propane injection.... - Page 2 - PeachParts Mercedes-Benz Forum

lietuviai · #16 10-22-2006, 11:00 PM

When I had my 300D, I was thinking about trying propane injection but with a far simpler approach. I wanted to try using a propane torch assembly. I would have set the cylinder in the console with the knob on the torch easily accessible. Then I would have attached a long hose to it and ran it to the air filter. When I would have wanted the extra boost, all I would need to do is turn the knob as much as I felt like. I'm curious if it would have worked.
But please, don't try it if you haven't.
It might have been dangerous to carry the cylinder in the console.

networkboy · #17 10-23-2006, 02:17 PM

Quote:

Originally Posted by Zeitgeist

That wastes fuel (and diesel/biodiesel is more expensive than propane). If you can get the same rate of acceleration at .5 throttle as you can get at .75, then you're clearly more efficient...and, it feels pretty good too.

I hate to burst your bubble, but you're not more efficent.
You are supplementing one fuel with another, that's why you need less throttle, because you need less diesel.

What you have to consider is wether propane is cheaper *(including ammortizing the injection setup's expense) per BTU than diesel. If the answer is yes then you are saving money. If the answer is no, then you are spending more on alternative fuel than your primary fuel.

With all the above said, I think it is likely that propane is currently cheaper than diesel (shouldn't be, but is), and likely some of that has to do with taxes. The geek side of me thinks it's awesome, but the practical side of me wonders if it's really worth it.

-nB

WD8CDH · #18 10-23-2006, 05:09 PM

It is slightly more efficient. Extensive testing with my Audi diesel showed that I could go farther on 9 gallons of diesel and one gallon of propane than I could on 10 gallons of diesel even thou diesel has more BTU/gallon.

pawoSD · #19 10-23-2006, 05:24 PM

Perhaps its slightly more efficient since the propane enters the engine as a gas rather than liquid?

Propane is quite cheap, I work at lowes, and I can get it for about $15 for a 17lb filled 20lb cylinder (cylinder exchange program) thats only 88 cents a pound!

mespe · #20 10-27-2006, 03:03 PM

What propane does is it allows for a more complete combustion of the diesel fuel. You really can't consider the cost of the propane because you are increasing the number of ponies pushing the car.

Think about it,,, when you turn on the propane, the amount of diesel that is being injected doesn't go down, i.e. burn propane instead of diesel. So when you turn on the LP, you get a net HP gain for the amount of diesel consumed. Or you get the same speed for less throttle position, but you really turned the LP on to increase your acceleration, so chances are you won't be letting up on the accelerator pedal.

You ever get a hold of Hank from Strickland propane yet?

Good luck.

Marty

www.benzbonz.biz

vstech · #21 10-27-2006, 03:48 PM

and .88/lb is around 7.00/gallon... doesn't sound cheap to me...
John

Kynetx · #22 10-27-2006, 04:27 PM

Quote:

Originally Posted by mespe

What propane does is it allows for a more complete combustion of the diesel fuel. You really can't consider the cost of the propane because you are increasing the number of ponies pushing the car.

Think about it,,, when you turn on the propane, the amount of diesel that is being injected doesn't go down, i.e. burn propane instead of diesel. So when you turn on the LP, you get a net HP gain for the amount of diesel consumed. Or you get the same speed for less throttle position, but you really turned the LP on to increase your acceleration, so chances are you won't be letting up on the accelerator pedal.

You ever get a hold of Hank from Strickland propane yet?

Good luck.

Marty

www.benzbonz.biz

Close, but not really. What you get is the net increase equal to the BTUs from the diesel plus BTUs from the propane. Propane does not cause the engine to get more energy from the diesel. You're just burning a second type of fuel with the oxygen remaining in the cylinder after the diesel has been consumed. That's the reason why there is little to no benefit to NA diesels. Turbos run much leaner, hence the increases in efficiency. VW made an "ECOdiesel" Jetta for one year (maybe two) in 1992. That model had a turbo, but no LDA (similar in function to the ALDA on the Mercs) the idea being that the diesel would burn more thoroughly with the increased leanness.
What you're doing by adding propane is just increasing the fuel. That's it. Your combustion is in two stages, first the diesel then the propane. Sharky posits that you burn residual fuel clinging to piston surfaces, but I doubt it.
One advantage is performance. You can get more power once fuelling ability has been exhausted. Hell, I bet you could lean the IP way out and run mostly off of propane.
The BTU rating of propane is expressed as BTUs/liquid gallon since that's how the fuel is stored. Add BTUs of your oil fuel plus the propane and you can arrive at BTUs/mile figure. From there you could begine to extrapolate an efficiency figure.

Zeitgeist · #23 10-27-2006, 04:51 PM

Ummm, I was suggesting the mode of metering and delivery were more efficient if tied to boost, rather than a WOT switch. I really don't know whether propane fumigation actually makes the engine more fuel efficient; there seems to be a variety of contradictory data out here on the web. YMMV

winmutt · #24 10-27-2006, 05:06 PM

What about on NA? Also are you guys sure the propane is firing after the diesel and not just creating a more efficient flame front?

Also are the MB diesels (617) IDI?