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Straight LPG on an Rb25det

calais25t

By calais25t,
in Engines & Forced Induction

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calais25t Enthusiast

calais25t

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thats not a bad idea considering how they're talking about price of petrol being well and truly over 1.20 a ltr and not coming down. I'll be interested to see the response also how much power could be expected to be lost.

Actually looking at a 10-15% gain in power.

Will keep updated but I was just wondering if anyone has done it?

Zahos Mentor

Zahos

Posted
Posted
thats not a bad idea considering how they're talking about price of petrol being well and truly over 1.20 a ltr and not coming down. I'll be interested to see the response also how much power could be expected to be lost.

LPG has a much higher octane rating than ULP, but because of it's lower density, you need to ungrade your injection system to get enough in there.

Many people have gained more power on N/A cars swaping to a straight gas system.

Dual / fuel is where you loose power as you need to tune the car half way between what would be optimal for LPG and optimal for ULP.

I have yet to see a stright LPG system with forced induction, but if setup properly, I cant see why you wouldn't gain power.

Sydneykid Grand Master

Sydneykid

Posted
Posted

Based on our experience with other LPG powered cars;

You will need to be carefull with your LPG supply, in the push to keep LPG prices low the octane ratings are not what they used to be. We were seeing over 104 ron about 4 years ago, now it is not unusual to get as low as 95 ron. The market for LPG is dominated by taxis and delivery vehicles where cost is important, not the octane rating.

The RB25DET has a 9 to 1 static compression ratio.

If you are doing it for a cost saving, then be aware that it will take a minimum of 150,000 k's to break even on the cost of a high performance conversion at current petrol and LPG prices.

It is also worth noting that the distance travelled between tank fills (asumming the same litreage) is considerably shorter due to the lower calorific value of LPG. Plus you are looking at a 40 to 50kg weight gain in the necessary hi pressure tank and components. This will require an upgrade in the rear spring rates which will compromise traction and handling due to the shift in weight balance. In addition there is a 75mm reduction in ground clearance if the tank is underslung (that means no lowering). Or a ~65% reduction in boot space if it is mounted there.

Hope that was of some help:cheers:

ylwgtr2 Grand Master

ylwgtr2

Posted
Posted
LPG has a much higher octane rating than ULP, but because of it's lower density, you need to ungrade your injection system to get enough in there.

Many people have gained more power on N/A cars swaping to a straight gas system.

Dual / fuel is where you loose power as you need to tune the car half way between what would be optimal for LPG and optimal for ULP.

I have yet to see a stright LPG system with forced induction, but if setup properly, I cant see why you wouldn't gain power.

Ummmm gas doesnt run through the injecton system.....and there are already loads of forced induction vehicles running this setup....many people buy import engines and use them in transplant conversions and use LPG to overcome the EPA and the no ECU problem....13BTs' are the most popular

Zahos Mentor

Zahos

Posted
Posted
Ummmm gas doesnt run through the injecton system.....and there are already loads of forced induction vehicles running this setup....many people buy import engines and use them in transplant conversions and use LPG to overcome the EPA and the no ECU problem....13BTs' are the most popular

Duel fuel systems don't use any form of injection AFAIK, but I have seen gas only systems that use injection. I cant remeber if it was direct injection, or throttle injection, but it was definately some form of injection.

This was in car mag 10 years ago, and I remeber them comparing size of injectors to cars standard injectors for ULP and they were considerably larger.

The setup did not allow to run ULP, it was LPG only.

DaGr81 Mentor

DaGr81

Posted
Posted

call this number 93194114, by the way did u hear about the guy who almost blew the f*k up that scares me, so i doubt id eva go gas, and yes there are more frequent gas fill ups , but i think its because u cant have more than 80% of the gas tank full or something along that line...

rs73 Grand Master

rs73

Posted
Posted
Based on our experience with other LPG powered cars;

If you are doing it for a cost saving, then be aware that it will take a minimum of 150,000 k's to break even on the cost of a high performance conversion at current petrol and LPG prices.

Hope that was of some help:cheers:

Wow, it's probably not worth doing it on our Skyline.

Right-foot throttle self-restrain is probably still the best to try saving fuel.

Or... how about V10 turbo diesel conversion :thumbsup:

Beer Baron Grand Master

Beer Baron

Posted
Posted
Duel fuel systems don't use any form of injection AFAIK, but I have seen gas only systems that use injection. I cant remeber if it was direct injection, or throttle injection, but it was definately some form of injection.

This was in car mag 10 years ago, and I remeber them comparing size of injectors to cars standard injectors for ULP and they were considerably larger.

The setup did not allow to run ULP, it was LPG only.

i am no expert on LPG in passenger cars but I know that they are no comercially available systems that use conventional 'injectors' the LPG is introduced pre-throttle in a 'gas mixer' which is sort of like a carbie in operation. ie. it's not electronically injected.

also I believe I can paraphrase Sydney Kids post nicely:

don't do it, it's a waste of your time/money and has more negatives than positives.

Zahos Mentor

Zahos

Posted
Posted
i am no expert on LPG in passenger cars but I know that they are no comercially available systems that use conventional 'injectors' the LPG is introduced pre-throttle in a 'gas mixer' which is sort of like a carbie in operation. ie. it's not electronically injected.

also I believe I can paraphrase Sydney Kids post nicely:

don't do it, it's a waste of your time/money and has more negatives than positives.

LPG Injection:

http://www-control.eng.cam.ac.uk/Homepage/...cts/manzie.html

http://www.abc.net.au/newinventors/txt/s1345083.htm

http://www.parnell.com.au/index.php?option...&id=3&Itemid=26

Like I have said a few times already, all dual fuel systems on EFI cars dont use an injection system, they use a vaporised gas carburettor system.

The system I am talking about is a gas only system.

Around the time I saw it, an LPG system with dual fule was about $1000 - $1500, and the straight gas injection system was $4000.

Weather it was direct or throttle injection, I don't know and I dont care, but based on those links I have provided, direct LPG injection seems to be a very recent development. So my guess lies with throttle injection.

Even with throttle injection, a greater mass of LPG can be consumed than a standard vaporised gas carburettor system allows (in theory, and it must have been in practice too to sell for double or tripple that of a conventional system)

And yes it is a waste of money unless you do lots of km, and intend on keeping the car for a long time. Even then, it requires more maintanance, and can increase the rate of engine wear.

Not worth it in my opinion either, but definately interesting.

psybic Proficient

psybic

Posted
Posted

Its funny you say about the better performance of dedicated gas cars.

The new fords have the option of dedicated gas, so there is no tuning compremise, it only runs gas, never petrol. There is a noticable difference in the performance of the dedicated gas falcon and the normal falcon.

The hi-octane sources are too rare to be viable.

Beer Baron Grand Master

Beer Baron

Posted
Posted

from the link you posted:

As a result, future generations of LPG vehicles released by the manufacturers are certain to use injection as the method of fuel delivery.

the second link is more promising showing one bloke who has made a prototype system.

the third link shows one set-up for sale, but their highest powered unit is only good for 200kw.

the GTI system (from the second link) seems pretty good. but it's hardly widely available having only been done on a handful of cars and seemingly still under development.

I do stand corrected though. however I have never laid eyes on an electronically injected gas system ever. all have used some kind of mixer. i am surprised that the technology was around 10 years ago yet still isn't widely available.

Zahos Mentor

Zahos

Posted
Posted
I have never laid eyes on an electronically injected gas system ever. all have used some kind of mixer. i am surprised that the technology was around 10 years ago yet still isn't widely available.

The system I saw I think was on a VR commodore in wheels, or one of those car mags, and it was a feature on a readers car.

I have not heard much of them either, but was only really aware of their existance.

JNR24 Proficient

JNR24

Posted
Posted

You would have to be talking about Mr sera? (VLS_BACK)

(i go for lunch with the guy allmost everyday) =P

Gas is fine however, The VL your talking about runs twin converters.. and runs allot warmer.

Not to mention he is running a GT40, with a 4K stall & transbrake....

All that into consideration, and it is by all means "QUICK" but his brothers car is evidence, that you cant beat a "petrol setup" for perfomance. (james is running 9s 1/4miles)

All that aside:

-He drives the car allmost everyday. - Thats gota be good.

-Its reasonably cheap to run

-No injectors, fuelrails, pumps, fuellines etc. - Good $$$ saving, not to mention very tidy -underbonet & no buzzing pumps in the boot?

-EPA Legel (From a emission perspective)

-Only need a computer to fire plugs. (dont need a expensive type computer to run the motor etc.)

Good luck

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