Is injected gas worth the extra cash

[cazzz12000]

I,'ve been reading the other thread about how many km's people are getting from gas and read P38a post that he is getting worse km's from injected than his venturie system.Ron could you please tell me how much more gas and has anybody else had or heard this as there is about $1k differance in pricebetween the 2 systems and could put that to use else where thanks zacc

[100I]

I think there's something wrong with yours Ron, it should be better than the old

[PAT303]

Spend the dollars.Would you take the injection off and fit a carby?That is what you are paying for.I have had both systems,there is no comparison. Pat

[loanrangie]

Possibly with the lpg injection as it is ecu controlled it may actually be running correctly ie enrichening and leaning out when required as opposed to the older system where it is tuned mid range hence why most are gutless when you try to accellerate hard ? Same diff between carby and efi, a well tuned carb will be economical when just cruising around but thirsty once you tramp on the loud pedal, efi will just open the injectors longer pumping the juice in.

[p38arover]

The injected LPG on mine is noticeably more powerful on hills. I can't pick the difference between petrol and LPG.

Note that the new engine has been worked so I could be driving it harder, too.

[thor2]

Just a quick note on my experience of converting to lpg, i have a series two V8 rang around quite alot of places in melb where i am based, some argued for injection others argued for the old, i chose the old system which was done at a long time lpg conversion business and i have logged my kilometres for 8 months, driving to and from work not going hard on the accelerator has seen consistent figures of 21/100 kms to 23/100 kms, country runs of long duration on the freeway and highway see 19/100 kms driving off road i have mainly used petrol just using the gas to get to the start and then home again, reflect on the figures i heard/read on a post where a guy had paid the extra for injection and was over the moon with 24/25 per 100kms does that seem worth it to you? I certainly have been very happy with the old style conversion and saved alot more than 1000 dollars by not choosing the vapur injection system, hope this makes sense or is helpful

[cazzz12000]

thanks for the replies still dunno which one to go for zacc

[RonMcGr]

thanks for the replies still dunno which one to go for zacc

Put it this way, do a search on the old LPG system and read the stories about back fire and damage to the intake system.

The injection system is almost identical to power from fuel injection and it WILL use a lot less than an old venturi.

As Pat303 says, why revert to an old system when there is a better one on the market.

[p38arover]

Re backfires, I had enough damage totally destroying air boxes (at nearly $300 each) to almost pay for the difference in cost of the two systems. In the end I fitted a steel aircleaner from an older Rangie

Backfires and blowing off hoses was so bad my wife refused to drive the Rangie on LPG. If it backfired on her, she wouldn't have known how/where the hoses went back on.

That's one of the reasons I pulled it off the car.

[GrahamH]

More re Backfires ...
I used to have an occasional backfire with my old 3.5Lt '88 Rangie but it had a flapper-type on-return valve in the air intake to protect the "dunny-door" airflow meter so that survived OK.

However it used to blow hoses off all round the plenum chamber which were a pain to find. My solution was to securely clamp all but the short U-shaped one on the driver's side of the plenum which was easy to see and refit. It usually backfired at start-up and I just hopped out, opened the bonnet and pushed the hose back on and Bob's your Uncle.

However this wasn't an acceptable solution for my wife and it contributed, ultimately, to my decision to sell the old girl (er... the car). The Rangie was always quite reliable for me - it always saved up it's "dying for no apparent reason" antics for my wife and I suspect this is another undocumented feature of Lucas electrics.

The Discovery, after some initial backfires when I first installed LPG, has been completely reliable and I haven't had a backfire with the fumigation system in a couple of years (I'm tempting fate here, I know!). The two contributing factors to the early backfires were a leaking vacuum hose and arcing between the HT leads causing cross firing. I can't stress how important it is to keep the HT leads clean and to run the engine at idle with the bonnet open in pitch dark to see if there are any arcs and rearrange the leads to stop them. New leads with 8mm insulation help too.

I fitted an O2 sensor in the exhaust and a stepper motor power valve in the main gas line to the mixer with a closed loop controller between them and it works brilliantly. I can't tell the difference between running on LPG and petrol and I get about 20Lt per 100Km on LPG (200Km per 50Lt fill-up around town and 225Km on the open road) which I'm pretty happy with.

Ron, your economy sounds a bit dissappointing but you do have a worked 4.6Lt against my 3.9Lt engine and I suspect the P38A is a bit heavier than the SI Disco so maybe that's not unreasonable. I'll be interested to hear how it goes as the engine beds in and frees up. Good luck.

[RonMcGr]

Has anyone from Queensland had LPG injection fitted in Brisbane?

Looks like I'll be doing that very soon.

Cheers

[Tank]

Put it this way, do a search on the old LPG system and read the stories about back fire and damage to the intake system.

The injection system is almost identical to power from fuel injection and it WILL use a lot less than an old venturi.

As Pat303 says, why revert to an old system when there is a better one on the market.
Ron Mc, Ron B (P38a), GrahamH, it seems that LPG backfiring is a common occurrence, do any of you have an explanation for it, is it something to do with having a plenum chamber with enclosed air horns, or some other cause, I have had many LPG equipped cars and trucks (all carbied) over the years and have never had a backfire through the induction system, not once, they ranged from LPG only Impco Carby system to various Jap and Italian systems, dual fuel. Yet all you seem to hear nowadays is this backfiring problem, is there a solution, Regards Frank.

[p38arover]

In my case, I'm pretty sure it was caused by the slipped liners and water getting past the liner.

After I changed the engine, the problem pretty much stopped. Nothing else was changed.

[tempestv8]

The injected LPG system is absolutely the way to go with a Rover V8.

There is no argument about that, assuming that we are comparing a well installed VSI system with a well installed fumigation system.

Of course it's possible to have a well installed fumigation system perform better than a badly installed VSI system.

The VSI systems are closed loop, meaning that they take advantage of the constant tuning that the factory's EFI system is doing to maintain the best possible fuel consumption and power.

[p38arover]

The VSI systems are closed loop, meaning that they take advantage of the constant tuning that the factory's EFI system is doing to maintain the best possible fuel consumption and power.

Lawrance, wouldn't that only apply if the EFI system was closed loop. My P38A Rangie is open loop - no O2 sensors in the system ex-factory.

[tempestv8]

Hi Ron,

Yes, you're absolutely right. I believe that the P38A up to a certain year 1999 (?) and indeed the Discovery I V8 (both with the GEMS ECU) are open loop systems.

The later generation P38A with the "banana" inlet manifold, code name Thor, came with O2 sensors, if I'm not wrong. I'd imagine that the Thor V8 would benefit most from the VSI system, being able to take advantage of the closed loop monitoring system.

Which model year P38A do you have, Ron? Ah, scratch that question, I just saw your sig.

Lawrance

[tempestv8]

I guess that the VSI system would still be good even with open loop simply because it's not likely to detonate the air cleaner box and MAF sensor into smitheens, which can happen with a carby LPG setup from time to time.

Any savings on LPG will be instantly reset to 0 each time this happens.

One of my friends sold his Disco II after the 3rd explosion. He bought a D3 diesel - I'm totally envious! :)

[Tank]

I guess that the VSI system would still be good even with open loop simply because it's not likely to detonate the air cleaner box and MAF sensor into smitheens, which can happen with a carby LPG setup from time to time.

Any savings on LPG will be instantly reset to 0 each time this happens.

One of my friends sold his Disco II after the 3rd explosion. He bought a D3 diesel - I'm totally envious! :)
Still nobody has come up with an explanation of why the Backfires, I've never had one on any vehicle I owned that was fitted with LPG (dedicated or dual fuel), why the big Bang, Regards Frank.

[tempestv8]

I had a Ford Falcon on the carby style LPG and it also backfired. Not sure why either.

:(

[tempestv8]

Lawrance, wouldn't that only apply if the EFI system was closed loop. My P38A Rangie is open loop - no O2 sensors in the system ex-factory.

Hi again Ron,

Interesting to note that the pre Thor V8s in the USA (GEMS ecu system) did have closed loop, so it must be something that Australia was able to get away with. Presumably because 4x4s in Australia are classified as farm implements and did not require the anti pollution gear on it.

Here's a document that talks about the GEMs systems and goes into some details with management tools like Testbook and Rovacom.

http://www.gomog.com/allmorgan/GEMS/GEMSbyPoole.pdf

See page 80 onwards.

Lawrance

(p.s. Maybe this thread should really be in the Technical section) :angel:

[p38arover]

Yes, I've got that GEMS document. Very useful. I'll re-read P80 on.

I've wondered if I fitted O2 sensors and connected them (the plugs are there beside the sump) if I could tell the ECU it now has sensors and have it work closed loop.

Backfiring seems to be very spark dependent. The spark on a P38A is not to be sneezed at - it is exceptional - so I'm at a loss.

Low gas pressure has been given as a reason on venturi systems as the tank approaches empty but that never happened with me.

The venturi system cost me more in servicing and damage than I think I may have saved - that plus the fact my wife wouldn't drive it on gas were the reasons I removed the venturi system and wen straight petrol.

We are still playing with injector sizes and gas pressures on mine. We might have the injector size too large and need to come back 0.5mm

[tempestv8]

Still nobody has come up with an explanation of why the Backfires, I've never had one on any vehicle I owned that was fitted with LPG (dedicated or dual fuel), why the big Bang, Regards Frank.

Hi Frank,

You asked a good question and I started to dig around to find out more. Here's something that I will cut and paste from some snooping around on the internet - hope it helps! :)

Lawrance


<start quote>

How can a modern engine backfire? It should not be possible on a fuel injected motor. Most LPG conversions use a single point injection system. LPG in it’s gaseous form is simply injected into the inlet manifold, like a rudimentary carburetor. When switched to gas the petrol injectors are switched off (this is the main reason they clog, they don’t get used enough)

A number of conditions make backfires happen. Because of the high temperatures, there can be hot spots in the cylinders, namely eroded valve seats, valves and spark plugs. The gas mixture entering the cylinder ignites prematurely before the inlet valve closes and the resulting explosion travels back through the inlet manifold.

Incorrect mixture is also another prime cause of backfires. Pumping the accelerator on starting will do it as will an incorrect installation. Some systems, particularly those on factory fitted new cars won’t start the engine on gas. The motor is started on petrol then switches over. An antibackfire flap can be fitted but there effectiveness is pretty limited. Some people in desperation have cut holes in the inlet manifold and put rubber plugs in them so they blow out or stick on masking tape so it blows before the meter.


<end quote>

[Tank]

Hi Frank,

You asked a good question and I started to dig around to find out more. Here's something that I will cut and paste from some snooping around on the internet - hope it helps! :)

Lawrance


<start quote>

How can a modern engine backfire? It should not be possible on a fuel injected motor. Most LPG conversions use a single point injection system. LPG in it’s gaseous form is simply injected into the inlet manifold, like a rudimentary carburetor. When switched to gas the petrol injectors are switched off (this is the main reason they clog, they don’t get used enough)

A number of conditions make backfires happen. Because of the high temperatures, there can be hot spots in the cylinders, namely eroded valve seats, valves and spark plugs. The gas mixture entering the cylinder ignites prematurely before the inlet valve closes and the resulting explosion travels back through the inlet manifold.

Incorrect mixture is also another prime cause of backfires. Pumping the accelerator on starting will do it as will an incorrect installation. Some systems, particularly those on factory fitted new cars won’t start the engine on gas. The motor is started on petrol then switches over. An antibackfire flap can be fitted but there effectiveness is pretty limited. Some people in desperation have cut holes in the inlet manifold and put rubber plugs in them so they blow out or stick on masking tape so it blows before the meter.


<end quote>
Lawrance, thanks for that, I can see where their coming from, but as I said I never had a problem with it and it seems to me anyway, that it's a recent thing. I am tossing up whether to Chip my 4L V8 (93 efi and dissy) and fit a 200L gas tank across behind the back seats or find or swap the V8 for a 300TDi and auto, a dilemma, Regards Frank.

[p38arover]

Lawrance, thanks for that, I can see where their coming from, but as I said I never had a problem with it and it seems to me anyway, that it's a recent thing. I am tossing up whether to Chip my 4L V8 (93 efi and dissy) and fit a 200L gas tank across behind the back seats or find or swap the V8 for a 300TDi and auto, a dilemma, Regards Frank.


I've got my old venturi system for sale......

[Larns]

In referance to the backfiring, I do have A answer but not THE answer. An this relates to the old style lpg systems (as that it what I have gathered from most posts people are asking about?)

A few years ago a friend had one of those brilliant (for their time) gas research systems fitted to his worked 351 clevo. Now the car ran like a dream, and had no power loss whatso ever from the crappy holly 650dp that was removed. But it had developed a backfire problem, this after 6-7months got beyond a joke as the finer filters were 30 clams each and he's destroyed enough for the founding members of finer filter corp. to retire on. Sounding familier so far.
Well being both mechanics, and well researched in lpg we decided to fix what no gas expert had been able to rectify.
We altered the timing, regraphed the dizzy, changed the plugs untill the correct temp plugs were found, had the gas jets changed, to no avail, giving up we decided one drunken night to do some durability testing on some tires, ironically enough this was when we solved the problem.

We invertably had the bonnet up when the engine backfired in total darkness, now this was quiet spectacular to say the least, especially in our inhebreated state!
This is what we worked out.
Electricity (the spark) will always take the easiest path of resistance, a cylinder under compression has a much much higher resistance between the plug gap as a cylinder that is undertaking the intake stroke. This resistance is magnified with old plugs. Now when you have standard plug leads (HT leads) that are old and have been mal-treated they have a substansual amount of resistance. And in our case the HT leads were touching between two cylinders that just happen to overlap with their strokes, the electrical charge was jumping leads!!!! and going to the cylinder on the intake stroke. Very speky we were quiet amused.
The rest as they say.....is history.
New Gas rated leads and lead seperators totaly solved the problem.

Hope this may help at leas one of you guys out there. an I hope it hasn't bored those that already knew.

Cheers

[Tank]

I've got my old venturi system for sale......
What brand, usable capacity of tank, how much? Regards Frank.

[Tank]

In referance to the backfiring, I do have A answer but not THE answer. An this relates to the old style lpg systems (as that it what I have gathered from most posts people are asking about?)

A few years ago a friend had one of those brilliant (for their time) gas research systems fitted to his worked 351 clevo. Now the car ran like a dream, and had no power loss whatso ever from the crappy holly 650dp that was removed. But it had developed a backfire problem, this after 6-7months got beyond a joke as the finer filters were 30 clams each and he's destroyed enough for the founding members of finer filter corp. to retire on. Sounding familier so far.
Well being both mechanics, and well researched in lpg we decided to fix what no gas expert had been able to rectify.
We altered the timing, regraphed the dizzy, changed the plugs untill the correct temp plugs were found, had the gas jets changed, to no avail, giving up we decided one drunken night to do some durability testing on some tires, ironically enough this was when we solved the problem.

We invertably had the bonnet up when the engine backfired in total darkness, now this was quiet spectacular to say the least, especially in our inhebreated state!
This is what we worked out.
Electricity (the spark) will always take the easiest path of resistance, a cylinder under compression has a much much higher resistance between the plug gap as a cylinder that is undertaking the intake stroke. This resistance is magnified with old plugs. Now when you have standard plug leads (HT leads) that are old and have been mal-treated they have a substansual amount of resistance. And in our case the HT leads were touching between two cylinders that just happen to overlap with their strokes, the electrical charge was jumping leads!!!! and going to the cylinder on the intake stroke. Very speky we were quiet amused.
The rest as they say.....is history.
New Gas rated leads and lead seperators totaly solved the problem.

Hope this may help at leas one of you guys out there. an I hope it hasn't bored those that already knew.

Cheers
Larns, that may explain why I never had a problem with backfiring, every vehicle I owned fitted with LPG always had the correct plugs, the best leads available, high performance coil and on LPG only vehicles I always had the dissy regraphed to suit LPG. I am also wondering with modern fuel injected vehicles, esp. V8's with Plenum chambers full of tuned length air horns or bunch of banana inlet runners that there is some residual LPG hanging around waiting to be detonated by a flame from an overlapping inlet and exhaust valve esp. with the advanced timing used on LPG engines, something to ponder, Regards Frank.

[ytt105]

I've had two Rangies with gas.
The first used to backfire occasionally until I upgraded the ignition system to a Bosch Scorcher dissy and new leads.
The second, and current one, I fitted a new gas system to it myself.
The system came complete with instructions and they made a big point of insisting that I tap the plenum chamber and connect the vacuum hose that goes to the bottom of the throttle butterfly to this new position.
I've never had a backfire with this system.
Their explanation was that the vacuum hose, which carries the fuel vapour from the carbon canister, could leave too much petrol fumes around the throttle that could backfire.
By moving these fumes into the larger air filled area of the plenum chamber negated this possibility.