Snorkel not suited to V8 running on LPG?

[I Love My Landy!]

G’day everyone,

I drive a 1984 County with a 3.5L V8 running on dual fuel with standard carbies, a Landi Renzo LPG convertor and ring mixer set up. I was recently thinking about building a snorkel for it thinking that the motor would run better being force fed with cool air, but first I decided to make a cheap prototype snorkel that poked up through the wing vent, just to test its effects when running on LPG. As it turns out it resulted in a loss of power and it increased my fuel consumption (I did not test its effects on petrol as I rarely drive it on petrol). Can anybody tell me why this happened? Would I be correct in saying that the ring mixer is not suited to having air forced through it? Or could these effects be due to incorrect tuning? I tuned the motor using an exhaust gas analyser, however the County was stationary at the time.

Thank you!

Edward :)

[Hardchina]

Is there a pressure balance pipe from the rear of the gas converter to the air cleaner / snorkle assembly ??

[I Love My Landy!]

Is there a pressure balance pipe from the rear of the gas converter to the air cleaner / snorkle assembly ??

No there isn't Hardchina. Is that where my problem lies?

Edward :)

[bee utey]

The lpg converter delivers gas to your engine by the main diaphragm reacting to the vacuum created by your ring mixer AND all the intake plumbing and aircleaner. So adding a snorkel means you have to run a balance pipe from your old aircleaner inlet to the back of the converter. A piece of 1/2 inch heater hose is sufficient for this. Then any pressure or vacuum generated by the snorkel plumbing can't affect the vac signal to the converter. On the Renzo Landi the main metering diaphragm is clamped between the back cover and the body. the gas outlet is on the front side and the balance fitting needs to be screwed into the back cover. If there is no pre-existing balance fitting you will have to take the cover off and tap in a 1/2 inch hose fitting. Plug up any small vent holes there may be in the back cover.

[DeeJay]

The lpg converter delivers gas to your engine by the main diaphragm reacting to the vacuum created by your ring mixer AND all the intake plumbing and aircleaner. So adding a snorkel means you have to run a balance pipe from your old aircleaner inlet to the back of the converter. A piece of 1/2 inch heater hose is sufficient for this. Then any pressure or vacuum generated by the snorkel plumbing can't affect the vac signal to the converter. On the Renzo Landi the main metering diaphragm is clamped between the back cover and the body. the gas outlet is on the front side and the balance fitting needs to be screwed into the back cover. If there is no pre-existing balance fitting you will have to take the cover off and tap in a 1/2 inch hose fitting. Plug up any small vent holes there may be in the back cover.

Wouldn't taking the vehicle to a specialist & getting it re- tuned for the new plumbing do the same job?

[I Love My Landy!]

The lpg converter delivers gas to your engine by the main diaphragm reacting to the vacuum created by your ring mixer AND all the intake plumbing and aircleaner. So adding a snorkel means you have to run a balance pipe from your old aircleaner inlet to the back of the converter. A piece of 1/2 inch heater hose is sufficient for this. Then any pressure or vacuum generated by the snorkel plumbing can't affect the vac signal to the converter. On the Renzo Landi the main metering diaphragm is clamped between the back cover and the body. the gas outlet is on the front side and the balance fitting needs to be screwed into the back cover. If there is no pre-existing balance fitting you will have to take the cover off and tap in a 1/2 inch hose fitting. Plug up any small vent holes there may be in the back cover.

Thanks bee utey, that makes perfect sense, i'll get working on it.

Edward :)

[big guy]

The lpg converter delivers gas to your engine by the main diaphragm reacting to the vacuum created by your ring mixer AND all the intake plumbing and aircleaner. So adding a snorkel means you have to run a balance pipe from your old aircleaner inlet to the back of the converter. A piece of 1/2 inch heater hose is sufficient for this. Then any pressure or vacuum generated by the snorkel plumbing can't affect the vac signal to the converter. On the Renzo Landi the main metering diaphragm is clamped between the back cover and the body. the gas outlet is on the front side and the balance fitting needs to be screwed into the back cover. If there is no pre-existing balance fitting you will have to take the cover off and tap in a 1/2 inch hose fitting. Plug up any small vent holes there may be in the back cover.

You are truly a freak, the precise answer to most questions posted here are answered in almost clinical precision.
No wonder I keep coming back to you.;)

[bee utey]

Wouldn't taking the vehicle to a specialist & getting it re- tuned for the new plumbing do the same job?
No, because the air pressure in the snorkel varies with speed and can't be tuned for, whereas a balance hose costs about $20 for parts.

[400HPONGAS]

An interesting thread indeed , opens up alot of not so clearly thought out assumptions .Lets start with this air-ram thingy , Ram more air in and cooler air ? Nice concept , Reality says you would need to be doing 200KPH Plus to make 1 inch of Hg through an orifice With a CSA of 75 t0 100mm 27InsH20 = 1 PSI . 1 insHG = .491 PSI So virtually no RAM effect ! Lets try Temp drop or ambient at the Snorkel and Inlet manifold , after average heat soak and temp rise from slight compression virtually nothing again . So Snorkels really supply good Clean air , alot free-er of Dust and alot less Moisture in the form of Water . Aint it funny when Im Dynoing a 500HP plus engine on the Dyno , not once do we try to give extra air by blasting air into the Venturi . That job is usually left for something like a Turbo or Blower !!!

Next little problem , our old FUMIGATED LPG system usually are made of two types , type 1 , the air valve style (Impco , OHG etc) that use Negative Convertors , and type 2 the Mixer ring orifice type mixer which needs a Positive Convertor .

Both the systems use a Unique single Vapor line from the Convertor to the Mixer , not to be Confused with the Standard inlet Pipe from your air cleaner Snorkel arrangement . So it is this Vapor line that delivers LPG to the Mixer Type . Now whats important is that rate of delivery , and that has more to do with engines Suck power or VE % or even required Load /Performance and indeed thats where most Fumigated systems become a closed Loop by fitting a stepper motor to the vapor line , stepped by a AFR wide band Lambda sensor. simple stuff .
Now that brings us back to those convertor Thingys , A positive one simply means at idle , the convertor will supply LPG at virtually No manifold vacuum ,(otherwise it will never start unless you use more priming circuits) so indeed it will have a primary pressure of between 1.5 and 5 PSI .So Positive convertors like the Landi/Airod or a Vialle or a OMVL are positive and have easily set able primary pressures (Usually a 20 c piece or 50 C piece )
Your Impco E , woodward, OHG , B2 Nolfs etc are negative convertors and use much lower primary pressures standard as the air valve arrangement controls the Suck of the LPG (for want of a better explanation) and use fine adjustments of the Primary and secondary springs
So where does this lead with before mentioned "Equaliser or Balance Pipe" Well unless you have a substantial positive pressure differential between the Secondary port pressure and the air supply/ pipe at the orifice than you dont need to Balance it . If its a Blown App then it needs Balancing . What size is the Mixing orifice , (annular if not a GRA which is AVCSA) No use running a 1 3/4 carbs and a 1 1/2s mixing rings ) Also make sure the Primary vent whole on the back isnt blocked or sitting in a negative air pocket There are just so many many combinations , of parts and Flows and pressures its a true joy whwn you get it set right , but with DUAL fuel installations its always a Compromise . Believe me, pulling good top end Power / good torque acrosss the range and still maintaining 5.5 to 7 Ks to litre with over 400HP aint easy !!

[Freestyler]

I am running a 1985 county dual fuel with a snorkel and it runs fine. I had some problems like you are till I fitted the balance pipe. It is originaly fitted to compensate for air clear as it slowly fills up with dirt and adjusts the mixture to suit. I did have the carbies as original until I went to the leyland v8 and now run it EFI with a gas carbie hanging off it.
Tim

[big guy]

An interesting thread indeed , opens up alot of not so clearly thought out assumptions .Lets start with this air-ram thingy , Ram more air in and cooler air ? Nice concept , Reality says you would need to be doing 200KPH Plus to make 1 inch of Hg through an orifice With a CSA of 75 t0 100mm 27InsH20 = 1 PSI . 1 insHG = .491 PSI So virtually no RAM effect ! Lets try Temp drop or ambient at the Snorkel and Inlet manifold , after average heat soak and temp rise from slight compression virtually nothing again . So Snorkels really supply good Clean air , alot free-er of Dust and alot less Moisture in the form of Water . Aint it funny when Im Dynoing a 500HP plus engine on the Dyno , not once do we try to give extra air by blasting air into the Venturi . That job is usually left for something like a Turbo or Blower !!!

Next little problem , our old FUMIGATED LPG system usually are made of two types , type 1 , the air valve style (Impco , OHG etc) that use Negative Convertors , and type 2 the Mixer ring orifice type mixer which needs a Positive Convertor .

Both the systems use a Unique single Vapor line from the Convertor to the Mixer , not to be Confused with the Standard inlet Pipe from your air cleaner Snorkel arrangement . So it is this Vapor line that delivers LPG to the Mixer Type . Now whats important is that rate of delivery , and that has more to do with engines Suck power or VE % or even required Load /Performance and indeed thats where most Fumigated systems become a closed Loop by fitting a stepper motor to the vapor line , stepped by a AFR wide band Lambda sensor. simple stuff .
Now that brings us back to those convertor Thingys , A positive one simply means at idle , the convertor will supply LPG at virtually No manifold vacuum ,(otherwise it will never start unless you use more priming circuits) so indeed it will have a primary pressure of between 1.5 and 5 PSI .So Positive convertors like the Landi/Airod or a Vialle or a OMVL are positive and have easily set able primary pressures (Usually a 20 c piece or 50 C piece )
Your Impco E , woodward, OHG , B2 Nolfs etc are negative convertors and use much lower primary pressures standard as the air valve arrangement controls the Suck of the LPG (for want of a better explanation) and use fine adjustments of the Primary and secondary springs
So where does this lead with before mentioned "Equaliser or Balance Pipe" Well unless you have a substantial positive pressure differential between the Secondary port pressure and the air supply/ pipe at the orifice than you dont need to Balance it . If its a Blown App then it needs Balancing . What size is the Mixing orifice , (annular if not a GRA which is AVCSA) No use running a 1 3/4 carbs and a 1 1/2s mixing rings ) Also make sure the Primary vent whole on the back isnt blocked or sitting in a negative air pocket There are just so many many combinations , of parts and Flows and pressures its a true joy whwn you get it set right , but with DUAL fuel installations its always a Compromise . Believe me, pulling good top end Power / good torque acrosss the range and still maintaining 5.5 to 7 Ks to litre with over 400HP aint easy !!

So the point is???
Proove Beeutey wrong or tell us figures, quotes and jargon most people don't know what they mean.
One thing I know for certain when I and many people I send to him(Bee-utey) get their gas installed or fixed, it always comes back running fine.
If its tuned to exacting standards of the likes of NASA is irrelevant as the more finely tuned they are the harder to maintain that level.

If I do want a rocket ship and be baffled by jargon I will come to you as it seems you know what you are saying.;)

[I Love My Landy!]

An interesting thread indeed , opens up alot of not so clearly thought out assumptions .Lets start with this air-ram thingy , Ram more air in and cooler air ? Nice concept , Reality says you would need to be doing 200KPH Plus to make 1 inch of Hg through an orifice With a CSA of 75 t0 100mm 27InsH20 = 1 PSI . 1 insHG = .491 PSI So virtually no RAM effect ! Lets try Temp drop or ambient at the Snorkel and Inlet manifold , after average heat soak and temp rise from slight compression virtually nothing again . So Snorkels really supply good Clean air , alot free-er of Dust and alot less Moisture in the form of Water . Aint it funny when Im Dynoing a 500HP plus engine on the Dyno , not once do we try to give extra air by blasting air into the Venturi . That job is usually left for something like a Turbo or Blower !!!

Thank you 400HPONGAS for your detailed reply (and now i understand what your user name means!). I was aware that the ram air effect may be a myth, however the loss in power and rise in fuel consumption after fitting the prototype snorkel was dramatic, making me think that there was some kind of ram air effect messing things up.

Edward :)

[bee utey]

It takes something like 0.01psi to move (by 1/4 inch) the diaphragm installed in a typical positive pressure converter. I have just calculated this using a digital weighing scale against a 5 inch diameter diaphragm installed in a converter. This would cause a major mixture change. Well within the range of air pressure change generated by a snorkel I think.

[cewilson]

Can you use a Donaldson pre-cleaner instead of the ram head - wouldn't that also fix the problem?


And yes I know it's dearer than a balance pipe :)

[bee utey]

Can you use a Donaldson pre-cleaner instead of the ram head - wouldn't that also fix the problem?


And yes I know it's dearer than a balance pipe :)

Not really, the air flowing across a pre-cleaner will cause a speed related pressure drop in the duct below it. I have even met cars that will start to stall because the converter is on one side of the engine bay, the air intake on the other, just behind a headlight, and is subject to a powerful crosswind. Seriously, a balance hose is a good idea.

[County4.4]

So which is the better style of converter for the old rover v8 ??
Positive or negative converters??
The ring mixer style would certainly be the easiest to adapt to a snorkle I would guess
Just asking because I have an impco setup via a quadrajet currently but would like to fit a snorkle to the county.

[101 Ron]

I play with LP gas alot for my living in Industrial applications.
balance pipe will fix the problem with a snorkel
I use balance pipes in hard applications where the air filter gets blocked often, or where extra precleaners and filters have been added due to a hard work environment.
A rover V8 with carbies will work with any type of system so long as it has the flow capacity and is set up correctly.
Donuts on each carby and three stage convertor is the neatest system.
Electronic looped systems .......more work, but can get better gas burn.
The rover carby motor will work on Impco mixers well, but the impco mixer may be harder to install because of its size.
A century under thottle system will even work on the rover motor.
Talk to a good gas filter about your needs, budget etc.
Ron

[LandyAndy]

Turn the snorkle head backwards;);););)
Solves the problem.
Andrew

[wattysan]

I fitted a snorkel to my 95 V8i disco about 6 months ago creating a stalling issue on LPG. $20 for some heater hose and a couple of bits to connect it as a breather hose fixed the problem straight away.

[Utemad]

The lpg converter delivers gas to your engine by the main diaphragm reacting to the vacuum created by your ring mixer AND all the intake plumbing and aircleaner. So adding a snorkel means you have to run a balance pipe from your old aircleaner inlet to the back of the converter. A piece of 1/2 inch heater hose is sufficient for this. Then any pressure or vacuum generated by the snorkel plumbing can't affect the vac signal to the converter. On the Renzo Landi the main metering diaphragm is clamped between the back cover and the body. the gas outlet is on the front side and the balance fitting needs to be screwed into the back cover. If there is no pre-existing balance fitting you will have to take the cover off and tap in a 1/2 inch hose fitting. Plug up any small vent holes there may be in the back cover.


Hi Beeutey. Further to the info you gave me previously, I'm going to fit a balance pipe as you describe here.

When you say it has to be fitted between your old aircleaner inlet and the hole at the back of the converter, does that mean on the dirty air side of the air filter?

What would be the best place to connect to the plastic airbox in a Disco 1 94-98 model?

[bee utey]

Hi Bee utey. Further to the info you gave me previously, I'm going to fit a balance pipe as you describe here.

When you say it has to be fitted between your old aircleaner inlet and the hole at the back of the converter, does that mean on the dirty air side of the air filter?

What would be the best place to connect to the plastic airbox in a Disco 1 94-98 model?

Usually when I connect a balance hose to a snorkel set-up I drill into the adaptor where it goes through the mudguard. The picture is from another AULRO member's snorkel install. If you connect to the clean side of the element you will not get the same power/airflow relationship as you had before. You would then possibly need a smaller mixer on the manifold. As I said before, it is the total restriction of the intake (up to the balance hose) that determines the gas mixture. If you change the intake length to the balance point it will certainly change the mixture. When you have finished just turn the main mixture 1/4 turn in either direction and test drive. You want the minimum amount of gas to give you maximum power. Any more is a waste.

[Utemad]

I fitted the balance hose on the weekend. Bought the correct fitting for the unit but used old gas vapour hose and garden fittings for the rest of it.

Connected up as per Beeutey above but my snorkel is a Safari so different execution.

No more stalling so I'm happy with that.
I also tried turning the ram head backwards which worked well too.

[PhilipA]

I tested the ram effect of a snorkel at 80-100Kmh in my 93 RRC 3.9 with a Minihelic gauge with input in the pipe between the aircleaner and MAF, compared to ambient pressure inside the car. Snorkel is LRA with standard head facing forward.
The ram effect was barely discernable but positive at approx 1 inch of water at 80-100Km cruise with very small throttle opening.

Interestingly the difference in throttle resonse is really noticable if you turn the head around.
Regards Philip A

[Waxenwane]

I tested the ram effect of a snorkel at 80-100Kmh in my 93 RRC 3.9 with a Minihelic gauge with input in the pipe between the aircleaner and MAF, compared to ambient pressure inside the car. Snorkel is LRA with standard head facing forward.
The ram effect was barely discernable but positive at approx 1 inch of water at 80-100Km cruise with very small throttle opening.

Interestingly the difference in throttle resonse is really noticable if you turn the head around.
Regards Philip A

Was it better or worse Phillip?

[PhilipA]

Was it better or worse Phillip?

I assume you mean the throttle response. It was as expected better with the snorkel top facing forward.
Very mild supercharging so more air for a given throttle opening. Fully sick man.
Regard sPhilip A
Just remember that if it is turned around you will have a low pressure area over the opening so the effect is magnified.
I couldn't be fussed to measure it.

[mmoff1970]

This also happens with forced induction and LPG the balance pipe solution does work