Hi,

I need to change my heads because I've been driving too much on LPG here in Europe.

Do you know of npi or pi windsor heads that would withstand LPG (or CNG) ?
I don't know what you think about it but I think that proper seats and valves stems or guides would already help a lot.

 

ROLFI,
I can't answer your question but I am insanely interested in your LPG fuel conversion........

Do you happen to know any details you'd care to share?

MPG
Power Output

Details on the conversion?

Thanks in advance for your time and any info you can share.

 

I've had an AG system till now. It was installed in 2002 (previous owner) and the company isn't anymore alive. The system is not very good and there is no other solution than to replace it.

I'm doing that today. It will be a Prins sequential system and will eventually be able to give some more details in the coming days.

All american pickup's here in Europe run on LPG because of the high price of regular gas fuel. So many motors eventually have the valve (seats) problem arising sooner or later.

Power isn't really an issue. Really you don't feel the difference.

Keep asking. I'll do my best to answer to the extend of my (little) knowledge.

 

Why does LPG cause valve seat problems? They are designed for unleaded fuel which doesn't have the lead lubricant that leaded fuel had. I have run LPG forklifts for years without any head problem. Not sure if they have special heads or not.

 

Ford offers LPG capable engines right from the factory, so maybe the heads are available by themselves.

I ran a 4.9L on LPG for 22 years, after about 100,000 miles the valve seats were shot and actually caused the head to crack. This lead to water in the sump and a bottom end knock. I had the motor rebuilt using harder valve seats. While I liked the performance on LPG, I'm not convinced, given the cost if modern conversions, that it is cost effective in the long run. Of course $10 a gallon gas might change my mind.

 

That's strange. it can't be a lack of lube in the fuel because new engines have direct injection into the cylinders do they have no fuel going past the valves at all.

 

I believe Propane go in Throttle body. I have see this in person before.


Need get new head that design for propane.


What about CNG?

 

CNG is a very low energy fuel compared to gasoline or LPG. Pound for pound, LPG has the energy of gasoline and about 120 octane. CNG is not very compeesed so it has a short range. LNG is very compressed but not readily available and is a different technology.

 

To clarify a few things, CNG actually has more energy than propane or gasoline. According to the US DoE:

• natural gas has about 20,267 BTU/lb
• propane has 19,904 BTU/lb (LPG has about 20,038 BTU/lb)
• reformulated gasoline has 18,211 BTU/lb
• low-sulfur diesel has 18,320 BTU/lb

As for octane, propane has a RON of 112 and a MON of 97 so the anti-knock index (AKI) works out to 104.5.

CNG stored as a compressed gas at 3000 or 3600 psi. LNG is a cryogenic liquid so at -240°F, it is a liquid with a saturation pressure of 18 psig. At -200°F, LNG has a saturation pressure of 100 psig.

CNG is sometimes available in big cities but LNG is mostly found in the Greater Los Angeles area. Some large trucking fleets are starting to use LNG at their central terminals so it's not publicly available. T Boone Pickens is trying to get the USA off of OPEC oil so LNG conversions will likely be more common in the future.

For LPG engines, the factory hardened valve seats normally work well. When they wear, it is common to install hardened valve seats so special heads aren't required. For heavy duty applications, sodium filled valves are sometimes used. If your valve seats are burned, it could be because your fuel mixture is a bit rich and/or your timing isn't optimized for LPG.