I built a boost controller for my '82 300 SD today and was wondering about spring tension. Does anyone know how stiff the spring should be so that the ball bearing starts to move. I went fairly light but have not tested yet? Any thoughts? Thanks!

I should mention that the adj scew is adjusted all the way out. if I push a small rod through the nipple to make contact with the ball bearing and spring should light finger pressure be able to move the valve(ball bearing) Thanks!

Usually you start with the screw all the way out, as you have it, and turn in the screw in increments until you have the boost level you want. If you have a MityVac, use it in pressure mode with a gauge and set it around 5psi as a start.

Sixto
87 300D

Springs are different, we have no way to know what diameter, length or thickness spring you have.

Put it on and keep adjusting until you get the pressure you want.

thanks, will use my mighty vac for this. My car is an '82 300sd, I assume that I am correct in connecting the turbo outlet hose to the inlet (ballbearing side) and the wastegate hose to the outlet? Just checking! Thanks!

http://www.geocities.com/chmwatson/FAQs/mbc/install_instructions.html

... except don't start at 15psi!

Sixto
87 300D

http://www.well.com/~mosk/boost.htm

Hey Sixto, am I just making one cut in the turbo outlet line and plumbing in boost controller there?

Yes. The t-fitting in the diagram is for the boost cust solenoid or a boost gauge in that non-MB application. You should have a boost gauge if you're installing a boost controller, don't count on the overboost protection system.

I prefer to take a boost reading right at the ALDA than at the compressor outlet. It's highly unlikely you'll melt the engine with too much boost if the ALDA isn't getting a boost signal. Conversely, it's nice to know when the ALDA isn't getting a signal so you can clean the banjo fitting and overboost solenoid. YMMV.

Sixto
87 300D

thanks! I have been reading off the ALDA , originally at 8-9 psi. I have installed the boost controller and no matter what I do in terms of adjustments, changing springs, etc. boost psi wants to climb to 14,16 and potentially higher when I get on it. What am I doing wrong? Too stiff a spring? I read somewhere that you should be able to blow on the ball bearing end and lift the spring loaded ballbearing valve with your breath. Any thoughts? Thanks!

Too stiff a spring, a leak in your MBC or you installed it backwards.

Sixto
87 300D

thanks, I am guessing that the spring should be in constant contact with the ball bearing so that it can travel under light tension which becomes increasingly greater as the ball travels further. I drilled a tiny spiking hole in the center of the body, everything else seems nice and tight. Just don't know at this point. the valve with bearing is connected to the turbo inlet while the other nozzle is connected to waste gate actuater . . . hmmm, don't know what else to do! Thanks for your help!

You would be surprised how little force it takes to get 10 psi on that little ball. I have made two and used ball point pen springs with much success. Only takes about 1/32-1/16" spring compression to get in the range you want.

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Thats helpful, thanks . I will keep playing with the spring set up

The spring was still too long and not weak enough so I found a shorter weaker spring and voila, boosting to 12psi from 9.5 after 4 roadside adjustments. You can feel the difference pulling on a hill, love it! I understand that anything higher than 12 psi is wasted so I will keep the boost maxed at 12psi. Thanks all!