I never got a clear answer on this, how much boost does the W123 300D Turbo engine (help me out here 617.??? what is the 300D engine called) produce? Is it 6 lbs.?

I have my boost set at 13-14 psi and have had no problems. If you're going to up your boost, make sure you have a boost gauge set up for atleast a while so you can monitor everything.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

I've run a gauge on mine and it got to around 9.5 PSI. I don't see where there is any need to change it. You could run it up to 20 psi if you wanted, it is based on how much fuel you want to put into the engine and how long you want the engine to last. I think I remember seeing that you can safely go up to around 13 psi.

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Jim

Thanks for the replies, I just wanted to know how much stock boost was from the factory. I thought it was only around 6-7 lbs. of boost.

I think factory boost was supposed to be 9.5 - 11 psi. You can go as high as 13, but beyond that you are exceeding the design horsepower of the engine and risking shortened life and/or blow head gaskets. By now, I'd not be surprised to see weak springs in the wastegate controller limiting boost.

The 6-7 psi number is about right for gasline engines -- even with intercoolers, you risk igniting the fuel at the injectors if you go any higher, and serious spark knock will occur as well. Mind you, that is LOTS of boost for a gas engine -- my sister has a Volvo 740 turbo that I repaired last summer -- couldn't figure out what my brother-in-laws complain was with the power. Felt like a road rocket to me!

The 603 is set for about 13.8 psi, still a mechanical wastegate. The TDI engines have electronic wastegate control

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Factory spec is 0.85-0.95 bar according to the engine manual. That's about 12.5-14.0 psi if you do the math (1 bar = 14.5 psi). If your car is at 9-10psi or less, you may see a performance increase if you turn it up. There is NO chance of damaging your car if you keep it under 14psi - that's the way MB designed it in the first place! The overboost circuit, if it still works on your cars, will trigger at 1.1 bar +/- 0.15. I tested mine on my 1987's, one triggered at 1.25 bar (18.5 psi!), the other at 1.15, both within spec.

If you have a Garrett turbo with a rubber hose to the wastegate, you can simply pinch it off or plug it (TEMPORARILY!) to test max boost and the performance gain. My 1984 is at 10psi, I pinched the hose and it jumped up to 13-14psi max, while shaving a few seconds off the 0-60 time. I plan to adjust the wastegate permanently to that setting when I have time (I left it alone for now). It was a noticeable power improvement between 10 and 13 psi.

I did the same on my Garrett-turboed 1987 and the max boost was 18+ psi. I didn't do a 0-60 test on that one, I was nervous about possible damage with the boost at 25% over spec. Oddly, I didn't "feel" a difference, so I left it alone (12.5 psi stock).


HTH,

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