Cng Kits: More Info Needed - Page 4 - Chevy and GMC Duramax Diesel Forum
Alternative Fuels - Diesel - Additives - Lubricants Discussion of diesel, its various additives, oils, lubricants and alternative fuels IE: Bio-Diesel ect...

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post #31 of 38 (permalink) Old 08-20-2011, 09:49 PM
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post #32 of 38 (permalink) Old 08-20-2011, 09:55 PM
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Originally Posted by JKans View Post
just fyi-propane is WAY safer than cng. its also much much easier to obtain and usually cheaper (unless you have an free supply on your property). I installed propane kits at my last job and we saw a gain of 50 hp and 800 ft/lbs on a cummins ISM (class 8 truck in Estes trucking fleet) from just propane. If you have any questions about propane injection feel free to shoot me a pm

propane is not safer because it has a lower octane and it is NOT even close to being as cheap as CNG

edit: you must be talking about some type of one in a million explosion and not the engine

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post #33 of 38 (permalink) Old 08-20-2011, 11:41 PM
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I agree, cng is safer actually because if it leaks it will rise up into the air and disipate, meanwhile lpg tends to sit low and could cause fire. You also will not get a noticable mpg gain with lpg like you will with cng, but you can get just as much power gain. If you are looking to use less diesel per mile cng is the way to go.

Don't have a d-max, but my family has 3, a 2005 with a 6" cst lift on 35's, a 2006 with a 6" rcd lift on 37's, and a brandnewish 2010 not currently lifted yet but plans in the works (he just traded in his 2003)
I do have a 93 jeep Cherokee with a 8 inch rustys off road long arm kit, 33-11.5x15 mudders and a "short top conversion" which means I rolled it and cut the roof off.
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post #34 of 38 (permalink) Old 08-21-2011, 03:33 AM
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this is an old post from 2008 up north we have to run the propane the cng just wont work in the cold temps we get here.
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post #35 of 38 (permalink) Old 08-21-2011, 06:05 AM
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Propane is NOT safer than CNG! Propane has a lower octane,will spike easier and is more money. Yes there are downfalls with cng. The tanks are bigger and it's not as easy to get but other than that it's better. I'm really surprised someone seen higher egt's, it always lowers mine. Maybe if your way over fueled with diesel it could add heat but if your tune is correct it should lower them. Jeff

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post #36 of 38 (permalink) Old 08-21-2011, 07:09 AM
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wish i still had the dyno sheet. motor showed 330hp and 2500ft lbs before the propane and 380 hp and 3300 ft lbs after. of course this is on a huge 6 cyl so the potential for improvement is higher.

as for propane being a safer fuel, i believe it is. lpg never reaches a pressure above 250-300 psi unless its in a pressurized system. cng never turns to a liquid and thus needs to be stored under immense pressure. this means propane will not explode from its tank if there is a leak or if it is heated past the PRV's blow-off pressure. A discharge of propane has no effect on the environment whereas cng is a greenhouse gas.

Also when i lived back in KC, cng was much harder to find than propane. its the same up here in maine. i think outside of ohio/penn and texas/oklahoma area propane is more widely available but i could be wrong.

Propane is safer for the environment as well as our trucks AS LONG AS it is a well tuned system. Vapor propane systems rarely ever spike. this is usually caused by a bit of liquid getting past the vaporizer and into the intake manifold. vapor systems usually have a diaphragm regulator as the first step in the supply line of the system and these tend to freeze up when liquid enters them which stops flow kind of like a fail safe measure.

I WILL ADMIT i have had very very little experience with cng kits. but i have seen the excellent things propane can do and I think its a much safer automotive fuel for our engines, the environment and passengers. If i am incorrect, please let me know.

these are the kits we put on trucks, i'll hopefully be getting one soon:ACME Alternate Fuel Systems- PRODUCTS

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post #37 of 38 (permalink) Old 08-21-2011, 10:29 AM
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Cars have had cng tanks installed in the trunk, and have been rearended to the point of destroyineg the car and the cng tanks were not damaged at all.
The original poster was curious about mpg gain and even skeptical. You will never see lpg get a mpg gain anywhere near cng.
If your lpg regulator is freezing up you have it installed wrong. You should have coolant running through your diaphragm regulator and that is where it phase shifts from liquid to vapor. On a cng build it is always vapor pressurized at either 3000 psi or 3600 psi depending on where you live. You have two regulators, one to reduce from tank pressure to close to 100 psi which has coolant in it to keep from freezing, and the second diaphragm style (almost exactly the same as the lpg one without coolant in it) which drops pressure to about 5 psi.
Cng in Utah costs around .60-.80 per gallon last time I checked. I. AZ it was more like 1.50 a gallon.
If all you are looking for is power in a working vehicle than lpg is the way to go. If you don't mind losing some bed space for tanks and getting 30 mpg on diesel then maybe cng sounds better. They both have their trade offs.
I had no tuner on the 04 dmax I had cng on. I saw higher egts while either going WOT playing with it, and when pulling a loaded two car trailer on steady up hills (phoenix to flagstaff). I did not have the ability to adjust the mix from inside the cab so I could only turn it off and back on via a pyro with a relay controller. I quit working for that guy after some shady business practices became evident.

Don't have a d-max, but my family has 3, a 2005 with a 6" cst lift on 35's, a 2006 with a 6" rcd lift on 37's, and a brandnewish 2010 not currently lifted yet but plans in the works (he just traded in his 2003)
I do have a 93 jeep Cherokee with a 8 inch rustys off road long arm kit, 33-11.5x15 mudders and a "short top conversion" which means I rolled it and cut the roof off.
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post #38 of 38 (permalink) Old 08-21-2011, 02:55 PM
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Both cng and lp are pretty safe, they both have advantages and disadvantages. You definitely can carry more lp in a smaller tank since it is liquified, but there is the pooling issue in an accident with a tank rupture or a leak in an enclosed area. Liquified natural gas helps the density issue by a good bit, but I think it will be a long time if ever it is used for anything but commercial trucks and large equipment. Plus, if you think it is hard to find CNG, try to find LNG.

They both give the same horsepower gains. Propane is easier to hurt an engine because of its lower octane rating, which makes it detonate easier than cng when using large quantities. I ran propane in my Duramax for tens of thousands of miles at a high percentage, one time averaging 64 mpg on diesel for 1500 miles. I never really averaged more than 55 diesel mpg on cng with my mechanical system. So, at light load, you can still run quite high percentages of propane.

I have been working on an electronic controller for the system for two years. I commonly average over 100 mpg on diesel while running cng. I doubt I could do much more than around 70 mpg diesel supplementing propane. The problem with propane is that it costs so much more than it used to. I used propane for many years in gasoline engines and for about 4 years in my Dmax. I now only have cng on the Dmax, and I do have reduced range, but the price difference is large. A GGE of cng at $1.50 would equate to $1.10 for propane. It is tough to find lp for less than $2.30/gal even in quantity.

Regarding EGTs, both fuel will send them to the moon. My Dmax is stock, and if I run full diesel and gas, I can hit 1400 in 7 seconds. This is because it is making 100 extra hp. I would imagine if it was all diesel making that extra horse, it would do the same thing. The key is back out of it when temps get high. My controller limits diesel so that temps never get out of line.

'04 CCLB D/A LLY w/supplemental CNG gas injection, Harvard bypass oil and trans filters
'05 Jeep Liberty diesel w/supplemental CNG
'95 Suburban 4BT Cummins w/supplemental CNG
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