is at the knock limit (and thus making about the same amount of power regardless of the mixture in this range), the richer mixture leads to a tiny bit higher piston temperature.
Last edited by mark kibort; 07-30-2018 at 06:41 PM.
I'd have to check more carefully, but I believe the only piston that is further out of the cylinder (than designed) is the #2 piston that has been contacting the head. I'll double check.
that would be interesting to know. PLUS, if it was true, what caused a corrillo rod to stretch.... RPM would have to be extremely high, like in a mis-shift... remember at the same track, with the awkward and rare, 4 to 5th shift, i did a 8500rpm shift 4th to 3rd too! (probably more like 8000 based on the sound frequency) otherwise, it would be intersting to hear of ideas of how the piston was higher in the bore. But, that certainly would cause issues, but it sounds like it wasnt the reason, because others were not that high and didnt show contact with the heads. (or show rod stretch)
Across lambdas in the below graph. Kibort, when are you going to believe that piston temperature and exhaust gas temperature are not the same thing?
" the TESTS conducted by Mahle were comparing rich with not so rich... NOT lambda 1.0 or 14.7.. because if they did , they would destroy the engine."
They did conduct this test and, no, it didn't destroy the engine. In fact, they continuously run a gasoline engine under knock for over 100 hours and examined the engine afterwards. It didn't blow up, but top land was quite pitted.
The only test so far that I'm aware from Mahle where the engine was destroyed was when they induced pre-ignition. I'm sure that they've destroyed others, it's big company that does a lot of R&D, but that's the one reported situation where they say the engine can be goner in seconds.
The rich mixture doesn't meaningfully cool pistons in the relevant range for a race car, as you can see. The piston runs a little cooler at lambda = 1 than at lambda = 0.9...
As long as combustion is regular and the peak cylinder pressure is at sensible crank angle, the mixture in the 0.8-1.0 lambda range has only minor impact on piston temperatures. You might as well accept this, as it's the result that Mahle got from various ways of measuring the piston temperatures of running engines. (Cylinder head temperature and exhaust gas temperature are different from piston temperature.) Furthermore, when you adjust the ignition such that the gasoline engine is at the knock limit (and thus making about the same amount of power regardless of the mixture in this range), the richer mixture leads to a tiny bit higher piston temperature.
Ptuomov, If i explain what i wrote above ,it looks like this (pic attached) in other words. to knock or not to knock.. that is the question! keep in mind that this chart, again, is ONLY looking at 11.5:1 AND 13.2:1 fuel ratios... if the mixture was NOT optimal and in the stoich range, there would be knocking and at a much higher temp. remember the timing needs to be constant to be able to read this graph correctly. and trust me, bad things happen at stoich. as turbo or NOS guys that have got it wrong!
that would be interesting to know. PLUS, if it was true, what caused a corrillo rod to stretch.... RPM would have to be extremely high, like in a mis-shift... remember at the same track, with the awkward and rare, 4 to 5th shift, i did a 8500rpm shift 4th to 3rd too! (probably more like 8000 based on the sound frequency) otherwise, it would be intersting to hear of ideas of how the piston was higher in the bore. But, that certainly would cause issues, but it sounds like it wasnt the reason, because others were not that high and didnt show contact with the heads. (or show rod stretch)
Read post #356.
As much as you wish it to be, the rods are not stretched, nor significantly altered in any dimension. (The cracked rod hasn't even changed significantly, in terms of dimensions.)
The piston structure got so hot and so hammered that the tops of the pistons are literally separating from the internal piston pin bosses.
As much as you wish it to be, the rods are not stretched, nor significantly altered in any dimension. (The cracked rod hasn't even changed significantly, in terms of dimensions.)
The piston structure got so hot and so hammered that the tops of the pistons are literally separating from the internal piston pin bosses.
i wasnt wishing.. i was commenting on the "what if" post of someone else. yes, i agree. detonation. but what caused it. 100 octane alone?? the program was different for joes and marks car this time around. both used the same different set up. what if that was the issue? is it plausable that the engine detonated due to a lean (stoich) mixture. It can happen?
why are you comparing a engine that is well below capacity of its power, to show piston temps. you are showing piston temps of a motor in operational mode, not full power mode. Of course piston temps are not the same as EGTs. i never said that they were. BUT , you can see based on your graph and my graph that they go up during near knock and certainly when knocking, temps will rise. you are showing , something that is omitted, is the reason that EGTs are highest at stoich, but lower piston temps are found due to more power being generated and fuel burned at richer mixtures. However, if the engine is near max capacity, then this example would change greatly. running near stoich would create detonation and also create higher heat for a given timing. you need to find temp data based on engines at full capacity running into detonation.
what is so hard to accept about that concept?
if what you say is true, then no one would care about running their car at 14.7 :1. because it would always mean its cooler piston temps than at max power air fuel ratios such as 12:5:1.. this is just not the case in real life.
your own graphs before this one, clearly show that the intensity of the knocks are an issue and that the temps are higher with same timing for different rich mixtures. IT IS NOT showing the lambda 1.0 mixture (stoich) . why? not because they cant afford it, its because it is known to destroy engines due to being the knocking zone.
I get what you are saying, but again, your graph shows clearly that you can make an engine knock, at different timing levels , and w also know that at different temp levels knocking can occur. if the new program for both cars had too much advance , knocking and the intensity of the knocks would be dramatically different. but i am assuming that during the knocking phase that temps were higher than normal. so, the damage can be caused by the knocks, but the temp has to be caused by something else, if the knocking doesnt produce excess temps. I think it would but thats an educated guess on my part.
Originally Posted by ptuomov
Across lambdas in the below graph. Kibort, when are you going to believe that piston temperature and exhaust gas temperature are not the same thing?
" the TESTS conducted by Mahle were comparing rich with not so rich... NOT lambda 1.0 or 14.7.. because if they did , they would destroy the engine."
They did conduct this test and, no, it didn't destroy the engine. In fact, they continuously run a gasoline engine under knock for over 100 hours and examined the engine afterwards. It didn't blow up, but top land was quite pitted.
The only test so far that I'm aware from Mahle where the engine was destroyed was when they induced pre-ignition. I'm sure that they've destroyed others, it's big company that does a lot of R&D, but that's the one reported situation where they say the engine can be goner in seconds.
The rich mixture doesn't meaningfully cool pistons in the relevant range for a race car, as you can see. The piston runs a little cooler at lambda = 1 than at lambda = 0.9...
Last edited by mark kibort; 07-30-2018 at 07:55 PM.
Ptuomov, If i explain what i wrote above ,it looks like this (pic attached) in other words. to knock or not to knock.. that is the question! keep in mind that this chart, again, is ONLY looking at 11.5:1 AND 13.2:1 fuel ratios... if the mixture was NOT optimal and in the stoich range, there would be knocking and at a much higher temp. remember the timing needs to be constant to be able to read this graph correctly. and trust me, bad things happen at stoich. as turbo or NOS guys that have got it wrong!
Nitrous oxide needs more fuel, because nitrous oxide carries oxygen that breaks out during combustion. Without additional fuel with nitrous oxide, the engine runs very lean.
As you see from those graphs, there is no discontinuity in the piston temperature with knock. Whether it is knocking or not knocking doesn't really matter to piston temperature, as the ignition angle (combined with mixture burn speed) determines the piston temperature. Calling the "knock diff" just exposes that you're not getting it.
Pre-ignition is a different matter. It's impact on piston temperatures can be the same as advancing the ignition by an additional thirty degrees (30, not 3) or so. This will overheat the piston in seconds off the scales of that graph
If you don't need to cool the cylinder head, exhaust valve, exhaust port, exhaust manifold, and turbine, then you should just pick the best power lambda which is about 0.90 lambda and run the ignition a margin of safety from the knock limit. If it then gets either leaner or richer while holding ignition constant, it's not going to hurt the engine badly because the ignition is relatively late. Contrast that to tuning the engine to run too rich (say, lambda 0.79) and then setting the ignition to a margin of safety from a knock limit. Now, if fuel delivery is disrupted and it goes lean, it will knock. So the entire case for running the engine rich of peak power lambda is about cooling the components around exhaust port and valve (and not about cooling pistons). It's a strong case, say, in an air cooled turbo motor, where you absolutely do want to run it rich just to cool that area around exhaust ports. Good things won't happen in the long term if the cylinder head overheats.
"why are you comparing a engine that is well below capacity of its power, to show piston temps. you are showing piston temps of a motor in operational mode, not full power mode."
Those are WOT tests for a four cylinder engine, I believe.
You're not getting it that piston temperature and exhaust gas temperature (as well as cylinder head temperature) behave in a different way in an engine. If you can't accept that based on the research that I posted, I feel that it's really not my problem in the end.
I'd have to check more carefully, but I believe the only piston that is further out of the cylinder (than designed) is the #2 piston that has been contacting the head. I'll double check.
Greg, let's say for the moment that the connecting rod bearing is missing. Would the resultant gap be enough to allow the piston to stand proud of the cylinder/deck at TDC, and hit the cylinder head?
Greg, let's say for the moment that the connecting rod bearing is missing. Would the resultant gap be enough to allow the piston to stand proud of the cylinder/deck at TDC, and hit the cylinder head?
Certainly. This is the case in almost every engine. If rod bearings go bad, the pistons almost always hit the head.
In this engine, the bearing shells are ~.062" thick and the piston to head clearance is ~.040", so if the bearing shell wasn't present....the piston would hit the head....hard.
This car has a fuel cell without a bottom drain....however, Mark said he "drained" it.
The only way to "drain" this cell is to turn on the fuel pump and pump out whatever fuel the pick-up can reach.....or to pull the top plate off , move the foam around, and look at the bottom.
What happens to the octane of the "new fuel" that Mark added if the pick-up didn't actually drain this cell?
How much 5 year old "turpentine" was left in this cell? One gallon? Three gallons?
"why are you comparing a engine that is well below capacity of its power, to show piston temps. you are showing piston temps of a motor in operational mode, not full power mode."
Those are WOT tests for a four cylinder engine, I believe.
You're not getting it that piston temperature and exhaust gas temperature (as well as cylinder head temperature) behave in a different way in an engine. If you can't accept that based on the research that I posted, I feel that it's really not my problem in the end.
i get it......... i understand fully the relationship between CHT, EGT and piston temps. all are different. you are showing me a set of curves of an engine running at 14.7:1 with no detonation under WOT. that is rare. if you dont understand why, then i guess, i cant make it any more clear. so, what you are saying is that there is no problem running a car at 14.7 :1 ..... all the mystery of the magical stoich level, is just an old wives tale.... all you loose is hp, no other down side. so amazing how many cars have detonated with bad fuel air mixtures, but according to your graphs, not mine, that should never happen. I just want to make sure i understand you. so, detonation due to stoich under WOT conditions is a misnomer. its all about piston temps and this can only be caused by pre-ignition. so, we are looking at rogue carbon as the real culprit here. If you are right, i want to learn the real story about the down side of 14.7 mixtures if it is not heat or detonation.
07-30-2018, 06:05 PM
keep in mind that this chart, again, is ONLY looking at 11.5:1 AND 13.2:1 fuel ratios... if the mixture was NOT optimal and in the stoich range, there would be knocking and at a much higher temp. remember the timing needs to be constant to be able to read this graph correctly. and trust me, bad things happen at stoich. as turbo or NOS guys that have got it wrong! 
