Propane to the max 1

[firefrog]

I've had it. Gasoline is now $1/L. I can get propane for .45/L. My goal is to build a naturally aspirated propane Ford 2.3L for maximum power. I searched and found a few sources that say the max CR is around 11:1 (sketchy details as to why - I'm assuming emissions and timing come in to play). But the odd story tells of 15:1 being possible. My question is (emissions not withstanding) just how high can you go? Of course I'll invest in forged pistons, programmable timing controls, cooler thermostat, cooled intake manifold, cold plugs, hi torque starter, stainless valves, porting & polishing, and a few other power goodies. I live with engines and I've done conversions before and feel ready to tackle a real challenge. I can do a head swap and machining and get to about 14:1 CR. I've already done the work with the checking with the engine. It will all fit. I already know there are cheaper ways to go (eg turbo, bigger engine, etc)and gasoline 'may' be the best route overall. I would like to hear of actual cases where this has been attempted. I don't want to hear why this is a bad idea, but rather what WOULD it take to accomplish it. Thanks

 

[DMan1]

Hi Franz,

Good points on the CARB and EPA cert. I left those details out, but thats what I meant.

I've seen lean burn work on a standard vehicle, but it takes some work and know how to keep the NOx down in the lean range. Probably beyond what a DIYer would want to tackle.

Denis



Denis Kefallinos

 

[contryredneck]

I'm new to this, site but read quite a bit of the alternative fuel forum, and I've been curious about swapping my 1/2 ton '97 Dodge Ram club cab 4x4 w/ a stock 5.9L w/ about 190,xxx mi. on the engine, used as a daily driver (mostly local {>50 mi.}, no interstate), and occasional off-road as well as pulling some moderate sized trailors (around 4000lbs), to propane right now. My other option is scrapping the gas guzzling (10-14 mpg) 5.9L and go with diesel. I've looked into going w/ a diesel, and found I could get one for around $3000 + the trans. I'm tryin to save some money on this for "the long haul". Mostly it's a debate on whether to drive it till the gas burner blows and go with the diesel, or if propane would be a logical choice even if i'm not planning on rebuilding the current engine, I'm just looking for some alternatives that might be a little bit cheaper than gas. I'm a gas and diesel mechanic and know about them, but i dont know much about the propane, for me it's all hear-say. The local Swans company drivers have mixed emotions but say power (shy of stop and go traffic in bigger cities and towns) is comparable to their old diesels as well as their milage (includes idling) and thats in a class 3 GMC thats made for the propane. Just tryin to get some input from people that are more familiar with the propane engines/ conversions. thanks

 

[turbocohen]

Franz wrote: (You will only realize about 770 btu's from vaporizing a gallon of propane from ambient temp/pressurized liquid state to atmospheric pressure vapor. (Latent heat of vaporization) This is not enough to lower the charge air temperature any significant amount. Propane air fuel ratio by volume is roughly 24:1 (not the stoichiometric ratio), so any heat transfer/absorbtion to the charge air would be negligible.)

Mr Hoffman, Do you have data to back up your claim that charge cooling due to latent heats evap have a negligible effect on air density?

 

[rdd48856]

I don't heve the data here, but air has a low thermal capacity , so I'm sure it isn't negligible...as it isn't for gasoline-air mixtures....

 

[franzh]

Turbo;
I was thinking about starting a lenghty thesis on thermal issues but in the interest of my sanity and the sanity and integrity of the forum decided to toss this out:

LPG (propane) at Stoich, in vapor form is approximately 4% of the air by volume. In liquid form, LPG is approximately .0148% of the incoming air. Assume that the air is anything above ambient temperature, and that propane is at vapor saturation temperature, at -44°F, and we can see that the temperature exchange is relative small. Now, we can toss in that the air mass is moving in turbulence and entering a relatively hot (700°F+) chamber, be it the intake manifold or combustion chamber, and the ability of a small amount of liquid propane having a significant effect becomes smaller.
The charge cooling effect is real, but very small. Is it enough for anyone to feel by the seat of the pants? I doubt it. Is it measurable in the lab on the dyno? Yes. Does it have an effect on NOx? Yes. Does it help with power and performance? Yes, but only in comparison with the vapor fumigation systems, and just about on par with a conventional gasoline systems.

This analytical study of thermodynamics and thermal interactions with fluid properties is for someone with more brain power than me to undertake, and frankly, I'm glad someone with your background is on the forum now! Glad to see you on board.
Franz

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[turbocohen]

The 9 oems that I visited/supported with liquid injection components & design issues all reported somewhere between zero to 6% increase in torque over same engine with gasoline and somewhere between a 5-15% increase over vaporized lp injected systems. m I beleive the higher gains were due to variations in measurement and differences in designs that may not be optimized. On a dyno with an old chrysler 5.2 we saw 2% less power than gasoline on lp vapor and 3% more using liquid. All the comparisons were with nothing other than injector and fuel supply changes and fuel/spark tables optimized for emissions legal lowest bsfc. Mass air meter data suggested 3-4% more air flow using liquid lp vs vapor.

It is a pleasure to join you Franz

 

[marcdeluca]

I have used lp on gasoline engines for 17 years. If you go over 10.5:1, you will get pinging with a warm engine. I have a roller 454 with 10:1, and if the water temp gets over 210 it will ping pulling a trailer. Any compression increase over stock will get you back the 4% loss from displaced oxygen. You will lose 20% on mileage since gasoline has 30% more btus, I think the other 10% isn't lost because of more efficient combustion. You also need to recurve the ignition timing or you will lose power and efficiency. Autotronics makes a controller to do this if you want to keep it dual fuel or the engine is computer controlled. I am running my Duramax diesel on lp and I can tell you, that is the hot setup. You have the better efficiency of the diesel, and you can run a very wide range of diesel fuel to lp ratio.

 

[turbocohen]

Marc, I have messed with LP for 29 years and I know less now than I did way back then.

a client demonstrated a 11.5:1 liquid injected Sulev capable 6.0 chevy cube van that showed no knock via sensor threshold values while pulling a tow dyno and running A/C at arizona proving grounds for hours. Coolant temps were stable at 230f. No round robin (wasted cycle) cooling required. Torque and Hp were similar to gasoline on a dyno but in the heat of the desert it pulled a tad better than the same gasoline model per the strain gauge reading. I drove it from Lake Havascrew back to mesa and punished the retarder for several hours, no knock, no problems except for the slight leaks that were as expected caused by non motorfuel grade LP leaving deposits inside the injector at the valve needle seat interface.

Head for the denver lp station near the airport and drive up the long grade pulling your max rated load and 2:1 lp to diesel. If you make it to the continental divide without grenading your duramax I'll buy a full tank of fuel for ya when you get back to the station.

Not trying to burst your bubble but I am not sold on fumigated diesels. Direct injection is the only robust way to fuel a diesel imo.

Respectfully, Turb

 

[marcdeluca]

I believe that the reason you can get by with 11.5:1 is because of the aluminum heads and reverse flow cooling. Regarding the diesel, I can't run the 2:1 ratio towing. I have to drop it back quite a bit. I don't let it detonate at all, and I would have an EGT gauge in it before I would tow heavy. Up to now, the most I have towed is 6K.