Now that things have settled down after the head replacement, time to revisit and refine the LPG settings and calibration. First thing I found was that it's much easier to calibrate if you have the ecu set to 2 banks rather than 1 (doh!).
Anyway, what I'm interested in are what the settings others have established as minimums for:
Threshold revs for changeover (on acceleration)
Reducer temp for changeover
Changeover from petrol-gas delay
Overlap time
It takes a lot of faffing to change 1 parameter a little, test and let it cool again so I'm trying to save a little time!
Threshold revs want to be pretty low, the revs on my SE were set at 2,000 rpm and if you are driving it gently they never got that high, I had to wait until the lights showed it was ready to change over then drop it into neutral and rev it. So you probably want to set something like 1,300 rpm. Temp for changeover was the one thing that was correct on the SE settings, again set it low, 35-40 degrees will get you running on gas as soon as the cold start enrichment phase has ended. If it runs a bit rough as soon as it changes over, raise it a little. Petrol-gas delay wants to be as low as you can get it. I found on the SE it was set at 60 seconds so even when the engine was fully hot, it insisted on running on petrol for a minute before it even thought about changing over when in reality it could have changed over immediately. Overlap is the delay between turning on the gas and turning off the petrol. That's going to vary on different systems but try 500mS if that is an option. If it tries to die at changeover, increase it a bit until changeover is smooth.
This is what I found with the eGas system on the SE so the settings and options may be different on an AEB system, but the theory is the same just the available settings may be different.
Ta!
I'll give those a try
Agreed with Gilbert's suggestions, though I doubt it'll be possible to set 1/2 second switching time.
I usually set changeover temp quite low on P38s at around 30C, 2 second changeover from 400rpm. The brand of AEB system, it's age and firmware and software combination can effect the options available but they generally all only allow switching/charging time in terms of whole seconds (and 0 seconds is possible with some) - Some will only allow minimums of 1600rpm and 10seconds, early versions don't allow as wide a range in settings or adjustment of some settings at all without a dongle, later versions usually allow adjustment of temperature compensation in v6.x software and have options such as temporarily switching back to petrol if temps (reducer and/or vapour) fall below additional settings while driving. The latter is useful in allowing a lower changeover temp than otherwise might be necessary, because applying a lot of engine load with temps that might be OK for low engine load can see the reducer and gas temps fall to the extent where they can bring about problems (so such settings can provide a temporary switch back to petrol when gas temp fell below the minimum setting). Some none AEB ECU's have even more settings such as allowing running on gas at low/medium engine loads when reducer and/or gas temp are low (during warm up) but switching back to petrol at higher engine loads at those temps, thereby preventing drop-off of reducer/vapour temps and any problems that might be associated with low temps but allowing running on gas under any driving conditions with normal reducer/vapour temps.
Thanks Simon
I'm guessing the 2 second changeover was 1400 RPM? I can't hit as low as 400 :)
Doing some spraying at the moment, while humidity's fairly low, but will plug it in later and see what I can get.
Gilbertd wrote:
Threshold revs want to be pretty low, the revs on my SE were set at 2,000 rpm and if you are driving it gently they never got that high, I had to wait until the lights showed it was ready to change over then drop it into neutral and rev it. So you probably want to set something like 1,300 rpm. Temp for changeover was the one thing that was correct on the SE settings, again set it low, 35-40 degrees will get you running on gas as soon as the cold start enrichment phase has ended. If it runs a bit rough as soon as it changes over, raise it a little. Petrol-gas delay wants to be as low as you can get it. I found on the SE it was set at 60 seconds so even when the engine was fully hot, it insisted on running on petrol for a minute before it even thought about changing over when in reality it could have changed over immediately. Overlap is the delay between turning on the gas and turning off the petrol. That's going to vary on different systems but try 500mS if that is an option. If it tries to die at changeover, increase it a bit until changeover is smooth.
This is what I found with the eGas system on the SE so the settings and options may be different on an AEB system, but the theory is the same just the available settings may be different.
Hi Orangebean and Gilbertd-just managed to join and probably just sent a quote of yours by mistake! but been following the LPG stuff as I'm having problems and already learnt lots from your posts at start of year. Have a P38 4.0 98/99 model with Alisei / Zavoli system (Jaymic labels) - has been wonderful for ten years - repaired rats chewed wires twice here in Spain - but renewed the spark plugs a day or so ago - what a job to get at the no 8 !! and pulled my wiring and pipes around a lot. So when I started yesterday it would not transfer to gas (plenty in tank) green light blinking - after a mile along the track slowly - came back fed up - read all you posts - today tried again and after much longer than usual it changed to gas but just as I came very slowly down my steep rough track it cut out and I restarted on petrol just for the last few yards. Have not been on a normal long and fast test -perhaps thats all it needs
Can you suggest anything I can test or check that is causing this please
A good place to start looking will be at the sensor wires- gas temp and reducer temp. If either of these are disconnected the system will never think its warm enough to change over. On my Zavoli installation both sensor wires are (were) unsheathed and pretty flimsy
Reducer temp sensor wire will be a couple of wires from the outer perimeter of the reducer. Gas temp will likely be a T piece after the vapour filter and before the pipes split to go to the injectors.
Mine is currently set on the King ECU (I copied the settings as they were set in the old Zavoli ECU) as:
Changeover type: In acceleration
Rev Threshold: 1200
Overlapping time: 0s (should I change this on mine?? was set at 0s on the old ECU and it seems to switch OK?)
Reducer temp for changeover: 35C (though I think I've since tweaked this to 40C as it lets the engine get a little bit warmer, and it seemed to not mess with the fuel trims as much once it had warmed up that little bit more
Change over delay: 30s
I found with the changeover temp on mine at 30C it would change over when the engine was still running pretty cold, and it didn't seem as happy as if I manually left it on petrol for a bit longer (basically until the temp gauge moved above the blue line) and then switched - so hence upped it to 35, and I think upped it again to 40. It's still running on gas less than a mile from home most of the time..
Orangebean wrote:
A good place to start looking will be at the sensor wires- gas temp and reducer temp. If either of these are disconnected the system will never think its warm enough to change over. On my Zavoli installation both sensor wires are (were) unsheathed and pretty flimsy
Reducer temp sensor wire will be a couple of wires from the outer perimeter of the reducer. Gas temp will likely be a T piece after the vapour filter and before the pipes split to go to the injectors.
Thanks Orangebean - makes good sense - but the wires look ok from the outside and I'm not sure how to test them as they are moulded in to pipes and fittings - I'll persevere - I must learn this forum thing as I seem to keep quoting your post back !! feeling a bit stupid.
Just type in the empty box at bottom and hit green Reply button :)
Don't suppose you have plug-in diagnostics for your system?
Martyuk wrote:
Mine is currently set on the King ECU (I copied the settings as they were set in the old Zavoli ECU) as:
Changeover type: In acceleration
Rev Threshold: 1200
Overlapping time: 0s (should I change this on mine?? was set at 0s on the old ECU and it seems to switch OK?)
Reducer temp for changeover: 35C (though I think I've since tweaked this to 40C as it lets the engine get a little bit warmer, and it seemed to not mess with the fuel trims as much once it had warmed up that little bit more
Change over delay: 30s>
I found with the changeover temp on mine at 30C it would change over when the engine was still running pretty cold, and it didn't seem as happy as if I manually left it on petrol for a bit longer (basically until the temp gauge moved above the blue line) and then switched - so hence upped it to 35, and I think upped it again to 40. It's still running on gas less than a mile from home most of the time..
Mine switches to gas just as I'm at the top of the track to the workshop at the moment. About 1/2 mile.
I'm spoiled by the blue one that starts and runs from cold on gas. The black one has the depressing dropping petrol gauge even though its running on gas. You actually use quite a lot of petrol (relative to the blue one) if you only do short runs several times a day.
Orangebean wrote:
I'm spoiled by the blue one that starts and runs from cold on gas. The black one has the depressing dropping petrol gauge even though its running on gas. You actually use quite a lot of petrol (relative to the blue one) if you only do short runs several times a day.
That is why I say to set the delay as short as possible. Doing lots of short runs, meant the SE was using more petrol than gas as it insisted on running on petrol for the first minute every time it was started. Like you, the white one on a singlepoint runs on gas from stone cold, the petrol in the tank has been in there since I filled up last September in Latvia.......
I wonder how long Latvian petrol lasts before it turns to varnish and turps?
No idea but I did buy the 98 octane good stuff. I must admit, the exhaust is a bit smelly when running on petrol so it may well be decomposing. Might be worth bunging a bit of fresh in there. What would you recommend? Tesco 99 or do I get some of the gold plated Shell stuff?
As the aromatics tend to evaporate over time I'd throw in a good dollop of injector cleaner to dissolve any deposits that might be forming. As I have it on the shelf I'd give it a shot of octane booster as well, to perk up the residual Latvian remnants, then use it up until down to the last few gallons.
Then, give it a treat of branded expensive stuff.
On the blue one I do actually run a few gallons of petrol through it every 3 months or so just to get the fuel trims back to where they should be, keep the fuel fresh and injectors clean.
Just to add to my last post on this thread...
Agreed with Gilbert's views on setting systems to switch as early as possible because that way you save most money. If you watch fuel trims from cold start on most vehicles they will be different with warming engine (when it first goes closed loop) to when the engine is up to temp, a lot of vehicles (particularly more modern ones) have a different set of trims for during warm up anyway. But how I set changeover on my own cars is a bit different to how I set changeover on customer cars - I know that booting it with cool reducer can lead to problems, while some customers would drive slowly while running on petrol and then boot it as soon as running on the cheap stuff.
Orangebean wrote:
As the aromatics tend to evaporate over time I'd throw in a good dollop of injector cleaner to dissolve any deposits that might be forming..
Chinese stuff, aromatic duck oil? lol ;-) Seriously though I'm interested in just how quickly petrol might degrade, I don't think I've ever seen a vehicle running poorly on even very old petrol even though I know in theory it's supposedly an issue. Maybe if the biggest issue is drop in octane it's more of a problem on higher compression engines, though varnish etc is potentially a problem for any engine?
Simon
You got me thinking about deterioration Simon, so did a bit of digging. BP have done several studies on ageing fuel in tanks. There's an interesting paper here if you fancy a bit of light reading
Bottom line is, according to Gary Whitfield, Senior Fuel Chemist at BP Australia:
In the right conditions, fuel can last up to 12 months. But once the container is opened, the fuel will start to degrade.
“Once the seal is broken, a vapour space is formed in the container and the fuel will start to deteriorate more rapidly,” he says.
Mr Whitfield claims fuel in a car’s tank can last for up to four weeks before it becomes considerably denser. When this happens, the engine is effectively over-fuelled (without any change in injector pulse-width) and there’s an increased chance of carbon deposition onto spark plugs and inside the combustion chamber. This can cause driveability problems such as stutters and misses.
“Regular unleaded fuel will lose a small amount of octane over time but in our low-sulphur and high detergent Ultimate fuel it might increase very slightly. It might increase 1 RON in four weeks – but it’s not something I’d bother chasing,” he says.
“Keep in mind that typical variation in BP Ultimate is 98 – 100 RON while normal unleaded ranges between 91 – 93 RON.”
Mr Warren says that in most cases, it’s only when fuel is left in the tank for several months there’s the risk of engine damage. This is much more likely to occur in cars running dual LPG/petrol systems.
“By this time the fuel will have gone dark and gummy and can clag the fuel pump, filter and injectors,” Mr Warren says. It can also leave a lacquer deposit on the inside of the fuel tank which is difficult to remove.
In addition, it’s important to be aware that fuel brews – specifically fuel volatility - varies on a month to month basis. Standards vary from state to state but, generally, volatility is reduced during summer months to reduce evaporative emissions. Mr Whitfield says this typically makes the engine slightly harder to start but there is no change in octane.
Hmm, well I did once try to start a car that had been standing for 7 years on the fuel that was in the tank. Took a good blast of starter fluid in the air intake to get it to fire and once running it absolutely stank. Didn't run that well either. However, you'll be pleased to hear that I now have a blend of roughly 25% 9 month old Latvian petrol and 75% BP Ultimate in my tank. I suppose I'll need to use some now.......