A turbo engine in a car is only a turbo engine part of the time.

That applies only to gasoline engines. A turbo diesel always has positive manifold pressure any speed and load above idle. Engines with a VNT/VGT turbo have boost even at idle (although its only 0.25-1psi).

No, it doesn't. It applies every time a turbo diesel gets underway.

Incorrect, as proven in my prior post. Please learn how diesels operate.

I totally missed the proof!!! But I did see flawed attempt to make an allegation. If a positive manifold pressure is all that's needed to overcome the reduced atomspheric pressure associated with increased elevation, why is a turbo needed in the first place? And how does a turbo become effective without spooling up?

You can't read?

You're embarrassing yourself with nonsensical gibberish.

The turbo is always spinning when the engine is running.

I read something in the Mercedez Benz 617.95 Turbo Diesel Engine Manual.

Regarding the turbocharger: "At low and lower partial power load no worthwhile precompression will occur, the engine operates as an aspirating engine."

'Nuff said.

Basically it appears that various members are using specific examples to justify their case.
Its not a black or white situation.
If the turbo has the capacity to maintain a certain charge pressure (absolute pressure), even at higher altitude, there will be little if any change in output power.
If you have a turbo that does not reach its max charge pressure (wastgate does not control pressure) then you can expect reduced charge pressure at higher altitudes & so loss of power.

The increased charge temp is theoretically the case assuming the ambient temp remains constant. But we all know that ambient drops with increased altitude so in the real world its not such a significant issue.

Forced is rightfully using his own car as an example. Best remember though this is a very well maintained motor, that has a properly operating turbo. If we were to consider some POS beater that has the waste gate jammed 1/2 open, we may see a different result from altitude as the charge pressure may never get to what it should.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Just asking a question, not at all able to jump into this one.

When I'm traveling on level ground at an engine RPM of 1500 RPM I cannot measure any boost pressure from the turbo. My car is pretty well maintained but not on par with Forced.

Is it being said that at those conditions that the turbo is contributing to the vehicle's performance?

Yes,
If it wasnt, you would have vacuum in the inlet manifold.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

That is precisely what has been said. And, for that matter, proven!

Are you not buying the "proof," either?

I have more than enough people wanting to 'tear me a new one' already.

I just want to learn.

I've got no dog in this fight.

Does that mean that my NA has vacuum (I think it does).

Since my boost gauge only read zero and up I don't know if I have atmospheric pressure or vacuum at 1500 RPM and light load.

So for all I know I do have vacuum then.

I don't know.

Nope. That is false information, ALL engines are aspirating.

Charge (manifold) pressure is gauge pressure, not absolute. 12psi at 5k' is less pressure than 12psi at 0'.
At 0', 4500rpm and 12psi boost the airflow is 20.85lb/min.
At 5'k the airflow is 18.27lb/min. You would need to run 18psi of boost to get the same airflow through the engine. However, adding an intercooler at the same 12psi would return ariflow to the same mass.

Your car IS making boost. Gauges are not very accurate except in the middle of their range, your gauge might not start reading until 2-3psi.

Yes. As said, if it wasn't, the restriction to airflow through the compressor wheel would cause some vacuum on the intake.

Yes. There is always a pressure drop across the air filter.

Hanging your hat on a minor translation error is quite disingenuous. It would be clear to any thinking and reasonable individual that the writer meant "normally aspirated."


ALL engines are maintained, too. Some well, some poorly.