How was the metal surround attached. Why did you peel it away?

Took the car for a short drive and the 1/4 turn CCW on the ALDA adjust did not produce any more smoke when throttle was floored. Boost didn't go up by much either. I'll give it another 1/4 turn and try again.

Here's the latest video. CLICK TO PLAY!


Overall, getting the switch over valve (I had been calling it the boost safety valve) to work made it feel like a different car. Much less throttle input is needed now to get the car to move.

The last fill up was only 4 gallons w. 64 miles on the odo, not the most accurate but that's 16 mpg! I was doing a lot of idling (estimate 1 to 2 hours) while doing tests on my RIV Xenon timing light so that surely made it worse. How much fuel is burned idling for 2 hours? Hopefully having boost now will get the fuel economy up to normal.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I can't recall, but I didn't have any issues turning the screw, the lock nut holds it in place.

I agree with 1983…, altering the screw will increase fuel flow, not boost. Once there is sufficient fuel to match the air, you get optimal performance.

BTW, you must be going extremely fast in that video, you're upside down!

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83 SD

84 CD

I would estimate a half gallon. A quick google search pretty much confirms that no one really knows. Numbers are all over the place (kind of like Craigs List mileage claims)

I don't think you had a boost problem at all. Your "boost problem" was taking the reading downstream of the clogged overboost solenoid. You had a fueling problem, in that the ALDA never got the signal that boost was being created to be able to add more fuel, hence lower power.

But your second statement does not make any sense. Boost has very little to do with fuel economy, but it has everything to do with power. A NA 617.910 puts out 80 hp while a turbo 617.952 puts out 125 hp. It does this with the same cylinder volume by increasing the effective air charge by introducing the air under pressure, 10 or so psi above ambient. You may gain just a bit of efficiency due to thermal efficiency, but negligible. The one place where you were hurting mileage some was spinning the turbo but not adding fuel to take advantage of it - just adding back pressure for no reason.

I think you're in pretty good shape with what you've got now.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica