Usually, once someone has done their homework, they regurgitate the things they've learned to share with others. To clarify a few points:
- Dual-Fuel: operating on 2 fuels simultaneously (EPA Definition - EERE Glossary D)
- Bi-Fuel: operating on 2 fuels on an either-or basis (EERE - Glossary B)
- Diesel-CNG Dual Fuel: operating on both diesel and CNG (ARB 2025, p6, item 25)
The way I understand it, fumigation is the delivery of a gaseous fuel with a mixing device, which usually has a venturi of some sort to cause the fuel to flow from the regulator. The Impco Model 425 mixer
is an example of a fumigation device. Injection is the delivery of a gaseous fuel with electronically controlled and solenoid-actuated valves. Technocarb's ESIP System
is an example of an injection system.
I do not believe there is a CNG cylinder recertification program. AFAIK
, once the cylinder reaches its expiry date, legally it must be scrapped. If this isn't true, please explain how a CNG cylinder may be recertified. If a cylinder continues to be in use after its expiry date, how would you reduce your liability if something goes wrong?
I must live a sheltered life. What's an AA Cooler?
The only way simple mechanical (on-off) diesel-LPG systems (like the Bully Dog) avoid detonation is by keeping the LPG supplied at a relatively low and constant rate. If it's high enough to have a significant effect on fuel economy, it can be high enough to knock at high loads. I expect that the Naturell CNG system was very similar to the Bully Dog LPG system.
After reading the DeLuca Fuel Products' description of "The Fuel Stretcher" (TFS) system, it sounds as if it is using a conventional propane regulator to supply propane or CNG to the engine. Their CNG page shows a photo of the TFS system, which appears to use an Impco Model VFF30 Fuel Lock and a Model J regulator. The output pressure of a Model J is either -1.5", -0.5", or -0.2" WC (Water Column) and my guess is that it is probably a Model JO (-0.5" WC). This means that the CNG won't flow until the pressure in the regulator's output vapor line drops below -0.5" WC. This is the vacuum required to lift water in drinking straw 1/2".
Since "The Fuel Stretcher" requires vacuum in the intake duct to work, as described in TFS's Theory of Operation, fuel doesn't flow at idle because duct vacuum is zero. TFS doesn't have any means of load-based control because it supplies fuel based on vacuum upstream of the turbocharger. The vacuum level in the intake duct (between the air filter and turbo) increases with the square of air flow so it is theoretically possible to overfuel an engine with it. The manual fuel control valve is there to minimize this possibility. Although not mentioned on the DeLuca's web site, the TFS uses a venturi in the intake duct (to boost duct vacuum) so fuel starts to flow when venturi vacuum reaches 1.5", 0.5" or 0.2" WC (see MrTruck.com - CNG
). I believe there may already be members of this forum that have experience with this system and bugmasta has installation manual that he could email. DeLuca appears to have a more sophisticated system in the works (expected Fall 2009) which recognizes the need to avoid detonation.
I'm not telling anyone not to buy the DeLuca diesel dual fuel system. I'm just suggesting that you're sure of what you're getting before you lay out any cash. I'm also suggesting that a sophisticated diesel dual fuel system that uses a fuel map to control fuel flow will be cheaper in the long run than a much lower priced simple mechanical system.