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