Cousindave, your thread has taken weird turns because in describing the valve function people are using different perspectives. Some are talking electrical, others pneumatic. Focus from the primary signal standpoint. The primary signal being relayed by the valve is Boost Pressure, call it BP which is pneumatic. Forget about the electrics right now. In the default low energy state (no electrical power) the BP is conducted through the valve thus the valve by definition is 'NORMALLY CLOSED'. This is a definition drawn from the world of electrical switches. Do not get hung up on the English word 'Closed' or it will confuse you. 'Continuous' might be a better word.

For your test here is the foolproof method as already suggested.

Connect directly from Manifold to ALDA (totally bypassing the OBPV). If your Turbo is ok you now will have turbo performance. If you now remove this connection your performance will drop. If you see no change then you are seeing no turbo effect and you have a problem.

__________________
Dionysius

TF is correct.

I'll further clarify:

When the valve actuates, flow will occur between the horizontal port and the top vertical port. The top port is vented to the atmosphere.

When the valve is not actuated, flow will occur between the horizontal port and the bottom vertical port. The bottom vertical port is connected to the intake manifold.

Again new terminology in the 'clarification'. Without a drawing the horizontal and vertical have little meaning. This valve is not orientation or attitude sensitive as I interpret it. Your explanation implies orientation is important. Is this intentional? Please explain.

__________________
Dionysius

To complicate matters even further, there are at least two distinctly different styles of changeover valve. Mr. Carlton's description is applicable to only one style. The other style has both hose nipples on the bottom and the vent on the top.

Whether orientation is critical or not, the fine folks in Stuttgart seem to do a good job when it comes to standardization. I don't think that you will find the orientation of the valves to be random. They were originally installed with the vents at the top.

The orientation of the drawing will undoubtedly present additional challenges!!!

Thank you TF for elaborating on this. Have you found any innacuracy whatsoever in my posting #31 of this thread. I am new to Turbos and I am now looking at the one on my 1979 300SD (Garrett I believe).

I do not believe there is any orientation requirement on this valve installation. My point is that Mr Carlton introduced confusion by using the language of orientation in his 'clarification'. If he has OEM specs that ordain orientation I would like a copy and if we place them on here then we will have a good reference.

As always, this is always about technical accuracy, never about the people.

__________________
Dionysius

There is likely no "requirement" that first aid kits be installed on the left side of the hat rack, either. But that's where you find them. Same concept applies to changeover valves.

Any comment on posting #31????

__________________
Dionysius

Horizontal and vertical are defined as the condition of the valve when it is installed in the vehicle.

If you need further definition:

Horizontal: parallel to the ground

Vertical: perpindicular to the ground.

It's unobtainable in normal driving conditions on a pre-85 SD. As I mentioned the old-style EPA rating (which was _NOT_ in real world conditions and nobody ever got that good in normal driving) was 27 mpg. At 55 mph. With the skinniest tires available, everything in perfect tune, and probably 1/2 a gallon of fuel in the tank and a driver that weighed less than 100 lbs. On a track designed for the lowest rolling resistance. I think you should get the point by now. It is simply not attainable in real world conditions in an engine with 25 years of wear and modern speed limits.

I've mentioned it before but from a discussion with an engineer who had fleet mileage and fuel records comparing claimed mileages with the records - "When it comes to fuel economy people lie a lot." Not one driver had actual economy anywhere near what they claimed. If you look a lot closer at the people with the outragious claims when they give detail it is never real mileage. You'll find that it was using the gas gauge (HIGHLY innacurate) for partial readings. Or the route was downhill! Or only in one direction with a tail wind. To get real mileage you need long distance round trips in similar weather conditions, especially wind, burning multiple tanks of fuel. Add all the mileage and subtract the 30+ gallons of fuel and you start to have close to an accurate measurement. I have yet to see that done with the outrageious claims. In short they are full of it.

Reread my earlier post. Your mileage may or may not be good depending on your speed. How fast were you driving? Was stop-and-go included in the numbers? Was city driving included?

Your thread has been going off in very strange directions. I have just learned much. Now to get back on topic.......

Mr Gene Horr agrees with what I say - MPG is too subjective of a measurement to be used for measuring fine detail. We are talking fine detail here. Read on and I will get back to this.....

The answer to this question is 'Yes'. The rack could be snagging or some other strange effect is surfacing. However having looked through the system in some detail a good troubleshooter would tackle the problem by first eliminating the more likely culprit viz. incorrect application of boost pressure. The reason that this is statistically far more likely is:
a. The components are slapped together with external plumbing
b. Uncontrolled events can happen in the manifold which may contaminate
c. People, from experience, have already identified this as a failure mode
d. The isolation of this subsystem is easy
e. The exhaust manifold heat can refer gain problems due to parts degradation

Again we are not saying anything new. It all comes down to your capability as a Tester to feel the effects of the turbo boost if you do the test I spoke of in #31. Not having any experience in this I do not know how expressive are the effects from this turbo. Beyond this then we must call for instrumentation - pressure measurements, accelerometers, fuel flow meters, etc. MPG, Performance, etc. like the previous poster said are far too subjective to be useful. However there are far more knowledgeable folks on board here who may be able to add more...... If they are not contributing more then contact me because in the next month when the weather gets me away from this keyboard I am going to be following your footsteps in characterizing my new to me 1979 300SD. I want the same answers that you are looking for. Am I at the same spec as when it left Stuggart in 1979 and if not what do I do to get it back there. And to hell with the begrudgers......

__________________
Dionysius

Thanks

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

I disagree with the above statement.

Both myself and others have sufficient data on the SD to show that a properly tuned SD with correct IP timing and camshaft timing can achieve real fuel economy of 28 mpg.

In the case of my SD, it makes a consistent 28.5 mpg overall mileage (90% highway) driving at speeds of 65-70 mph. Please note that the valves are two years of age and the diff is a 2.88.

My fillup procedure is flawless and the odometer is calibrated to an error of less than .1%.

I agree that many fuel mileage claims are lacking in truth or proper technique. However, a properly tuned 617 in an SD can honestly achieve these figures after some work is performed by the owner.

To check your turbo without so much thought and discussion, buy a boost gauge and tee into your line. Watch it on plastic tee around the exhaust manifold, may have to buy metal 1/8" pipe and three brass hose adapters. Boost gage pn GM272653 with underdash mount is $28 plus 10% shipping from JCwhitney. Buy by mail, 761 progress parkway, Lasalle Il 60301-300. If you buy by website, they send you 3 emails a day about specials for your volkswagen beetle for the rest of your life.

__________________
'80 240D biege "Mercey Bird"
'80 240D light blue "Slug"
'80 300SD dark blue "Theodin"