#1 is the shutoff valve. applying vacuum to that will shut down the engine.

#2 goes to #15.

#11 is the return fuel flow back to the tank.

#12 is the return from the injectors.

#6
is the egr activation switch (i think). It is FOR SURE related to emissions and should just be left there unhooked. Ignore it.


#7 is a temperature probe or switch. You probably wont need it.

#5 is the main fuel supply.


#4 goes to #14

#13 goes to #3


#8 is just a good place, in your case, to tap vacuum. I beleive its real purpose is to supply vacuum to the emissions systems and the transmission vacuum modulation for shift smoothness.


#9 should just be considered another good place to tap vacuum, but beware it has reverse flow direction (they used this to make sure the in-cabin vacuum systems that were hooked to that nipple wouldnt drain back vacuum with the engine off). if you need vacuum for anything in cabin or for your improvised engine shut off, these are the places to get them.

Thanks very much Turbo!

That is one heck of an impressive build thread man. A small economical 4x4 diesel SUV like that is something some of us DREAM about!

An overboost situation with full fuel enrichment will give you EGT's outside of acceptable limits. It will not kill these robust engines instantly that is true, but it will eventually cause damage.

The engineers did not put a superfluous overboost protection system in the car because they were bored. And, they did not design it because they wanted a few more hours of pay. They were keeping the numbers within acceptable limits.

But like I said, it's your car.
Do what thou wilt.

I would not remove overboost protectiong without a boost gauge.

It may raise EGTs slightly, but I don't think it will take them past the limit. In fact adding boost pressure will actually reduce EGTs in some cases. I think it is more of a "limp mode" so the doofus driver knows something is wrong. If you have ears (at a minimum) and a boost gauge (preferred) and can walk and chew gum at the same time it is not needed.

That being said it is still operational in all of my cars that came with a 617 turbo from the factory. I did not transfer the system over when I swapped one into my 240D though, but not much about it is stock. ;)

ForcedInduction had a wastegate failure when he still had that old WW2 design wastegated turbo in his car. Perhaps he will chime in.

Not a wastegate failure, I was setting the boost pressure and the line going to the gauge cracked at the fitting and gave false-low readings. It was about 10minutes in the mountains before I decided the turbo's cool whistle was much too loud for only 10psi. I found the crack, fixed the hose and the turbo quickly pegged my 15psi gauge! In the end there was no damage at all and the engine is still running great several years later. :)

The K26 becomes a heat pump at 15psi, I wonder how hot the air was when it got up to 20+psi! :flamethro

The problem is that the switchover valves fail. Thats why i just rip them out. On my 85 however they remain functional and intact.

What do you suppose the intended purpose of the overboost protection system is if not to protect the engine during an overboost condition?

I'm not trying to be a smart ass here. Do you really, truely, honestly believe that it serves no function at all? It is not a vestigial organ. It was not a hold over from a previous design. They added it with the turbo.

Its to protect the engine from long term overboost. Short term is dicey but probably not going to kill the eninge. 2hrs at 120km/h might do the trick.

Exactly

I think it would take more than that. Maybe if you were going uphill with a headwind. :D

And what are you concerned about? What do you see as the possible negative effects of a long-term overboost condition? What exactly is it that is going to go kaput?

It could be several things. The turbo will be over-speeding, the engine will have to work much harder to exhale through the turbo and to compress 30 psi of pressure, the turbo will be putting out higher temperature air than it should, etc.

All of these are bad, but they will not cause engine failure in minutes or even hours.

While this is all occurring the car will still drive fairly normally, so the average driver would not know anything was wrong and would likely just drive it until something eventually failed. That is why I believe that they installed the over-boost protection system. Low power is a sure way to get a driver to take the car to a mechanic, and limiting the fuel will also limit the amount of over-boost the engine can make since it can no longer run at full load.

So, you suggest that the only negatives from an overboost situation is that the turbo will spin too fast, and back-pressure will be increased? Horse puckey. They wouldn't have bothered.

And the other items I listed...