So i had a direct injection LPG conversion done about 6 months ago which has been great besides a leaking gas tank which was fixed straight away so no problems there,however in the last 5-6 weeks i've noticed on cold start (petrol) it's running really rough and sounds like it's missing in park then when i put it in drive the revs drop and the car shudders,when i accelerate it hesitates and sounds like a wrx,it then switches over to lpg and run's perfect.

About a month ago i put in $20 of bp ultimate and the problem almost went away but it's now worse than ever

Any ideas guys?

take it to an LPG specialist?

As a side question - why did you keep petrol aswell as lpg?

This is one reason why I wouldnt - straight lpg hardly hear of problems.

Dual fuel you do though.

do you run it on LPG all the time?
or sorta use both?
might be clogged fuel injectors

i've sent the installer an email but havn't heard back from him

the guy told me dual fuel was the way to go,something to do with cold start and the ability switch back to petrol for added power when needed.

edit:roberto,yer i run lpg most of the time but usually about once a fortnight i switch it over to petrol and give it a few hits to help keep petrol side of things running but might not of been enough by the looks of it.

Sounds like a dodgy fuel injector to me. If it misses you should be able to find the dodgy cylinder quite easily if it one of the front ones.

Regards

I had the same problem, Sounds like too much gas at idle, and the ECU lowers the fuel flow, so when you Idle with petrol the ECU keeps the injector flow at a minumum. = lower idle.
You can either get it tuned properly properly, a hard task so I've found, or idle on petrol a bit more at the expense of a higher Gas idle.

As for the lumpiness, a goods quality injector cleaner in bottle sorted this for me.

thats for the TW, but my 380 has been perfect!

BTW, your profile says you have a Direct gas injection system, but the price you paid suggests a sequential vapour injection system.

One is Direct gas liquid injection into the chamber usually spraying on to the valve to assist in cooling, the latter is vapour injection released into the lower intake manifold.

Can I ask which system you have.

i've just got the vapour injection one,i did try and get the liquid injection system but they hadn't developed a kit for the magna's so just went the vapour injection.

the problem has seem to improved but i'll chuck a bottle of injector cleaner in with some more BP98 and see if that helps get rid of the problem.

yeah you should run petrol for a full day AT LEAST once a month, otherwise the petrol in your tank gets stale if not used. The supplier would of told you that anyway.

When I go to fill up LPG I always sneak in 5L of 98 octane petrol in aswell. Keeps it fresh and every now and then i will fill the tank full and wait till it hits half tank till i switch back to gas.

i've sent the installer an email but havn't heard back from him

the guy told me dual fuel was the way to go,something to do with cold start and the ability switch back to petrol for added power when needed.



I dont want to be an anus here but going dedicated lpg could have meant a much better lpg tune and thus no loss of power and economy on gas, all the benefits still and the cold starting on petrol thing is kinda no-pointer. Im glad you went something other then a venturi setup, im planning on at least vaopour injection later this year, hopefully lpg injection is on the market.

Lionel

On the LPG topic, does the Govt still give a rebate on new installations?

May look into using my K.Rudd money for something useful...

What sort of costs would I be looking at to go dedicated LPG with the tune etc?

$2500 - $2650

http://www.lpgconversioncentre.com.au/government.html

As far as I know, the only dedicated system is the mixer style LPG system ex factory $2,500-3,000, and there ain't no tune as far as the car goes(see SKR), and not much in the way fiddling with the Gas system.
A goverment rebate of 2k applies maybe more from your state gov. see W.A.

The most powerful ATM is a Sequential gas system.$4,000 - 4,500. Which there is more tweaking in the Gas system, I think (hope) Steve Knight Racing can flash the ECU to get the most out of this style of system.

There may well be a Direct injection system on the way, but as usual, we'll have to wait til all the Falcodores are sorted out first. $5,000 +

Thanks for the info...

If I get the tank in the boot, where should I locate my amp? I remember reading one day about not being allowed to have the amp in the boot?

sounds like you got yours fitted at the same time as me... did you get yours pit passed at welshpool.... inspector was raving on about a leaking toroidal tank like mine when i went thru.

the VSi systems shouldnt interfere with the original ecu but they do cut into the injector lines and simulate the injectors for the ecu whilst delivering the gas based on the injection pulse

dual fuel is better in the fact that a) you get extended range/ b) it resolves the starting on gas in the cold/ and c) it resolves the rapid heating of the head when cold and running on gas which can crack the head

the vsi system doesnt use petrol when on gas unless it is programmed to do so and only if needed
VSi only loses 3% power so a stock exec 3.5 = 155kw vs 150kw on gas
it also doesnt require physical adjustment of the timing

and if there is and ignition problem then it would show up on gas before petrol due to its being a drier fuel

perhaps the joins in the injector circuit are no good, or you have a blocked injector/fuel filter or poor fuel pressure

my magna (romano VSi) runs slightly rough on lpg but i know that it is the cap leads and rotor that need attention
and when i fix them ive got to get it retuned

ers: the fuel tank needs fuel all the time because the pump is always running... helps to keep everything lubed

ers: the fuel tank needs fuel all the time because the pump is always running... helps to keep everything lubed

Makes little sense to me.

Well, your post more so than anything.

My question was about why people go dual fuel, rather than straight gas. (Which you answered above....this post im quoting makes SFA sense, my apologies)

I have lpg installed in mine with the dual fuel setup, I believe there are a number of reasons for having both... The motor starts on petrol and switches to gas to assist starting. It allows you to switch over to petrol and run premium to clean the injectors. It gives you a dual fuel tank as a backup. Its also really good to know that you dont have to rely on being able to find a station that stocks lpg.

sounds like you got yours fitted at the same time as me... did you get yours pit passed at welshpool.... inspector was raving on about a leaking toroidal tank like mine when i went thru.

the VSi systems shouldnt interfere with the original ecu but they do cut into the injector lines and simulate the injectors for the ecu whilst delivering the gas based on the injection pulse

dual fuel is better in the fact that a) you get extended range/ b) it resolves the starting on gas in the cold/ and c) it resolves the rapid heating of the head when cold and running on gas which can crack the head

the vsi system doesnt use petrol when on gas unless it is programmed to do so and only if needed
VSi only loses 3% power so a stock exec 3.5 = 155kw vs 150kw on gas
it also doesnt require physical adjustment of the timing

and if there is and ignition problem then it would show up on gas before petrol due to its being a drier fuel

perhaps the joins in the injector circuit are no good, or you have a blocked injector/fuel filter or poor fuel pressure

my magna (romano VSi) runs slightly rough on lpg but i know that it is the cap leads and rotor that need attention
and when i fix them ive got to get it retuned
Also with the vsi system the coolant temp gets up to about 40 degress c before it changes over from petrol to gas
This can be programed into the lpg computer by the lpg installer but about 4o degrees is the norm.

Ash! cracked cyclinder head on gas when cold?

I have lpg installed in mine with the dual fuel setup, I believe there are a number of reasons for having both... The motor starts on petrol and switches to gas to assist starting. It allows you to switch over to petrol and run premium to clean the injectors. It gives you a dual fuel tank as a backup. Its also really good to know that you dont have to rely on being able to find a station that stocks lpg.

a dual setup with a venturi style lpg system is a given. THe venturi setup is like retrofitting carbies to your EFI car. well almost

I have driven from rockhampton to melbourne, via the coast route and the inland route and every servo had LPG. 2600km trip each way.

If you go dedicated, then who cares about cleaning injectors? Ofcourse all the petrol hardware is best to be kept wet with petrol, but if you dont use it at all, via a dedicated gas setup, who will loose sleep? Ive driven a couple of those new factory gassed falcons, and driven several non-gassed and ultimately the only difference i noticed was at the pump. Granted a sequential injection system is a lot newer technology than a mixer, i was really impressed

Yeah, Im not talking about the new falcons, those things are optimized to be run on gas, unlike my 14 year old TS which I dont think was ever considered by the manufacturers to have gas running through it one day.

The mixer system on my TL exhibits the same rough running on petrol after running on LPG for a while. Makes sense that the car leans out the mixtures to compensate....I haven't got it checked for a while and it runs too well on LPG to worry about at this stage

i have the mixer too for about 8 months now every week i fill up i run petrol for about 20km it runs good on both get some good plugs to run makes the diffrence as to dedicated well here on the gold coast somtimes there will be a shortage and have none for three to four days always happens in summer all the bbq i recken

sumpoiler: according to people in the LPG industry running a engine with a head not designed specifically to take LPG can cause it to crack from the rapid heating due to the higher cylinder temps.... or so ive been told by multiple sources.

on the Romano systems it is programmable to change over at 20 or 30 degrees with 30 the recommended for LPG and 20 for CNG this is also so that the evaporator can get warm enough so it doesnt ice up.

Ers: does it really matter if the fuel pump is running? will it end the world as we know it? the average life expectancy of a fuel pump is 300000km and thats with the hydraulic hammer effect of the injectors opening and closing.

another good reason to have the pump running all the time is so that when the gas runs too low the system changes over to petrol and that could be under accelleration when overtaking.... i think i'd want fuel pressure at the injectors when that happened...

besides it's not a hard thing to change a fuel pump... on most cars
i can do a gen 3 magna pump and sender change in about 20 minutes without breaking a sweat :ninja:

I have never seen a fuel pump do 300,000km yet!.
You might get 300,000km out of a pump with regular filter changes.
Never heard of a cyclinder head being cracked on lpg? (FROM LPG RUNNING HOTTER)
The only thing different to a lpg head & non lpg head is the valve inserts in the exhaust.

Have duel fuel on the KJ AWD being the SVI Unit. The only way to go.

As the-ash said, a svi system has its own ECU and doesn't in any way effect the running of petrol. When on petrol, it uses the full factory ecu and its settings. The gas ECU doesn't in any way change/effect the factory ECU.
I have had it for 8 months now and no problems. I wouldn't even know if it was running on petrol or gas because it runs that well on gas. Can't even feel any power loss at all.
It runs for about 5-8 mins on petrol every morning until it reaches 40 deg i think it is, so it gets plenty of fuel through it to keep everything lubed.
Highly recomend the Head lube system(valve saver). Some people say you dont need it with SVI and some do. Worth having for peace of mind if nothing else.

In regards to non factory fitted lpg, i had my for over 100,000ks now, mixer setup, engine has done 240,000 all up (all mine) on my TJ. I rarely drive on petrol (only when i race someone). Only service my car every 15,000 (with $80 oil though). Guess what no cracks in engine, valves did not recess, i get around 450 on average from 70 litres lpg.
Few facts about lpg on non lpg designed engines.

The main one, valve seat recession, now this happens in petrol engines aswell, IN OLDER engines which used leaded fuel this was quite an issue. Since lpg is a clean fuel with no additives it does not lubricate valves as petrol does. NOW, leaded petrol is gone forever, todays high octane pertol PRACTICALLY has no additives, especially who drives on 98 ron. ALSO all today we have multi valve engines, hence decreasing stress on each valve, valves are also stronger. Yes you can get those flush lube kits, like i have said ive done high KS already without any problems, so i thinks its a waste of money.

Next one HIGH TEMPERATURE, now LPG has less calorofic value then petrol, so it physically can not burn hotter then fuel BUT fuel being liquid serves as a coolant when injected into the cylinder for combustion hence engine indeed runs cooler. New liquid LPG injection kits overcome this limitation of LPG, thus reducing strain on exhaust valves. Again we are talking about modern multi valve engines.

I had the same problem with car missing on petrol, had my fuel filter changed, throttle body cleaned and i was told the car was runing waaaaaaay to lean on petrol so needed tuning, all up $70 fixed the problem.

i get around 450 on average from 70 litres lpg.

I must be doing ok then. I get just over 600 combined with my system!

Dave those are impressive figures.

Good stuff.

gee,im only getting 350-360 ks from 65 litres....

gee,im only getting 350-360 ks from 65 litres....
I get 600 from that amount... Driving elderly style and changing up at 1800 rpm. So as i do 600 ish a fortnight it costs about $30. Whereas petrol was costing me $120 ish. And the power loss is minimal with my system so it is very drivable and you can give it a squirt at the lights and not be embarrassed! :happy:

gee,im only getting 350-360 ks from 65 litres....

On an SVI system?

That's waayyy too much. I get over 500kms from 65l in my AWD!!

last 3 weeks
291km averaging 40km/h using 40.5L = 13.92L/100
304km averaging 43km/h using 40.49L = 13.32L/100

ive only got a 50lt usable toroidal tank... price to pay for a boot (but it is still quite convenient)

On an SVI system?

That's waayyy too much. I get over 500kms from 65l in my AWD!!


nah....this is on the 'old' mixer system-lovato i think it is...