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      11-15-2011, 04:47 AM   #1
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LPG for 335i in 2012

Hi

Just been informed that prins are developing an direct injection system for the 335i ready for qtr 1 next year.

Very temping to pay 70p ltr rather than 1.35p ltr.

Thought some of you would appreciate this development. However there many true petrol heads and shoot me at dawn just thinking of this lol
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      11-15-2011, 04:50 AM   #2
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Eh? Are you sure that isn't the hybrid which is under development?
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      11-15-2011, 05:49 AM   #3
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Quote:
Originally Posted by kaishang View Post
Eh? Are you sure that isn't the hybrid which is under development?
I asked the question, and been told its not a true hybrid system, both gas and petrol at the same time. But it will auto switch from gas to petrol with heavy load. However at high speeds it should be gas.

I post more info when I know more.
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      11-15-2011, 07:05 AM   #4
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Quote:
Originally Posted by BIGBOYQ View Post
Quote:
Originally Posted by kaishang View Post
Eh? Are you sure that isn't the hybrid which is under development?
I asked the question, and been told its not a true hybrid system, both gas and petrol at the same time. But it will auto switch from gas to petrol with heavy load. However at high speeds it should be gas.

I post more info when I know more.
Sorry but just been given more information. This system is prims "direct liquinax" so it users liquid gas not vapour. So it starts from gas also apparently gives more POWER!

http://www.prinsautogas.com/en/products/directliquimax_system/directliquimax_system.html

It users the cars injectors so I don't know how this will affect the hpfp.
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      01-03-2012, 09:36 AM   #5
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I'm getting quite excited by this. A few reasons are:

Prins sell a product called valve care which lubricates the valve seats and reduces carbon buildup.

They replace the fuel pump - hopefully negating HPFP issues

I'd save £1800 per year in fuel! based on current prices and my 20k a year mileage.

no loss of power while on LPG - claims of 10% gains infact.

£10 cheaper tax per year!


Of concern however:

My car is modded (JB4, DPs, FMIC etc) and about 420bhp, would JB4 work well with LPG or would I need a bespoke remap?

No idea of cost yet but I'd expect north of £2k.. Maybe a group buy??

How do insurance companies view LPG?

No spare wheel - hence where will the tank fit? What range will a tank give?


Anyone else interested or have the answers?
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      01-03-2012, 10:10 AM   #6
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LPG is commonly used in taxis in Australia. It's not popular with private vehicles.

The tank goes in the boot, so you lose a lot of boot space.

The "more power" is BS. LPG develops less power, except for some OEM systems which are the same power as petrol.

It can smell funny.

It uses more fuel, which partially negates the lower cost of the fuel. It is still cheaper if you do a lot of miles, which is why it is used in taxis.

Also LPG vehicles are not permitted on the Eurotunnel. The idea of installing it into a BMW seems horrific to me.
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      01-03-2012, 10:26 AM   #7
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I think your experience is based on vaporiser systems, the systems being developed inject directly as a liquid.

copied from another forum:

1. Power—The LPG-Liquid-Inject System shows an increase, typically 10%, over that obtainable from the same engine using petrol as a fuel. The balance in favour of LPG can be increased by increasing the compression ratio (say 13:1 maximum), or adding boost pressure (turbocharger / supercharger) to optimise the higher octane rating (RON) of LPG. Vaporiser systems are normally 15% down on power versus petrol.

2. Torque—Figures are some 10% above the equivalent using petrol, particularly in the important low revolutions range, largely due to the volumetric effect of the phase change from liquid to gaseous (ratio 1: 243) LPG as the liquid is squirted onto the inlet valve. This very important physical principle is denied to the gaseous systems. Acts as an intercooler for turbo systems, now becoming common, or superchargers. Gas systems displace a large volume of incoming air and rarely mix well.

3. Fuel Economy—Liquid Injection is far superior to vaporiser or gas injection systems. The liquid injection kit is from 5% to 20% better. Distance travelled on LPG per litre of fuel, can equal petrol systems. A thermal efficiency figure of 40.23% has been achieved, equalling petrol. The multi-point injection system, injecting liquid LPG gives excellent fuel distribution. Again, the volumetric effect assists. The problem of moving the vapour mass (gas systems) is almost eliminated by liquid injection, as in multi-point petrol injection.

4. Variations in LPG composition—These do not worry Liquid Injection as LPG vapour pressure and temperature are read to give fuel composition. The injector pulse is altered to give the required energy input. Vapour systems cannot do this and suffer the consequences of variation.

5. Driveability of the Liquid Injection system is an excellent feature. Embarrassing backfires as on gaseous systems are eliminated. The risk of engine damage caused by premature explosion as in blowing off the engine air box is eliminated. Multi-point, liquid LPG injection sharply reduces accelerator lag. Spark timing can be adjusted to give optimum performance with Liquid Injection.

6. No petrol needed—Liquid Injection is almost the only LPG fuel system which can run permanently as a mono LPG system. Does not need to start or stop on petrol, or need petrol to offset higher combustion temperatures. The petrol tank can be removed and the space utilized.


If you think adding LPG to a BMW is a travesty, check out this v8 M3!!
http://www.oxfordautogas.com/bmw/bmw-m3
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      01-03-2012, 10:35 AM   #8
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My uncle runs an LPG conversion garage and we have 3 LPG converted cars in our family. As Kaishang says, the myth of extra power is untrue and you will see a decrease in your MPG (obvious savings due to cheaper fuel in the first place). But I have seen LPG make cars unreliable and to such an extent that my brother removed the system on his Cupra R. I'm sure he said he only got 50 miles to £10 of LPG compared to 40 with £10 of petrol.

I wouldn't use it on my 335i for the simple fact that the n54 has enough issues as it is already without bringing more parts that could potentially fail into the equation. TBH to me, modded engines and saving money on fuel doesn't go hand in hand.

From what I read and was told, the direct injection LPG system uses the original injectors with a modified fuel pump. The n54 injectors are bad enough on petrol, and using them to inject LPG which doesn't contain a lubricant might cause issues. The valve care product that I have seen used is called flashlube and you can buy a system without having LPG if that interests you:

http://www.flashlube.com/component/c...article/8.html

I don't know if it works in direct injection engines.
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      01-03-2012, 12:44 PM   #9
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I had an LPG powered Vectra in 2004. LPG cost 39p a litre then.

Thieving bastards!
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      01-03-2012, 12:50 PM   #10
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Personally I hate it when I see LPG converted powerful cars. Seems a little "tight".

So what are "prins"..?
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      01-05-2012, 05:28 AM   #11
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I could be interested in LPG - for people like me that dislike the characteristics of diesel engines, want something fairly quick, but do plenty of miles (30k+) it could make sense.

I, too, would worry about an LPG conversion on something as complex as the N53 or N54 engines. I have often considered a slightly older AMG V8 Merc with LPG but the other running costs besides fuel are likely to be horrific.

However, I get 34mpg average out of mine anyway (34.4 over the last 3 months), a Merc V8 on LPG in the low 20's would be too similar a cost per mile to make it worth the potential extra hassle.

I'll keep my eye on LPG but I think I would only buy a car that was already converted and had a history of running perfectly.
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      01-10-2012, 05:40 PM   #12
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On the JB4 front the LPG question was posed to us a while back. Basically you on your own as there's no testing been done with a JB4 LPG converted car.
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      01-10-2012, 07:53 PM   #13
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I'd love to do this but I use the Eurotunnel too much

Carlos why is it 'tight'? If there is a way to save money on running costs then why not?
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      01-11-2012, 08:21 AM   #14
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Just a bit nerdy "ooooow look at me LPG"

Just buy something economical in the first place.

I personally think it looks cack with that extra little fuel filler.
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