Auto-LPG Conversion Thread

[dencio1976]

oh and also, it's not only the engine parts that need lubrication. you also need lubrication for your combustion chamber. that's why lpg guys recommend that you run your cars atleast once a month with gasoline.

[ssalonga]

oh and also, it's not only the engine parts that need lubrication. you also need lubrication for your combustion chamber. that's why lpg guys recommend that you run your cars atleast once a month with gasoline.

Dencio, actually the combustion area needs no lubrication at all. Any lubrication in that area would result in more smoke and would increase pollutants in the exhaust pipe. Only two stroke engines receive oil in the combustion chamber.

Besideds, all engines after 1992 are already designed to run without lead sulfides in the fuel (thus "unleaded fuel") and do not depend on the fuel for "partial" lubrication. You are arguing on a myth.

please read a bit more on fuel theory and practice so you can distinguish urban legend and opinion from facts. Tom Jennings article is a practical and scientific analysis, and would be quite informative for any machine head who wanted the facts, check it out at:

http://www.wps.com/LPG/LPG-book-final.html

with these basics you might be able to explain why your taxis do what they do!

cheers!

[dencio1976]

What about reduced maintenance costs and improved performance?
LPG, as it passes through carburetors and vaporizers, deposits heavy-end buildup, which inhibits performance and requires disassembly and cleanup of these components. This is a time consuming process that can disable vehicles in the fleet for prolonged periods. Labor costs to regularly clean these components can add significantly to the cost of maintaining each fork lift truck in the fleet. CGX-4® Premium Propane Fuel greatly reduces these buildups. Valves and upper end engine components do not get lubrication from the crank case, and LPG does not naturally provide proper lubrication to these components. This leads to greater wear and major engine failure. CGX-4® Premium Propane Fuel improves the lubrication of these components.

picked it up from a website. http://www.energyadditives.com/html/...additive_.html

ok so maybe i was not entirely accurate with the combustion chamber lubrication but rather that your engine valves need lubrication. one that gasoline provides. it's obvious that your research is biased. after all, there wouldn't be complaints or rumors if there was none to talk about in the first place. and i hope i really get to learn from a mechanic to speak on your behalf. i would really love to be proven wrong on this. lpg is good business for taxi operators despite an up in maintainance.

[dencio1976]

also, there's a thing called fuel oil additives. why the oil on it? basically it is said to prevent sludge buildups. there's a whole lot of list but im particularly interested with the sludge buildup on the piston which is evident on lpg ran taxis compared with the sludge buildup on the pistons which are ran on gasoline.

oil = lubrication. it's no myth sir.

[dencio1976]

with regards to private owned cars, id like to clarify that with regards to maintainance, cost up would be negligible to none i assume. my guess is since private cars wont be facing as much traffic as taxis, it can get a lot of cooling down compared with a taxi that has to go on traffic after traffic.

however id prefer not to still go with the lpg not only becoz of the tank in the trunk but becoz of reduction in optimization of power in your rpm bandwidth. what the heck am i saying? let's say u drive regularly under 3k rpms. you'd have an lpg guy tune your settings to conform with your under-3krpm-style of driving. with an emergency at hand or just a rush, try going let's say 5-7k rpms... observe the sparkplug color burn. i can only say this for the cheap lpg conversion kits. not the lpg kits with control units used for fuel injection. even worse for the naiadss 1st gen kit since lpg flow does not vary within rpm range.

but then again, lpg kits are for those who want to save up in fuel cost. but that's just not me.

[dencio1976]

ive read a couple of issues that you've posted. i find that it's only 1 guy on a lpg research. one actually says that he's been using his car for 14years no prob on lpg. which ive no doubt. but then examine his findings. too many numbers, too many theories. mostly just theories. again, no doubt that his 14yr old car is in superb condition with his lpg. why is it so, becoz he can tune his car to his driving style. with his theories and experiment that backs what he's saying. unfortunately, there are lots of variants that make a theory non-applicable to all.

but then he did say that his mpg on lpg is better on gas. which really leads me to think that he does know his thing on lpg. but i recall shell, on their website, saying that kilometers/liter is greater on gasoline than with lpg. only that lpg is heck a lot cheaper. hmm, curious! i find that shell was right about this based on my experience.

[ghosthunter]

oh and also, it's not only the engine parts that need lubrication. you also need lubrication for your combustion chamber. that's why lpg guys recommend that you run your cars at least once a month with gasoline.

regarding this point, isn't it more that the gasoline in the fuel system will not "stagnate" than lubrication?

[ghosthunter]

.... becoz of reduction in optimization of power in your rpm bandwidth. what the heck am i saying? let's say u drive regularly under 3k rpms. you'd have an lpg guy tune your settings to conform with your under-3krpm-style of driving. with an emergency at hand or just a rush, try going let's say 5-7k rpms... observe the sparkplug color burn. i can only say this for the cheap lpg conversion kits. not the lpg kits with control units used for fuel injection. even worse for the naiadss 1st gen kit since lpg flow does not vary within rpm range.

I am using a NAIADSS LPG kit. My driving habits range from cruising at under 3K rpm to gunning the engine to the redline when the road is open. I have already changed my sparkplugs and my old plugs' colors are "normal", no evidence of lean burn, overheating, etc.

The LPG flow system is controlled mainly by the vacuum pressure at the venturi ring. So at idle, my engine only uses the basic flow rate but at higher RPMs, the engine will suck in more LPG fuel.

Personally, I have toyed around the settings (adjustment screws & knobs) for my LPG kit when I first had it installed so I think I know how it functions. I have driven over 160kph on the expressways in my Corolla 1.6L A/T. I don't think LPG limits my performance that much.

but then again, lpg kits are for those who want to save up in fuel cost. but that's just not me.

Given the higher prices of gasoline today, LPG is a viable alternative.

[ghosthunter]

What about reduced maintenance costs and improved performance?
LPG, as it passes through carburetors and vaporizers, deposits heavy-end buildup, which inhibits performance and requires disassembly and cleanup of these components. This is a time consuming process that can disable vehicles in the fleet for prolonged periods. Labor costs to regularly clean these components can add significantly to the cost of maintaining each fork lift truck in the fleet. CGX-4® Premium Propane Fuel greatly reduces these buildups. Valves and upper end engine components do not get lubrication from the crank case, and LPG does not naturally provide proper lubrication to these components. This leads to greater wear and major engine failure. CGX-4® Premium Propane Fuel improves the lubrication of these components.

picked it up from a website. http://www.energyadditives.com/html/...additive_.html

ok so maybe i was not entirely accurate with the combustion chamber lubrication but rather that your engine valves need lubrication. one that gasoline provides. it's obvious that your research is biased. after all, there wouldn't be complaints or rumors if there was none to talk about in the first place. and i hope i really get to learn from a mechanic to speak on your behalf. i would really love to be proven wrong on this. lpg is good business for taxi operators despite an up in maintainance.

Your quoted article comes from a site SELLING the propane fuel additive. Won't that fact bias the facts posted on that site?

[ghosthunter]

also, there's a thing called fuel oil additives. why the oil on it? basically it is said to prevent sludge buildups. there's a whole lot of list but im particularly interested with the sludge buildup on the piston which is evident on lpg ran taxis compared with the sludge buildup on the pistons which are ran on gasoline.

Curiously, how did you come across the above mentioned sludge build up on the engine pistons on LPG taxi cabs as compared to gasoline taxi cabs? Do you maintain a taxi fleet?

[ghosthunter]

ive read a couple of issues that you've posted. i find that it's only 1 guy on a lpg research. one actually says that he's been using his car for 14years no prob on lpg. which ive no doubt. but then examine his findings. too many numbers, too many theories. mostly just theories. again, no doubt that his 14yr old car is in superb condition with his lpg. why is it so, becoz he can tune his car to his driving style. with his theories and experiment that backs what he's saying. unfortunately, there are lots of variants that make a theory non-applicable to all.

Let us point out the facts here:
- For 14 years, this guy has used LPG as his choice fuel for his vehicle.
- His engine valves did not have any accelerated wear & tear issues.
- His engine did not have any sludge build up on his pistons.

[ssalonga]

Hhh! Well said ghosthunter!

Dencio I believe is the son of a taxi operator though he has not mentioned in his previous posts the occurence of sludge in their own cabs.

Dencio, if sludge build up is a fact, why would you continue to use LPG in your cabs? Why haven't you convinced your dad of the evils of LPG?

BTW, haven't you found the propanebashers website yet?

cheers!

[diesoline]

could it be that the sludge that dencio is referring to is similar to the residue that builds up on the rings of lpg burners and those found on the bottom of cooking pans used on lpg burners?

[Alpha_One]

Any unleaded capable engine does NOT need any "lubrication" of the valve seats. Leaded fuel used to serve as the protection of exhaust valve seats (due to high exhaust temperatures, compared to much lower temperatures from the intake mix). With modern engines, it's a non-issue. A lot of cities (such as Hong Kong) run their taxi fleets on LPG.

Two-stroke petrol engines (because the fuel serves as the lubrication itself) and diesels (for the high-pressure injectors) need lubrication in the fuel (diesel is actually an oil). Four-stroke petrols take in a fuel/air mix, which does not have ANY opportunity to lubricate anything and adding oil to it will NOT have any benefit (unless being invisible to the car behind is a benefit to your particular application, for those of us who aren't James Bond, no oil in petrol = good).

LPG will require a few tuning changes for the most benefit, but the same can be said for ethanol blends or high-octane fuel. Ignition timing and correct air/fuel mix is a bit different with LPG than it is with petrol, among other things. However, LPG and petrol are fundamentally the same in how they work (or shall we say, they work in exactly the same way, considering that they fuel the same engines). Driving style and conditions (whether you drive hard, stop go traffic, crusing, etc.) is a red herring. LPG vs. petrol is really more along the lines of regular vs. unleaded or 100% petrol vs. ethanol blend. As opposed, of course, to petrol vs. diesel which use DIFFERENT engines that are PRINCIPALLY different hence require different driving styles.

What I'm saying is that among the many practical reasons NOT to get an LPG kit (such as lost trunk space and high initial cost which may take too long to recover), driving style/conditions and valve seat wear are not in that list. We don't use LPG kits ourselves - because we need the space and don't run around much.

The Early Petrol Engine
One of the first things that early engine designers noticed was that valves and valve seats wear out. Hardly earth shattering news because all highly loaded mechanisms wear out of course but exhaust valves and seats tended to do it rather fast. Early engines were made out of cast iron which is a pretty decent structural material but not ideally suited to the temperatures and loadings experienced inside a combustion chamber. Valves were, and still are, made from various grades of steel. Valve seats were machined directly into the cast iron parent material of the cylinder head. The problem that became apparent was that the material comprising the valve seat gradually wore away leading to the valve sinking deeper into the "throat" of the port. This reduced and eventually eliminated the necessary valve lash clearance in the valve opening mechanism leading eventually to the valve not closing at all and the seat then burning out very quickly indeed. Research into this wear, or "erosion" revealed what was actually happening.

The Mechanism Of Valve Seat Erosion
The rate of wear was far higher than pure frictional or mechanical considerations alone could account for. If one were to construct part of a dummy engine consisting of just a valve and a cast iron seat and cycle it open and shut millions of times on a test bench, very little wear would take place. What this fails to account for is the temperatures that are reached inside a running engine. Copyright David Baker and Puma Race Engines

Components inside the combustion chamber of a running engine are exposed almost continually to the heat of the burning air/fuel mixture. In the absence of any cooling this would be enough to melt the hardest steel. As it is, most of the heat is transferred away into the cooling system or flushed out as hot exhaust gas and the steady state temperatures of the various internal components obviously stay well under their melting points. The hottest component is the exhaust valve and its seat. All the heat picked up by the valve head has to be conducted away though the seat and to a lesser extent through the valve stem into the guide. The thinner the valve seat the less area there is for this heat to be conducted away - something many race engine builders ought to bear in mind. Temperatures in these critical seat areas can reach 800c which is enough to make steel glow red. This is still well below the melting temperature of steel (or iron) but enough to soften it somewhat and significantly reduce its strength. Part of the increased wear rate can be explained by this reduction in the material strength but it still only accounts for a fraction of the wear experienced. To understand the rest we need to make a quick trip to Japan.

In conventional welding it is necessary to melt both the parent material and the filler rod. A "weld puddle" is formed directly under the torch or arc in which the two materials melt, run together and then cool as one. There is another way of joining metals without melting them though. When a sword is made it is heated till it glows yellow and then hammered into shape. As the strip gets thinner and wider it is folded over onto itself and then heated and hammered again until the two layers join together and the process repeats until many layers have been rolled over and forged into one. The process is one of heat and pressure which together achieve a similar result to that of the higher temperatures of "melt welding".

Now back to valve seats. The temperatures over a seat won't be the same everywhere. High spots and minute flaws in the material can reach higher temperatures than their surroundings because they are less well cooled although they still won't be anywhere near melting. Under the pounding of the valve these imperfections form microscopic pressure welds between the valve and its seat just like the forging of a sword which then get burst apart next time the valve opens and a speck of material is lost. Each weld might be too small to see but over millions of cycles they combine to form erosion which wears away the seat and pits the valve. Copyright David Baker and Puma Race Engines

The higher the temperatures inside the combustion chamber the more these welds are created and the erosion speeds up. So a very important factor is how hard the engine is used. At low rpm and small throttle openings there might be very little wear even when the materials are not ideal because valve and seat temperatures stay low. Under more severe operating conditions the wear rates can increase exponentially. What might be deemed acceptable wear rates then depend very much on the expected life of the engine and its operating conditions. Inlet valves are not generally a problem in any case because they run at much lower temperatures than the exhaust ones.

Solving The Wear Problem
The first and most obvious thing to do is use tougher materials for the valve and seat to resist the wear. Exhaust valves already had to be made of a very tough steel just to withstand the operating temperatures and it was the cast iron seat in the head that was the primary concern. Machining a recess into the seat area and pressing in a tougher steel insert provided an easy solution to the problem but was expensive. So research took place into additives to the fuel to find out if anything would help resist the erosion process more cheaply without modifying the cast iron seats. This also came about as part of the research into raising the octane number of fuels to enable higher compression ratios to be used without detonation and hence increase power and improve fuel economy. A substance that stood out as being very effective in both raising the octane number of fuel and also preventing seat wear was tetraethyl lead (TEL). How exactly it reduces the erosion is not clear but it seems that a thin coating of this material on the seat prevents the microscopic welds from forming. TEL was added to petrol in amounts up to about 4 grams per gallon depending on the level of octane boost required. As concern about lead emissions grew, the amount of TEL per gallon dropped until finally unleaded fuel became mandatory.

From http://www.pumaracing.co.uk/unlead01.htm

[dencio1976]

Curiously, how did you come across the above mentioned sludge build up on the engine pistons on LPG taxi cabs as compared to gasoline taxi cabs? Do you maintain a taxi fleet?

yes i do. its really not much. i and my dad maintain 44 units of taxi,(along with 1-3 helper/s), all running in lpg. it's not really that often that i change headgaskets on a xl corolla with a 2e engine. but compared with the gasoline, sludge build up is more evident on lpg. i've also worked on 4g13s on a lancer el(we have 4units among the 44). same find. then about 4units of sentra series III among the units with the surplus blacktop engine. ive only had about 2 times replacement of the head gasket with the same sludge buildup. ive never really opened the engine for the sentra back when it ran on gasoline. i'll try to get pics next time i have a headgasket replaced.

good for you that you know how to tune your own car. not everyone knows how to thinker with their engines.

with the macro lpg, the lpg flow is controlled by the "rpm" tick given off by the distributer. when u turn the key to on, it will let lpg flow for a few seconds then cut off. i had a chance to work with only 2 naiadss kit and i find that it consistently gives lpg flow to the carb once the key is set to on. i was on the impression that it gave a consistent flow to the carb regardless of rpm the engine was on. thanks for this correction.

[Alpha_One]

Sludge buildup can be caused by a lot of things. Among them low-grade oil, and most probably in dencio1976's case, too rich air-fuel mixture (i.e. too much fuel being fed into the engine, bad for fuel economy too obviously).

[dencio1976]

Hhh! Well said ghosthunter!

Dencio I believe is the son of a taxi operator though he has not mentioned in his previous posts the occurence of sludge in their own cabs.

Dencio, if sludge build up is a fact, why would you continue to use LPG in your cabs? Why haven't you convinced your dad of the evils of LPG?

BTW, haven't you found the propanebashers website yet?

cheers!

well regardless of my find and with the up in maintainance, a list of reasons againts just 1 reason why we go on with the lpg kit on our taxis:

1. boundaries have increased 16.67% in gross. our cabs have an average of about 2k-4k in maintainance monthly. with the lpg went up as much as 5k on average. expense is rather negligible compared to the profit gained. but maintainance guys aint so happy thou. however still more profitable compared with gasoline-ran taxis.

2. most drivers profit about 300-700 in average from gas-ran taxis. then about 700-1.2k with the lpg converted taxis. the obvious choice for most drivers then. back when premium hit 44, an average of 4-7taxis where without drivers. lpg kit, all 44 have drivers with extra drivers even.

3. ltfrb gives +2years more of franchise to lpg taxis. now that's really something.

im rather interested on finding a solution rather than debate on it if it's ok.

[dencio1976]

could it be that the sludge that dencio is referring to is similar to the residue that builds up on the rings of lpg burners and those found on the bottom of cooking pans used on lpg burners?

i was referring to oil seep from the valve seals to the combustion chamber. the valve seals weared down faster with the lpg as compared with premium. but then found that drivers who used unleaded gave faster wear down compared with the premium also. but not as fast as lpg wears down with the unleaded. so back to when we ran our taxis with gas, i had stickers put premium only as it gave out the best result. thats mostly speaking for a 2E engine.

[dencio1976]

Sludge buildup can be caused by a lot of things. Among them low-grade oil, and most probably in dencio1976's case, too rich air-fuel mixture (i.e. too much fuel being fed into the engine, bad for fuel economy too obviously).

so it's basically comparison of lpg versus premium for me. lets try and get a fix on this one.

i read an article about sludge build ups with low grade oil. ive been fixated on the lubrication properties of the premium since, with the same oil, standard setup(valve clearance to .203mm, distributor timing to middle) gave more durability than with lpg, same oil, adjusted to advanced timing for ignition, (since i think lpg has higher octane.. anyone for this correction...), same valve clearance thou. fact regardless of most read theories.

your post prior to this one is an interesting one. gave me a lot of thinking about upgrading to a better oil. may just be the answer i need. thanks!

i thought i mention that lpg has better fuel cost than on gasoline... i alone do the adjustments for the lpg on all our 44 taxis(n still aquiring more). sparkplug color is orange with most. some with red(some drivers prefer their rides faster). white colored sparkplug meant lean n higher temps. black.. rich af mix. im aware of these conditions atleast.

[ghosthunter]

i was referring to oil seep from the valve seals to the combustion chamber. the valve seals weared down faster with the lpg as compared with premium. but then found that drivers who used unleaded gave faster wear down compared with the premium also. but not as fast as lpg wears down with the unleaded. so back to when we ran our taxis with gas, i had stickers put premium only as it gave out the best result. thats mostly speaking for a 2E engine.

Could it be you are running the engines a touch on the lean side (possibly to maximize fuel economy)?