lpg for taxi?

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micsey
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lpg for taxi?

#1 Post by micsey » Sat Jan 26, 2019 4:39 pm

thinking of lpg for my next taxi but a read a review online that for every 4 tanks of lpg used you used a tank of petrol
hope its wrong as it just wouldn't be worth it? tell me this is wrong guys

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Re: lpg for taxi?

#2 Post by LPGC » Sat Jan 26, 2019 5:32 pm

You didn't say what vehicle you'll be buying to use as a taxi..

Most vehicles / engines run port fuel injection, with these as soon as the engine gets above around 30degC (which takes only a minute or so on a cold morning) the system automatically switches from petrol to LPG and runs entirely on LPG for the rest of the journey (or until you run out of LPG). If you stop and turn the engine off for a while then restart the engine it won't take even a minute or so before it switches automatically to LPG because the engine will still be warm. If you park up for 10 mins with the engine off then restart it it will most likely immediately switch to LPG. So, with port injected engines you use much less than a tank of petrol per 4 tanks of LPG... Some people doing average mileages only use a tank of petrol a year. When we convert port injected engines we add a second set of injectors (there is already a set of petrol injectors which squirt petrol into the inlet manifold, it is easy to add a set of injectors right beside the petrol injectors to inject LPG. Being right beside the petrol injectors means the LPG injectors squirt fuel into the same place as petrol injectors.

Then there are direct injection engines where petrol is squirted through direct injectors directly into the engine's combustion cylinders instead of into the inlet manifold, on these engines the injectors are fitted into the cylinder head. It isn't possible to modify a cylinder head to fit a second set of direct injectors (for LPG) but it is possible to use the petrol direct injectors to squirt LPG instead of petrol (because direct injection systems run at much higher pressure than port injection systems, LPG at direct injection pressure is a liquid, direct injectors can squirt liquid LPG just as well as they squirt liquid petrol). There is a type of LPG system (for direct injection engines) that does exactly that but they are expensive, at the moment such systems are not without problems and only a few manufacturers are producing such systems.

There is another type of system for direct injection engines which works similarly to the port injection systems (described above) and uses LPG parts which are mostly the same as LPG port injection systems.. like an LPG system for a port injected engine a set of LPG injectors is added to the inlet manifold. The main problem with this type of setup is that the petrol direct injectors need to be cooled and lubricated by petrol (or LPG) flowing through them while the engine is running or the injectors are damaged. To get around that problem port injection LPG systems for direct injection engines always allow a little petrol to flow through the petrol direct injectors, so with these systems you do use some petrol whilst running mostly on LPG. Besides the fact that with this type of system you always use a bit of petrol there can be other downsides too which are due to the fact that fitting a port injection fuel system onto an engine that is designed for a direct injection fuel system isn't ideal, especially since the vehicle's original engine control computer still has to have overall control over the LPG fuel system (there are many reasons why the original vehicle ECU has to have overall control over how much LPG is injected).

LPG systems for direct injection engines are not generic - For LPG systems which use petrol direct injectors to inject (liquid) LPG a plumbing solution must be made to suit the exact model vehicle, for LPG systems which use a set of LPG vapour injectors specific electronics must be made to suit the model of vehicle. Depending on the model of vehicle, both types of LPG system, only one type or no type of LPG system at all may be available to suit the vehicle, there are some direct injection vehicles we can't convert with any parts currently available off a shelf.

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micsey
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Re: lpg for taxi?

#3 Post by micsey » Sat Jan 26, 2019 6:25 pm

thanks for the info i will be using a vauxhall astra 14 reg 1.6 vvt 16v how much are these to convert and is it a good choice

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Re: lpg for taxi?

#4 Post by LPGC » Sat Jan 26, 2019 6:47 pm

That car has port injection and is a good bet for LPG conversion. If you bought a 2015 model instead of the 2014 model it'd probably be direct injection.
I'd charge around £1150 to convert it. Doubtless you'd get lower and higher quotes than mine... but regardless of what you paid you'd be unlikely to get a better conversion, could very definitely get a lot worse a conversion though.
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micsey
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Re: lpg for taxi?

#5 Post by micsey » Sat Jan 26, 2019 7:13 pm

cheers simon this is something that scared me from honest john website

If the LPG Focus hadn’t needed any petrol, it would have won hands down. I had expected it to use maybe a couple of litres. But 17.74 litres over 598 miles spoiled the sums. And this is in line with Autogas’s own figures.

Which is why what had at first seemed to be a no brainer wasn’t.

But at least it showed Ford’s 1.6 EcoBoost 182 to be cheaper to run on Autogas than Ford’s 1.0 EcoBoost 125 is on petrol.

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Re: lpg for taxi?

#6 Post by Brian_H » Sat Jan 26, 2019 8:14 pm

Fords generally will suffer with VSR on gas (or at least did historically) though a lot of that can be reduced by using flashlube. On some setups they will use part petrol operation to try and achieve the same thing. I'm fairly sure thats what the autogas promotional van/car was doing from the little info in the write up (the one they loan out as a promotional demo vehicle).

I've tended to find (with older vehicles than your looking at) that your more concerned with the fuel going off in the tank more than having to top it up regularly - The most likely time i'd end up running on petrol was if the gas tank was empty, but for general use I'd stick some in around once a year usually and not find it dropping noticeably over time, most of my journeys are longer ones rather than short ones though so petrol usage probably only in the region of 1-2% of time it was running.

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Re: lpg for taxi?

#7 Post by micsey » Sun Jan 27, 2019 8:31 am

do you fit these Prins Direct Liqui Max

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Re: lpg for taxi?

#8 Post by LPGC » Tue Jan 29, 2019 4:14 pm

micsey wrote:
Sat Jan 26, 2019 7:13 pm
cheers simon this is something that scared me from honest john website

If the LPG Focus hadn’t needed any petrol, it would have won hands down. I had expected it to use maybe a couple of litres. But 17.74 litres over 598 miles spoiled the sums. And this is in line with Autogas’s own figures.

Which is why what had at first seemed to be a no brainer wasn’t.

But at least it showed Ford’s 1.6 EcoBoost 182 to be cheaper to run on Autogas than Ford’s 1.0 EcoBoost 125 is on petrol.
I expect those figures are from a port injection system on the direct injection (Ford Ecoboost) engine. Even so I'm surprised it used 17.74 litres (3.9 gallons) of petrol over 598 miles in addition to LPG usage - If the car does (say) 50mpg, that petrol usage (if only petrol was used) would be 153mpg, it means it's running on 1/3rd petrol which seems an overly excessive proportion. If those figures are true I would still expect the savings on LPG (on average, with average driving) to be higher than those figures would suggest because in average driving the car wouldn't achieve as many mpg and would expect the proportion of LPG usage versus petrol usage to increase when the driver puts his foot down a bit more. In other words the pence per mile might never be better than the results of the test but in the real world (where you might expect to do less mpg) a greater proportion of LPG would be used so the benefit of having the LPG conversion would be greater than in the results of that test.
micsey wrote:
Sun Jan 27, 2019 8:31 am
do you fit these Prins Direct Liqui Max
The Liqui Max system is a system which uses petrol DI injectors to inject liquid LPG so doesn't need any petrol to flow through DI injectors to keep them cool/lubed... So the potential savings are higher and this type of system should be less prone to drive-ability problems because it doesn't involve the 'fudge' associated with fitting a port injection fuel system onto a direct injection engine, the original vehicle engine electronics and engine itself were designed for direct injection and still run direct injection.
But there are some downsides - I don't fit Liqui Max, it's only available to Prins dealers... Prins is a bit of a closed shop and in my opinion the closed shop could do with some talent injection, most dealers not the most clued up installers and even VSI2 (port injection LPG system for port injected engines) seems to be proving a problem for a lot of them. It's expensive even if they've already done the R&D to implement the system on your model of vehicle but if they haven't done the R&D for Liquimax on your model of vehicle you might be asked to pay £thousands extra for the R&D on your car abroad (your car goes abroad for a few weeks, you pay a higher price for your conversion than the next customer with same model vehicle). There are some issues (on some vehicles) with cold starting - The fuel rail contains the same fuel when you start it that it contained when you turned the engine off, so will contain LPG if you turned the engine off when the engine was running on LPG, this has been known to cause starting problems on some vehicles.
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Re: lpg for taxi?

#9 Post by Gilbertd » Tue Jan 29, 2019 6:21 pm

If you are contemplating a standard port injection engine rather than a direct injection, you'll only use petrol on a cold start. It'll run on petrol until it reaches change over temperature (usually within a mile) and then run on gas after that. Some systems will restart on gas on a hot start, others will start on petrol but change over within a few seconds. With my experience of taxis, once the engine is running it doesn't get turned off until the end of a shift so you'd use no petrol at all other than the initial warm up.
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Re: lpg for taxi?

#10 Post by LPGC » Tue Jan 29, 2019 7:14 pm

Agreed with Gilbert and Bri.

I also meant to write that there seems to be a lot of misinformation regards LPG on sites such as HonestJohn. Wouldn't surprise me at all if the HonestJohn info you referred to was about port injected vehicles and totally incorrect. As said by a few of us on this thread, with a port injected engine you'd expect to use very little petrol at all, I've converted lots of taxis over the years, the owners saved lots of money over running a similar sized diesel.
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