Performance of complete lpg conversion

[betts]

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

[jules]

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.

[1991_Vn2nV]

Originally Posted by betts

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

If you are so concerned about fuel prices, perhaps you should stick to your V6.

[J_D]

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.

[IMCRZY]

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

[Shounak]

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.

[betts]

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!!

[Cane_It]

Raso Enterprises Main Page

go here...

[feistl]

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.

[greenfoam]

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

[Blown V6 Hatch]

Originally Posted by Shounak

1)Petrol is $1.60pl and gas is $0.605. Why the hell wouldn't you be running it on gas?

2)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.

3)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.

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.....

[Shounak]

Originally Posted by Blown V6 Hatch

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.....

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.