Double banger
Performance of complete lpg conversion
i'm a first year apprentice, and used to own a clubby, but sold it due to apprentice wages. however, i am determined to own another v8, a vx r8 would be nice. im saving like all hell, but i reckon by the time i can afford one petrol is going to be much higher through the roof than it already is. i'm wondering what kind of performance can be achieved by completely converting a car to run on only gas, and having it properly tuned to run that way. can performance be kept the same or better, or does it suffer? any help or links or anything would be great, because im going to thoroughly research the subject. cheers
we like the bun
if you replace injection with one of those god-awful carby type mixers, performance will suck. the modern LPG injection systems are good though, no real loss of power usually.
Donating Member
If you are so concerned about fuel prices, perhaps you should stick to your V6.Originally Posted by betts
LPG is a good way to go from a performance standpoint because LPG has a higher octane rating than petrol, this means you can modify the engine to run a higher compression ratio or run forced induction at higher boost than an equivalent petrol powered engine. The only reason LPG has a reputation for poor performance is because most LPG setups are dual fuel and the LPG is metered thru a carby which means the engines performance has to be compromised to be able to run on both fuels as the engine is still made and tuned to run on petrol even when it is running on LPG and an LPG carby has the same metering disadvantages as a petrol carby. Running a straight LPG injection setup allows you to tune and build the engine specifically for LPG and not compromise on performance.
Im not a complete idiot, some parts are still on backorder!
RESPECT!
I thought you could not put gas on the alloy v8's from what i'v been told....
And it wont be long before gas is up over the dollar mark. Personally you are better off just putting up with the petrol prices than going gas
I WISH MY GRASS WAS EMO SO IT WOULD CUT ITSELF
The Kicking Horse
Good choice mate. My mum has an XR8 on Gas and it's perfect.
Here are the reasons
1. Direct injection so there's no power loss. If you put your foot to the floor, you feel it slightly backing off at red line, but that problem's easily solved by switching it over to petrol.
2. Unlike driving in my Commo 6 (with a mixer), you really can't tell the difference between petrol and gas.
3. The economy is within 0.3litres/100km of each other. So it doesn't burn much more gas than petrol.
There's slightly less boot space, but I've got a 7x4 trailer for that, not that I ever need that much boot space. Plus the LPG tank gives me some nice tie down points.
Petrol is $1.60pl and gas is $0.605. Why the hell wouldn't you be running it on gas?
The oil stays cleaner and possibly after 300,000km the engine might wear out a bit faster than a petrol one. But I doubt we're going to keep the car that long.
Gas is awesome. Especially on V8's, it's where you need them the most. You get the best of all worlds (provided your system is a good one). Power of a V8, with the fuel costs of a Daewoo Matiz.
Double banger
cheers shounak, heaps of people bag lpg, but if prices keep going the way they are, then a lot of people are going to be doing the changeover in the next few years. also, J_D what you said was exactly what I needed to know, and now i'm going to save like crazy for that clubbie!!
Ive been researching this a lot lately, same boat as you (saving for a VX SS). Anyway there are 3 main types of gas conversions.
1. Mixer, Dual fuel.
Basically a mixer is placed in the air intake system, a single gas injector/carby puts gas in the intake
Advantage - Cost (Free to convert an older commodore), simplicity (not much to go wrong), can be done by any gas place.
Disadvantage - Lower power (due to being carby), poor economy. Have to run petrol through occasionally
2. Gas injection, LPG Only.
Basically petrol injectors are switched for gas injectors (gas to gas). The gas is "expanded" in a heat converter (which is attached to the cooling system) and injected into the fuel rail
Advantage - More power than petrol, only 1 system (dont have to run petrol occasionally), the same economy as petrol,
Disadvantage - Cost, requires piggyback ecu hooked up to normal car ECU
3. Liquid gas injection, LPG only
Similar to normal gas injection, but rather than the gas being expanded in a heat transfer thingy the gas goes to the injectors as a liquid. This is perfect for F/I engines as it actually has an "intercooler effect". Basically the expansion of gas rapidly cools the air around it.
Advantages - More power than petrol, "intercooling effect", better economy
Disadvantages - Very expensive to convert.
Basically for normal engines go the standard gas injection. For high performance engines use the liquid gas injection.
I've not a substantial amount of extra people that ask me for tunes telling me their car is booked in for a lpg conversion in the next few weeks, just starting about a month ago there's been a big spike. Prime minister Dudd is only commiting himself for one more year at the moment so I guess the delays will go up in another 6 months time
Too many projects.....
1) Beacause on a lot of cars it becomes a false economy when the head/s have to be taken off because they have no valve seats left......Especially on Alloy headed engines!
2) Might??? No 2 ways about it mate.....No matter what anyone says, LPG definately takes its toll on an engine!
3) No way would i say LPG is awesome.....
I used to fit LPG conversions, now where i work we are constantly fixing the effects of LPG! I have been on both sides of the fence (even had a gas powered car, and it was definately the first and last. All got removed after 12 months of being on gas) and let me tell you the grass is never greener on the other side!
I would never advise anyone to put a car on LPG nowadays, let alone a Gen 3 or Ford Boss engine.....
The Kicking Horse
Well my Commo has 230clicks on it and is going strong. I know another guy who had over 300k on his Commo and it was gassed its whole life.
Even if my engine happened to cark itself now, I wouldn't think it was such a big deal. I'd buy a 2nd hand engine for $300 and would probably have it in by the afternoon. It would cost me 5 weeks of opportunity costs based on below.
Atm, petrol is $1.60pl and gas is $0.60. So for every litre I use, I save $1. I typically use 80litres a week for gas, therefore I save $80 a week.
To figure out the true costs/benefits of LPG, let's consider it from a finance point of view. You're telling me, when you do a cost/benefit analysis, LPG isn't actually that much better, if better at all.
So to analyse, let's say I put the $80 a week away in an ING saver, earning 7.9%pa. For the effects of LPG to show up, I'm going to say it will take 5 years. It may take less and I can do a calculation, but for now 5 years is perfectly reasonable. I'd say very few LPG engines last less than this.
Putting my saved $80 a week into a savings account for 5 years will lead to me having a sum of $25,287.83. So anyone who uses 80 litres of fuel a week will be better off by $25 grand if they run their car on gas.
I know you have to take away slightly worse fuel consumption (for mixer systems), initial set up costs and cost of the dyno tune every year. But even if you knocked off $10,000.
You're still left with $15,000 at the end of the 5 year period to buy another engine or pay the gods to rebuild yours. I do a fair few kays because I'm on the highway a bit.
Even if I only did a tank a week, which is pretty average, putting $60 a week away. That works out to over $18,000 over 5 years.
So if you ask me would I prepare to convert my Commo to gas and buy a replacement engine in 5 years time with plenty of change left over, my answer would be hell yes.
It seems that many people are intransigent when it comes to LPG. It's obvious that the benefits outweigh the costs, especially on Commo's, yet they choose not to accept the facts. Surely the side effects of the gas system on your VN V8 weren't that bad and even if they were, your cost savings would have compensated you for it.
Btw, if an engine can go 300,000km on gas than the VSR won't effect us. My parents aren't planning to keep the XR8 much beyond 150,000km. They do about 20,000km PA, so the long term effects don't really bother them.
If you were getting a rental Commo and you had the choice between BBQ Juice or Petrol, which would you choose? I'd choose the BBQ J00S in a heartbeat.
The Kicking Horse
Btw Timbo, just how long would you expect an engine to last on a gassed Commo, on average? Or for minimum?
250,000km of driving before VSR rears its ugly head is perfectly reasonable I would assume.
Most people wouldn't even do that many kays in their car before getting it replaced.
WA Cruise Moderator
And I find myself saying this yet again....Mine duel fuel, factory system, 370,000kms and the head has never been touched.
Just hand me the pliers.
I've been thinking about going gas for a looong time, my last car was on gas and I miss the savings.
Too many projects.....
Ok, i'm not having any more particapation in LPG threads........I'm over it! Everybody, get you cars converted to LPG, It's AWESOME.......
For the record Shounak, no i can't say that i found the savings with my VN V8 THAT good. Infact, i don't even think the LPG conversion was worth it. Hence why the LPG is now non existant.....First & last LPG powered car that is for sure!
WA Cruise Moderator
DW I'm a Spray Painter!
so what $$$ difference is there between the gas injection and the liquid injection?
As for 'damage', what exactly is VSR?
VZ SSZ- LS1
Banned
anyone know how much longer the gas rebate will be around for?
Too many projects.....
VSR stands for Valve Seat Recession.
Its when the valve seats wear away, to the point where the valve can't seat anymore causing a missfire/dead cylinder because the Valve/s is unable to hold compression anymore.
supercharged intercooled
i still feel buying a v8 and putting it on gas is like buying a bicycle and walking next to it
Banned
hahhahaha, well said.
Not if you use this stuff.
Liquid injection will INCREASE horsepower on ANY injected vehicle by injecting the LPG as a liquid and freezing the intake charge, making it more dense and forcing more oxygen into the combustion. The injectors are driven purely by the petrol ECU and in that way with a flash tune to optimise ignition and injection, ect, big gains can be made..
The 6.0L I did not see on the dyno, but I did see a XR6 T BA and it made 18RWKW more than petrol with NO tuning.
SO eat that.
Question it all you want, but I saw it with my own eyes, and being in the LPG industry for the last 15 years, I can tell you this system will revolutionise the gas industry as a whole.
There is currently a big waiting list for conversions, but I and other selected installers will be fitting it as of next month.
Prices are not 100% finalised but expect to pay around 500 more than a current vapor injection system.
Heres a pic of a VE calais.
Cheers.
Double banger
well, im convinced, shounak made some excellent points. 18rwkw, awesome, and with tuning, obviously there would be more.
Banned
Doesnt sound right to me.
?(small point, freezing the intake charge? frozen oxygen, nitrogen, lpg? ...perhaps cooled below 0C?) The amount of oxygen drawn is dependent on the drop in pressure caused by the piston moving downwards on intake stroke, and cooling of the gas(due to the phase change of the lpg) inside the cylinder would cause a further drop in pressure increasing intake flow, however, isnt the principle reason more power is developed is because the fuel is injected into the cylinder as a liquid and doesnt displace oxygen in the intake?
Last edited by commsirac; 29-06-2008 at 08:40 PM.
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