Liquid Injection

[IanFearn]

Apologies if this is being discussed elsewhere but does anybody have any experience of the Vialle liquid injection system?

[Brian_H]

Simon has posted a bit about it at this thread here > viewtopic.php?f=33&t=14194&p=114256&hil ... le#p114256

Theres some other threads on the subject, but nothing really recent about it. As said in the linked thread, I was under the impression Vialle went bust but that may not be correct.

[IanFearn]

Thank you for the info.

Vialle do have a current website that certainly looks like they are still operating but the info from Simon on the link you provided suggests the negatives probably outweigh the positives.

Thanks again.

[Brian_H]

To some degree, it would depend on the vehicle - it might be a more suitable option for a direct injection engine, but probabbly not worthwhile for a port injected one. DI options are somewhat scarce and tend to be a very limited choice anyway.

[LPGC]

Liquid injection options for some direct injection engines include using the petrol direct injectors to inject liquid LPG at very high pressure instead of liquid petrol at very high pressure... But this is a different technology/methodology to port injection liquid gas injection systems.

The idea of liquid port gas injection for port injected engines isn't a bad one but in practice the available systems were never great and even if they were good wouldn't really have much in the way of advantage over an LPG port vapour injection system... while port vapour injection systems are well sussed and can have just about all the same functionality of a petrol port injection system.

Liquid direct injection may be the best way to convert a direct injected engine, it is the only way of keeping the direct injection aspect so is the only way of keeping all the same types of fuel system functionality. This type of system involves stopping flow of petrol to existing (on the vehicle) DI petrol injectors and supplying them with high pressure LPG instead, so the direct injection methodology is maintained. But it isn't simple as just shutting off flow to petrol injectors and supplying them with gas instead, and there are technical problems with this type of system - for starters when you switch fuels (between petrol/LPG LPG/petrol) you don't want any gas to be able to return to the petrol tank... and there have been cold/hot start problems.

The only other way of converting a DI engine to LPG is to feed the LPG into the inlet manifold (because we can't just make our own hole through a cylinder head to the cylinder), so isn't direct injection, so isn't the same methodology and cannot do all the same things with fuelling as direct injection... regardless of whether the LPG is introduced to the inlet manifold in liquid form (port LPG liquid injection) or vapour form (port LPG vapour injection, or gas carb, or mixer system).

Most systems available to convert DI engines are port LPG vapour injection systems (which work very similarly to the familiar gas injection systems we fit on most port injected engines) but use a different ECU which can read the DI injector pulses and convert the total pulse length to a suitable pulse length (to deliver correct fuelling) for gas vapour injectors, and emulate the DI injectors electrically (so the petrol ECU doesn't see disconnected DI injectors) - Port injection, so when running on LPG you may lose advantages of the direct injection fuel system that the engine designers intended (or why did they design the engine to have DI in the first place..). The installer of a port injection LPG system for a DI engine is at the mercy of the LPG system designer, the part of the system that equates DI pulses to a single pulse length for port LPG injectors is seldom adjustable, the amount of petrol that is still injected through DI injectors (to keep them cool/lubricated and prevent damage) is seldom adjustable, it may not be practical for the installer to deviate from the type of injectors or working pressure that the LPG system designers had in mind (different latency of injectors etc may not work well).

[IanFearn]

Thank you for the detailed reply.

I was interested specifically in converting my Fiat Panda 1.2. I was led to believe there was zero power loss with a liquid kit. My previous LPG car was a V8 with abundant power but I can’t help but think a 1.2 Fire engine will struggle on gas.

[Brian_H]

The 1.2 engine does appear to be the one that Fiat chose to give the LPG conversion option to over any of the others, a properly specified and setup lpg conversion shouldn't give a noticable lack of power over using petrol on the same engine. What can be an issue with smaller cars, is having enough space for the tank though.

[IanFearn]

Yes, Fiat did sell a 1.2 called the Easy Power. It had a 31 litre tank in place of the spare wheel.The car is great to drive but I am a little concerned even a small power loss would make a big difference to driveability. I had also read Liquid Injection allowed you to start on gas.

42968EC2-BEBA-4386-A51E-C206C6F40C16.jpeg (475.23 KiB) Viewed 3283 times

BA0AC453-BA0C-499F-96CF-705DE090615C.jpeg (318.06 KiB) Viewed 3283 times

They also did a CNG version called Natural Power but that sat on 4x4 type suspension with the tanks under the passenger compartment. It was also only available as a 1.4.

[LPGC]

It would be easier to have a liquid injection LPG setup start on gas than a vapour injection system but this isn't to say that the liquid system's ECU will necessarily allow it.

Don't know if this Fiat factory fitted liquid injection setup will start on gas (unless you know?). Factory fitted vehicles using similar liquid injection systems such as Subaru Tribeca's usually start on petrol and switch to gas when the engine has warmed a little, same as vapour injection systems do.

The factory CNG setup must use vapour injection (and therefore use a totally different setup to the Fiat's factory liquid LPG injection setup) because as I'm sure you're aware CNG is vapour even inside the tank.

[Brian_H]

Don't think the one illustrated above is liquid though - if it was, it wouldn't have the gaseous filter shown would it? (not sure they have a regulator either, nor the injector setup in the same manner as shown?).

Point being was that if they supplied them from the dealer with LPG, they must have thought the performance acceptable?

Might help to know what year the Fiat actually is as well. You'd probabbly get a slightly bigger tank than the 33 litre one they show, as most torroidal ones now have the middle filled in as part of the tank capacity, though depends where you need the valve to be if thats possible.

[LPGC]

Good point Bri, I did see the gaseous filter but put it down to a language interpretation problem and assumed it meant a liquid filter... But since reading your post looking again the pressure regulator pic looks like a vaporiser rather than a liquid pressure reg.

Some of the 'fire' engines are 'multi-air' which means they have similar features to BMW's Valvetronic system, such engines run better on LPG if the LPG system's ECU is capable of properly addressing this aspect.

[IanFearn]

Sorry I didn’t make a lot of my info clear. This is the 169 Panda, made between ~2003 and 2012.

The illustrations above are for Fiats own ‘Easy Power’ factory fitted LPG system. As far as I know, it was not sold in the UK despite the English language format. I have been interested in Pandas since before 2003 and never recall any factory UK LPG models. I showed the pictures in reference to Brian’s comment about small cars and tank sizes.

I think 31 litres would be acceptable in something that does 50mpg on petrol but if you could squeeze another few litres into the centre of a toroidal tank, even better.

It is as you suggest a normal vapour system, Fiat did not sell a liquid system. Only the Gaseous LPG Easy Power model and CNG system called Natural Power which was totally different.

So in reference to Brian’s comment, Fiat must indeed have considered the performance to be acceptable.

Thanks for all your comments. Then general technology side of things really interests me. I think perhaps I had been a little too inclined to believe the hype on the Vialle website.