Kubota Gas vs Kubota Diesel engine option

   / Kubota Gas vs Kubota Diesel engine option #122  
Would it be possible build a gas motor that doesn稚 spark and instead runs like a diesel? Maybe the fact it痴 never been done or at least mass produced would suggest the answer is no, but why not?
Gas is measure in Octane and Diesel is Cetane. I Racing car engine has about 9-11 pounds of compression and the help from a spark plug. Diesels run, what, 60:1 compression/ I think you would need a lot more then diesel compression to compress gas enough to explode on its own.
 
   / Kubota Gas vs Kubota Diesel engine option #123  
No problem to ignite gas by compression, the problem is to do it in a controlled way.
 
   / Kubota Gas vs Kubota Diesel engine option
  • Thread Starter
#125  
What did you decide?
Kubota 3 cylinder engines .. BOTH Gas and Diesel are great.

I bought the diesel model. Very pleased -- it does a good job.
 
   / Kubota Gas vs Kubota Diesel engine option #126  
Gas is measure[d] in Octane and Diesel i[n] Cetane. I Racing car engine has about 9-11 pounds of compression and the help from a spark plug. Diesels run, what, 60:1 compression/ I think you would need a lot more then diesel compression to compress gas enough to explode on its own.

Typical compression ratios for gasoline engines range from 8:1 to 10:1. (A gasoline engine with a 10:1 compression ratio is considered a high-compression engine.) Typical compression ratios for diesel engines range from 15:1 to 20:1.

Gasoline is more volatile (has, on average, lower molecular weight) than diesel fuel. So, gasoline ignites considerably more easily than diesel fuel does. This is why one must carefully control the spark timing in a gasoline engine, especially in a high-compression engine, to prevent excessive pinging/pinking/knocking.
 
   / Kubota Gas vs Kubota Diesel engine option #127  
Typical compression ratios for gasoline engines range from 8:1 to 10:1. (A gasoline engine with a 10:1 compression ratio is considered a high-compression engine.) Typical compression ratios for diesel engines range from 15:1 to 20:1.

Gasoline is more volatile (has, on average, lower molecular weight) than diesel fuel. So, gasoline ignites considerably more easily than diesel fuel does. This is why one must carefully control the spark timing in a gasoline engine, especially in a high-compression engine, to prevent excessive pinging/pinking/knocking.

I think you are living in the past, modern high efficiency gas engines run as high as 16 to 1 on regular gas. My 4500P only turns 3100 to 3200 max. while the Kubota diesel turns 3600, .1 to.2 a gallon per hour difference plus more HP. and torque and the engine will work on steeper slopes. The cost of diesel here is over .50 a gallon more for diesel..... jim
 
   / Kubota Gas vs Kubota Diesel engine option #128  
I think you are living in the past, modern high efficiency gas engines run as high as 16 to 1 on regular gas. My 4500P only turns 3100 to 3200 max. while the Kubota diesel turns 3600, .1 to.2 a gallon per hour difference plus more HP. and torque and the engine will work on steeper slopes. The cost of diesel here is over .50 a gallon more for diesel..... jim

I do not see how one could achieve an actual 16:1 compression ratio in a gasoline engine without uncontrolled detonation (pinging/pinking/knocking). I think that the upper limit is ~ 11:1.

There are some gasoline engines, so-called Atkinson Cycle engines, e.g., the ones used in the Toyota Prius, that have a volumetric compression ratio in the range of 13:1 or 14:1. However, such engines employ delayed closings of the intake valves.

In such engines, for a portion of the compression stroke by a given cylinder, the intake valve associated with that cylinder remains open. Some of the air that had been drawn into the cylinder during the intake stroke is pushed back into the intake manifold. After the intake valve closes, the remaining air is compressed until the piston continues its upward travel and reaches top dead center. As a result of the delayed closing of the intake valve, the effective compression ratio is a good bit less than bottom-dead-center-to-top-dead-center travel distance, by itself, would indicate.
 
   / Kubota Gas vs Kubota Diesel engine option #129  
I do not see how one could achieve an actual 16:1 compression ratio in a gasoline engine without uncontrolled detonation (pinging/pinking/knocking). I think that the upper limit is ~ 11:1.

There are some gasoline engines, so-called Atkinson Cycle engines, e.g., the ones used in the Toyota Prius, that have a volumetric compression ratio in the range of 13:1 or 14:1. However, such engines employ delayed closings of the intake valves.

In such engines, for a portion of the compression stroke by a given cylinder, the intake valve associated with that cylinder remains open. Some of the air that had been drawn into the cylinder during the intake stroke is pushed back into the intake manifold. After the intake valve closes, the remaining air is compressed until the piston continues its upward travel and reaches top dead center. As a result of the delayed closing of the intake valve, the effective compression ratio is a good bit less than bottom-dead-center-to-top-dead-center travel distance, by itself, would indicate.

I agree John. I had a 70 chevelle SS Ls-6 with 11.5 to 1 compression and I had to use Sunoco high test in it or it would ping like crazy.
 
   / Kubota Gas vs Kubota Diesel engine option #130  
I do not see how one could achieve an actual 16:1 compression ratio in a gasoline engine without uncontrolled detonation (pinging/pinking/knocking). I think that the upper limit is ~ 11:1.

There are some gasoline engines, so-called Atkinson Cycle engines, e.g., the ones used in the Toyota Prius, that have a volumetric compression ratio in the range of 13:1 or 14:1. However, such engines employ delayed closings of the intake valves.

In such engines, for a portion of the compression stroke by a given cylinder, the intake valve associated with that cylinder remains open. Some of the air that had been drawn into the cylinder during the intake stroke is pushed back into the intake manifold. After the intake valve closes, the remaining air is compressed until the piston continues its upward travel and reaches top dead center. As a result of the delayed closing of the intake valve, the effective compression ratio is a good bit less than bottom-dead-center-to-top-dead-center travel distance, by itself, would indicate.

They do it and that is all figured in, my crv is a 1.5 and even has turbo and runs on regular. The best part is the high MPG. average is 31.5 for 16000 miles. Mazda has been running high compression for years on regular. yep old time high compression engines couldn't do it, that was then .... this is now..... jim
 

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