Gaseous fuel conversion ideas

[Fast355]

So I am considering switching over my 5.7 Express to a gaseous fuel. Either Propane or CNG, not sure which yet. Considering propane because I can get it at almost every truck stop across the nation due to the fact many Refer units run on LPG.

I currently have a weak fuel pump and I am not too keen on the 18 year old rigid plastic 5/16" fuel lines running from the back of the engine to the fuel tank over the top of the exhaust. Although I have a new Delphi fuel pump in my garage for the application, I am considering building a gaseous system. I am considering a dedicated system, however if I keep the liquid fuel system it will be of much less capacity than stock and likely E85 due to the compression ratio I plan on running.

Now I am getting conflicting information in my research. The engine the gaseous system will need to feed is approximately 450 HP @ 6,000 rpm and 5.7L displacement but may go as much as 383 (3.75" stroker) or 396 (3.875" stroker)one day and thinking of building it for very high compression.

Really looking for your input Caleditor. I know you have experience with gaseous fuel conversions.

[Caleditor]

The fuel pressure regulator is going to be an issue. I like the GFI regulators, but when you have the 9.5 bar regulator "that would be used in your application" that rattle after a few hundred miles. They also can not keep up with the flow requirements. I just had a conversation with Joecar about the injector flow table. I explained it was because of the regulator flow issue. The ITT regulators seem to keep up better, but they are bigger. I would want to attempt to get a sample regulator from them and test the flow on it first.

As far as the injectors go. The old Bosch gaseous injectors have been discontinued, but they have a new NGI2 injector. They flow about 280 # and are a dirrect replacement for the old part number 0280150842

The new NVGI2 short injectors #0280158821 NOTE: the short injectors come with Sumitomo or EV6 type connectors
The new NVGI2 long injector with the EV1 connector is #0280158827

[Fast355]

The fuel pressure regulator is going to be an issue. I like the GFI regulators, but when you have the 9.5 bar regulator "that would be used in your application" that rattle after a few hundred miles. They also can not keep up with the flow requirements. I just had a conversation with Joecar about the injector flow table. I explained it was because of the regulator flow issue. The ITT regulators seem to keep up better, but they are bigger. I would want to attempt to get a sample regulator from them and test the flow on it first.

As far as the injectors go. The old Bosch gaseous injectors have been discontinued, but they have a new NGI2 injector. They flow about 280 # and are a dirrect replacement for the old part number 0280150842

The new NVGI2 short injectors #0280158821 NOTE: the short injectors come with Sumitomo or EV6 type connectors
The new NVGI2 long injector with the EV1 connector is #0280158827

Here is where I get confused. The largest regulator TTI makes for CNG shows to be 165 lbs/hr or less than 21 lb/hr per injector on a V8. However by weight, stoichiometric afr being 17.2 for natural gas, means you need over 15% more gasoline by weight for combustion. Does this mean that natural gas runs a lower BSFC than gasoline? Does that also mean that 21 lb/hr of natural gas is equivalent to slightly more than 24 lb/hr of gasoline? What should the equivalence or lambda ratio be for wide open throttle as opposed to closed loop part throttle on CNG? When you say 280 are you talking about cc/min? Based off initial investigation it looks like I am going to need more fuel than a single regulator can support. At that point, what would it require, dual regulators?

[Caleditor]

I had to change the text color on the old injectors part number

http://www.fiveomotorsport.com/0280150839-turquoise-top
Flow rate: (heptane) 1600 cc/min - 154lbs/hr at 43.5 psi/3bar

The spec's I have are 180lbs/hr. I am guessing that is at the 105 psi, but I am not sure.

I will answer the other questions a little later, I am headed to lunch

[Caleditor]

This is a EPA certified calibration. You can the EQ ratio out of here. I think the GFI 9.5 bar regulator with the 3.9L would be able to hold pressure.

[mecanicman]

I have zero cng experiance, its only run here by the cng supplier company vehicles. Propane I have a lot of experiance with. Propane has less available energy in it than gasoline. You can gain some of it back by taking advantage of its high octane rating through tuning, but your current dyno sheets will be down just switching to propane. If your serious about it, pop some high compression pistons into that 5.7 when you do the swap, something in 12.5-13:1 range. Then your horsepower will be at least the same and probably higher. Straight propane conversion is usually a disappointment from a performance aspect.

[Caleditor]

I have not use for propane except for the BBQ grill my wife uses. The stoich is what about 12 to 1? That's my opinion and I have talked to the propane guys and have listened to them. The 1 and only advantage to propane over CNG is the storage capacity. I will not even argue that point. Hands down Propane blows CNG away in that one area. Other than that one area that could be a HUGE factor for some customers CNG wins out.

I don't want to argue my opinion. I understand why some people like Propane aka Autogas.
I am a certified installer of both fuels

[Caleditor]

This is something to think about

The unique version of the 6.0L engine – identified by an LC8 engine code – features special hardened valves and valve seats that enable it to run on CNG or gasoline. It is rated at 360 horsepower (268 kW) and 380 lb-ft of torque (515 Nm) on gas, and 301 horsepower (225 kW) and 333 lb-ft of torque (452 Nm) on CNG.

GM states that 17 GGE of CNG and 36 gallons of gas will go 650+ miles. They came up with the numbers by running 1 fuel and then the other. You will not be able to empty the CNG tank and it will have 2 GGE or more in it when the pressure is too low to operate on.

A few months back I was at large CNG company. They had a F-250 Texas edition with a Whipple. This truck ran BOTH fuels at the same time and Ford racing did the calibration as they do on all of the QVM vehicles. The salesman said by running both fuels at the same time it extended the range by over 20%. Now this could be all talk, but 20% is huge. I am not sure about all of the facts, I did get several questions answered about the blend. He told me that the 2 Ford ECM's blend the fuels for MPG and load requirements. All of the QVM vehicles run to factory Ford ECM's