Turbo will not kick in - Page 2 - PeachParts Mercedes-Benz Forum

Brian Carlton · #16 08-17-2007, 03:20 PM

Quote:

Originally Posted by pjc

Clue me in here, Brian and RRG. Are you saying the aperture of the wastegate hose is so small, compared to the compressor/intake manifold aperture, that even if the wastegate hose is fully vented to the atmosphere, it will not meaningfully reduce the boost from the compressor? (Ignore for the moment the function of the wastegate valve.)

Precisely.

Jeremy5848 · #17 08-17-2007, 03:41 PM

One thing that, if damaged, will in fact reduce boost, is the flex line from the exhaust to the EGR. My '85 had such a problem; repairing (and later, removing and blocking) that line improved performance of that car. Caveat: This is, of course, a CA-version with the trap catalyst. It's possible that the Federal version might respond less (or more) to such a repair.

The difference is that this problem is an exhaust leak (less drive for the turbo) whereas a cracked wastegate hose results in loss of pressurized clean air to the intake manifold. The result is the same but they are two different animals. Perhaps Brian might venture a guess as to the relative importance of the two kinds of leaks.

Jeremy

Brian Carlton · #18 08-17-2007, 03:55 PM

Quote:

Originally Posted by Jeremy5848

The difference is that this problem is an exhaust leak (less drive for the turbo) whereas a cracked wastegate hose results in loss of pressurized clean air to the intake manifold. The result is the same but they are two different animals. Perhaps Brian might venture a guess as to the relative importance of the two kinds of leaks.

Jeremy

It all depends on the size of the leak. A 3/8" hole in the intake manifold can't leak enough air to become a problem for the engine. Effectively, it doesn't exist.

A 3/8" hole in the exhaust manifold would be equally meaningless in the capability to spin the turbo up the the necessary speed for full boost. Boost might be somewhat delayed and might not reach the wastegate limit for a few hundred more rpm's, but, it's not significant.

Now, if you had a loss of the corrugated tube and had a 3/4" leak........that's a completely different issue and boost would be significantly affected.

PanzerSD · #19 08-19-2007, 03:35 AM

LOW boost at WOT conditions after a high boost spike is the spring in the actuator getting hung up on something.
I was making less than 4PSI at WOT and I stopped the engine, tapped the turbo with a screw driver lightly, and I heard a *sproing* and after that I had normal boost untill my next boost spike. (of only 18PSI) Seems to have cleared itself up now. I attribute it to crud from burning an, only-once-filtered batch of WVO in an emergency fuel shortage.