Prpane as a MPG Booster
 

So a while back (during the last gas crises) along with testing HHO…(did not work)

The idea of running propane as a booster came up.

The claim was adding some propane could give you a 20 to even 40% MPG boost.

The problem then was I was looking for a way to run a company SELLING MPG systems and to do so they would have been required to buy the propane for a car at a propane for cars station witch with the much higher cost meant no savings. You ended up with the same cost per mile.

Plus you out say a 1K for the set up.

But now with gasoline prices at over $5.50. and no real hope they will ever come back down, propane might be a better idea.

So the only thread on this was done in 2008.

So is it a good idea nowadays?? If so data, and any how to add a system to say Ford Crown Vics etc??

Rich

Damn cannot edit title, missed the "o" in propane...mods please fix if you can.

Cannot even delete post to do a do over.

Rich

Obviously you can set an engine up to run on propane

To use it as a booster or additional fuel you're going to have to have full access to the engine control parameters. Otherwise you are just going to add the same amount of fuel AND the propane

The O2 sensor should be able to compensate pretty well for as much as 15-20% offset in fueling. If you can monitor your fuel trims by OBD to make sure you're not exceeding what the ECU can compensate for, it would probably work. Propane has greater resistance to knock, which is good. A quick search suggests flame speed is significantly higher (I wasn't confident about the exact numbers I was finding), which is also good, but with a caveat - the ignition timing required for propane would be different. Specifically, an engine would need to have its ignition timing retarded significantly, or it would actually run worse. If at any point the ratio of propane to gasoline changes, your ignition requirements will also change. Multifuel systems are very much a moving target and you'll probably spend over $1000 in dyno time getting it dialed in across the entire map, not to mention the cost of the engine management.

My question would be, at what cost can you fill a tank of propane? A standard 20lb tank has about the same energy content as 3.5 gallons of gasoline, or $15.40 worth in Minnesota at the time I'm writing this.

The O2 sensor should be able to compensate pretty well for as much as 15-20% offset in fueling. If you can monitor your fuel trims by OBD to make sure you're not exceeding what the ECU can compensate for, it would probably work.

I can.


"Propane has greater resistance to knock, which is good."

That can be a help to stop knocking in engine.

"A quick search suggests flame speed is significantly higher (I wasn't confident about the exact numbers I was finding), which is also good, but with a caveat - the ignition timing required for propane would be different."

Even mixing it in WITH gasoline?? By its self only yes.

"Specifically, an engine would need to have its ignition timing retarded significantly, or it would actually run worse. If at any point the ratio of propane to gasoline changes, your ignition requirements will also change. Multifuel systems are very much a moving target and you'll probably spend over $1000 in dyno time getting it dialed in across the entire map, not to mention the cost of the engine management."

Will need to test that.
I feel the main cost is a controller system to control the feeding of the propane.


"My question would be, at what cost can you fill a tank of propane? A standard 20lb tank has about the same energy content as 3.5 gallons of gasoline, or $15.40 worth in Minnesota at the time I'm writing this."

The question remaining is how much propane will it take to get that boost?? Back in the day it was said one 20 pound bottle of propane was good for a 19 gallon tank of gas.

So 19Gal @$5.60=$106.40 less 20%= $85.12 + $15.40= $100.52

OK that kills that.

NEVER MIND....

Rich

What's fascinating to me is that the price per unit energy is actually pretty close right now. All else equal, propane is probably a superior fuel. To my understanding it burns cleaner, and if an engine is designed to run on it specifically (higher compression, geometry optimized for faster burn) it would be more efficient. But, I don't see it being a game changer for an engine retrofitted for it.

Interesting: Seems it will not cause enough improvement to be even worth the trouble.

I believe I came up with the same answer last time.

My idea of a double overdrive still seems the best, but my research shows it will only work with a engine that has plenty of low RPM torque, other wise you end up lugging the engine.

That and a lean burn cruising setting which also is said to give 5+ MPG.

Rich

Propane as an enhancement doesn't make much sense for a gasser, while there were some folks resorting to it on Diesels. As propane is outlawed as a motor fuel in my country, even though it's allowed for forklifts, I have already seen some big rigs using CNG enhancement for both mileage and emissions, decreasing the usage of DEF noticeably too.

When it comes to spark-ignition, propane is not so bad at all, but I'd rather take a look at some of those newer liquid-phase injection systems, instead of the vapour-phase setup which is still more usual. But neither propane or CNG are worth as MPG boosters on a gasser, yet under some circumstances while being used instead of gasoline at least CNG may be cost-effective. Too many people resort to an excessively lean AFR with CNG in my country, as it has anti-knock properties even better than ethanol, to the extent such an excessively lean AFR could eventually lead to an overheating, not to mention a performance loss. A proper AFR, even though the cost-per-mile advantage of CNG would go a little down, wouldn't cause much of a performance loss and decrease the likelihood of an overheating.

I posted here before about this. It definatly can be done pretty simply

https://ecomodder.com/forum/showthre...ars-39664.html

Squad cars in Wisconsin run off gas / propane , you can purchase the retired cars with the systems intact.

Tmugz88

Any details why?? What does the systems so for the cars?

Rich

Propane is heavier than air. Don't store it in the basement.

Sorry for the delay, I tried reaching a buddy who I worked with at the Sheriff's office but he's been busy.

Here is a useful link Wisconsin departments use them pretty regularly.

https://www.amerigas.com/amerigas-bl...olice-vehicles

Looked at the link.

Those are 100% converted to Propane cars, not a mix of propane and gas.

I find the claim of greater performance with Propane, must have done some work on the engine (higher compressed ratios) and computer programming.

A straight non engine mods have always reported LESS power.

Rich

Propane as a fuel, has about 15-20% less energy than gasoline. If you raise your compression ratio and change your timing you can get a propane set up motor close to the output of a gasoline motor.

When used in a dual fuel motor, you have to pick one or the other setup. Usually it is set up as a gas motor, that can switch to propane but it will be down about 20% in power when using propane. IDK about gas mileage. They usually compare it as $cost of fuel per miles driven. Propane usually wins since its cheaper, that is why they use propane in fleet vehicles that do not need a very long range.

Caddylackn

That has always been my understanding BUT on this site:

https://www.amerigas.com/amerigas-bl...olice-vehicles

They claim:


"Unit 1075, as this vehicle is called, is used to promote propane run vehicles to law enforcement agencies throughout the south .While the car is on location officers are encouraged to test drive the vehicle so they can fully compare it to their normal squad cars. Every agency who has tested the vehicle has agreed this car has more power and torque than its gasoline powered counterparts."

If so it was specially preped.

Rich

Basically the same situation that used to happen with dedicated-ethanol cars in my country, even though they couldn't resort to some "extreme" tuning as they would still often require a gasoline cold-start at least during winter.

From my understanding, an unmodified gas engine running on pure propane will give around 10% less fuel econ, it's not super common here, but some vehicles are swapped over to save on fuel costs.

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.

The setup for those tests were a ford power stroke turbo, I think 7.3L if I remember right, with a tuner. I think they were around 400ft/lb of torque on diesel, propane or nos was around 600ft/lb and combined it was like +10-20 ft/lb. I don't recall if there was a 10% mix figure as well or not, been a while since I watched the vid.

I've seen those claims all over, and never really seen anyone debunk those claims. So if my 7.3L powerstroke normally gets 20mpg, a 30% increase in mpg would be 26mpg + 260mpg of propane (10% target). 1000 miles normal would be 50 gal diesel vs 38.5 gal diesel + 3.9 gal of propane (almost a 20lb tank). Today's price for diesel is roughly $6/gal, so $300 vs $231 + propane (should be like $3-4/gal in bulk, even a tank swap out place is $20-25). So MPG alone it saves money, plus you get extra power if the figures are true and accurate.

The OP doesn't say if their vehicle is gas or diesel, but I think for diesel it makes sense, for gas I'd say full conversion is probably the best route if you can get a high compression engine that's more ideal for propane use.

I've always wanted to modify a gas engine to be more ideal for propane and compare the econ of before and after. It's been a while since I researched it but I think the ideal compression ratio for propane was something like 12-14:1. Compressed natural gas engines should be somewhat similar I'd think.

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.

Back at the earlier gas crunch when I was trying a number of so called MPG devices and systems one was propane.

The claims was just about the same for running propane was reported as above: A 20% improvement it power and MPG.

These systems were computer controlled.

It was said when you ran out of propane you felt it in how you engine lost some power and smoothness.

It seems to cost just as much in fuel costs so it seems to be a break even set up.

IE There is no savings.

The 20% savings in gas mpg was off set by the 20% costs for the propane.

And your out the then cost of around $1K in the system.

So as far as I can tell it is a dead end.

Rich

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

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.


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.

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).

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.

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.

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

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

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

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.