scimjim Posted May 13, 2011 Share Posted May 13, 2011 hi to all. i'm about to fit an lpg system and a megasquirt to a 3.5 v8 with 3.9 inlet manifold. my lpg system runs with 2 lambda sensors, 1 in each exhaust header. if i was just fitting megasquirt then i would fit a lambda rearwards of the exhaust y-piece. fitting lpg and megasquirt.....leaves me a bit confused. can i run the megasquirt utilising the 2 lambda sensors of the lpg system or do i have to fit a 3rd sensor purely for the megasquirt? any help would be much appreciated. scimjim Quote Link to comment Share on other sites More sharing options...
bobtail84 Posted May 13, 2011 Share Posted May 13, 2011 hi to all. i'm about to fit an lpg system and a megasquirt to a 3.5 v8 with 3.9 inlet manifold. my lpg system runs with 2 lambda sensors, 1 in each exhaust header. if i was just fitting megasquirt then i would fit a lambda rearwards of the exhaust y-piece. fitting lpg and megasquirt.....leaves me a bit confused. can i run the megasquirt utilising the 2 lambda sensors of the lpg system or do i have to fit a 3rd sensor purely for the megasquirt? any help would be much appreciated. scimjim How are you going to use the MegaSquirt to run the LPG? Are you firing the LPG injectors with MS? Is it a single point system? What is the air-speed velocity of an unladen swallow? More info please... Jeff Quote Link to comment Share on other sites More sharing options...
Quagmire Posted May 14, 2011 Share Posted May 14, 2011 What is the air-speed velocity of an unladen swallow? This would seem to be an important question in this section of the forum Quote Link to comment Share on other sites More sharing options...
scimjim Posted May 15, 2011 Author Share Posted May 15, 2011 would that be an african or european swallow? the lpg system is an OMVL Dream Sequential Injected System, got it from rpi. as to your other questions jeff, i haven't gotten that far, i only decided to fit ms 2 weeks ago. andy Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 16, 2011 Share Posted May 16, 2011 Don't know much about your specific LPG system but they are usually designed to work independant of the cars engine management, be it factory standard or aftermarket so I would fit a 3rd lambda otherwise your going to have to try to get the MS and LPG systems to talk to each other. The only links on my open loop system were shutting off the injectors by putting a relay at their common - still the same with MS, and it monitors rpm from the coil / ignition module on the dizzy, starts on petrol then automatically switches from petrol to LPG at a given RPM, as there is no coil / dizzy anymore i just switch it manually, yet to look into getting it back to automatic, the signal at the coil seemed to jump from around 3v to 9v when the engine was running so i'm guessing the LPG controller just counted these pulses. Have a look at the wiring for the LPG and check there isn't supposed to be a link to any component that your going to pull out If you were good enough i'm sure you could have the MS box configured to do all this for you, but i'm only a beginner Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 16, 2011 Share Posted May 16, 2011 Modern LPG systems use the injection timings of the petrol injectors to decide their own injector opening times, I've not dealt with the OMVL Dream system before, but they are all much of a muchness. So..... you will need to do the injector cuts anyways, despite having a funky MS driving it all and ability to table switch. The two lambdas that the OMVL system use may just be there for troubleshooting rather than on-the-fly mixture adjustment, as this is normally carried out by the engines existing ECU and lambda, or in this case it would be the MS ECU and the single lambda. I think you're slightly in uncharted territory, and you may end up working a lot of this out yourself... sorry I can't be of much more help, but if it's MS related I will happily anser any questions Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 17, 2011 Share Posted May 17, 2011 I would ditch 90% of the LPG kit, run the megasquirt in table-switch mode and let it run both sets of injectors direct, saves all the p*ssing about (usually a thinly veiled horrible bodge) that LPG kits do with injector cuts, injector emulators, etc. etc. which mostly involve hacking the engine loom about and adding loads of extra failure points. The megasquirt doesn't need all the gubbins to "fool" it into behaving itself like the Lucar5e EFI setup, so you're just adding lots of complicated gubbins for nowt. As for Lambdas, if you do what I just said then just run one, if not then the easiest is to give the MS its own one after the Y piece, more out of mistrust of the LPG kit than anything. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 17, 2011 Share Posted May 17, 2011 I do agree with you Fridge, but I am yet to hear of many people successfully running LPG injectors with Megasquirt, but very few real successes. I am sure it is all just making sure the injectors get the right power requirements etc, but it's all a bit unknown to most people Problems such as gas pressure and temperature compensation rear their ugly heads, and there's very little without becoming a MS-guru you can do about it. Quote Link to comment Share on other sites More sharing options...
bobtail84 Posted May 17, 2011 Share Posted May 17, 2011 As Fridge has said just squirt it. I have maps for LPG and have successfully MSed with LPG injectors BUT... and it's quite a large but.. LPG injectors are by and large all low impedance so you have to set the engine constance to suit which the buggers up the hot wire settings... There are ways around the problems such as low impedance petrol injectors but thats another thread. Jeff Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 17, 2011 Share Posted May 17, 2011 Jeff, How have you compensated for gas temperature and pressure variations? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 17, 2011 Share Posted May 17, 2011 I'd expect the LPG kit to compensate/regulate for that to a greater or lesser extent, petrol systems are not really any different in the grand scheme of things. If you're having to use Low-Z injectors you can just strap a load of ~6 Ohm power resistors in series with them, TSD did similar on his hybrid years ago. May even get away with one BIG low-ohm (~1.5 Ohm) power resistor per bank, depending. It's certainly not insurmountable. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 17, 2011 Share Posted May 17, 2011 As you are dealing with a gas its far more critical to get that right, and no, the lpg hardware doesn't compensate for it, that's the job of the ecu, so you have more over it than a carburettor Quote Link to comment Share on other sites More sharing options...
woodytz Posted May 19, 2011 Share Posted May 19, 2011 hi , here,s my 2 bobs worth, you only need 1 lambda, fit it as close to the collector on 1 bank of cylinders, otherwise it will go cold on low revs and idle. you only need lambda,s to aid tuning of the lpg due to the fact that you have no OBD11 facility to read fuel trims. Lucarse CUX14 has no facility to log fault codes relevant to injector emulation or lambda simulation[its basic. Can you run low Z lpg injectors with squirt?? yes of course you can...as jeff said you have to alter engine constants to suit, this then fecks up the petrol side , if you try and run low z lpg injectors with engine constants set for high z petrol injectors ,it will run , it will rev up , but thats it , put any load on it and you will do 1 0f 2 things or even both, fry the low impedence lpg injectors[you are on a hiding to nothing to start with as the omvl wet dream 21n is a splendid system very cheap and chearfull with poor quality injectors] or and wipe the MS chip from a massive short across the lpg injectors as they are peak and hold not on off. How do we know all this ?? months of trial and error between Jeff and myself, we are working on an answer for the lpg injection and as Fridge has said resisitors may be the answer.One thing for sure when we get it right you will be the first to know. Woody Quote Link to comment Share on other sites More sharing options...
bobtail84 Posted May 19, 2011 Share Posted May 19, 2011 Jeff, How have you compensated for gas temperature and pressure variations? Gas temp will be some where near engine coolant temp because that's what flows through the vaporiser. It might be a nats lower but nothing to worry about. Pressure variations... the OMVL vaporiser is not adjustable so no issues there, all the vaporisers we use are adjustable. Also you can adjust pressure via the VE map as you only inject what's needed. But don't forget it's all just playing with our cars so it's not an exact science. Jeff if you try and run low z lpg injectors with engine constants set for high z petrol injectors ,it will run , it will rev up , but thats it , put any load on it and you will do 1 0f 2 things or even both, fry the low impedence lpg injectors[you are on a hiding to nothing to start with as the omvl wet dream 21n is a splendid system very cheap and chearfull with poor quality injectors] or and wipe the MS chip from a massive short across the lpg injectors as they are peak and hold not on off. Woody We are very good at re-flashing CPU's now.. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 20, 2011 Share Posted May 20, 2011 You could always bung flapper EFI (Low-Z) injectors & fuel rail on, and run PWM current control in the Megasquirt for both sets. Worth a look maybe? Quote Link to comment Share on other sites More sharing options...
scimjim Posted May 20, 2011 Author Share Posted May 20, 2011 hi guys and thanks for all of the replies. i think i'll go belts and braces and fit 3 lambda bungs, 1 in the y-piece and 1 in each exhaust header and concentrate on the petrol side of the vehicle before i enter into the scary world of lpg. and in reply to your question bobtail84, the airspeed velocity of an unladen swallow is roughly 11 meters per second, or 24 miles per hour although i cannot confirm if that is a european or african swallow. scimjim Quote Link to comment Share on other sites More sharing options...
woodytz Posted May 20, 2011 Share Posted May 20, 2011 you are right there mr fridge, twood be a simple solution, looking to the future when these resistors run out is the problem,and also the lpg manufacturors wont be making high Z injectors so some where along the line we need to find the fix. As jeff said were real good at reflashing firmware woody Quote Link to comment Share on other sites More sharing options...
bobtail84 Posted May 22, 2011 Share Posted May 22, 2011 hi guys and thanks for all of the replies. i think i'll go belts and braces and fit 3 lambda bungs, 1 in the y-piece and 1 in each exhaust header and concentrate on the petrol side of the vehicle before i enter into the scary world of lpg. and in reply to your question bobtail84, the airspeed velocity of an unladen swallow is roughly 11 meters per second, or 24 miles per hour although i cannot confirm if that is a european or african swallow. scimjim I think 3 lambdas is slightly over doing it but it's up to you. and how do know so much about swallows?.... Quote Link to comment Share on other sites More sharing options...
scimjim Posted May 22, 2011 Author Share Posted May 22, 2011 i'd rather fit 3 bungs whilst the bodywork and the exhaust system are off the vehicle than retro fit the whole lot with the bodywork fitted. as for swallows...Well, you have to know these things when you're a king, you know.( My surname is King) Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 23, 2011 Share Posted May 23, 2011 Woody - I don't think the global electronics industry is likely to stop making resistors any time soon, they're quite popular you know... Quote Link to comment Share on other sites More sharing options...
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