Turbos

[hihoslvr]

Turbos: gas vs diesel

what is the difference between diesel and gasoline, that requires gas turbos to use a higher octane rating than a comparable non-turbo'd engine... anyone follow me?

 

[Will]

Gasoline gets unstable when it heats up and it detonates before the spark gets a chance to light it off. The higher octane is more stable and can withstand more compression.

With a diesel, the fuel is not compressed with the air. Only air is compressed and then the fuel is sprayed into the hot air and it burns.

I would like to point you to the MazdaSpeed3. It is a turbocharged direct-injection gasoline engine. It's a 9.5-1 compression turbocharged engine with almost 2hp per cubic inch--263hp at only 5,500rpm and 280ft# by 3,000rpm. That's serious thump for a little 4-cylinder. It can run lots of boost (18psi) with that compression because the fuel is not compressed with the air.

 

[Bob Ayers]

Gasoline gets unstable when it heats up and it detonates before the spark gets a chance to light it off. The higher octane is more stable and can withstand more compression.

With a diesel, the fuel is not compressed with the air. Only air is compressed and then the fuel is sprayed into the hot air and it burns.

I would like to point you to the MazdaSpeed3. It is a turbocharged direct-injection gasoline engine. It's a 9.5-1 compression turbocharged engine with almost 2hp per cubic inch--263hp at only 5,500rpm and 280ft# by 3,000rpm. That's serious thump for a little 4-cylinder. It can run lots of boost (18psi) with that compression because the fuel is not compressed with the air.

The Honda S2000 2.0L (120 CI) gets 240HP without forced induction!!

 

[hihoslvr]

alright, thanks. I love the sound of a turbodiesel spoolin' up
but hate gettin' left in a cloud of black smoke

 

[BlackBII]

The cloud of black smoke is just unburnt fuel
A brand new diesiel truck with no mods running as it should will hardly blow any smoke, if any at all

 

[JohnnyU]

what is the difference between diesel and gasoline, that requires gas turbos to use a higher octane rating than a comparable non-turbo'd engine... anyone follow me?

Gasoline and Diesel engines are two completely different animals. They both have blocks, pistons, rods, etc, but that's where the similarities end.

An 'Octane Rating' of gasoline is the measure of the gasoline's resistance to detonation, also commonly referred to as spark-knock or auto-ignition. The gasoline engine is a Spark Ignition (SI) engine, which relies on the spark plug to ignite the compressed charge at precisely the right time. High compression, low octane and high cylinder temperatures can cause auto-ignition which is EXTREMELY detrimental to the engine.

Diesel on the other hand is a Compression Ignition (CI) engine. As Will mentioned, only air is compressed in the cylinder, then a precisely timed injection (or multiple injections) of finely atomized fuel causes a violent explosion, a turbulent flame front. This explosion is partly the cause of a Diesel's higher noise level when running.

There are several good books on different styles of IC engines, everything from beginner's guides to advanced knowledge. Here are a few:

http://search.barnesandnoble.com/Internal-Combustion-Engines/Colin-R-Ferguson/e/9780471356172/?itm=2

http://search.barnesandnoble.com/Th...Charles-Fayette-Taylor/e/9780262700269/?itm=3

http://search.barnesandnoble.com/En...ne/Willard-W-Pulkrabek/e/9780131405707/?itm=7

The cloud of black smoke is just unburnt fuel
A brand new diesiel truck with no mods running as it should will hardly blow any smoke, if any at all

One would think, however even my stock 04.5 CTD can blow decent smoke. It's really the advent of the DPF that has caused the absence of smoke from Diesel engines.

 

[hihoslvr]

right on, yeah one of the other posts a few days ago got me thinking about turbos. I like the Subaru Forester and you can get'em with a turbo, but in the long run, I don't think it's worth the extra money.