Prpane as a MPG Booster

[ps2fixer]

Originally Posted by Piotrsko

Looked at all those 7.3 propane enriched claims years ago (2005). Diesel mileage went up, total mileage calculating adding the total quantity of both fuels went down. (Funny the enriched people hardly ever added the propane to their totals) Propane also has gotten crazy expensive. However, the Propane did improve emissions somewhat particularly reducing the soot particle quantity and size.

Hmmm you have me by .34mpg lifetime.

Funny, I haven't been driving my powerstroke that efficient, roughly half the trips are loaded, huge boost leak (broken exhaust up pipe bolts on the manifold on one side), had a massive vibration, was down to transfercase when I had a tire get a busted belt, ended up the other tire was bad for a long time too and I guess the rear tires were so out of balance it was causing the vibration, that was only fixed a few days ago. The things the truck has going for it mpg wise is 3.55 gearing and manual ZF5 trans and it only has just under 200k miles on it, think it's at 198k last I checked. I was going 55mph everywhere, about 60mph on the express way and most trips were 30+ mins long. No tuner or anything aftermarket on the truck besides a home built heavy metal C channel bumper that probably hurts areo more than it helps. Back when I first got the truck, I had a topper on it too, it does get better mpg with the topper by a fair bit, with out I'm seeing around 17-18mpg average unless I do more unloaded driving than I can see around 20.



I found the video I saw before. Guy covers a lot of other subjects and seems to know what he's talking about. I think the numbers he put on the chart are from dyno runs, so I wouldn't think they would be spoofed numbers. The Superchips DPI system is what I wanted to get, but I might have to build some home brew version. I only want very mild propane injection, just enough to get the mpg increase if one exists. A LOT of people are going after more power when installing those systems, so they are running 20-30% propane and pushing the limits. I've read 10% can get the effect and I would like to try more around 5%. No point in wasting propane if it doesn't need to. The chart is more mid to end of the vid.

https://www.youtube.com/watch?v=DnhpZ-sWcvo

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

If you switch over to the diesel world, propane injection is known to act like putting NOS in the diesel engine, but it's much cheaper and it doesn't have to be floored if it's metered going in. I've seen claims of around 30% better fuel econ. I've read up a fair bit and that 30% most people don't account for the propane used. The propane is used as a 10-20% mix with diesel and the theory is the propane helps ignite and encourage a more complete burn of the diesel. The other added benefit is more power which is the most common focus for people wanting those systems. I've seen figures of propane vs NOS and they were real similar, propane + NOS had just at tiny bit more power but separately it was a huge jump over just diesel. Of my understanding, the only extra power from propane over NOS is propane is also burning as a fuel while NOS isn't. The guy doing the tests found even at 10% the jump was massive, I don't think he tried under that figure.

Propane is already at the vapour phase once Diesel starts to ignite, so it will increase the flame spread leading to a more homogeneous and accurate burn of the Diesel fuel. Then, besides decreasing the amount of soot because of a more complete combustion process, more energy is extracted and turned to motive power from the Diesel fuel. Unless it's a computer-controlled setup which would trim the Diesel down when propane is added, as the total AFR gets a little richer there is a higher performance due to the total energy content of both propane and Diesel. Under certain conditions, it may actually lead to fuel savings, as it would allow to cruise on a higher gear while going uphill, or at a lower RPM also with a higher gear.

Compressed natural gas engines should be somewhat similar I'd think.

You mean spark-ignition engines such as either dedicated-CNG or the bi-fuel conversions I usually see in my country? On a sidenote, in the last 3 years I have seen more big-rigs with CNG enhancement in my country, and it serves to the same purpose as propane, but since I have only seen it added to trucks with electronically-governed engines the Diesel fuel is trimmed down in order to increase savings more than performance.

[ps2fixer]

That's pretty interesting. My diesel is pre cat era, but it also has a computer, first era of the power stroke. Of my understanding, the computer just takes the TPS signal and temp signal, and injects the amount of fuel it thinks is right. There's no O2 sensor or any kind of feed back system that I'm aware of. The newer trucks 99+ had a exhaust pressure sensor before the turbo if I remember right, or maybe it was a boost sensor. They also have a bigger turbo with waste gate, mine has no waste gate, all of the air gets forced into the engine. I don't recall if there's a cat on those 99+ trucks or not. I suspect there isn't an O2 sensor on them if there's no cat since diesel doesn't really care too much about AFR, as long as there's enough O2 in the air and enough pressure (heat technically), it will combust. Maybe big rigs are designed differently than consumer trucks though.

I haven't gotten too close to too many semi trucks, but I suspect most are still purely diesel powered, I never see a semi getting filled up for CNG or propane, I don't think the truck stock gas stations even have those fuels.

Anyway, if under the same throttle the engine used to make 550 ft/lbs of torque, and with propane it jumped up to 630 ft/lbs (floored max power dyno run I'm assuming from the vid, my stock engine is rated 450 ft/lbs), then that's + 80 ft/lbs, or a 12.7% increase in power. I suspect he's running 20% propane so I guess I need to check out the energy content of each fuel and see how much of a gain it really is based on his numbers.

Probably not the best figures to use, but I'll base it on BTU of energy per fuel.

Diesel 1 gal = 137,381 btu
Propane 1 gal = 91,502 btu

So propane has 33% less energy content than diesel. Diesel alone in this math works out to being 250 btu per ft-lb. So if it was possible to run a diesel 100% on propane, it should make roughly 366 fb-lbs, of course it will burn differently and more completely so not a perfect measurement. Interestingly enough.... 20% of 366 is 73.2 fb-lbs, almost a perfect match to the power difference of pure diesel vs diesel + propane. Maybe I just debunked this concept with this shotty math lol. Either case, propane is cheaper than diesel, so using 20% of a fuel that costs less should in theory save money, but the extra time for fill up and the cost to add the second fuel system doesn't seem worth it.

I wonder if those mpg claims originated from IDI engines.

Either case, I know my math isn't a perfect way of doing that, but should be ball park figure close enough (I don't know how to do it in a better way off the top of my head).

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

There's no O2 sensor or any kind of feed back system that I'm aware of.

So propane would have an effect closer to nitro, as the Diesel injection would not get trimmed down. Unless the expanding propane causes the Diesel injection trim to go down the same way it would on a lower charge air pressure.

[ps2fixer]

Originally Posted by cRiPpLe_rOoStEr

So propane would have an effect closer to nitro, as the Diesel injection would not get trimmed down. Unless the expanding propane causes the Diesel injection trim to go down the same way it would on a lower charge air pressure.

Yea, most people say NOS and Propane are effectively the same for Diesels. The difference is, NOS can only be done at WOT, propane the turbo just needs to be spooled up.

Diesels run at wide open intake, so they are always very lean. More air makes the diesel burn better so that's why they get turbo'ed, then cold air has more O2, so that's why they run inter coolers. My 95 didn't come with a factory inter cooler, I want to add one though. The newer trucks with the intercooler are something like 525 ft-lbs factory, while mine is 450, but they also have a larger turbo, probably to offset the extra intake air volume in the system.

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

The newer trucks with the intercooler are something like 525 ft-lbs factory, while mine is 450, but they also have a larger turbo, probably to offset the extra intake air volume in the system.

Most likely the larger turbocharger is there because of the intercooler, not the other way around. The smaller turbocharger may decrease turbo-lag, yet it would limit the air flow at a higher RPM. A colder charge air is also better for reliability under a more extreme power and torque rating.

[Piotrsko]

My '00 is 530 lb/ft and the last year with no cat, although some have one possibly by location or build date. No O2 sensor. The 7psi wastegate is to keep from blowing apart the intercooler system and limit torque as the zf6 input shaft and bearing fails around 550. Many wire the wastegate shut then proceed to thrash the trans. The auto doesn't have this limitation. Fwiw, mine doesn't know what the mixture ratio is, but has a map sensor so it boosts and fuels based on air density in the filter box. I really think the turbo is bigger because it changes with the bump hood mid year '00. they had more room and you can never have too much turbo..... more air means you can add more fuel and get more power, doesn't necessarily mean more efficiency

[cRiPpLe_rOoStEr]

Originally Posted by Piotrsko

Fwiw, mine doesn't know what the mixture ratio is, but has a map sensor so it boosts and fuels based on air density in the filter box.

So, unless propane fumigation would be done before the MAP sensor, it won't trim the Diesel fuel down.

[racprops]

Well this thread has been totally highjacked.

I asked about using propane as GASOLINE booster....

I have no interest in using it in a diesel and no interest it switching to a diesel engine.

All my cars are not diesel they are Gasoline powered.

So as the subject is now only talking about diesel, I will drop out.

Rich

[cRiPpLe_rOoStEr]

Originally Posted by racprops

I asked about using propane as GASOLINE booster....

Seemingly it doesn't work that way on gassers, even though maybe those new direct-injection engines could eventually resort to it in a way more similar to a Diesel engine, as it would enrich the AFR. However, even for direct-injection gassers, most of the setups I know rely on liquid-phase injection alone through the stock fuel rail as an alternate fuel, but never as a gasoline booster. CNG on the other hand, as it's only injected at the vapour phase, I have already seen vehicles fitted with direct injection for the stock fuel resorting to it and CNG through a dedicated port-injection, as the stock injectors must always have some fuel flow in order to prevent them to get damaged as they're directly exposed to the flame spread, even though the gasoline and/or ethanol (just to remind, flexfuel engines have been prevalent in my country) flow is trimmed down in order to replace more of it with CNG for economy purposes.