Dedicated LPG system
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  1. #1
    Fellow Frogger!
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    Default Dedicated LPG system

    Hi guys,
    I need some advise on how to upgrade the duel fuel system on my DS to dedicated LPG, I just never use petrol!
    My converter is an BRC AT90E running to a simple mixer ring above the carby.
    So, should I get rid of the DS carby and replace it with an LPG throttle body, say off a BA Falcon?
    Then, convert to closed loop with a DEG-103 Lambda Control Unit?
    I would then remove the fuel tank and replace it with an LPG tank and swap the large LPG tank in the boot for a smaller toroidal one.
    Basic outcome is to have a much neater more efficient dedicated LPG system... Thoughts?

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    Cheers,

    Harley

  2. #2
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    I have a Renault Fuego on dedicated LPG. I changed over because it offered legal and performance advantages in a turbocharged applications.

    I have a Gas Research Gas Carby and it runs faultlessly. The unit has a separate adjustable idle and progression circuit (jets) for fine tuning of light throttle and cruise mixtures and then a metering rod for the load circuit. The metering rods are available in lots of different diameters to allow different enrichment curves (or you can even fine tune it on a lathe).

    The Gas Research system can be tuned with a wideband o2 sensor and some time but one of the Gas Research tuners can set it up on a dyno really quickly.

    Once you have it tuned it is tuned.

    I had a 400 cfm carb on a n/a 2000cc and it ran fine but there is a smaller sized one that would be ideal.

    The only thing I could advise is that you try and have the converter as close as possible to the mixer. It means the car will first crank and you wont need a primer or any guff.

    You can set it up with a closed loop too although I was advised that if it was tuned properly, you shouldn't need to.

    I removed my fuel tank also, and have a Torodial tank where it once lived.

  3. #3
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    Thanks for the info Mistareno, I've had a look at the Gas Research gear, my business partner just had his Bedford converted with it, cost him a fortune though!

    After some more research I have stumbled cross the BLOS lpg mixer, it operates in a similar fashion to an SU carby but sits before the throttle body. I've been reading some great reviews about it and I like the fact that it does not require a closed loop system.
    I will look at accompanying it with a 40mm throttle body.
    Has anyone had experience with the Polish made Blos?

    Harley

  4. #4
    Fellow Frogger! Rally's Avatar
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    I have a Sprint Gas Injection system on my tow car .
    The system installs one electronic injector in the inlet manifold as close to each inlet valve as possible . It runs closed loop using the origional O2 sensor . Tuned by laptop very quickly.
    It is designed to start on petrol with auto change over at 40 degree coolent temp , am sure you could set it up as a dedicated LPG system.
    It offers all the advantages of EFI over carby that apply to petrol.

    Andy
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  5. #5
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    Quote Originally Posted by Rally View Post
    I have a Sprint Gas Injection system on my tow car .
    The system installs one electronic injector in the inlet manifold as close to each inlet valve as possible . It runs closed loop using the origional O2 sensor . Tuned by laptop very quickly.
    It is designed to start on petrol with auto change over at 40 degree coolent temp , am sure you could set it up as a dedicated LPG system.
    It offers all the advantages of EFI over carby that apply to petrol.

    Andy
    The car has to be efi to start with. There is little info available on using an aftermarket ecu with LPG but it appears it is possible.

  6. #6
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    Quote Originally Posted by mistareno View Post
    The car has to be efi to start with. There is little info available on using an aftermarket ecu with LPG but it appears it is possible.
    Definitely possible and there is lots of information, even for old Citroens, but you need to know where to look:
    http://www.youtube.com/user/BozzDrift/videos
    This system is based on megasquirt controlling ignition and lpg.
    Vapour injected lpg works ok in batch fire mode but you wont get the most out of it unless you can tune your ignition, therfore modifing the DS by drilling a trigger pattern in the flywheel is required. See bozzdrifts vids for flywheel drilling.
    I have successfully converted my 2cv to multi point EFI using megasquirt for fuel only.
    I wanted to avoid the complexity of going down that path with the DS.

    Cheers
    Harley

  7. #7
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    Quote Originally Posted by Pastinha View Post
    Definitely possible and there is lots of information, even for old Citroens, but you need to know where to look:
    http://www.youtube.com/user/BozzDrift/videos
    This system is based on megasquirt controlling ignition and lpg.
    Vapour injected lpg works ok in batch fire mode but you wont get the most out of it unless you can tune your ignition, therfore modifing the DS by drilling a trigger pattern in the flywheel is required. See bozzdrifts vids for flywheel drilling.
    I have successfully converted my 2cv to multi point EFI using megasquirt for fuel only.
    I wanted to avoid the complexity of going down that path with the DS.

    Cheers
    Harley
    I'd be interested to know how they handle the fuel pressure compensation on a standalone install.

    The piggy back LPG systems have a pressure sensor so they can calculate the injector pulse based on the converter output pressure.

    Most of the newer aftermarket ecus have several configurable analog inputs which I suppose could be connected to a pressure sensor and then mapped to achieve the same result?

    The other option I had considered when I was considering the vapour injection route was just to disconnect the vacuum signal to the converter or reverse the spring so it would just run at max pressure all the time.

    The problem with that was that the output pressure (on the converters I could get info on) would've been very marginal once boost was taken into consideration and even with the biggest injector size, the duty cycle would've maxed out at lowish boost.

    I have since found there are boost suitable converters available with higher vapour output pressures, but tbh the advantage of vapour injection on a dedicated lpg car (especially a turbocharged one) is minute compared to using a liquid injection system.

    I will probably install a Haltech Sprint 500 or similar at some stage so I can have better control over the ignition timing and I suppose the jump to lpg injection would be a bit easier then, but I'd only spend the time if I could go liquid injection.

    With regards to the BLOS, I've heard nothing but good things about them. The only thing that would worry me would be parts for servicing the unit as it has a rubber diaphragm if memory serves. I must admit though, they have been selling them on Ebay for atleast 5 years so they seem fairly reputable.

  8. #8
    1000+ Posts PeterT's Avatar
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    I've been running LPG for approx 25 years now on various vehicles. The major point many get wrong is the advance curve for LPG. There's three key points:
    1. Ease of starting - you still need 5-10 deg. BTDC
    2. Rate of advance - needs to come in very quickly, like 15-20 deg @ 1250 rpm
    3. Max advance - far less than petrol, 21-22 max

    With an aftermarket ECU you can achieve this easily for LPG only. For a dual fuel installation you can still do it providing the ECU has "dual maps". The Sprint 500 supports single maps only. The Sport 1000 has dual maps. Plenty of older ecu's have dual maps however, such as the E6X, E8 etc. Even really old ECU's such as the E6 or E6A, which are single maps only, can be bought for silly money and are great for LPG only applications.

    I use AVI inputs for oil pressure and oil temperature. You can either make it voltage vrs resistance, or just as a switch, eg a change from 0V to 5V.

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  9. #9
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    Quote Originally Posted by Pastinha View Post
    Hi guys,

    I would then remove the fuel tank and replace it with an LPG tank and swap the large LPG tank in the boot for a smaller toroidal one.
    Basic outcome is to have a much neater more efficient dedicated LPG system... Thoughts?

    Cheers,

    Harley
    Novel LPG tank alternative?

    http://www.ppidts.com/propanep/gallery.html

  10. #10
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    Thats interesting mistareno, I've not considered it and assumed the converter would set a constant pressure. I will ask some guys who have diy injected lpg how they achieve it.
    You should email Bozzdrift and ask about his systems and kdfi, they are very well priced and he can supply all the equipment to install. If I went down that route that's how I would do it.
    PeterT that is great info which isn't often shared or even known! Thanks.

    Harley

  11. #11
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    Here is a reply I received from a Dutch college who runs all his cars on lpg and has developed his own multi spark ignition system for the 2cv and is now running it on 4culinder vehicles.
    He has an lpg injected turbo 2cv running kdfi.
    Oh Harley it is so simple............
    The lpg converter keeps the lpg pressure at about +1 bar, so the gas is injected with 1 bar of pressure....
    Now for a turbocar you can connect a hose from the inletmanifold to the converter at the backside of the membran, so when boost increases in the inletmanifold the gas pressure will also rise in the converter at the same level so the pressure of the lpg gas will still be + 1 relative to the inletmanifold, Clever hey and simple......
    Look at the hose running from the inletmanifold to the LPG converter.
    the VE table is relatively flat because the injection is regulated by the gas pressure and less to the opening time of the injector.....
    Hope you understand once again what I'm trying to say....
    https://www.youtube.com/watch?v=zfOfg7I_1VA

    Does that solve the issue Mistareno?

    Harley
    Last edited by Harley; 17th May 2013 at 04:29 PM.

  12. #12
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    Yes. But it sounds like that's a different convertor to what's available (or what was available) in Australia.

    The highest pressure output convertor I could find in Australia was 2 bar maximum (adjustable to that level).

    The converters (that I could get data on) seem to react to vacuum only and are at max ouput pressure at 0psi manifold signal and don't move the other way to allow for more pressure.

    This was based on research 3-4 years ago so there may be others on the market now.

    I assume that the turbo converters I found available in the UK and europe would have a higher output (maybe 5 bar?) and that the diagphram (membrane) can move both ways from a base setting (under both vacuum and positive pressure) to allow that higher injection pressure when under boost.

    At the time I looked, the most boost I could've run before maxing out on duty cycle would've been about 9psi and that was still a vapour injection system which just doesn't provide that much in the way of advantage over other systems.

    If I go injection it'll be with liquid LPG as the advantages on a Turbo car are far more substantial.

    The car is straight Gas so I really only want the adjustable ignition capabilities of an aftermarket computer to make the most of what I have and implement some knock detection.

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