Gas injection

Discussion in 'Alternative Fuel' started by White ls400, Jan 17, 2008.

  1. White ls400

    White ls400 New Member

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  2. cribbj

    cribbj "Supra" Moderator Staff Member

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    That's the Romano system from Italy.

    It's supposed to be an OK system, and I understand it's one of the most popular in the UK.

    At least with the Romano, you have the choice whether to manifold mount those injectors, or use the provided fuel rail to centralise them, and run copper or PE tubing to nozzles mounted above the injectors. The 2nd way doesn't seem the optimal way to plumb, but it's very popular and seems to work OK.

    There are other Italian LPG systems whose "injectors" are simply a bank of solenoid plungers in a common machined case, and you can't separate them.

    Try to get the biggest toroidal you can possibly fit in your boot because:

    1) Their capacities aren't that high to start off with

    2) You're going to take a hit with your mileage on gas because you can't optimise your engine and ignition for the gas.

    3) Your gas supplier should only fill the tank to 85% maximum anyway, so you'll have some room for expansion of volume due to heating. (You don't want to top that tank off completely full in the early morning when it's 10 degrees outside, then that afternoon when it's 25 degrees and it's been sitting in the sun all day, find your car spewing LPG from the pressure relief!)
     
  3. White ls400

    White ls400 New Member

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    The tanks are set up to fill to only 80% because of Aus design rules. My injectors are going to be straight plumbed into the manifold. Im going for a 72 litre torodial as even its going to sit 20mm higher than the wheel well. My mechanic reckons if you sit there long enough and set up the ratios for all rev and loading ranges you can get similar economy to fuel(will be tuned on dyno eventually) So you say the injectors are ok? sounds like your not too confident or you just havent had 1st hand experience with them? I havent put this question forward to my mechanic yet but im also getting my starter reco's at the same time so would it be a benefit to mount the injectors in the lower part or the highest part of the manifold or would not make any gains and just be a pain to service if something goes wrong
     
  4. cribbj

    cribbj "Supra" Moderator Staff Member

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    Sorry, not to paint anything negative, just no 1st hand experience with the Romano system.

    The two photos below show how the Prins' injectors (which are actually Japanese Keihin units) are commonly mounted - the first photo (courtesy of ProFire EMS) is a conventional port mount where they've replaced the liquid injectors with the Keihins.

    [​IMG]

    The 2nd photo (courtesy of Prins Installation Manual) is the 2nd method that I referred to in the previous message. Each bank is mounted in a block of 4, and their inlets are connected to a common rail, then they have flexible hose/tubing running to 1/8" NPT elbows mounted in the manifold runners. So when an injector pulses open, the gas has to travel down this tubing to enter the manifold, and then to the inlet port. Doesn't seem like the optimal way to do it, but apparently it works.

    [​IMG]
     
  5. White ls400

    White ls400 New Member

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    the way i got explained to me is that the injectors are tapped into the manifold runners then joined back to a rail so like a combination of those 2 sort of because im still retaining fuel injectors
     
  6. White ls400

    White ls400 New Member

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  7. White ls400

    White ls400 New Member

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    ok its all done now, the way its set up is the gas goes to the gas rail then runs through a tube from the rail to the injector then from the injector it runs through another tube to the inlet manifold, all of these are equal length at 110mm
     
  8. cribbj

    cribbj "Supra" Moderator Staff Member

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    Let us know how it drives. Pics would be great.
     

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  9. White ls400

    White ls400 New Member

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    No pics as yet they will be coming.Th car drives better than ever real smooth idles nice feels a bit torquier, although it is a dog to drive when cold but hey what ya expect. Pretty happy with it
     
  10. edz

    edz New Member

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    gas injection - cold weather

    Where are you located White ls400, because I read that the gas injection system won't work in a cold climate as the gas pressure is too low in winter? Yet Europe is cold, so not sure of the truth of this?

    Great to hear you have it running, are you able to provide any costings as I'd rather do this that have the current dual vapor system I have setup?

    Ed
     
  11. edz

    edz New Member

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    gas injection system won't work in a cold climate

    This is the article-
    http://lextreme.com/forums/showthread.php?t=1628, interested in comments as I'd still like to go gas injection with twin turbos?
     
  12. cribbj

    cribbj "Supra" Moderator Staff Member

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    The problem with the LPG in some parts of the world (and Oz) is that it has a high percentage of nButanes and other heavies in it, which drastically lowers its vapor pressure in cold weather.

    I had a mate in Oz who put together a very nice Prins system on his turbocharged car c/w dual injectors, only to find out he didn't have enough gas pressure to run it.

    Here's a cut & paste from an email he sent me when he made the unfortunate discovery:

    "Well the news with the injection is not good. I was worried about the pressure the tank would drop to in our cold ass winters. So I have a 4.5kg bbq cylinder that I filled from the cars LPG tank. First off I tested the pressure at 35 degC = 85psi. Yup, this is pretty low huh. Lower temps did not bode well for it. Then I popped it in the fridge to lower the tank to about 4degC. Now this one is the eye opener......28psi!!! Now considering that when on boost I will be running a rail pressure of 45psi....yep, Houston, we got a problem."

    He wound up "liquidating" his whole Prins setup on eBay for a fraction of what he had in it, then put on an ancient "suck through" Impco setup, then finally sold the car.

    Ed, I can probably put you in touch with my friend, if you're interested in emailing him about the problems he had? PM me your email address if you're interested, and I'll try contacting him for you.
     
  13. Deuce

    Deuce Member

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    "Edz", the Romano system that "WhiteLS400" is using (I think) is Gas injection. The system "Cribbj's" mate made was Liquid Lpg injection. The only successful Liqiud LPG injection system I have heard of is the one used by "Cyberdiamond" which was bought out and shelved.
     
  14. cribbj

    cribbj "Supra" Moderator Staff Member

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    Deuce, no, the Prins system I was referring to was vapor injection also.

    The problem with any vapor injection system is that it requires at least a bar of pressure differential to operate vs a carby setup which operates at ounces, or inches of water. So a carby setup will operate in just about the coldest winters, while the vapor injection will have a tough time when it gets around freezing, especially when there are nButanes and other heavies in the gas.

    You might get by with it for a naturally aspirated motor, but as soon as you start boosting, the gas pressure will need to be at least 1 bar plus the boost pressure. That's where my mate Pete ran into trouble. He could get the car started, but it would fall on its face as soon as he tried to boost. A draw through carby setup won't have these problems, but it'll have other problems.
     
  15. Deuce

    Deuce Member

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    I stand corrected.
     
  16. White ls400

    White ls400 New Member

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    I live in Oz, the car is a bit jumpy when cold, just like driving a carbied car when cold, bit hard to start in the morning when cold so last drive of the night i let it idel on fuel before shutting off and its all good... Total cost was $4400 fitted but alot of that was screwing round due to the system had never been fitted to a lexus before
     
  17. White ls400

    White ls400 New Member

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    heres the pics
     
  18. edz

    edz New Member

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    Not sure where you live in Oz White Ls400, but I live in Canberra -12deg C in winter is common with days warming up to 0deg C sometimes (check the pic - working on my car in a tin garage on a 'warm saturday in June - Celsius on the left and farhenheit on the right for our USA friends).


    Sounds like I'd be wasting my time fitting this with such cold weather. I'm hoping for a daily driver that can handle the cold weather, and I'm trying to go straight gas. Have included a pic to show where I'm up to with the blow through setup.
     
  19. White ls400

    White ls400 New Member

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    If you stay dual all youd have to do is let the car completely warm up on fuel and switch over no probs, although this setup is not ideal for straight gas in my opinion, considering that the manual says do not ever start car on gas unless emergency
     
  20. marc280

    marc280 New Member

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    I've recently had a gas injection system installed in my daily driver falcon (I know not a lexus/toyota V8) and like White LS400 has said if you get some temp into the engine before switching over you don't have any problems.

    The system I have automatically starts the car on petrol and runs on it until the coolant reaches 40 degrees (celcius), which only takes about a minute. Once this point is reached the computer is set to automatically change over to LPG. It does all of this without having to press any buttons or anything and drives just as well as petrol. You can't even notice when the change occurs other than hearing the solenoid click on the tank.

    I've already started it a driven without any issues on a 2 degree morning, so I can't recommend it enough! I will be making a trip to the ski fields soon, so I guess this will be a good test.
     

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