Contemplating CNG conversion

[getnpsi]

I dont know much about gas laws and pressures aside from what I can google but if there is a lower teir of cert's and equipment at say 2400 psi or something and the equipment would still work ok would that lower upfront costs? Understood a boom is a boom and a horrible thought, but we ARE festiva owners and cheap is awesome.

You can take a man who's blown his money on the most dumb things his whole life, but if he has a competitive nature and sees someone else braggin' about saving money he can turn into the worst tightwad ever overnight. I've watched this happen on ecomodder and other sites online. They have a 500 benz(for sale) and a metroxfi/honda vx/some random subcompact diesel in their signature LOL

[getnpsi]

yeah, and another item i have been researching lightly is making my own PHILL-like system... stepper compressor.. but by what other people are saying about it.. little bit of safety issues arise. Still need to contact a local compressor place to see what they know about compressing to 3600+psi... safely.

Its "apples to pears" i guess but what about propane? If you are sitting on significant land and have a tank already that gets deliveries, can you fill smaller tanks with the home storage tank somehow? Probably answering my own question but that's probably a worse safety issue that something plumbed into a home line with a compressor. I think those retailers of propane have EPA titles and junk

[hefty]

Has anybody here actually torn down a CNG engine after 100k? I have. From what I've seen the CNG doesn't provide the lubrication to the valve body that gasoline does. The valves and valve seats on almost every 100k+ CNG engine I've seen are completely shot. The valve seats are so worn down the heads need to be replaced. Valve stems look like a beaver has chewed them down. )(

On a side note: We run liquid to gas LPG conversions on several of our off road rigs. Basically a dual fuel set up to allow the engine to run at extreme angles (like upside down) I haven't seen any issues with this but we run gasoline most of the time and only switch to propane when needed.....or the gas tank runs dry. Propane also has an octane level of about 110 so plan on advancing your timing.

[Eaglefreek]

Will they fill your tank if it was a DIY conversion? When I was looking into it a few years ago, it had to be installed by an EPA certified installer in order for most places to fill your tank.

[ejp2fast]

Has anybody here actually torn down a CNG engine after 100k? I have. From what I've seen the CNG doesn't provide the lubrication to the valve body that gasoline does. The valves and valve seats on almost every 100k+ CNG engine I've seen are completely shot. The valve seats are so worn down the heads need to be replaced. Valve stems look like a beaver has chewed them down. )(

On a side note: We run liquid to gas LPG conversions on several of our off road rigs. Basically a dual fuel set up to allow the engine to run at extreme angles (like upside down) I haven't seen any issues with this but we run gasoline most of the time and only switch to propane when needed.....or the gas tank runs dry. Propane also has an octane level of about 110 so plan on advancing your timing.

Very interesting on the accelerated wear on the valve body.. I ran across this 'lubrication' topic in my research, but many people didn't seem to know the true long term life. My thoughts are- running BOTH cng / and gas.. if you still run your gas occasionally, then it would provide some 'better' lubrication than a sole CNG car... I wonder how the Civic GX deals with this issue of valve seat wear?... hmmm...

Will they fill your tank if it was a DIY conversion? When I was looking into it a few years ago, it had to be installed by an EPA certified installer in order for most places to fill your tank.

CNG Conversion kits that are EPA certified are supposed to be installed by someone who is certified. The CNG kit in the original post is NOT EPA certified, and therefore is a 'install at your own risk' but certified installers will still install it.
As far as tank filling- totally separate from "EPA Certification" discussion.. Here in Oklahoma, you pull up to a place, swipe your card (or pay cash), and fill your tank as needed... Just like a regular gas station pretty much.
May be different in other states..

[Pu241]

Has anybody here actually torn down a CNG engine after 100k? I have. From what I've seen the CNG doesn't provide the lubrication to the valve body that gasoline does. The valves and valve seats on almost every 100k+ CNG engine I've seen are completely shot. The valve seats are so worn down the heads need to be replaced. Valve stems look like a beaver has chewed them down. )(

OK, so your "the man" on this topic!
What did the pistons and cylinder walls look like?
Just thinking upper cylinder lubrication would also be an issue for the cylinder walls too, might be wrong at that though.

[hefty]

multiple hair line cracks in the cylinder walls. We ditched the block.

[Pu241]

multiple hair line cracks in the cylinder walls. We ditched the block.

Do you think it was directly caused by using CNG?

[getnpsi]

100k is a magic number for automakers to look the other way, what do they care.

CNG also uses 12:1 compression ratio on OEM applications so that is like being in boost all the time for engines that may or not be designed for those kind of stresses.
So, if you wanted to do a rebuild for CNG, after addressing a few issues you are pretty much making a turbo build w/o the fun factor

I know CALI is first on a lot of the pollution issues as we no longer have diesel buses or trash trucks anymore. I see trash trucks breaking down or smoking like a train quite often, and as a commercial vehicle they have to be maintained and inspected like every other big truck out there. the top ends simply fail more often.

[ejp2fast]

CNG also uses 12:1 compression ratio on OEM applications .

Yes, the Civic GX, (only OEM application as of now sold to US) has a 12:5 comp ratio..

Hefty, very good information that you have... Please give a little more details of your teardown for the CNG vehicle. IE, make, model, year, specs bi-fuel or cng only, reason for teardown, gaskets/seal condition and other info you have. You seem to be one of the only ones that have truely torn one down (as PU said "the man" on this topic), so lets pick your brain!

Edit: Any pics of the teardown? If so... you know what to do....

[Larry Hampton]

Yeah, we need more information.

[ejp2fast]

Hefty pm'ed me as i was asking about details on his cng teardown. to paraphrase his msg:
"As gasoline is petroleum (oil) based and provides lubrication to the top end of the engine.. The teardown he did was on a Ford Service truck that had 120K ish miles and was SOLELY on CNG, not bi-fuel. Cylinders, cylinder walls, Pistons, Valves, stems and seats all end up wearing out at a much faster pace on the CNG only engine, as no lubrication is there. "

Interesting info. I would say that a bi-fuel engine then would at least have some lubrication when running on gasoline. My take, even IF the top end were to wear out on a B3 engine "faster" (as in 150-200K), top end is easy to replace
Now, a 2009 or newer SUV? Maybe a little different.

[JT399696]

Hey,thanks for posting the CNG info.Me and my landlord have half a dozen Festivas.Some are carbed and some FI motors. The reading that I did a while back on CNG conversion could have been dated info,but it claimed you had to have a carbureted motor.But I really dig the part about being able to switch back to unleaded when necessary.
I used to work at a local VW/Audi shop in Macon,Ga. The owner was big on CNG and bio diesel for the TDI cars.I saw him run a 1600 air cooled VW engine on the stand with a propane line stuck in the carb.It ran very well.And if you turned the gas up a little it would pulsate pretty blue flames out the exhaust tips.Very cool.
I did not know that the tanks could be such a problem.I thought that if we did the conversion that we would just use a standard forklift size tank. Please continue to update us on the subject. We are very interested in doing this same project.

[Larry Hampton]

I'm calling bull on gasoline providing lubrication to the cylinders and top end. That's what oil is for.

[skimsucka]

that things so awesome