Ah, so now we can just ass-u-me what "the writer meant". Keep the entertainment coming!

It's because I could not measure the positive pressure (gauge) that I couldn't make sense of what was being said.

The reason you cannot measure it is because it is insignificant. No material altitude compensation occurs at low load. It's a lot like exhaust thrust. In theory, it helps move the car. In reality, it's of no consequence.

I don't understand why you even respond to that DB. Just put him on ignore and be done with it.

He adds absolutely no value or intelligence to this forum in any way shape or form and it's pathetic that the moderators have let him return for the fourth time.

Same behavior continues to this day. Once a DB...........always a DB. Never was any different...........never will be.

It did take me a bit to realize that I was dealing with a cowboy who is all hat and no cattle. But the picture is clearly in focus now. Thanks.

Actually, he's got both hat and cattle. Most of the info he provides is genuine. However, he takes great pleasure in parsing words in a valiant attempt to intimidate others. Although his knowledge is compelling, he brings no value to this forum because he's not here to help anyone...........only to propel his own ego.

He'll be departing again in short order............be certain of it.

I kinda see where Tango is going on this one. Until the turbo spools up, any positive pressure in the manifold is minimal AND the turbo actually acts as an impediment to airflow. This obviously depends on the type of turbo and it's level of repair.

Now, as I explained earlier, the oxygen content in the air at 15K feet is going to be less than at sea level. There are two factors as I understand it. Both lower ambient pressure of gas and the fact that the oxygen is heavier than nitrogen which is heavier than helium which is heavier than hydrogen etc... This causes the gasses to stratify to a degree. Wind tends to mitigate stratification but doesn't prevent it. Oxygen tends downward (otherwise we'd suffocate) and therefore is less by percentage at higher altitudes (this is why you don't find any appreciable oxygen in space).

Turbos DO work at higher altitudes but they still suffer from progressive lack of oxygen not lack of gas the higher you go. No intercooler is going to fix that though it might delay it.

__________________
Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

I was just thinking about how a waste gate control diaphragm works & yes you are right. its a combination of the force against the spring & the atmospheric pressure on the back of the diaphragm.

Simple solution would be just to have an adjustable waste gate pressure controller and compensate appropriately.

__________________
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

This post for some reason reminds me of the biblical saying ;

"Let he who is without sin cast the first stone!!"

__________________
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's the simple picture I have.

Can you provide a reference showing oxygen percentage varying bewteen sea level and say, 5,000 feet?

I did a quick search and found just the opposite --

National Institute of Health cites a 1998 British Medical Journal article --

Oxygen at high altitude with this quote "... the percentage of oxygen in inspired air is constant at different altitudes ..."

So they question your assertion.

True. But it seems much of the thread has been about the behavior at low RPM with low boost.

In that range the wastegate will be closed and experiencing a small fraction of the boost pressure required to open.

The force constant of the spring doesn't change. If atmospheric pressure was to vary by 20%, heck 50%, and you're asking questions in the 0 to 3 PSIG range, which, at least some of this discussion was, then I don't see the wastegate opening.

It is true that at low revs the waste gate is normally closed.
If we are talking about loss of power though, low revs/little throttle is not what needs considering.
Under significant load, the turbo is up to speed & working. Thats when the waste gate comes into play. When you are after all the grunt you can muster. The waste gate opens if the charge pressure gets too high. If at altitude the waste gate is opening prematurely as it is controlled at gauge pressure not absolute, you miss the full power gain from the turbo. I suspect that industrial diesel motors have their turbos set different to compensate for this. Probably F. I. knows more about the details of this than many on here.

__________________
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

The % oxygen does not vary much from sea level to the altitudes we are considering. Our friend was probably trying to mention is that the concentration in lb/cu ft or moles/cu ft is less as the pressure & so density is lower.

__________________
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

Correct.

As is often the case there are 3 or 4 simultaneous conversations occurring.

I think I understand the mechanisms at work here but an exchange between Force and tango (I think) lead me to ask this --

That was the piece that had confused me.

Your comments don't address this but certainly appear to be valid and to be contributing.

He spent time with concepts like stratification, varying gas densities, etc so it sure seemed to me he was saying a pound of air at sea level has more oxygen than a pound of air at Denver's 'Mile-High" stadium.

I said to myself, really I did not know that. After looking I still don't know that.

Thanks for the input.