Hard numbers on my overboost protection acceleration disparity - PeachParts Mercedes-Benz Forum

TylerH860 · #1 02-01-2009, 02:24 AM

Sorry for the long thread title.

To summarize from other threads, Dieselkraught awakened the sleeping giant in Ol' Turbo, disabling restrictive '85 specific elements and EGR, and bypassing the overboost protection system. While I was initially comfortable with this setup, some knowledgeable forum members have suggested I reconnect the overboost system in case of a rare catastrophic incident with the turbo.

When I reconnected the system, it immediately went back to the dog it was before. My I-phone has a very accurate dyno application that aided me with these results.

Averaging two runs back and forth on the same terrain I had these results.

With Overboost connected: 23.52 second quarter mile at 60mph...

Obviously a 23 second 0-60 ridiculously slow. We're getting close to 240 territory there.

With Overboost disconnected: 19.55 second quarter mile at 71.4mph.

A 13.75 0-60 time...

With a mildly flaring transmission! I estimate another half second would come off with some adjustments to the tranny modulator.

I have results from August, when the car was completely stock: 19.81 second quarter mile at 74.3 mph. 0-60 at 14.13. It was a quick firm shifter at the time.

It seems that something has gone wrong with the overboost system, which was gradual enough for me not to notice. With performance numbers that slow I imagine the car is getting no boost at all. I have read it can be cleaned out, but don't understand how to go about that. I may just replace the entire part and go from there.

Any suggestions? I believe that there is a vacuum leak in the Overboost protection valve itself, because my shifts firm up with the system connected.

JimmyL · #2 02-01-2009, 02:37 AM

White wagon's overboost solenoid has been bypassed since I got it. I've seen very few that aren't bypassed.
I've still yet to read where somebody's turbo went ape &#%@!!

Your results may vary......

TylerH860 · #3 02-01-2009, 02:55 AM

I couldn't find a documented event on the forum either, but if I can get it to perform just as well with the system connected, I'll take the peace of mind.

Would the car send off warnings during an overboost situation before BOOM? Other than a boost gauge, how could someone notice imminent doom?

I do like the cleaner look under the hood. It was fun ripping out all the useless bundles vacuum lines marring the left side of the engine bay.

I bought some copper BBs (surprisingly they were the cheapest) to plug some things up for good measure. Of course, in attempting to open the package I sent half the BBs flying in every direction.

My spring garage cleaning will be more interesting this year.

turbobenz · #4 02-01-2009, 04:32 AM

hmmmm

I would leave it without the over boost protection, but if your concerned then replace the over boost sensor on the manifold (very very easy) and get a new switchover valve. As far as I know, there's really not much else to it.

Btw, nice sig pic

bgkast · #5 02-01-2009, 04:49 AM

Your switchover valve must be plugged up with crud. You could try cleaning it out with brake cleaner, or just replace it with a junkyard one. It should allow pressure to freely pass through it when it is not activated.

dealwithit · #6 02-01-2009, 05:44 AM

what year did they start using this overboost protection? my engine im using is a 82 om617 from a 300SD, all i really see on it is just the line to the wastegate.

Brian Carlton · #7 02-01-2009, 10:49 AM

Quote:

Originally Posted by bgkast

your switchover valve must be plugged up with crud. You could try cleaning it out with brake cleaner, or just replace it with a junkyard one. It should allow pressure to freely pass through it when it is not activated.

x2.

TheDon · #8 02-01-2009, 10:52 AM

Quote:

Originally Posted by TylerH860

I couldn't find a documented event on the forum either, but if I can get it to perform just as well with the system connected, I'll take the peace of mind.

Would the car send off warnings during an overboost situation before BOOM? Other than a boost gauge, how could someone notice imminent doom?

I do like the cleaner look under the hood. It was fun ripping out all the useless bundles vacuum lines marring the left side of the engine bay.

I bought some copper BBs (surprisingly they were the cheapest) to plug some things up for good measure. Of course, in attempting to open the package I sent half the BBs flying in every direction.

My spring garage cleaning will be more interesting this year.

I have a 5 lb box of bb's from when I was a kid and had a red ryder bb gun. I have enough BB's to every diesel on this forum.

I was smrat and used a pair of scissors to cut off a corner on one of the packages so they didn't fly everywhere.

Brian Carlton · #9 02-01-2009, 11:04 AM

Quote:

Originally Posted by TylerH860

I couldn't find a documented event on the forum either, but if I can get it to perform just as well with the system connected, I'll take the peace of mind.

Would the car send off warnings during an overboost situation before BOOM? Other than a boost gauge, how could someone notice imminent doom?

I do like the cleaner look under the hood. It was fun ripping out all the useless bundles vacuum lines marring the left side of the engine bay.

I bought some copper BBs (surprisingly they were the cheapest) to plug some things up for good measure. Of course, in attempting to open the package I sent half the BBs flying in every direction.

My spring garage cleaning will be more interesting this year.

The vehicle won't provide any warning when it's in overboost. The turbo will be screaming, however, so you might notice that if you're perceptive.

One additional point to note........the overboost valve can be brand spanking new and you still have no overboost protection if the manifold sensor is plugged. After 20 years, the overboost sensor is plugged........what do you think the condition of the manifold sensor might be? The SD has a properly functioning overboost protection valve but the system doesn't work because the sensor won't respond to boost levels above 15 psi (confirmed with boost gauge during wastegate adjustments).

Why bother with random BB's in various places. Determine which lines are not required for EGR and get rid of them. Most of the time, you get rid of two T's as well. That's what gives you the clean underhood look.

TylerH860 · #10 02-01-2009, 01:38 PM

Misspelled acceleration in the thread title... How do I fix that?

MBeige · #11 02-01-2009, 01:53 PM

Quote:

Originally Posted by TylerH860

Misspelled acceleration in the thread title... How do I fix that?

Edit your first thread...

Not much I can suggest, it has been covered by the other members.

Which reminds me I'm also long overdue to clean it as well. I need to get a new ALDA line, it's still the original. Removing the original dirty white lines from the banjo bolts is a PITA, so I heard.

Brian Carlton · #12 02-01-2009, 02:01 PM

Quote:

Originally Posted by TylerH860

Misspelled acceleration in the thread title... How do I fix that?

........magically.....

mispelled "disparity".........as well........

TylerH860 · #13 02-01-2009, 02:08 PM

Haw!

Apparently my automatic spell checker with firefox does not work with thread titles. Perhaps I was tired.

I was a school wide spelling bee first runner up in the fifth grade. How the mighty have fallen.

Wait, did you do that to disparity????