hangover Posted January 28, 2006 Share Posted January 28, 2006 This should make fridge's ears prick up, i have recently swapped an lpg setup from 1 rangie to another and will soon be swapping the 3.5 with a leyland 4.4 V8. Now i have been toying with efi'ing the 4.4 using a tbi unit of a local aussie ford, so i am thinking out loud here, have also been reading with interest about closed loop lpg systems and how it would be possible to have a seperate map in a MS ecu to control the lpg as well as one for petrol ? Does this sound feasible or a bit way out ? I believe once the parmeters are set there shouldnt be any reason why it couldnt work. Regards, Nick. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 28, 2006 Share Posted January 28, 2006 <sloping shoulders>Geoff is more your man for this sort of thing</sloping shoulders> You'll need the "extra" code, read all about it here: http://megasquirt.sourceforge.net/extra Dual table info is here: http://megasquirt.sourceforge.net/extra/dualtable.html And here: http://megasquirt.sourceforge.net/extra/tableswitch.html If I'm reading it right, you have a switch and basically it's like switching between two different ECU's, so you can set the lambda sensor (closed loop) and all that sort of gubbins separately. TBH I didn't realise they'd managed to squeeze dual 12x12 spark and fuel tables into the current setup. It'll be making the tea next... Ideally you want a V3 ECU as they are more easily modifiable. If you don't want to modify it yourself, when you order a built ECU you can ask for it to be modded as required. Quote Link to comment Share on other sites More sharing options...
hangover Posted January 28, 2006 Author Share Posted January 28, 2006 By my thinking, if you can tell the ecu what the parameters are for lpg, you could build it all in to the one the unit instead of having the seperate ecu for the lpg, since it will need an ego, tps input that MS will need anyway ? Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted January 30, 2006 Share Posted January 30, 2006 <sloping shoulders>Geoff is more your man for this sort of thing</sloping shoulders> Iam? Scary thought, my megasquirt is still sat in a cardboard box... Wot fridge said, basically... If I'm reading it right, you have a switch and basically it's like switching between two different ECU's, so you can set the lambda sensor (closed loop) and all that sort of gubbins separately. TBH I didn't realise they'd managed to squeeze dual 12x12 spark and fuel tables into the current setup. It'll be making the tea next... You can have it use two lambda sensors now - needs a small amount of extra circuitry, but maybe worth it if you're doing a V8. Thinks it's coffee only at the moment, and the milk frother is not recommended for production use By my thinking, if you can tell the ecu what the parameters are for lpg, you could build it all in to the one the unit instead of having the seperate ecu for the lpg, since it will need an ego, tps input that MS will need anyway ? You're talking at cross purposes with fridge - the table switching is like having two ECUs - you don't actually need two. You should be able to achieve what you're after by something like this; set up all the petrol injectors on the first bank of injector outputs and all the LPG ones on the second bank. You then set up fuel maps for these such that you have one set of maps that gives you petrol but no LPG and another that gives you LPG but not petrol. If you have megasquirt controlled ignition timing you can change the ignition maps too. I guess you'd need to wire a few other bits of the system up to megasquirt too, but you might be able to either cheat and say share the petrol fuel pump switching to also operate the LPG solenoid valve, or use the arbitrary switchable outputs if the conditions available are suitable. The table switching simply takes a switched 5V input. I'm picking up a 12V input off the gas kit to operate a relay which switches the 5V when the gas kit kicks in and changes the ignition map. My gas kit is a venturi one, so I can't control it with megasquirt, but switching to LPG injection and putting it all in megasquirts hands is something I've considered for the future. All this is from memory, and megasquirt's got quite a bit cleverer over the last few months, so it's probably not entirely accurate - read the links fridge gave, and ask questions on the megasquirt forums. Quote Link to comment Share on other sites More sharing options...
hangover Posted January 30, 2006 Author Share Posted January 30, 2006 I found thison ebay, what do ya reckon ? Impco systems are popular here and cheap, my rangie uses one .Closed loop lpg. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 30, 2006 Share Posted January 30, 2006 My initial response is that's a (fairly well executed) bodge-up, it seems to look at the lambda sensor voltage and cut the LPG supply to try and reduce the pressure (hence the fuelling) to hit the "correct" mixture. A bit like switching your fuel pump off rather than just leaning the mixture down. The problem as I see it, is that normal Lambda sensors are ONLY right when the mixture is 14.7:1, which is the right mixture for economy but wrong under high load. All you can do outside of that point is say "it's rich" or "it's lean" but not if the mixture is right or not. This is what wideband lambda sensors are for. Basically that unit is taking an educated guess at your fuelling based on not-a-lot of information. If it was me I'd save my money for a decent system. Quote Link to comment Share on other sites More sharing options...
hangover Posted January 30, 2006 Author Share Posted January 30, 2006 Yes, i agree its not an ideal setup, i have been searching but can find bugger all info on any CLLPG systems apart fron the expensive vapour injection ones. Do you know of any good sights or links ? Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted January 30, 2006 Share Posted January 30, 2006 Yes, i agree its not an ideal setup, i have been searching but can find bugger all info on any CLLPG systems apart fron the expensive vapour injection ones. Do you know of any good sights or links ? If you can possibly afford to, go for the injection ones. The venturi type suffer from one or two issues such as a tendency to flash back (frontfire?) if you start on LPG (bad news, it can blow your intake hose apart or worse. Much worse if you've a flapper type EFI system) and poor idle stabilisation (because they put the gas in before the throttle so there a significant lag before a change in fuel mix takes effect at low revs). They also tend to be less efficient, although I don't think there's a lot in it. If you do go down the megasquirt route you have to go injected - megasquirt isn't able to run a venturi stepper motor (although I'm sure it could be made too - just no-one's written the code, so far as I'm aware). I've got a venturi kit but if I was fitting a new one I'd go injected. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 31, 2006 Share Posted January 31, 2006 No-one's written the code exactly, but there is stepper-motor idle valve control code that could be very easily tweaked to suit. All the hard bits are done, and if there's extra hardware required it will already exist for the idle control. Quote Link to comment Share on other sites More sharing options...
hangover Posted January 31, 2006 Author Share Posted January 31, 2006 Would MS have a learning function ? Reading on RPI's site that the later efi systems will learn the lpg mapping and then have to re learn the petrol map again once switched. If there are the right inputs, ego, tps, tach, map wouldnt MS using maybe MS tweak Learn to map for lpg ? I already have an impco lpg setup and also have the sprintgas 4brl mixer but soon going to fit a leyland 4.4 in so may have to change the setup i use, ideally i need to be able to fit a snorkle for the dusty summer conditions we have plus to bring some cooler air into the engine - the 4.4 is approx. 20mm higher and wider and rover manifolds only work with spacers which tend to have leakage problems. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted January 31, 2006 Share Posted January 31, 2006 Would MS have a learning function ? Reading on RPI's site that the later efi systems will learn the lpg mapping and then have to re learn the petrol map again once switched. If there are the right inputs, ego, tps, tach, map wouldnt MS using maybe MS tweak Learn to map for lpg ? The Lucas Hotwire (and, I think, the earlier flapper) EFI systems coarse tune themselves for the first five miles or so after being reset (disconnected from a power source). They then switch into a fine tuning mode that is only capable of small adjustments. Under normal driving conditions they are in fine tuning mode while you are on LPG and do not lose their saved course tuning, so switching back to petrol is no different to starting the engine on petrol. Where you can run into problems is if you've had the battery disconnected and cleared the coarse tune settings. If you run the car on LPG while the ECU is in coarse tuning mode it'll save wildly incorrect settings and be unable to correct them once it's in fine tune mode. The fix is simple - if you've had the battery disconnected, drive the first five miles on petrol. Megasquirt, on the other hand, isn't intended as a generic 'one size fits all' black box - you tune it specifically for your engine (well, you could just drop someone else fuel maps in - but you'd lose one of the benefits of MS). As such it has no need for a self tuning mode and your fuel maps will remain exactly as you set them up. If it's being used with an EGO sensor it will do the fine tuning, but that is 'on the fly' not saved - same as the hotwire fine tuning mode. Quote Link to comment Share on other sites More sharing options...
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