Diesel + lpg = big mpg

[Stubby79]

I'd assume you need to use propane or CNG, due to the compression igniting said fuel...as far as I understand it, diesels inject at/close to TDC, so the power stroke starts then...if you have already introduced a fuel that will ignite before TDC, it will combust as soon as there is enough compression, before TDC, causing knock/detonation. Not good for your engine. Propane has a notably higher octane rating, so it is less likely to happen with it.

Also, from what I understand, "they" claim you get better mileage because you get better/more thorough combustion with propane mixed in, which is part of the reason you don't need to run a whole lot to get a benefit. While gasoline might vaporize well, I doubt it's anywhere near as thoroughly and evenly vaporized compared to a gaseous fuel, so it would not give as much of a benefit.

My thoughts (with no real proof) are that having a bit of propane mixed in effectively increases the compression the cylinder when it ignites, which in turn allows you to get more work(actual mechanical work/power out) out of the same volume of diesel injected. Less pumping losses effectively.

[teoman]

The claim is that lpg helps burn the diesel but i highly doubt that modern diesels are not burning all the fuel. It may have a minimal effect.

The cooling effect will be larger in my opinion. And it is a cheaper fuel.

[oil pan 4]

Originally Posted by teoman

I am not sure, a fuel pressure sensor, and the injector can be pulsed accordingly.

That way one would also have the benefit of water injection (lowering intake air temperatures).

Did you not mention 9 deg C was the lowest temp for diesel intake, lower and combustion suffered?

According to Cummins they recommend their engines draw air from inside the engine enclosure if the engine will be regularly started and operated in temperatures less than +20F.
The reasons given were to reduce start up wear and increase fuel economy.

[teoman]

-6 deg C

[euromodder]

I looked into partly substituting CNG or LPG for diesel in my previous car (Volvo V50 1.6D)
Wasn't economically worth it - savings are low, investment relatively high.
For trucks, diesel-mix systems are available, with up to 50% gas subsitution.

That system wouldn't have costed 50$ or €, but a lot more.
We can't drive around with DIY engine adaptations - yearly inspections starting @ 4 years.


Some research show environmental benefits, others don't when adding LPG/CNG
The right amount of gas (wether LPG or CNG) is essential though
In part-load situations, you may even see an efficiency loss ...


https://www.sciencedirect.com/scienc...10016815000162

[teoman]

I fully agree with what you say. But i have a second hand complete kit for 50 (came off a motorbike) used for 3 months. It will not be an official conversion. But i will get it inspected by the lpg guys for leaks.

Lpg is almost half the price of diesel.

[teoman]

I missed the opportunity to purchase the lpg setup

I also have a new car now, and I am thinking about methane injection. My route is 30 km * 2 (40 mi round trip) which usually involves traffic.

Although i have most of the equipment, i do not want to mess around with CNG.

I am thinking low pressure natural gas, pumped with a small diaphram air pump.

Methane stored in an air mattress with roughly 200*100*20 cm dimensions. That would be 0.4 m^3 of volume or 0.4 liter diesel equivalent of volume. 40 cents worth of fuel.

Car burns approx 5l/100km on average on this trip. So 3 liters.

Seems I can get %10 substitution from 1 airmattress.

[redpoint5]

I'd be tempted to get a pump and tank capable of high pressure natural gas. NG is cheap at my house, and I'm surprised people aren't running off the stuff.

[teoman]

Sorry guys for using this thread as the back of a napkin...

At 100 -130 kph the car consumes about 6l/100km so 6l/h.

If i only use the methane as a cruise assist, at %10 i would need 600 ml / hour equivalent of diesel. This is very roughly 600 liters of methane (@1bar)

600/60 = 10 liters per minute for the pump specifications.

[RustyLugNut]

Originally Posted by teoman

Sorry guys for using this thread as the back of a napkin...

At 100 -130 kph the car consumes about 6l/100km so 6l/h.

If i only use the methane as a cruise assist, at %10 i would need 600 ml / hour equivalent of diesel. This is very roughly 600 liters of methane (@1bar)

600/60 = 10 liters per minute for the pump specifications.

I'm glad someone is keeping this thread going as I have an interest in it too.