On a 1984 300CD with automatic and rebuilt turbocharger .

I installed a boost gauge to - day and was surprised to see it jump right up to 10 ~ 15 # in normal driving, goosing the throttle at freeway speeds with the engine turning 3,500 RPM's made it go to 20 # in a jiffy .

What's the maximum boost from the factory ? .

Yes, the overboost valve in the ALDA line is present, I thought it would cut the boost off before it got too high .

Thoughts ? .

TIA,

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

In this case it's the 50 year old turbo compressor design being more of a heater than an air compressor at those boost levels than any engine issue. Personally I think it's pointless having more than about 14psi on the stock turbo - from memory (dangerous) it' meant to be .7 or .8 bar which is 10-12psi or so.
Sounds like the overboost line might be blocked etc (but IMO a waste of time having it in the first place even when working)

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

THANK YOU ! .

I removed and carefully cleaned the overboost valve,lines and banjo bolt, why I was asking about when that valve should have closed .

I was directed to this excellent thread with lots of good technical details :

http://www.peachparts.com/shopforum/diesel-performance-tuning/293297-9-psi-max-boost.html

I'm not looking to Hot Rod this car, there appears to be a problem with the wastegate so I'm gathering information before I dive in to it .

The wastegate's diaphragm is bad, it doesn't hold any pressure nor vacuum .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Aside from non-functioning wastegate, the overboost switch might be gummed up. IIRC on a 617 it threads into the intake manifold by the AT dipstick tube.

Sixto
98 E320s sedan and wagon
02 C320 wagon

I would get an EGT probe just to be safe ...

Thanx Sixto ;

I was thinking the same thing since the ALDA's banjo bolt was fully plugged when I bought the car .

? Where would I insert and Pyrometer probe ? .

Part of the deal is : it's my primary daily driver so I try to do things in one day or less bites ~ since retiring I have so little time it's scary . Foster boys and SWMBO take up most of my time and of course, whenever my Son or Grand Daughter calls (she's 5-1/2, he's 39 - 10/12ths) I drop everything and dash off.....

Good thing I have two Motocycles I can use when I have to leave my Coupe in pieces in the driveway .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

jump over to S T D dot com ... bunch of pictures over there. About inpossible to describe without a picture. But, in the middle, and underneath is where i see them.

On 'Desert Rose', here is the first location I used when I only had an pyrometer.

http://www.peachparts.com/shopforum/3397527-post46.html


And here is the current exhaust manifold with a pyrometer and exhaust pressure probe.

http://www.peachparts.com/shopforum/3747441-post1.html

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

THANK YOU ! .

That's a bit more involved than I want to go, as soon as I find a serviceable wastegate diaphragm I'll install it and tweak it not so high .

Your manifolds look terrific .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better