highest compression for propane

Anonymous-0

Well-known Member
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
 
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.
 
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........
 
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 .
 
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.
 
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.
 
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.
 
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
 
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
 
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.
 
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.
 
(quoted from post at 20:01:06 10/08/12) 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.
The piston being drove down on the power stroke is driving a piston up on the compression stroke. The gains on compression do get porpitionally smaller as compression goes up for instance 8.1 changed to 12.1 will show a higher gain than 12.1 to 16.1 but theres still a gain in power. When the power gain gets so proportionaly low its basically non existant there still gains in overall torque. The old science for every action theres equall or greater reaction.
 
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.
 
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
 
Flat top will make more power as long as the smaller
combustion has room for the flow from around the valve
heads.
Should state as well we are assuming both engines have a
cold clearance between the flat portion of the head and the flat
porting of the piston . Of being 20-40 thou depending ,to allow
for the growth from heat . To allow the piston and head to have
a hair's clearance from touching when hot.
 
(quoted from post at 07:42:14 10/17/12)
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .
 
(quoted from post at 13:03:56 10/17/12)
(quoted from post at 07:42:14 10/17/12)
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .
I am not against dome pistons they have their place . A 426 hemi naturally aspirated has to have a dome piston usually . On inline engines theres not much of a reason for angle milling either .So in order to get some power out of what you have to work with knowing your combustion chamber in the head you have and if need be laying the chamber back to unshroud the valves making even a larger chamber then a dome is the answer for compression unless a blower or turbo or manufacturing and designing a new cylinder head is in the equation
 
(quoted from post at 15:03:56 10/17/12)
(quoted from post at 07:42:14 10/17/12)
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .


All things being equal for discussions sake the flat top piston in general would allow you to run more advance, because you would not need the time to overcome the piston dome blocking the flame front.

I was basicaly just trying to make another simple point that many overlook when building a performance engine. All the go fast goodies don't always, play nice together. Now if you took the engine examples I mentioned and changed just the cam shaft, you could make them perform in two arenas.

The flat top build would do nicely for tractor pulling or road / flat track racing. Because you could build a torque engine that would respond well to throttle inputs for road racing or a high map , low speed load seen in tractor pulling.

The pop top piston build would work the best when used in a high rpm WOT situation, such as drag racing or Talladegia type, super speedways. In tractor pulling the pop top build would give up too much "streetability, for lack of a better word" when used in MPH or gear limited classes.

Again I'm just generalizing. Each build could be made to work in both scenarios, with alot of forthought put into matching the rest of the components. But again the flat top would be a better WOT engine than the pop top build would be if used in one of the mentioned flat top builds in overall usefulness just because of the piston dome.
 
(quoted from post at 13:58:14 10/18/12)
(quoted from post at 15:03:56 10/17/12)
(quoted from post at 07:42:14 10/17/12)
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .


The flat top piston would allow you to run more advance, because you would not need to overcome the piston dome blocking the flame front, there by need more time to properly propagate the burn.

Flat top piston requires less advance .
The idea is not to run an engine with as much timing advance as possible. The least amount of advance that is required to make peak power is a better way to make the most and reliable power.
An engine that makes lots max power with 30degrees advance is more efficient than the engine making max power using 35 degrees advance.
 
(quoted from post at 11:41:04 10/18/12)
(quoted from post at 13:58:14 10/18/12)
(quoted from post at 15:03:56 10/17/12)
(quoted from post at 07:42:14 10/17/12)
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .


The flat top piston would allow you to run more advance, because you would not need to overcome the piston dome blocking the flame front, there by need more time to properly propagate the burn.

Flat top piston requires less advance .
The idea is not to run an engine with as much timing advance as possible. The least amount of advance that is required to make peak power is a better way to make the most and reliable power.
An engine that makes lots max power with 30degrees advance is more efficient than the engine making max power using 35 degrees advance.
I disagree somewhat if the dome has been contoured no hot spots the timing would be the same unless the shape of combustion chamber changed which most of the time the chamber shape doesnt change its just reduced in ccs. .
 
(quoted from post at 13:41:04 10/18/12)
(quoted from post at 13:58:14 10/18/12)
(quoted from post at 15:03:56 10/17/12)
(quoted from post at 07:42:14 10/17/12)
(quoted from post at 14:32:03 10/15/12) 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.


Since no one ventured a reply. I have to wonder, if the question was too hard?

B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .


The flat top piston would allow you to run more advance, because you would not need to overcome the piston dome blocking the flame front, there by need more time to properly propagate the burn.

Flat top piston requires less advance .
The idea is not to run an engine with as much timing advance as possible. The least amount of advance that is required to make peak power is a better way to make the most and reliable power.
An engine that makes lots max power with 30degrees advance is more efficient than the engine making max power using 35 degrees advance.

What I was trying to say was that a pistom dome, all things being equal requires that timing be retarded because of the dome masking the flame front. You could run 30 degees no problem with a flat top piston wheres as you may only be able to get 22-23 degrees with the dome build to make max. power. Based on the primis that the map loads each build is seeing is the same. I wasn't try ing to get into what is needed to accomidate each piston type to make it a viable canidate for "A" job.

Most don't match build components to the job they want the engine to perform. Generally a home build is the "mostest of the mostest. Big Domes, long duration high lift cam, carb four sizes to big, huge valves and ports that would swallow Texas. And believe they have a horsepower monster, and they do @ 8000+rpms with a 200 rpm power band. Not at all suited for pulling in a MPH or gear limited event.
 
I havent really ever experenced a timing change due to a piston design. I have experienced timing changes due to cylinder head chamber designs. For instance a 23 degre small block with 12.1 compression will need more timming than a 14 degree small block with 12.1 compression
 

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