Dedicated LPG - Vapor and Injection System

[Radar]

There is a new LPG system about "JTG"
The JTG system is a liquid gas injection setup, it's designed for direct port injection.
It injects like it says liquid petroleum gas, straight into the combustion chamber, where it atomizes, expanding 270x all the while acting like a intercooler per cylinder.
The injectors them selves cost around $600 ea, they are custom built to suit the type of motor and induction system you are running.
They also don't handle fuel pressure curve (What I was told)
(Custom built = expensive to replace if it gets broken or if it's the wrong size.)
The main downside to this system is it requires petrol to start the motor and get it warm before it will flick to LPG.
Therefore it still needs dual fuel.

Vapor injection has been around for a few years now, It works well its reliable and it works 10x better than the mixer and feed ring.
It works roughly like the liquid gas injection but instead of injecting liquid, it pre-atomizes the LPG and injects the vapor into the intake runner just before the port.
This system though also requires petrol, just not to start, It requires it under load.
To be exact its 49hp/cyl flywheel and over.
So basically while you are just soft footing it around it, you are just using the vapor LPG but when you hit the gas it instantly changes to petrol without a slight drop in the power.
The system can be run as dedicated LPG but, you cant exceed that power limit!

So my question to people who understand this better than I do:
Can I run vapor injection to start the car, then use the liquid gas injection once the motor is warm and only use the vapor injection to help with the fuel pressure curve?

I'm guessing you would need separate LPG tanks, per system to avoid fuel pressure drop off. The JTG tanks are fitted with an internal 3PSI (could be BAR can't remember) fuel pump.

Cheeers for any info guys.

[amichie]

Are you wanting performance out of an NA LPG engine? You could just use a mixer setup and go turbo. Seems to work well and is not expensive.

BTW my NA dual fuel starts pretty well on gas.

[-=DV=-]

radar i was unaware of the power limit using lpg injection. my uncle owns gaspower australia and they prettymuch pioneered the gas injection here in australia...he has had success with a few turbocharged applications..im not sure if it was purely on lpg or switching back to fuel under heavy load tho....as for liquid injection...ill have to have a chat to him about it

[timbosaurus]

Basically, three types of LPG systems:

Mixer - Old school, simple, can run in dedicated mode, but needs to be tuned well and will still suffer at high low/low coolant temps when the vapouriser freezes.

Vapour injection - pretty much the standard at the moment. Improves the efficiency and driveability of the car (a fair bit actually!) just like injectors did with petrol, and can still be run in dedicated mode. Still suffers on cold mornings/highl oad like a mixer system (the main problem is the vapouriser... which is the same in both systems), but because of the slightly less amount of fuel used and better tuning opportunity of injectors, it tends to be slightly better.

Liquid injection gains the benefit of charge air-cooling, but it is showing to not provide the gains people expected. It's still the ultimate system, but with the high cost at the moment, probably not worthwhile.

JTG make (or sell) the computers to intercept your factory injector signal and use that to drive the injectors. Hopefully, one day, someone wakes up to themselves and lets the backyarder get his/her hands on injectors at a reasonable price, because any aftermarket ECU can be setup to run LPG without anything more exotic than LPG injectors. Even closed loop O2 control can be performed to keep the mixtures spot-on.

FWIW, if running in LPG-only mode, any of these systems should also be fitted with a pump to get maximum range out of a tank. Otherwise, on cold days with a bad LPG mix (common), you might run out of pressure in the tank when you think it's still 1/4 full. Usualy cars run dual fuel to avoid this.... that way you're never going to be stranded from a frozen vapouriser, your not going to unexpectedly run out of fuel on your way to the snow (try getting RACQ to bring you a jerry can of LPG ).

[Radar]

amichie - Nah mate not NA... Twin screw supercharged.
As for the ring feed, simply not going there...

Timbo - I thought the JTG tanks were fitted with a pump?
I had a thought that it would properly require one tank per injection system.. One for vapor, One for Liquid.
That's if you ran both systems as one system, so you avoided any pressure drop off to the injectors.
Solves the problems of a frozen set of injectors, or running out of LPG in one of the tanks.

So my question is, to start the car could I tune an ECU to use the vapor then tell it once its warm to switch to liquid injectors?

[timbosaurus]

Running two LPG systems in parallel would be so many levels of bad, from complexity, cost, space... and still does not solve any of the problems. Both vapour and liquid have issues at cold temps. if you're freezing your liquid injectors, there is a good change you may also freeze your vapouriser.

If you are going run two systems, dual fuel with petrol is a better option... as most cars are already set up for petrol, it will work even at cold temps, and also helps if for some reason you can't find an LPG servo or you run out of fuel on the side of the road.

[amichie]

What engine are we talking about? If you search the net you can find lots of high power turbo LPG falcons etc running an IMPCO carb. An Impco 425 will flow 460cfm with only 1.5" Hg pressure drop.

For simplicity and ease of fitting you can't beat it.

You can still run closed loop feedback mode using your O2 sensor and regulating the feedback to the vapouriser.

[Radar]

Timbo - Agreed with the costly and space wasting. It looks more and more like dedicated liquid gas injection is still a couple of years off being affordable. Petrol is a no go, its a purpose built car, has to be dedicated LPG. So vapor it is.
The issue isn't the liquid injectors freezing but just the car not being able to start from them.

Amichie - The motor is a rebuilt 2TC, so I'm not really in it for the simplicity. Like you said yourself there are already plenty of high HP LPG ring fed turbo's running around. Appreciate the suggestion though, if I used a carby it would be the way to go, but it's just not the path I want to take.

[amichie]

OK. No worries.

[timbosaurus]

Car's can definately start from Liquid injectors... don't worry about that! There are problems with liquid... but that's not one.

Yes, the most practical dedicated solution at the moment is vapour injection. It's very system dependant as to how often you get stranded due to a frozen vap or too-low tank pressure (low coolant temp and high load is bad for vapouriser... low ambient temp and inconsistant propane/butane fuel mix is bad for tank pressure).

Then you have to consider what you do yourself... as it makes sense to have a shop do the work given the rebate.

Personally, I'd probably have a shop fit a tank, lines, vapouriser, mixer and get it all up and running. Shops should do most of that for not much more than the rebate.

Then rip out and sell the mixer and fit an injection system controlled by an aftermarket ECU and bob is your uncle.

[Radar]

Cheeers for that timbo, Only ONLY reason why im saying that they cant start the car is because I was given a quote of $5000 for the JTG system installed, but the installer told me the liquid gas injectors will not start the car :S ?? (why i still needed petrol injectors)
The vap system installed is only $2000 but limits to 180hp, but it will start the car and run dedicated.

Ideally id love to not have to the vap system at all and just use the liquid injection.

[Radar]

Email I received from the installer:

* Petrol injector PROFILE is paramount on the JTG system and to match it takes the manufacturer considerable R&D cost that may be unviable on a single vehicle installation so they generally refuse support and will not sell the system other than an engineered ready to go kit for each specific model car. This is why they do not support as much as the vapour systems.
* Liquid LPG injection is very good in the sense of efficiency and power output when compared with others. (It can run full power on most cars without switching petrol on)
* Liquid CANNOT be programmed so fuel curve is not able to be mapped. (Relies on exact matching of injectors)
* Liquid system should be exceptionally reliable.
* Liquid system spare parts will be comparitively costly.
* Vapour injection is approx $2k cheaper and functions very well.
* Vapour systems are reliable and spare parts are comparitively cost effective.
* For conditions where power may exceed the stated 37kw / cylinder flywheel power, the system can be programmed to either add petrol during conditions where the load AND rpm combined conditions require or go directly to petrol. It will sequentially change over each cylinder at at time during such conditions and is seamless in operation. It then drops back to lpg in the same manner when one or both of the load OR rpm conditions falls below programmed levels.
* Fuel curve can be completely mapped for best power and economy.
* Both Liquid and Vapour systems are designed to operate as a DUAL FUEL system.
* Vapour could be set up to run GAS ONLY but would require purchase and full mapping of an after market computer system such as Vipec which was engineered to use injector drivers capable of running gas injectors. This may or may not run the Liquid systems but fitment and full mapping expenses would be expended before results of pass / fail would be known. (Entirely at client's expense regardless of results)

[wagonist]

Where is this limit of 37kW/cyl coming from?
First I've heard of such a thing.

There's someone running LPG on a Caldina here in Aus on LPG injection, it certainly doesn't have only 148kW.

If it's an injector size problem, then that could be solved by running multiple injectors/cycle, or having auxiliary ones kicking in.
Reminds me of aftermarket turbo/supercharger installs of the late 80s/early 90s where extra piggyback injectors would kick in after certain boost thresholds were reached.

[timbosaurus]

yes, they all sound like limitations with the system he sells... not necesarily the system in general.

LPG setup is damn simple, but installers tend to try to keep it all mysterious. Wonder why

[Radar]

Hahaha good call.
So you think this liquid injection can be run dedicated with a properly programmed ecu?
What do I have to look at when figuring out an injector size? Flow rate, Duty Cycle?