Kubota Gas vs Kubota Diesel engine option

[MossRoad]

My 2013 Impala is 11.5:1 compression ratio and uses 87 octane gas. It's GDI with variable valve timing, can make 300hp, and gets 31mpg on the highway at 75mph.

 

[johara1]

My 2013 Impala is 11.5:1 compression ratio and uses 87 octane gas. It's GDI with variable valve timing, can make 300hp, and gets 31mpg on the highway at 75mph.

MR, if you want to talk highway that is different story, 39-40 will happen and with all wheel drive to boot.... jim

 

[MossRoad]

MR, if you want to talk highway that is different story, 39-40 will happen and with all wheel drive to boot.... jim

What I'm getting at is 11.5:1 compression used to be HUGE in the late 60's/early 70's. Today, it's normal.

 

[johara1]

What I'm getting at is 11.5:1 compression used to be HUGE in the late 60's/early 70's. Today, it's normal.

Compression ratio for a Mazda sky active 2.0 is 18 to 1, My CRV is 10.6 to 1 but turbo boost is 18-20 psi..... both on reg. gas...... jim

 

[buickanddeere]

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?

The direct injection gas engines rely on the spark plugs for ignition at idle , light loads and low rpm. At high loads and high rpm the gasoline starts burning as soon as it is injected .

 

[buickanddeere]

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.

Ever hear tell of the L86, LT1 and LT4 Chev V8 engine痴 ?

 

[murphy1244]

Man times have changed since I last dove in a engine!