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mike puig
08-28-2006, 03:34 PM
anyone have an idea as to how much boost a turbodiesel would take before critical mass?

08-28-2006, 04:14 PM
factory setting for your 300D Turbodiesel
is .5+ bar (7 ...10 psi) boost

want to adjust for more boost ? -do you feel lucky ?

08-29-2006, 12:18 PM
Boost Pressure Adjustments
Made Easy
by Richard Easley

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Garrett Turbochargers
If you have a Garrett turbocharger (w/ waste gate adjustment inside cover), removing the cover takes some time and perseverance. It is not particularly difficult, just tedious. Make sure that the turbo area is cool (use a fan between adjustments) and when re-installing the spring, "squeeze" it to reduce its diameter before inserting. Then, with a screwdriver push on the flat part of the spring until it seats.

KKK Turbocharger
If you have a KKK turbo, the adjusting screw sticks right out of the top (sideways on engine) of the waste gate chamber and does not require removal of a cap.

Remember both of these turbos are capable of over 40 pounds per square inch of boost and they run against an open waste gate all the time so these adjustments are really critical. Don't get carried away or you are going to buy a motor. However, please note that it is hard to get a tremendous amount of boost (i.e., well beyond safe ranges) from an original 617 turbo now that the cars have a few years on them now and the springs are fatigued somewhat. Still, confidently proceed with caution.

If you have an exhaust temp gauge in-line you can carry the boost procedure a little further, but even at 0.9 bar (upper limit of factory specifications) they just fly.

Preliminary steps necessary before adjusting waste gate valve spring tension

Prior to adjusting the waste gate valve spring tension, there are two necessary preliminary steps that need to be taken.

The first step is to ensure that the injection pump is timed correctly.
Checking the boost sensing lines and over boost sensing switch is the next step in this process.
After successful completion of the above two steps, you are now ready to adjust the waste gate valve spring tension (i.e., boost adjustment).


Tools needed for adjusting waste gate valve spring tension on turbocharger

High quality vacuum/pressure gauge (needed for checking boost pressure only)
"T" fitting for vacuum gauge and 6 - 8 foot length of vacuum hose for monitoring boost pressure while driving vehicle (needed for checking boost pressure only)
Phillips screwdriver
10 mm socket and 1/4" drive ratchet and extension for removing air horn
Pliers for removing sensor hose clamps at turbocharger
Small mirror for clarity during cover removal
High powered flashlight or shop light

Remove the u-shaped air intake and the intake to the air cleaner. Make sure to re-install before testing boost pressure.
Cool the turbo area with fan.
Spray the cap cover "spring" area with Liquid Wrench or other similar solvent.
Using a couple of small screwdrivers (a very thin bladed 5-8" shafted one is great), "spin" the spring around until it starts popping out.
Pull out the spring with needle nose pliers or fingers.
Remove waste gate valve cover. Be careful not to damage the rubber seal behind cap (but attached to body of turbocharger) when removing. There will likely be a small quantity of oil that will leak out when the cover is removed; this is normal not a problem.
Completely remove locknut on waste gate valve.
Make a note of measured length of exposed threads on valve.
Turn spring assembly (it has flat, thin edges for wrench) clockwise. Begin with 3 full turns - it sounds like too much, but it isn't! If our approximations are
correct, for every 1/8" of threads exposed (by screwing spring assembly in),
this equates to 0.15-0.20 bar of boost.
Reverse disassembly procedure. To reinstall spring as easy as possible:
Make sure that you've thoroughly cleaned the groove where the spring
Make sure that the spring is thoroughly clean.
Lightly file or grind the flat side of the spring at each end so that it's
shiny. This enables you to maneuver better when inserting 'cause shiny end
Make sure that rubber gasket is firmly seated before replacing cover.
Compress spring with fingers to reduce diameter when placing in groove.
And, push cover hard simultaneously.
Then, push spring with biggest screwdriver that you can use. Tap
screwdriver with rubber hammer. You should "feel" spring seat.
Do this only on fan-cooled turbo area.
Road test using Stu's guidelines: having the boost gauge in the car, start driving a fully warmed up motor and engage "S" and go up to 4,000 rpm and full throttle, read the boost. Good luck and hold on to your hat.
If further adjustment is needed, cool turbo area with fan.

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