lezsi
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« on: March 04, 2013, 12:41:56 PM »
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I'm collecting ideas how to tune for LPG properly.
It is a gaseous injection system for the LPG (mainly propane/butane) gas. The LPG ECU takes care of controlling the gas injectors, based on petrol injection time, MAP, rpm (transformation maps involved). Plus all of it depends on gas temperature and pressure.
Usually the system cold-starts on petrol, and switches to LPG at a certain coolant temperature.
The system is working OK,- but not perfectly- for years on many cars, now I'm talking about a 1.8T 180HP, wideband
pros:
- high octane (100-110?)
- cheap
- no wall wetting
cons:
- phase change happens in evaporator ->no cooling effect in combustion
- evaporator gets heat from coolant -> slower warmup
- big gaseous fuel volume occupies oxygen's place (lower VE)
ME7 specific setting I've found so far:
- tune KFZW, KFZW for higher octane, lower flame speed, especially at low RPMs
- disable wall wetting above switchover temp. ZBAKM , ZBALM, ZVAKM, ZVALM
- disable warmup enrichment in KFFWL_0, KFFWL_1
I'm not sure these will cover things I seek.
High load enrichment is another story..
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lezsi
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« Reply #1 on: March 05, 2013, 04:30:36 AM »
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These settings seem to work OK -for the brief test I did today.
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prj
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« Reply #2 on: March 05, 2013, 08:57:19 AM »
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What lambda do you run at WOT? There are pretty big differences between vapor and liquid fuels.
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lezsi
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« Reply #3 on: March 05, 2013, 09:43:24 AM »
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Stockish now. -Still haven't found much info on that.
Some people say, go leaner on load to prevent detonation for gas (CNG) engines.
But I assume they're already starting from a very lean (lambda >1.1) base in those industrial engines, so leaning is a proper way to make burn slower and colder. (see attached pic)
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prj
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« Reply #4 on: March 06, 2013, 01:32:22 PM »
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I will give you a tip.
The reason you ever run anything richer than lambda 0.9 (lean best torque) on a liquid fuel is so that the fuel can evaporate and cool the cylinder.
On a gaseous fuel, if you run richer than lambda 0.9 all you will do is increase EGT, because more fuel is wasted, and there is no cooling effect from adding gaseous fuel.
So stuff like BTS and ATR on a gaseous fuel must be disabled completely, as they will do completely the opposite of what they are designed to do.
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vagenwerk
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« Reply #5 on: March 06, 2013, 03:42:15 PM »
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Yeap prj, I also discover this few years ago. Adding more lpg was making turbo much more hot, and red light  making leaner cause that engine push harder , and turbo wasn't shining:) maybe little in complete darkness. |
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lezsi
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« Reply #6 on: March 08, 2013, 07:02:24 AM »
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Thank you guys. Very valuable info!
I'm trying to tune this way.
Unfortunately there's no real EGT in this car but I thought maybe I'll need to cut max power down without the cooling capability of the extra gasoline?
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prj
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« Reply #7 on: March 08, 2013, 08:13:25 AM »
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If you don't do stupid stuff, then EGT's on LPG will be even a bit lower.
But if you leave BTS and ATR in tact then it's a different story...
You need real EGT.
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lezsi
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« Reply #8 on: March 08, 2013, 11:50:02 AM »
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If you don't do stupid stuff, then EGT's on LPG will be even a bit lower.
But if you leave BTS and ATR in tact then it's a different story...
You need real EGT.
OK, I've set 0.9 lambda for high load all over the place in KFLBTS, running 1.09...1.00...0.94 in between. 0.9 values in KFLAMKRL also, and TABGSS -> 1200C, effectively disabling ATR I guess. Looks good in the logs so far. I won't push max power limits until I see real EGTs. Thanks! |
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papasound
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« Reply #9 on: March 24, 2013, 11:42:23 AM »
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*
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« Last Edit: March 27, 2013, 06:29:24 PM by papasound »
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papasound
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« Reply #10 on: March 25, 2013, 10:20:51 AM »
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tried to adjust following those tips:
KFFDLBTS all off,
KFLBTS 0.9063 bottom right,
TABGBTS - 810C,
TABGSS - 1200C,
DSLOFS off,
Rear O2/Kat off
KFZW and KFZWOP 1.5% - 9% up,
So far runs good, what i have noticed is ecu rendering much lower mileage on LPG +- 6.5l/100km.
Here is my log, maybe you could check that quickly and tell me what is going wrong direction:
(b.t.w. why you would want to adjust KFLAMKRL?)
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« Last Edit: March 27, 2013, 06:33:02 PM by papasound »
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cocktailyogi
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« Reply #11 on: April 02, 2013, 03:09:21 AM »
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Hi papasound,
I am actually also converting an Audi A3 1.8t ARZ to LPG and trying to tune it a little bit.
I found your post and it is very helpful to me. I have a few question regarding my basic understanding and what you have done one your ME7.
You are saying that your are completly disabling BTS, but in Fakt aren't you using LAMBTS-Funktion almost the hole time for lambda-regulation? LAMFA seems to be disabled by default. (set to 1)
So it looks to me, that you are using LAMBTS for setting the AFR dependig on load and RPM. Please correct me, if I am wrong. I am trying to understand, what is going on. ;-)
KFFDLBTS all off
By doing this, you will not allow an AFR-Adaptation by ignition angle or cylinder filling rate. Are there any disadvantages by doing this?
KFLBTS 0.9063 bottom right,
This seems to be the wishmap for AFN, is it right?
TABGBTS - 810C
I don't really understand, why you set this to 810 (Mine isby default 400)
It seems, that this is the minimum temperatur (calculated from EGT-model) when function LAMBTS gets active. Who s controlling your AFN under 810*C ?
TABGSS - 1200C
This disables real EGT-monitoring with hardware-sensor?
DSLOFS off
What is the purpos of this? It seems to affect boost pressure?
This is a very interesting project and without your post I had no idea, where to start with LPG-tuning.
Yogi
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pedrosousa
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« Reply #12 on: April 02, 2013, 06:45:49 AM »
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I'm going for LPG to, does the LPG injection follow the ME7.5 strategy? Or it uses one one external ECU that overrides the OEM ECU??
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papasound
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« Reply #13 on: April 02, 2013, 08:06:17 AM »
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Hi there, i'm just gathering all sorts of information about LPG from all around the web. To be honest this BTS/ATR, LAMBTS/LAMFA concept became total mystery to me since i have started to mess with it. - KFFDLBTS all off because LAMBTS = KFLBTS + (KFDLBTS x KFFDLBTS) *Note from S4 Wiki* "Therefore, setting KFLBTS to 1 where you don't need it won't disable bts, you also have to set KFFDLBTS = 0 to disable bts completely.[16] Note that Mbox has DLBTS (2D), not KFDLBTS (3D)" - *Note from S4 Wiki* "The lowest value of the three (lamfaw, lamfawkr, lambts) become your requested AFR." this is where the mystery for me is still trying to figure out. - TABGBTS - 810C because my default 820C, other cars have different defaults 400-970C. you need to see ur logs. - TABGSS - 1200C, in this case ATR will never kick in unless you melt your exhaust *Note from S4 Wiki* ATR (closed loop) - when measured EGT (block 112) reaches TABGSS (980°C), ATR will add fuel via dlatr, which is generated by the ATR PID. - DSLOFS off - i was experimenting, should be stock. ---- So regarding LPG from what i gather - is that LPG burns slower until 3000-3500 RPM and burns little bit faster afterwards. So if you try to adjust KFZW* for LPG raise timing from 1k rpm by 3-8, all in until 3k rpm, and litlte bit lower after 4k rpm (-1.5-3). That way you stay safe for petrol when you need it and it works great with LPG. Otherwise if you are using only LPG ive seen safe timings delta + 12-15 < 3k > - 5-7. The other thing is to get AFR right everywhere. Some usefull links: http://www.megamanual.com/ms2/tune.htm#emissionshttp://www.acl.com.au/web/acl00056.nsf/0/359683e8a538a3e64a2566c0007bb33e?OpenDocumenthttp://forums.evolutionm.net/evo-x-engine-management-tuning-forums/557403-lpg-tuning-guide.html |
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« Last Edit: April 02, 2013, 08:09:50 AM by papasound »
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prj
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« Reply #14 on: April 02, 2013, 09:13:25 AM »
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It is pointless to use LAMBTS at all, just disable it by FFing TKATBTS and TABGBTS or set FBSTABGM to 0 or whatever other method you desire.
Pointless to edit the maps.
ATR - CATR to 0.
Just drive fueling with LAMFA and advance the timing.
The problem is, if you drive on gasoline with these settings you are going to probably do some damage to the engine - so to do this right, you need to do map switching, for example using the signal for the evaporator relay...
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