Best compression ratio for propane? 1

[vintageAP]

Hi all, new here - great site!

I'm investigating propane conversions for performance engines and understand that because of the higher octane with propane a higher mechanical compression ratio is desired for optimum performance.

Does anybody have this information handy or experience with this?

I'm sure that the same laws apply as with gasoline engines; too high and pre-ignition will come into play, but about where is that magic number? In gasoline engines there are factors that won't apply in a propane fuled engine such as quench area, puddling of liquid fuel, etc.. Am I still looking for the same aproimate A/F ratio - 14.7? Will cylinder temp affect flame travel and pre-ignition in the same way with propane? Any info and discussion is appreciated.

 

[GunMuse]

I have a 54 Mack Truck that came from the factory with LP on it(We contacted the Mack Museum to verify). I would like to bring that beast back to life. Most of the Mack enthusiasts that interested in the truck stop being so as soon as they find out its not diesal and run scared when they find out someone ordered a propane engine 62 years ago. I think a modern day upgrade of a classic that did propane would really be a valuable marketing asset to the right corp.

Here's a side note question. "Why is propane cost increasing its not tied to the cost of a barrel of oil but seems to flucate with it?"

http://www.prnewsnow.com

 

[turbocohen]

Propane is the bastard child of oil refining. So are the companies that market it. The big oil companies are busy marketing other fuels and lp is a nuisance for them. In the past much of it was flared off because it was safer than allowing it to pool on the ground.

 

[franzh]

Propane is indeed tied into the price of oil production. In Texas, about 75% of propane comes from Natural Gas, the rest from raw crude. Propane is a residual from the refining, distillation, and condensation process of "making" other hydrocarbon products.
As Turbo stated, for many years, propane and butane was flared off, the cost to transport was more than the product sold for. That is no longer the case.
LPG is a cost break-even for refineries now, as the product usage is growing. It is the worlds third most widely used motorfuel and one of the most versatile fuels (home and business heating, cooking, industrial and recreation uses, motorfuel).
Gee, sounds like a marketing spiel, doesnt it?

Franz

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[patprimmer]

It's pretty handy for making plastics like Polypropylene and Polyethylene, brake fluid, coolant, detergents to list just a few.

It can also be used to make various intermediate products that are then used to make a very wide range of plastics and chemicals.

Regards

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[vintageAP]

Thanks all for the continuing great info! To run this thread just a little bit farther and elaborate on some info provided:

My original thought was to use propane in the gaseous state using a standard-type mixer replacing a carburetor. I'm intrigued though with the thought of LPG injection. This may present some disadvantages, but I'm also seeing some distinct advantages that are desirable.

Modern FI gasoline engines run a fuel pump pressure of about 35lbs (varies for make and system but let's use that as a number) and regulate the fuel rail pressure with a regulator. Am I oversimplifying here or could I just feed LPG to the regulator and regulate the pressure to the correct PSI (whatever that is determined to be) using all of the OEM system intact? Would a gasoline fuel injector not handle LPG in the same manner if the supplied fuel pressure was where the compensation was made?

This would certainly make things easier on a late model and using the feedback functions would be sweet.

 

[vintageAP]

Also to add; if the A/F ratio needs to be 15.3 (thanks JBlack) then that compensation could be done electronically at the O2 sensor. The computer would never even know...........

 

[franzh]

Do NOT even attempt to run liquid LPG through a gasoline system, it wont come close to handling the pressures. This topic has been discussed many times on this forum. To keep LPG liquid at 100 degrees F, you would need around 190 psig. Underhood temps can exceed 200 degrees, and over 350 psig would be needed.
I've seen gasoline injectors blow themselves apart at 125 psig.
The gasoline injectors do not flow enough volume for liquid LPG use, hence the necessity for specialized injectors (re Turbocohens previous life).

Franz

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[vintageAP]

Hmmmm..... I overlooked that. I knew it too...........

OK, Turbocohens injectors. These replace the gasoline injectors in a FI LPG conversion? Are these readily available? Will they run with the signal supplied by a typical modern FI control circuit?

 

[vintageAP]

So slap me. Turbocohen is a user name not a brand name.

 

[turbocohen]

Geez Franz.. never considered branding thyself. lol

It takes a bit more moxie to open the LP version of Deka II when the fuel tank temps are elevated during a hot start after a 20 minute hot soak. These are modified gasoline injectors with higher operating pressure capability and additional attention to low leak rate due to the smaller molecule of lp.

The parts needed to make a lpfi system are on the road in asia and the EU but on the shelf in the US. Problem is the LP industry here is not in step with the EPA and CARB. If they adopt the relavent fuel quality standards THAT ARE ALREADY REQUIRED for gasoline retailers then the maybe the US market will get so called taxi tested OEM lpfi injectors and pumps.. The future availability of proven LPG liquid phase port injection hardware depends on the LP marketers taking the responsibility for deploying fuel detergents. Since auto use is relatively minimal except for forklifts, there is no united front to establish requirements for using LPG motorfuel additives.
Here is a link to a page with the lp injectors I put on the GTO LS2 :

http://www.siemensvdo.com/products_...stems/alternative-fuels/alternative-fuels.htm

and a pic of the pump is here

http://www.vialle.nl/

 

[franzh]

There is currently a working group looking at establishing a motorfuel grade propane in excess of HD-5, especially to work with LPPFI to enable them to comply with the EPA and ARB. I am a technical member of that working group (at this point, it is is initial phases, similar to what HD-5 started out as in the late 60's).

We sure are off topic by this point, arent we?

Franz

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[turbocohen]

Vintage AP, the injector driver requirements are dependent on the injector coil impedance and performance expectations. The good news is that a stock gasoline engine O2 sensor will shift close enough to LP stoichiometry to work ok with a little biasing. Forget the worring with the numerical a/f ratio, just shoot the o2 sensor output from a reliable location that measures a good average of all the cylinders.

My ecu switchpoint voltage is initially .380mv after 7 sec and .460mv hot.

 

[GunMuse]

"comply with the EPA and ARB" This is the problem I have with most research. More concerned with the EPA than the advancement itself.

Isn't the sheer fact that propane is a huge improvement over gasoline enough some paper pushing weasal has to create a new standard on how to restrict engine performance before the technology is released.

http://www.prnewsnow.com

 

[GregLocock]

Why shouldn't a new fuel have to meet the same external standards as the old one?

After all, I could take a current gasoline engine and get a measurable improvement in efficiency if I didn't have to meet EPA. Presumably there is some social mechanism that ensures that the EPA target is meaningful.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GunMuse]

You just proved my point. You could increase effiency as we all have done if you didn't have to meet epa requirements.

In fact by doing so you will have decreased the amount of toxins produced per gallon of fuel consumed. Truly greener thinking anyway.

You will consume less fuel overall. Truly conservative thinking and better for national defense.

You will have engineered an advancement that can be improved upon by someone else who may gain experience in the field of engineering by seeing your idea's in action and actually improve upon them.

Most engineers are more tinkerers than inventors and as such need to see odd ball idea's actually work to think up improvements.

Lawyers in congress and especially those "who seek to save the enviroment" want to "engineer" a result instead of seeking a standard.

I have a 350 chevy with no smog equipment, no cat convertor, straight up a 1960's style engine build but with all the modern equipment and thinking and it Passes epa. But then again its technically illegal because I didn't drain the power by adding all that garbage required by law back onto the engine.

I am not saying that propane shouldn't meet a standard. But that is not what this guys role will be. He will be setting up regulations on how to licence the guy who does the install(creates schools to get the licencing from). Getting a list of "mandatory equipment" written into law.

Anything beyond setting a standard for air quality, any attempt to "require a device" is just an attempt to kill the use or graft money into the grant system. In a free society we don't tell others how to achieve greatness we just set the bar and see who gets over.

http://www.prnewsnow.com

 

[GregLocock]

Rubbish.

Take a million of your smog producing devices down to LA, and see what LA's inhabitants think of the soup of HC, CO and NO2 they produce.

Tailpipe emissions /are/ a real world concern.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[franzh]

The reason for ARB and the EPA is concerned about establishing a fuel standard is consistency, the same reason gasoline (oops, petrol) is regulated. At this time, there is no legal standard for LPG, and as stated earlier, HD-5 is a touchy-feeling non-regulated, non mandated fuel. All manufacturers require it but there is no way to verify usage in the field. There are no field test kits, and even when taken to a lab, it takes an GC-FIC at minimum.

HD-5 does not guarantee the elimination of heavy ends in fuel, just a vapor-pressure, propylene, and corrosion standard.

Franz

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[turbocohen]

Heu Gunmuse , got data to back up your thinking that your 60's 350 chev passes todays?
Put your car on a set of rolls and at least run an ole 3 bag ftp cycle. Just tryin to keep this thread honest.

Respectfully, Tubinator

 

[franzh]

I also want to know how that EPA test was run. If you mean a tailpipe sniff test for a '60's era vehicle, thats a piece of cake, but a full blown EPA FTP-75 or US-06? No way.

By the way, thanks to organizations like the EPA to force the automakers to develop the high efficiency engines we have today, like the ones that get mid 20's mpg in a 4000 lb car, engines that last 200,000 miles instead of the 60's and 70's junk that was worn out at 75,000 miles.

Franz

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[turbocohen]

Ditto Franz! It had to be said right here and you the man!
Every 60's car ever built would fail an 06 even without starting it lol.