Diesel + lpg = big mpg
 

I have not found much about using LPG along with Diesel to boost MPG but after seeing it on a Chevy 6.5 a friend of mine has been running LPG on and reported 30% improvement in MPG, I decide to give it a try. I have an 06 Jetta TDI 1.9 PD that usually gets about 42-45 MPG hand calc. I added a LPG regulator and small 5 gal LPG tank, piped it into the intake just in front of the turbo inlet. My MFD claims that I have jumped from 48 to over 62 MPG. :thumbup:

I am testing a full tank of Diesel + full tank of LPG to see what the real numbers come out to be but it looks really good so far.

If any one else is interested in trying this it really is simple and not that expensive, maybe $200 if you have to buy everything.

The regulator that I am using came from Impco and is a mod. E. the rest is just hose and shutoff valve and a home made venturi, made from a 1/8 " brass "T", I installed in the inlet pipe to the turbo.

Dieseltim

Ah, but the catch is you must calculate the cost and energy of the propane in your calculations too. With that taken into account I've not seen evidence that engine efficiency is actually improved.

We pay $1.85/gallon of propane. About twice that for diesel.
Just remember it didn't happen if you don't have pictures :)

Yes, assuming your goal is economical, then you need to compare cost improvement (cents/mile). This will include the cost of diesel + the cost of the LPG. If you wish you could calculate an "equivalent fuel economy" on a cost basis like this:

MPG_equiv=M/(Gd+C*Gl)

where
M = miles travelled
Gd=gallons of diesel used
C= cost ratio of LPG to diesel, e.g. (price of LNG per gallon/price of diesel per gallon)
Gl=gallons of LNG used


That way if the cost per gal for LNG is half that of diesel it "counts" as half a gallon of diesel.

If you objective is technical equivalence, then you'll have to do something similar with energy content instead of price. If your objective is carbon dioxide related that you can weight it by the carbon content.

This am on the way to work.
 

Ok, well the forum will not let me post pic yet.

This am I got to work with the reading 66.4 MPG, and miles till empty 535, with 363.3 miles traveled on the MFD.

I realize that the MFD is not real accurate but I will be hand calc. the total diesel + the total LPG to see what the MPG verses dollar is.

If it comes out close to what it is looking like so far I will have about a 30% improvement in MPG over just D2 and only have used maybe 2 gal. of LPG per 14 gal of D2.

So, at $3.85 per gal D2, thats $54 dollars to fill up. That usually gets me real close to 550 miles to a tank. Yes it is a PD so it only holds 14.6 when dead empty, There is no way to purge the 06 Jettas.

So, if I use even 3 gal of LPG @ $1.99, that would be $5.97 per tank of diesel. Or, $59.97 per tank including the D2 + LPG.

So, now all I can do is drive and see how far I can go before I have to refill the D2, then refill the LPG and see how much I have used. :turtle:

Dieseltim

I read a very informative site where the blogger experimented with several improvised systems, one of which used a regulator scavenged from a small BBQ, and a small disposable Coleman camp bottle.

It looked like an interesting option for short term 'on demand boost', particularly for non-turbo'ed Diesels.

If it turns out you get lower combined fuel operating cost/mile, all the better!

I think it should be possible to use (re-purpose) a nitrous solenoid to introduce the LPG, similar to how nitrous is used, no? I believe they have jets of various sizes that can be used. Does that sound correct???

I think your right Beau, i found this wiki on Nitrous where it is mixed with Propane or CNG

It is possible to combine the use of nitrous with a gaseous fuel such as propane or compressed natural gas. This has the advantage of being a dry system and yet still maintaining proper air/fuel mixture. Such a system requires exact choice of jet sizes and gas pressure regulation to provide a consistent pressure to the jets. Other advantages include better air/fuel mixing and distribution and less risk of knocking due to the increased octane of propane and CNG.
Nitrous oxide engine - Wikipedia, the free encyclopedia

Very interesting read for the Diesel propane injection DIY'er... discusses basis, different experiments, crude then more refined systems, safety, variable power level jets

http://www.mrsharkey.com/lpg.htm

So if piping LPG into your engine helps (whether for power or FE) what about piping pure oxygen? An ember in pure oxygen will burst into a fire, and gas would presumable burn cleaner. Say just double the atmospheric percentage of o2.

I've always wondered what would happen if you drove a car in the prehistoric dinosaur era when they say we had a much richer oxygen atmosphere.

I think you just answered your own question, think about it.

The propane injection sounds like a fun project really,if it delivers more miles a gallon and more hp it is on the verge of unbelievable,yet much like the x-files i want to believe.. I can see the reasoning behind the reported benefit of the enhanced burn it may/would cause.

Oxygen "enrichment" has been done by some folks at Argonne National Labs:Clean Diesel Technology.

Thanks for the info. I suppose with all things if you just happen to have a spare or free o2 tank and you can get really cheap refills thats great. 2-10% efficiency across the whole range, more HP, and better emmisions. As long as you invest little, what more or less you gain gives a faster return on that investment.

I guess why this isn't standard stuff is it adds consumer involvement in the refueling process. And leaking LPG or o2 in a crash isn't so good. Not that the tank will rupture, but what safety disconnects will you have that stops leaking the gas on impact?

I don't remember the exact details, but I believe the Argonne system had the technology to chemically change the incoming air onboard (no high pressure O2 tanks). The details are in that link.

MPGs with propane?
Yeah it works, propane just replaces diesel fuel.
After testing on and off for about a year I figured propane on a suburban was too much of a hassle.
The plan was to experement with propane then test water and water methanol injection.
Well I tested the propane, didnt much care for it and never got around to testing the water and water/methanol till 2012.

Wished I would have followed through with water and water/methanol testing or tested had tested it first.

I like the water based system better than the flameable gas based system.

The problem with high compression diesels and propane is if you add too much propane you get detonation, which will ruin the engine pretty quick.
I injected water/methanol (80proof) l mixes with enough methanol at high enough volume on several runs to make around 150 horsepower (had there been enough air to burn it) with no knocking.
The suburban took off like a bat out of hell and left a good cloud of smoke.

Ok. So I'm seriously contemplating this for my 1.6L non-turbo 23:1 CR 1985 VW Golf diesel.

I consistently get about 55mpg gallon already on the highway. But perhaps what I'm more interested in is reducing emissions, black smoke, etc.

Any thoughts? How would this best be hooked up?

One problem I foresee is that on the Golf the air cleaner is in the top of the plenum. So if I add propane it would either have to be before the air cleaner or into each intake runner or I'd have to relocate the air cleaner.

Also this is mechanical injection. So I can't meter propane electronically by taking data off of an EFI system.

There are "illegal" systems that inject CNG instead and can include their own electronic crapola.

Personally I would not waste any effort on LPG unless it were nearly free (which it usually isn't in the US)

CNG is cheaper in most areas and cannot detonate.

Still likely a long payback.

How about LPG plus water. You could maybe inhibit the detonation with water.


Also, could you inject the lpg with a gasoline injector? That would make it much easier to control for us computer oriented guys. I suppose one could have to read the pressure and the temperature of the lpg before injection.

Also the evaporisation of the lpg would further cool the intake charge.

I'd like to know the long term effects of regular use, preferably on different types of engines. Not much point to saving a few bucks in diesel if you'll be replacing your engine within 6 months.

And would a small dose be beneficial to the combustion process without the risk of knocking?

LPG saves nothing over diesel and can detonate.

CNG is about half or less the cost of diesel, and it can notdetonate.

I would not waste time on lpg

Cng requires high pressure tanks and is more of a burden. Lpg already has fueling stations all over.

Besides that cng is more advantageous.

In some places the pricing of the fuel is what provides the benefit.

LPG 3
Diesel 4.5
Gasoline 5
CNG unavailable at the gas station

Money units per liter where i live.

I notice the OP is from 2012, and is long gone now. I suspect it proved to be the low yield burden that many have found it to be.
When it works out, it is usually on pickups that have spare bed space and room for the plumbing, and when the diesel to propane price is closer to 2:1 or better.
Carbon is carbon; Diesel weighs 7.1 pounds per gallon and propane 4.24 pounds per gallon. This is a ratio of 0.597.
Now look at the BTU of each fuel:
diesel = 128700 LHV ( Low Heating Value ), propane = 83500 LHV
This is a ratio of 0.648
Detonation has not been a problem I have heard of when used at the low power settings of cruise.
In a car I would not touch it at all ever, as it involves keeping a pressurized container and potentially leaky plumbing inside your car 24/7/365. I don't mind bringing a bottle home for the barbeque a few times a year, but the other condition sounds a little too risky for me.
If you go the proper route and install a whole certified and vented LPG system, they often use the space from the standard fuel tank for that installation. Not so hot when you want to burn both :)
I kicked it around when diesel was over $4 and propane under $2, for my 12V Cummins truck. In the end I found it did not work for me, as I don't daily drive a heavy truck when it is not needed. Even my sad Toyota Camry approached 30 MPG on road trips and close to 28 mixed driving. Nothing I could do to the truck was going to touch that.

Agreed. I tested it back around 2007 or 2008 and found it to not be worth the trouble.
I would rather use water methanol.

Opposite is true here in Wisconsin, every main city has CNG at the gas station.
LPG is only available in back lots of specialty providers that have limited hours

that's the problem with CNG I looked at the CNG maps here:
CNG Stations | Refueling | Prices | Map
In my area, it is very sparse on the ground. OK is like the CNG capital of the world :D

Well, the economic situation over here has gone for the worse.
New costs

lpg 3.5
Diesel 6.3
Gasoline 7

Monetary units. And salaries have not increased.

Still considering LPG for a diesel. I found a second hand complete kit for 50 bucks. I want to hook it up to a gasoline injector and inject in liquid form after the turbo or intercooler.

If i find that it absolutely has to be in gas form, i would consider injecting it inside a radiator and use it for AC.

Oilpan what did you not like about the system. And how did you implement it? Was it sophiaticated or just bbq bottle and valve?

I built mine for testing only.
I'm pretty sure you need gas or a way to regulate liquid pressure.

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?

The kit i am buying has a gassifier that circulates coolant. But I hope not to be using it to benefit from the cooling effect.

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.

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.

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.

-6 deg C

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

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.

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. :)

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.

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.

Don't worry about it.
 

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