Understanding boost
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Understanding boost
First off I really don't know a whole lot about diesels so here goes the question.
I thought with a turbo diesel there was always a positive pressure or readable boost even at idle but after installing a boost gauge I may have been wrong.
Idle = 0
1200-1500 rpm =2-4 psi
2000-2200 rpm = 7-9 psi
3000-3200 rpm = 17-19 psi
RPM's and boost numbers are approximate. Do these sound like there in the range of numbers I should be expecting at the given RPM.
I love playin with a my new toy cause your never too old to learn a new game.
Thanks
Richard
I thought with a turbo diesel there was always a positive pressure or readable boost even at idle but after installing a boost gauge I may have been wrong.
Idle = 0
1200-1500 rpm =2-4 psi
2000-2200 rpm = 7-9 psi
3000-3200 rpm = 17-19 psi
RPM's and boost numbers are approximate. Do these sound like there in the range of numbers I should be expecting at the given RPM.
I love playin with a my new toy cause your never too old to learn a new game.
Thanks
Richard
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From: IOWA
Yep, they look right on.
With a turbo, there is not always a readable pressure, as you have found out. If you do enough reading or listening, you'll hear the term 'turbo lag', which means there is a small period of time from when you step on the go pedal to when your boost kicks in. The turbo is driven off the exhaust, and the time from the exhaust to build up to drive the turbo to building pressure on the intake side is where you get your turbo lag. A supercharger is a different story, where it's mechanically driven and have instant reaction with it. But I don't know if there is always a readable pressure for that as well.
With a turbo, there is not always a readable pressure, as you have found out. If you do enough reading or listening, you'll hear the term 'turbo lag', which means there is a small period of time from when you step on the go pedal to when your boost kicks in. The turbo is driven off the exhaust, and the time from the exhaust to build up to drive the turbo to building pressure on the intake side is where you get your turbo lag. A supercharger is a different story, where it's mechanically driven and have instant reaction with it. But I don't know if there is always a readable pressure for that as well.
Fleet Owner
Joined: Jun 2004
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From: Rio Rico, AZ.
You'll only get boost when there is enought exhaust velocity to drive the turbine. At idle there is just not enough heat generated inside the combustion chambers to expand the air that much. Besides at idle you don't need that much fuel energy to maintain engine speed. So there is very little pressure on the exhaust side to drive the turbine. Now if you start to give it some throttle, more fuel gets injected, more heat gets generated inside the combustion chamber and you get greater expansion of the air trapped inside the combustion chamber. Since the chamber doesn't get bigger that greater expansion has to go somewhere and it does in the form of increasing PSI inside the combustion chamber and then the exhaust manifold once it exits the engine. Now there is no longer any constraints on the size of the air and like water, air pressure always seeks it's own level. So it starts blowing forcefully out the turbine wheel housing as it's the only way out. Turbine starts to spin and boost starts to be generated. It's all about the amount of fuel injected, the amount of heat generated as a result and the resulting exhaust velocity through the exhaust housing.
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From: Chicago suburbs
Also to the above posts, if you are in neutral or park, and rev the engine, you will probably not see the needle go up at all. With no load, the engine will rev high, but the exhaust pressure is low, so the turbo is not spinning as fast.
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NOW I get it. Thanks for the information.
The other deep question that inquiring minds want to know<O
"is there a cure for the dreaded PMS"<O
That would be the powerstroke modification syndrome not the one the other half gets<O
<O
Richard <O
The other deep question that inquiring minds want to know<O
"is there a cure for the dreaded PMS"<O
That would be the powerstroke modification syndrome not the one the other half gets<O
<O
Richard <O
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Posting Guru
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From: Near DC
Yes, a cure has indeed been found...
It is very drastic and has negative effects on your home, family and lifestyle.
It's called unemployment.
Don't seek the cure, you won't like it!
It is very drastic and has negative effects on your home, family and lifestyle.
It's called unemployment.
Don't seek the cure, you won't like it!
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If I seek that cure it's most likely I will be living in my truck. I sure like my truck but not that much. Good thing I bought the extended cab, maybe I should have looked at the crew cab just in case.
Richard
Richard
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From: Braham MN
Originally Posted by Steve_250
Yes, a cure has indeed been found...
It is very drastic and has negative effects on your home, family and lifestyle.
It's called unemployment.
Don't seek the cure, you won't like it!
It is very drastic and has negative effects on your home, family and lifestyle.
It's called unemployment.
Don't seek the cure, you won't like it!
I work to support my trucks.
Diesel Rod
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Joined: Jan 2004
Posts: 37
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From: Colorado (Native)
Originally Posted by Steve_250
Yes, a cure has indeed been found...
It is very drastic and has negative effects on your home, family and lifestyle.
It's called unemployment.
Don't seek the cure, you won't like it!
It is very drastic and has negative effects on your home, family and lifestyle.
It's called unemployment.
Don't seek the cure, you won't like it!
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