what makes the diesel engine compressed at a higher ratio?

i recently acquired 10 year old toyota suv, and it seems not fuel efficient. accdg to my reseach, a diesel engine must be compressed at a much higher ratio, the higher the compression, leads to better fuel economy.
im now, sending it with my mechanic, and of course just want to know better, than what would my mechanic would just tell.
thanks

Tags: compressed, Diesel, Engine, higher, makes, ratio

5 Responses to “what makes the diesel engine compressed at a higher ratio?”

1. Pedro S says:

   November 24, 2011 at 7:57 am

   yes they have high compression. . . 22 to 1 where most gas engines have 8 or 9 or 10 to 1. . . . smaller head space. . . if you had same compression in gas engine u would get better milage and more power but the gas is not high enough octane. . .
2. fordman says:

   November 24, 2011 at 8:04 am

   Diesel engines use a much denser fuel. There are more BTU’s pf energy in a gallon of diesel than in a gallon of gas.
   This denser fuel must be compressed to a higher degree to allow it to auto ignite. The compression is about 3 times that of a gas engine.

   Increasing the compression ratio of a gas engine will increase HP, but will also require more expensive fuel with a higher octane rating.
3. hunting4junk says:

   November 24, 2011 at 8:17 am

   the higher compression is achieved by reducing the amount of clearance between the top of the piston and the bottom of the valve chamber in the head with the piston at Top dead center. The higher the compression the more volitale the explosion when the fuel ignites thus the increase in horse power. However a higher compression gasoline engine requires higher octane fuel to perform properly. also at 22 to 1 compression I would imagine the spark plugs blowing out and posibbly the heads blowing off a gasoline engine due to the intense explosion cause by the faster burning gasoline
4. alphonse v says:

   November 24, 2011 at 8:56 am

   diesel engines need more compression because they dont use spark plugs. more compression, the easier it is to ignite the fuel

   –good luck
5. Don O says:

   November 24, 2011 at 9:31 am

   i’m going to break down your question to the very first sentence. what makes the diesel engine compresses at a higher ratio: is the distance between the top of your piston (power stroke) and the bottom portion of the cylinder head ,for that cylinder. the shorter that distance is,the greater the compression. it doesn’t take much difference to greatly increase this ratio. thank you