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SB_GLI
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« Reply #45 on: January 27, 2017, 01:24:52 PM »
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What do you suggest to do in top end of this map(s) ?
Increase it significantly. |
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marian_gbg
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« Reply #46 on: January 27, 2017, 01:49:50 PM »
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Increase it significantly.
The angle values in the red zone should increase ,do I understand correctly ? Increase in "-" or "+" degrees ? PS: Below is my stock and modifed KFZW. |
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« Last Edit: January 27, 2017, 01:58:08 PM by marian_gbg »
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prj
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« Reply #47 on: January 27, 2017, 02:31:23 PM »
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If it burns more slowly you have to advance NOT retard.
Engine basics!!!
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marian_gbg
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« Reply #48 on: January 28, 2017, 02:54:07 AM »
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If it burns more slowly you have to advance NOT retard.
Engine basics!!!
Sorry, I expressed myself wrong in post #44  In my tuned KFZW(2) map(s) from: - 1000 to 2520rpm ( top end) i advance the angle with +1.5 ÷ +5.25 degrees (slowly burning lpg) of stock map; - 3000rpm - 0 degree; - 3520 ÷ 6720 rpm (low down) i retard the angle from -0.75 to -3.00 degrees (fast burning lpg) of stock map. Is this correct? |
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prj
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« Reply #49 on: January 28, 2017, 06:13:55 AM »
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No, because it also has higher octane level.
You are doing this WRONG.
You need to DRIVE the car and not make theoretical maps on forum!
Log -> feedback -> adjust, repeat.
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marian_gbg
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« Reply #50 on: January 28, 2017, 08:33:21 AM »
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I will made and post here .csv log, but first I have to start somewhere.
So I ask what is the idea in LPG tunig ignition curves.
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TijnCU
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flying brick
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« Reply #51 on: January 28, 2017, 10:14:37 AM »
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The idea with ignition timing is you put the car on a dyno and add timing untill you start to lose torque. Or better, take out a little timing before you begin just in case it was already at mbt. I will do a full ignition recalibration for lpg on the dyno later this year, I will put my global results here when it is done.
I would not just add or subtrqct timing everywhere, you have no way of measuring if you are making or losing power... my engine is currently only calibrated for wot because the knock sensors give feedback for that range..
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kacperoooni
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« Reply #52 on: May 29, 2022, 07:52:51 AM »
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It's been some time since this topic was created. Despite this fact I want to clarify some some things.
LPG on lambda lower than 0.9 still has cooling effect. Also, richer lambda helps reducing the knock and EGT. Same as the gasoline.
I have done some test runs varying lambda on the LPG and double checking it with wideband o2 sensor because I wanted to test prj's LPG tuning theory. 2.7t here, FMIC, dp, stock k03s, RS6 WB EGT sensors, same tune, same road, same day, same conditions, only lambda changes:
Here I attach some charts:
0.9 vs 0.81 - here is comparison of 0.9 lambda vs 0.81 lambda tune I daily drive. It can be clearly seen that even if 0.9 lambda run was started on the lower EGT, it is higher on the redline.
0.87 vs 0.81 - same history, higher egt on the redline than 0.81, even though the 0.87 run started on lower EGT than the 0.81. Also, the 0.87 run egt is lower than 0.9.
I have also checked it ATR works properly on the LPG, lowered tabgss to 850, and the car was richen to almost 0.76 but the EGT was steady. On the 0.81 tune There was slighty lower knock retard, but it wasn't that obviuos to show it on the chart like EGT.
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prj
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« Reply #53 on: May 29, 2022, 01:44:23 PM »
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LPG on lambda lower than 0.9 still has cooling effect. Also, richer lambda helps reducing the knock and EGT. Same as the gasoline. There is no cooling effect unless you inject liquid LPG. If you do then it works exactly the same like gasoline. If you have evaporators and you are injecting gas, then there's no cooling effect, unless your evaporators freeze and you start injecting liquid lpg. The entire evaporation and cooling happens in the evaporators which are being heated by the coolant. Then gas enters the combustion chamber, it does not cool anything. Your observation with EGT is related to burn rate correlation. There is never any point to go richer than lean best torque on gaseous LPG. The graphs actually show that, the difference is irrelevant, you have 25C in there. Advance the ignition to knock limit on both and they will be equal. It makes sense to at least study the subject a little and get some education instead of running random lambdas and drawing wrong conclusions based on 3% variance in EGT. |
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« Last Edit: May 29, 2022, 01:47:20 PM by prj »
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kacperoooni
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« Reply #54 on: May 29, 2022, 03:24:48 PM »
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Can’t advance more timing if there is actually more knocking on 0.9 lambda than on 0.81… 0.81 tune is at its knock limit, when i get to pc ill upload charts The difference is 50c between 0.9 and 0.81 bcs its only gear 3 run. Already done 3-4-5 run and egt reaches 960 on 0.9 compared to 890 on 0.81. This is not a small difference. I had read some research publications and havent spotted any information of not richening mixture on gas LPG. As far as I know petrol when evaporates from intake valves is gas too. It does not evaporates on exhaust valves. So whats the difference besides IAT cooling?  Do you have any evidence that what youre saying is true? If so, please share. I am open to change my view. But currently reality shows opposite. |
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« Last Edit: May 30, 2022, 09:14:04 AM by kacperoooni »
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prj
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« Reply #55 on: June 01, 2022, 05:01:22 AM »
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As far as I know petrol when evaporates from intake valves is gas too. It does not evaporates on exhaust valves. So whats the difference besides IAT cooling? The only cooling that you get is charge cooling from evaporation with gasoline. If you inject gas, there is no charge cooling. This does not have too much to do with EGT. Also, gasoline evaporation temperature is iirc about 200C. It mostly does not evaporate until it enters the combustion chamber, you do not have 200C in your intake manifold. Otherwise atomizing injectors would not be needed. EGT is dependent on how far the combustion happens from lambda 1 and on the ignition angle efficiency. The problem with LPG is that the flame speed is already lower than on gasoline at rich lambda, and with a much richer mix at high rpm the flame speed is so slow, that the burning continues during the exhaust stroke. With stoichiometric mixture the flame speed on lpg is actually a little faster than on gasoline, but the dropoff is much more severe. This results in cracked exhaust manifolds, damaged exhaust valves and so on. Your EGT at the turbo might show lower, but the temperature of the exhaust valves and their seats is going to be much higher. Obviously the tradeoff point is different for every engine, but running 0.7 lambda on lpg is not it and ATR is a very bad idea on LPG. If you are richening the mixture more, you need to advance the ignition just to get back to roughly the same point, but at some point it is no longer possible or reasonable. See attachment. Put a car with LPG on the dyno, just to get the same power as on gasoline with 15 degrees or so ignition at higher rpm's you will need 20+ on LPG. Anyway, it is not my job here to educate you on this topic. Pick up a book, because right now you are making the wrong conclusions and you do not understand what is happening in the combustion chamber. And the worst thing is, you are stating so many things as fact. Maybe it's a language barrier, but if you are not sure about something, then better not be too loud about it. |
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« Last Edit: June 01, 2022, 05:19:46 AM by prj »
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kacperoooni
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« Reply #56 on: June 01, 2022, 11:07:45 AM »
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Thanks for your answer prj, that makes sense what you wrote about. However: The problem with LPG is that the flame speed is already lower than on gasoline at rich lambda, and with a much richer mix at high rpm the flame speed is so slow, that the burning continues during the exhaust stroke. With stoichiometric mixture the flame speed on lpg is actually a little faster than on gasoline, but the dropoff is much more severe.
I've been searching for some research results to compare laminar flame speeds LPG vs gas. And yeah, you are write that flame on lambda 1 during lpg burn is litter higher and its right. However, If we compare (see attachments) flame speeds for similiar initial temp, speed for lambda 0.8 for lpg is actually higher than gasoline. I skipped the fact that lpg is little warmer when it leaves evaporators than gas, which makes flame speed even higher. https://www.sae.org/publications/technical-papers/content/2010-01-0614/ Here is citation that seems to confirm that. Unfortunately I do not have acess to full publication. https://www.researchgate.net/figure/a-Comparison-of-maximum-burned-gas-temperature-for-gasoline-and-propane-combustion-at_fig14_263874565 - chapter 5.1 "LPG is used in SI engines, the burning rate of the propane is faster than the burning rate of gasoline. On other words, propane burns more rapidly and thus the burning process in the engine occurs in shorter times than gasoline engine. Thus, the combustion duration of propane is decreased" https://www.sciencedirect.com/science/article/pii/S1876610216314242 Chapter 3.1 "This is because LPG having higher flame propagation speed and higher adiabatic flame temperature when compared to petrol, hence combustion duration will be less" This results in cracked exhaust manifolds, damaged exhaust valves and so on. Your EGT at the turbo might show lower, but the temperature of the exhaust valves and their seats is going to be much higher.
That's the point that I dont understand. If LPG on rich lambda burns slower and continues during exhaust stroke then egt should be higher too. I do not have thermocouple on the exhaust valvetrain part, but If the measurement enviroment does not change and the burn rate is lower, EGT should be higher. |
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« Last Edit: June 01, 2022, 11:45:49 AM by kacperoooni »
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R32Dude
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« Reply #57 on: June 01, 2022, 05:44:27 PM »
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I can walk faster than 60cm/s. Those laminar graphs are useless for IC engines.
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prj
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« Reply #58 on: June 02, 2022, 01:29:58 AM »
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I can walk faster than 60cm/s. Those laminar graphs are useless for IC engines. Precisely. All they show is that burn slows down, but it does not show how it works under huge pressure. As I said before. Put the car on dyno. Make the lambda and charge the same and see how much more advance you need on LPG just to make the same power. There is a reason so many people complain about burned exhaust valves on LPG, and there is a good reason the engine makes less power on LPG at the same advance and charge. Or really, just do what you want. The fact that you have LPG on a RS6 already means you should be shot. |
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« Last Edit: June 02, 2022, 01:31:55 AM by prj »
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kacperoooni
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« Reply #59 on: June 02, 2022, 05:09:41 AM »
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I can walk faster than 60cm/s. Those laminar graphs are useless for IC engines.
Even if they are, prj used it as a confirmation of what he said. As I said before. Put the car on dyno. Make the lambda and charge the same and see how much more advance you need on LPG just to make the same power.
There is a reason so many people complain about burned exhaust valves on LPG, and there is a good reason the engine makes less power on LPG at the same advance and charge.
The fact that you have LPG on a RS6 already means you should be shot.
Well, I didnt want to say that but thr car was previosly on dyno, without advanced ignition for lpg. It made 7hp and 15nm less than on gasoline. I think thats a good result for gasoline ignition, considering the fact, that for the same lambda lpg is 6% less to burn than gasoline. Thats my 4th car with lpg, previous ones were 1.8t and none of them got valvetrain damaged, even if i made each of them 100-150kkm… Btw Its 2.7t with rs6 egts not the rs6  |
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