Getting the most out of a LPG/Petrol GQ

[Tayls]

G'day all

I have been looking at purchasing a gq shorty for awhile now, just have not made up my mind on weather to go down the diesel or dual fuel road.

Have taken a couple 4.2TD with the aftermarket kits on them for a drive, is an ideal set up just hard and expensive to find a diesel shorty. The other option was doing an 8 conversion, which sounds great to, but im being constantly talked out of, not only because bad economy but just the general problems associated with the conversions.

Which has led me to thinking about going for an LPG/Petrol, economy is good on gas, just goes like crap.

I just wanted to if anyone else out there has tricked up a dual fuel gq? What types of mods did you’s do and did you’s get the desired power out of it?
What should you expect to pay for a rebuilt?

Cheers
Daniel

[Beastmavster]

Should be able to run a turbo with higher boost on LPG and get heaps more power... there's enough threads about some pretty wicked LPG TB42's around here to give you a good start.

[Tayls]

Was thinking about doing the mods on a naturally aspirated engine.

[jessie928]

i dont know who you are talking to about V8 conversions, but you may have some mis-information. A well done conversion should look,feel and drive origional, with gobs more power and heaps better economy to boot.
no matter what you do to a lpg 4.2, its still going to be a heavy arse underpowered donk.

Cheers,
Jes

[viperguy]

i have a straight lpg set up in my mav shorty. started life as a carby 4.2 but now it has a ohg 450 lpg throttle body, crane xr3000 elect ignition kit, fireball coil, regraphed dizzy, iridium plugs, 8mm msd leads, extractors, straight through 2 1/2 inch exhaust, custom snorkel...all this through the standard auto and 4.3 diff ratios. there is nothing bout my mav that is under powered.normally aspirated ur tb42 can be made into a sweet motor, just needs to breath better and get batter spark. before i sorted my ignition system, the motor wouldnt rev into the red zone (about 4200rpm)..now it revs smother and more willingly all the way up to about 5500 still making power all the way.

the performance u will get comes down to the tuning and state of tune of the motor. after my mods i had it set on a dyno and tuned so everything was doing its job.

when i need to, the head will come off and after a bit of shaving and flowing, i think i will have a rocket ship. obviously wont have the bang of a turbo or supercharger or v8, but for the dollars i spent it wont be far behind and will be heaps more reliable than.

just remember dual fuel is a tuning compromise. u will never get the benefits of either if u run both.

by all means if u have the money and resources engine swaps and turbos etc are awsum. i wish i could have dropped a injected 8 in mine..but those heavy lazy underpowered tb42's can be made to dance with the right mods thrown at them...

[Tayls]

viper guy

is the ohg 450 lpg throttle body is that a gas research system?

also do u run dual gas tank, if a single, what size did u end up getting in?


jessie928
im not disputing that you cant get a succesful V8 conversion, i think the key word u said was a "well done" conversion. viperguy said it all, its expensive, if additional problems had to be ironed out i dont think i could afford it.

[viperguy]

i have dual 90l usable tanks in my shorty..one under where the fuel tank used to be and the other in the cargo compartment. i know being a shorty i have noroom for nothing else but you would be surprised at all the different places u find to stash things u need to carry around.

im getting about 650kms from about 150-160 ltrs of lpg around the city/suburbia and that can get upto 750-800kms when highway driving. i use the mav for lots of touring and offroading as well as it being my daily driver.

the ohg system is made by OHG. its a different company to gas research but gas research is very very good too...but maybe a bit pricey. plus gas research needs there complete system to work...cant mix and match different systems. was guna go down that path but meant changing my converter and lines etc etc adding to dollars.

google OHG..some good info about the simplicity and effectiveness of the ohg throttle body

[chimpboy]

G'day all

I have been looking at purchasing a gq shorty for awhile now, just have not made up my mind on weather to go down the diesel or dual fuel road.

Have taken a couple 4.2TD with the aftermarket kits on them for a drive, is an ideal set up just hard and expensive to find a diesel shorty. The other option was doing an 8 conversion, which sounds great to, but im being constantly talked out of, not only because bad economy but just the general problems associated with the conversions.

Which has led me to thinking about going for an LPG/Petrol, economy is good on gas, just goes like crap.

I just wanted to if anyone else out there has tricked up a dual fuel gq? What types of mods did you’s do and did you’s get the desired power out of it?
What should you expect to pay for a rebuilt?

Cheers
Daniel

My LWB is not THAT much worse on gas than it is on petrol, and it goes fine on both. I really and honestly don't know why people say these things run like crap on LPG... they sure as hell run better on LPG than they do on diesel. Yes, I can feel a slight loss of power on gas, but it's not that much of a big deal.

I also don't really know why people would talk you out of the V8 conversion based on reliability. The problem with them is just that to do it properly costs a fair bit. I am pretty sure I'll be dropping a V8 in my LWB in the next two years just for some tax-deductible fun. Generally economy at least as good as it is with the TB42 anyway, from what I've read and heard. But yeah, I think you'd have to budget $5k at the minimum to do it right.

Petrol shorty GQs are a really lively vehicle, they actually go pretty fast for a big car. And LPG doesn't kill power as much as people say, at least not in my experience. The TB42 is not a world-beater but as a low-revving motor it's not as bad as it's made out to be. It certainly excels in the bottom of the rev range. It will pull and idle smoothly at 400rpm if tuned well, and by the time it gets to 1000rpm it's already quite grunty.

Jason

[Tayls]

jason,
i've never owned either a diesel, petrol or any other patrol previously, the only experience i have is with the short test drives i have been taking. I can only really go by what people have been telling me.

in regards to the V8 conversions, it sounds ideal if all goes well, if all doesnt it could prove to me an expensive journey.

My aim in posting this topic up was originally to see if anyone out there has done a few mods on a pet/gas, with the dizzy, more air, exhaust system etc etc

have u got LWB pet/gas, how many km's u get out of that....

[Beastmavster]

Dont have LPG on the patrol (do have a kit off an old datto I had though).

I just dont do enough miles in it to justify the expense of installing it right now.

I found that ease of starting and all those sorts of issues on the datto the LPG won hands down.

You can run more ingnition advance and all that - with the consequence she runs worse on petrol (which is ok cos you'll rarely use it on petrol when you can run LPG). With aftermarket electronic ignition (even a $50 Jaycar type) you could also set it up to have multiple ignition settings with a bit of work - so you had a switchable timing for both fuels.

Most of the mods you do on a petrol engine work on an LPG engine - just remember that LPG has a higher octane (normally about 114 octane) but lower calorific value.

Hence if you can use that 20 point higher octane of the fuel more efficiently (eg higher compression, better air intake) you can get better power or better economy. Newer gas injection systems are much better at this than old dual fuel systems.

If you can't get the settings right it will use more fuel but it's not twice as bad like diesel people say - it might be 10%-15% worse.


A carby shorty is 125kw and 1700kg, so power to weight wise is not much worse than a Commodore V6 anyway. The difference is made smaller by the shorter gearing of the SWB, although the manual gearbox is pretty slow to shift.

Keeping in front of most traffic in a shory on 33"s is very easy. As proven by my only QLD speeding ticket........

[jessie928]

i have a straight lpg set up in my mav shorty. started life as a carby 4.2 but now it has a ohg 450 lpg throttle body, crane xr3000 elect ignition kit, fireball coil, regraphed dizzy, iridium plugs, 8mm msd leads, extractors, straight through 2 1/2 inch exhaust, custom snorkel...all this through the standard auto and 4.3 diff ratios. there is nothing bout my mav that is under powered.normally aspirated ur tb42 can be made into a sweet motor, just needs to breath better and get batter spark. before i sorted my ignition system, the motor wouldnt rev into the red zone (about 4200rpm)..now it revs smother and more willingly all the way up to about 5500 still making power all the way.

the performance u will get comes down to the tuning and state of tune of the motor. after my mods i had it set on a dyno and tuned so everything was doing its job.

when i need to, the head will come off and after a bit of shaving and flowing, i think i will have a rocket ship. obviously wont have the bang of a turbo or supercharger or v8, but for the dollars i spent it wont be far behind and will be heaps more reliable than.

just remember dual fuel is a tuning compromise. u will never get the benefits of either if u run both.

by all means if u have the money and resources engine swaps and turbos etc are awsum. i wish i could have dropped a injected 8 in mine..but those heavy lazy underpowered tb42's can be made to dance with the right mods thrown at them...

Viperguy, if you drop your exhaust size down from teh 2-1/2 inch to a 2 1/4 you will find some more power in your donk aswell.

Jes

[viperguy]

i have been thinking bout using a standard exhaust manifold rather than the extractors and seeing what that wil do? i was told that with lpg the extractors and larger exhaust are causing my gas/air mix to lean out..
i had to change the standard manifold on my tb42 because it had a massive crack and just ended up with extractors.

what u think? keep extractors and go to smaller exhaust or standard manifold and bigger exhaust?

[Beastmavster]

Sounds like BS to me...... enrichen the gas mixture rather than restrict your exhaust.....

doh!

[viperguy]

sounded like bs to me too.. just that i was with the guy as he was tuning for me on the dyno.. if we richened the power runs to be perfect it was way rich at idle..and to get a good idle it was marginally lean on power runs.. no biggy...still got chunks of power for a tb42..im happy. just seeing what people thought

[jessie928]

if your extractors are causing your engine to lean out at high RPM your LPG converter may be inadequete for the engine. ( thats if this is indeed happening)

As soon as you re-install the origional headers you will find that your low RPM tourque has doubled, but your high rpm performace drops.

a better idea is to leave on the extractors and sacrifice some of the low down torque and fit a smaller ID exhaust pipe like 2 1/4. the patrol engine is 4.2 litre and the 2 1/2 pipe is ample for even a 6 litre motor so what happens on the 4.2 is your over exhausting the engine.

Muffler configuration has an impact aswell.
Jes

[Draven]

Ive got a tb42 with 2 1/2" zorst and pacemakers....if anything i gained bottem end after the change from std exhaust and manifold.

[jessie928]

there is no way you would have gained torque just off redline with extractors and exhaust on a 4.2 patrol, you will loose it because the extractors take the backpressure away from the exhaust valves.

furthur up in the rev range is another story, THe change is MOST noticable in a auto vehicle.


Jes

[Tayls]

so would's you's think that it would be worth going down the gas path?

what do you's reckon, if you had around $5k to spend on getting more power and better fuel economy, what would you's do? thats either looking at buying a pet, diesel, pet/gas all price depand....

i wanted to get a gq lifted, powered up and ready to go for under $15...(thats including the car)

[Beastmavster]

An engine transplant of any sort will cost $5k plus so you need to decide now if you're happy with the LPG/Petrol or Diesel engine and start from there.

Getting a diesel SWB is a very hard task and will probably chew up another $5k over what a petrol costs to buy.

[Tayls]

its looking a bit that way... the diesels are hard to come across.
what about an 8 on gas? how do the gen 3's go on juice compared with the original petrol 4.2?

[jessie928]

your best bet is slotting in a v8 on straight gas, more power, more economy, better when 4 wheeling.
you should get it in at under 5k if you leave the origional box in place and go with a 327 or a 307 chev small block. dont waste your money on fuel injection if you are wanting to run gas, just run a quality dual plane intake manifold.

Jes

[Tayls]

then comes the problem of where to put the tanks....

if you ran a chev, that means you could get the adapter kit from marks...
from my understanding, marks dont make one for ford....

[jessie928]

the gq lpg tank replaces the fuel tank, teh sub tank for petrol goes between the transfer and the chassis rail.

why would you put a ford engine in it and go backwards?

Jes

[Tayls]

nothing wrong with a well built cleveland. I had a 351 in my old ford, was strong and didnt miss a beat. Plus ive still got the engine.

[jessie928]

Clevelands make good boat motors, Cause you cant overheat the river.....

[RN]

I have always thought of putting a Ford V8 into my Mav but it sounds like a lot of trouble. I think Dellow does a adapter but Marks won't.

Does anyone know of any GQ's that have gone down that path. Seems to be GM is the majority with some Jap V8's making an impact.

[jessie928]

you carnt argue with the worlds most modified, and most accessorised V8 engine.



Jes

[MrMaxi]

My Mates neighbour has one with a 351 in it, the kit cost around $800 from dellow, although he did say if he was to go out and buy a motor for the conversion he'd go the 350 also. apparently the 351 sits too far back.