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diesel engines and turbochargers

Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.

 
Turbos pair well with diesels because they have tons of down low grunt, and the turbo can help keep the power smooth throughout the rev range, that and N/A diesels usually don't make much power from what I've seen
 
yeah i know a diesel can make lot of extra power from bolt on, I was watching trucks tv one day. They added some computer add on, it had settings from like 25hp all the way up too 100+ hp
 
A 2001 HO CTD in the Dodge Ram use a 17:1 compression ratio and 26 PSI of boost.
By comparison, the 5.9L V8 uses a 9.1:1 compression ratio (no boost), and the reletively high strung 2004 WRX STI uses 8.2:1 compression ratio and 14.5PSI of boost.
 
Originally posted by: sonoma1993
arent most diesel engines compression ratio around 18:1
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As far as I know, 17:1 is on the low scale (if you only have that much compression, you risk engine not starting during mild winter). Compression ratio of 25:1 are standard on some engines when new (but will degrade over time).

A high compression ratio allows the engine to run hotter, so it is more efficient
 
Originally posted by: geno
Turbos pair well with diesels because they have tons of down low grunt, and the turbo can help keep the power smooth throughout the rev range, that and N/A diesels usually don't make much power from what I've seen
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The diesels don't make that much power compared to gasoline engines - however, their low end torque is absolutely brutal. The turbo chargers allow the engines to run better at higher rpm - with little effect on the low end torque.
Only newer diesel engines on cars are turbocharged (starting from some 1985 I think). Even now there are (at least in Europe) cars that have non-turbo diesel engines (the SDI engines from Volkswagen is an example). You can buy new cars with those engines!
However, the SDI 1.9l engine has 65HP and the TDI (depending on version) 90 or more. While the low-end torque is mainly similar, the high-rev performance is different
 
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
 
Originally posted by: FrustratedUser
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
Click to expand...

Not the static compression, but the dynamic. You are effectively pre-compressing the air before it enters the cylinder.
 
Originally posted by: Demon-Xanth
Originally posted by: FrustratedUser
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
Click to expand...

Not the static compression, but the dynamic. You are effectively pre-compressing the air before it enters the cylinder.
Click to expand...

The effective cylinder pressure is increased, as the intake air is already, as you have stated, under pressure - However, the cylinder compression ratio remains unchanged. This is a mathmatical formula involving cylinder volume and stroke and does not take into consideration the pressure of the intake charge.
 
Originally posted by: boggsie
Originally posted by: Demon-Xanth
Originally posted by: FrustratedUser
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
Click to expand...

Not the static compression, but the dynamic. You are effectively pre-compressing the air before it enters the cylinder.
Click to expand...

The effective cylinder pressure is increased, as the intake air is already, as you have stated, under pressure - However, the cylinder compression ratio remains unchanged. This is a mathmatical formula involving cylinder volume and stroke and does not take into consideration the pressure of the intake charge.
Click to expand...

Note: nowhere did I say that they change the RATIO, but they do change the compression.
 
Originally posted by: FrustratedUser
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
Click to expand...

You're putting more air in the same volume, of course it's changing the compression ratio. Just because your head can only comprehend the ratio of the cylinder's volume at the bottom of the stroke compared to the top, doesn't mean that the compression ratio of the air itself isn't changing.
 
Higher efficiency.
Originally posted by: mercanucaribe
Originally posted by: FrustratedUser
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
Click to expand...

You're putting more air in the same volume, of course it's changing the compression ratio. Just because your head can only comprehend the ratio of the cylinder's volume at the bottom of the stroke compared to the top, doesn't mean that the compression ratio of the air itself isn't changing.
Click to expand...
I don't know what I was thinking of. I'm with FU on this one.
 
Originally posted by: mercanucaribe
Originally posted by: FrustratedUser
Originally posted by: Demon-Xanth
Diesels work by using compression to fire the cylinders. Normally, in a gas engine a 25PSI turbo system would cause massive detonation. But with a diesel, it's no problem. It NEEDS a much higher compression just to fire. The turbo setup for a diesel allows it to effectively be a 6L engine at idle, and a 16L engine under load. It helps alot for gas milage. (good) Diesel engines are typically overbuilt because of thier long use applications, so they handle the extra stress well.
Click to expand...

A turbo or super charger DOES NOT CHANGE THE COMPRESSION RATIO!
Click to expand...

You're putting more air in the same volume, of course it's changing the compression ratio. Just because your head can only comprehend the ratio of the cylinder's volume at the bottom of the stroke compared to the top, doesn't mean that the compression ratio of the air itself isn't changing.
Click to expand...

No it doesn't change the compression. What you actually do is raise the pressure. The compression ratio stays the same.
An engine with a compression ratio of 10:1 will still have that compression no matter if you put a turbo or a supercharger on it.
 
everyone's missing whole the point of a diesel engine.

Diesel engines do not have spark plugs; it soley relies on engine compression to detonate its fuel/air mixture. Since diesels usually run at a 24:0:1 high compression anyway, a turbocharger was invented to use this special property to its fullest potential. The engine now would have a gain in horsepower, torque, and have a higher/wider rpm range compare to a NA diesel. In fact, turbochargers were invented and first designed for diesel engines.

And forced induction does not change the engine head compression. Force induction simply increases pressure at the intake, causing a higher amount flow of air, and ultimately cause an increase of pressure in the cylinder wall.
 
Originally posted by: infestedgh0st
everyone's missing whole the point of a diesel engine.

Diesel engines do not have spark plugs; it soley relies on engine compression to detonate its fuel/air mixture. Since diesels usually run at a 24:0:1 high compression anyway, a turbocharger was invented to use this special property to its fullest potential. The engine now would have a gain in horsepower, torque, and have a higher/wider rpm range compare to a NA diesel. In fact, turbochargers were invented and first designed for diesel engines.

And forced induction does not change the engine head compression. Force induction simply increases pressure at the intake, causing a higher amount flow of air, and ultimately cause an increase of pressure in the cylinder wall.
Click to expand...

Like trying to breath using a snorkle. Kinda hard to do on your own but if some one were to force the air down the snorkle to you, you breath bettter and become more productive not haing to use alot of lung power and waste energy doing it on your own.


 
Originally posted by: infestedgh0st
everyone's missing whole the point of a diesel engine.

Diesel engines do not have spark plugs; it soley relies on engine compression to detonate its fuel/air mixture. Since diesels usually run at a 24:0:1 high compression anyway, a turbocharger was invented to use this special property to its fullest potential. The engine now would have a gain in horsepower, torque, and have a higher/wider rpm range compare to a NA diesel. In fact, turbochargers were invented and first designed for diesel engines.

And forced induction does not change the engine head compression. Force induction simply increases pressure at the intake, causing a higher amount flow of air, and ultimately cause an increase of pressure in the cylinder wall.
Click to expand...

This is all correct but to further clarify: Diesel engines are unthrottled, the engine speed is controlled by how much fuel is put into the engine. (Hence the familiar knocking sound at idle, as the engine is being leaned out, and the tone gets more fluid an normal sounding towards the top of the power band). Because of this design diesel engines cannot rev very and hence do not make lots of horsepower. (Keep in mind that horsepower is not an actual force but a number calculated from torque i.e. HP = Torque * RPM / 5252). Enter the turbocharger, it can help move more air in to the unthrottled engine at higher RPMs, therefore more fuel. More fuel and more air at the correct ratio = more power. It has been referred to as having a variable dispacement engine, while not entirely correct, it is a pretty good explanation. At idle the turbo is basically idle, so less fuel is used to maintain the lean idle. Even with a turbo, diesels still have really low redlines due to the inherit nature in the way they combust fuel. And because of the limitations of the way the fuel is injected. No pintle style electronic fuel injectors here, usually a fuel pump with rails (or common rail) to inject fuel directly into the port (or cylinder sometimes).
 
Originally posted by: Captain Howdy
Originally posted by: infestedgh0st
everyone's missing whole the point of a diesel engine.

Diesel engines do not have spark plugs; it soley relies on engine compression to detonate its fuel/air mixture. Since diesels usually run at a 24:0:1 high compression anyway, a turbocharger was invented to use this special property to its fullest potential. The engine now would have a gain in horsepower, torque, and have a higher/wider rpm range compare to a NA diesel. In fact, turbochargers were invented and first designed for diesel engines.

And forced induction does not change the engine head compression. Force induction simply increases pressure at the intake, causing a higher amount flow of air, and ultimately cause an increase of pressure in the cylinder wall.
Click to expand...

This is all correct but to further clarify: Diesel engines are unthrottled, the engine speed is controlled by how much fuel is put into the engine. (Hence the familiar knocking sound at idle, as the engine is being leaned out, and the tone gets more fluid an normal sounding towards the top of the power band). Because of this design diesel engines cannot rev very and hence do not make lots of horsepower. (Keep in mind that horsepower is not an actual force but a number calculated from torque i.e. HP = Torque * RPM / 5252). Enter the turbocharger, it can help move more air in to the unthrottled engine at higher RPMs, therefore more fuel. More fuel and more air at the correct ratio = more power. It has been referred to as having a variable dispacement engine, while not entirely correct, it is a pretty good explanation. At idle the turbo is basically idle, so less fuel is used to maintain the lean idle. Even with a turbo, diesels still have really low redlines due to the inherit nature in the way they combust fuel. And because of the limitations of the way the fuel is injected. No pintle style electronic fuel injectors here, usually a fuel pump with rails (or common rail) to inject fuel directly into the port (or cylinder sometimes).
Click to expand...

that should be the complete guide of "why turbos are meant for diesels"

Originally posted by: funboy42
Like trying to breath using a snorkle. Kinda hard to do on your own but if some one were to force the air down the snorkle to you, you breath bettter and become more productive not haing to use alot of lung power and waste energy doing it on your own.
Click to expand...

but sometimes, when someone pushes too hard, you might hurt your lungs 😉

 
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