Anybody considering CNG conversions, check what I found

[Soul]

Do you think those power goals are realistic with just minor mods? I've been kicking the idea around, thought that would be pretty cool in my 87 ranger I have waiting for a motor.

[cgrey8]

I updated my thread over on EECTuning.org with pics of the tank and valve.

[MalcolmV8]

Looks good man. Can't wait to see this thing running on that gas.

[Warpig Racing]

My brother is looking into a CNG conversion. He bought a tank and is buying a conversion kit from somewhere outside the US. Something like $450 for the kit to retrofit the fuel injection. The tank was purchased from china. Something like $180 shipped.

He mentioned that some DIY are using scuba tank compressors at a cost of $500 or so. There is currently a handful of fill stations in the city. I looked into doing this about 14 years ago just to do it. Problem was gas was too cheap then to justify it.

[cgrey8]

...He bought a tank and is buying a conversion kit from somewhere outside the US. Something like $450 for the kit to retrofit the fuel injection...

If you buy it direct from China, I expect that's about the right price. Although you get next to no support on it. But if you don't need any, then that's an excellent deal. The cheapest EFI kits I've seen for a V8 from American vendors (selling Chinese kits) is $670.

...The tank was purchased from china. Something like $180 shipped...

CNG tanks are rated in Types from Type 1 to Type 4. Do you know what Type and how many GGEs the tank is? Even if it's only a Type 1 3 GGE tank, that's not a bad price at all especially if it is new. If it is nearing expiration or is an expired tank, that would explain the good price. I paid $500 for a used Lincoln Composites Type 4 12 GGE tank (including valve) that has another year of "rated" use on it. Another $150 for the mounting hardware, and $250 to have it boxed, crated, and shipped. The tank is huge. In fact, when I get it in the bed, the top of the tank will be right at or just a little higher than the bed rails:

These tanks sell new for something like $3500!

But put into perspective, its a small Type 4 compared to commercial refueling station reserve tank skids Lincoln Composites also makes:

...He mentioned that some DIY are using scuba tank compressors at a cost of $500 or so...

I never considered that. Scuba compressors do have to get up to some really high pressures although I have no clue what their fill pressure is or if it is different from tank to tank. It's still interesting since I never considered that a scuba compressor could also compress NatGas to CNG. I also had no clue that scuba compressors were that cheap compared to CNG compressors. I wonder if there are safety differences? After all, when compressing air I doubt there's nearly as much to be concerned about if the compressor leaks (while running or after being shutdown).

Doing a quick Google search, it seems Scuba compressors aren't cheap either. In fact, new electric driven compressors run in the thousands too just like CNG compressors. And it seems the fill pressures for scuba tanks are all over the place. I found some that fill to ~2500PSI. Others that can fill to ~4500PSI.

[Dave]

The one thing I'd be concerned about using a Scuba tank compressor with CNG is in what type of seals/"O" ring material they use. I've got some books here that tell what material works for each application. Air is usually Buna N while some of the other fluids use Viton. Last high pressure tank I designed was good for 2200 psi and 700F. 36" id with 4" walls, 40 ft tall. It was used to destroy what was left over from VX nerve gas.
Dave

[cgrey8]

I doubt the NatGas would affect rubber seals. But the lubricant in the crank case of the compressor could. Doing some research on exactly what goes into those compressors is not encouraging. The Part Numbers spec'd by the mfg don't seem to exist. These are the 3 lubricants they recommend:
ESSO SLG150
BP GCS150
Elf P125

I did find that Elf is a synthetic lubricant company that has recently been bought out by Total Oils. And most of the Elf product line is being relabeled as Total brand oil. But I am yet to find a P125 part number for Elf products on their website or on Google searches. I found nothing on either of the other two listings either.

So I've been researching other lubricant mfgs, both automotive and industrial to find an acceptable extreme pressure, anti foaming, compressor oil that could conceivably be used in a CNG compressor. It seems the best lubrication properties come from Group 5 synthetics. However most synthetic oils for cars are only Group 3 oils and motor oils have no extreme pressure additives, only acid-neutralizing detergents that fight off the acid produced by combustion and partially burned fuel that blows by the rings. Interestingly, synthetic gear oils such as rearend and transmission oil have extreme pressure additives and anti foaming agents, but do NOT have acid-neutralizing detergents and thus look to be the most ideal for compressor duty. Anybody else have experience with industrial high pressure compressors to know what oils they generally take?

[Dave]

I just went to my book on "O" rings and seem to have missed chapters 7-8 that cover compatabilty. Oh well. Did remember seeing a chart while at work, oil and gas industry, showing world reserves of oil and gas. Don't think the world is going to run out of gas. Just looking at Russia, that's a lot of gas!

Rank country (cu m) Date of Information
1 Russia 47,570,000,000,000 1 January 2010 est.

https://www.cia.gov/library/publication ... 9rank.html

[Warpig Racing]

I'll find out where the tanks are from. He said that it was type 2, new, and 6.2 gal equilvant.

He is also considering converting his school bus conversion to CNG. I guess the massive tanks are cheaper and would be way too big for small cars and trucks.

As far as the kits go. I don't think it would be that involved to install and get the bugs worked out. I have a friend that works for the local gas company and they do all their conversions in house. They use the fogger setup similar to a NOS fogger.

[cgrey8]

Foggers are the mixer setups and they are very straight forward and easy to install. But they also kill performance. The fogger goes in the flow path of the air and at cruising RPM/Loads, it's no big deal. But at high RPM WOT, the mixer is a huge restriction on airflow. The SEFI conversion kits where you drill taps into the intake don't restrict airflow but require you take the intake off to drill-n-tap it.

For anybody that owns a diesel, I'd think would really benefit from a CNG conversion.