highest compression for propane

[1948 mm]

I am building a 403 propane engine and wondering how high can I get the compression using stock parts. I have a G gas with 4.75" pistons 10a4210 heads and I am running around 11.3/1 compression with no detonation on pump gas. It does diesel when shutting down hot. I was wondering how high you could go with LP? Thanks
 

[unstylish]

11 to 1? No detonation on pump gas? I bet it does, or it sure does not have much timing. I wouldnt go more than 11 to 1 on LP.
 

[Dblair]

won't take to much to melt those pistons down you better get some octane .
 

[buickanddeere]

There is a huge lack of understanding here that nobody seems to be learning . No matter how many times it's explained here and elsewhere.0
Compression pressure is controlled every bit as much by the cam as it is by compression ratio.
Take a look at how a reciprocating engine works. High compression robs power from the engine. High expansion ratio adds power.
Detonation is caused when the air fuel mixture is heated from compression. Rising above the ignition temp of the fuel.
So keep he air fuel mix cooler or raise the fuel's ignition temp.
Depending on timing, cam, compression and combustion chamber design. Something between 8 and 16 to 1 depending........
 

[MLPANKEY]

yeap just stick a cam in with alot of duration on a long rod engine that doesnt dwell long at bdc and when the valves close after pistons traveled a 1/4 ways up the bore can run alot lower octane than one that has valve closed before piston moves up the bore . piston speed its simply the best way to move air .
 

[mm585]

compresion = horsepower! M&W, heiseler, and the rest of the lot made pistons with a dome to make power. Ask any engine builder thats the way it is. Im not saying a good camshaft doesnt assist in the combo but compresion is the place to start my my book. I know for a fact a 900 inch moline at eleven to one with 345 pounds of cyl. press. runs very well on LP.
 

[MMMMMMMMM]

345 psi is more than a MM diesel has. Try running your MM diesel only on LP and then tell me how well it runs.
 

[buickanddeere]

Tell me if it takes more power to push a piston to TDC with 11 to 1 compression that it does on an otherwise identical 8 to 1 engine?
Tell me how many more times the gasses can expand on the power stroke of an 11 to 1 engine vs an 8 to 1 engine.
 

[MLPANKEY]

unleas we are talking about two cylinder jd. Compression increases will always increase torque.The piszton gets drove to tdc by the same combustionmn force driving another piston from tdc to bdc
 

[VicS]

What about a little eco-boost Ford? They inject gasoline at 2200 psi. Just like a diesel does. Someone is probably working on putting that fuel injection on a old tractor now. Supposedly good for 20% more hp
 

[buickanddeere]

Ever heard of a reciprocating engine making power
on the compression stroke?
Power is what happens on the power/expansion
stroke.
" Power" is the mean average pressure exerted on
the piston top during the power stroke.
Expansion ratio is just as important as peak
pressure at TDC.
There are diminishing returns when increasing
compression, up to no power advantages.
 

[LarryM]

What may seem easy to some may seem particularly hard for other people. For example explaing to people that with my phone I can log into work and see everything from the fire alarms to lighting to temperature control and have the ability to operate many things is to them mind boggling. To me it is quite simple. You have people of all skill sets on this site. Some people on this site have a hard time wiring up an alternator. Some of us still have equations from physics class 20 years ago floating in our head. For example the acceleration due to gravity. Why that is still in there I do not know. Maybe it is because we tested it with an empty half barrel off an 80 foot tower. What I have learned is to accept that people come with varying skill sets and varying talents. As smart as you are I am amazed that you cannot see that.
 

[MLPANKEY]

[Dodgeit]

I'll throw this in just for Shitzengiggles. Two indentical make and model engines. Both at 11-1 compression. The only difference between the two is dome height on the piston. One is flat topped and the other has a 20cc dome. Running 91 octane pump gas.
All build componets to include, setting, temprature, humidity, and anything else you can think of is the same for both engines.

Which engine will be able to run more advance without detonation, in a high load situation?

B&D, MLpankey, please refrain from ruining the fun for others. I know you know the answer. I want to see how many others do.

Hint the answer is the same for any fuel type.
 

[Dodgeit]