Turbo Questions - PeachParts Mercedes-Benz Forum

PanzerSD · #1 05-21-2006, 01:52 AM

The Turbo on my '80 SD, can the waste gate be adjusted at all? or is it redundant due to the ALDA/overboost protection system??

In stock unmolested form what's the max boost i'd ever expect to see? how much Boost can a strong healthy 617.095 handle?

Can I use the HOLSET turbocharger from a Cummins Diesel on these 617's?

Tnx guys in advnce.

Hit Man X · #2 05-21-2006, 01:56 AM

Yes you can adjust it. It's easier to install a manual boost device, they're about $7 in parts only. I did this on my SD. Went from 8psi to 12psi, runs a lot better on the high-end. i.e. freeway cruise. Factory spec is about 11psi if I recall. More air won't do anything without fuel, seems the pump is setup to be maxed around 12-14psi

I think the overboost cuts around 16psi?

Holset has a different flange, custom work needs to be done to have one on there. Pretty useless on a stock injection pump 617. A T3/T4 hybrid is a bit better choice as it'll use stock exhaust manifold and have a larger compressor side.

Then you'll need an IC along with modifying your IP.

1983/300CD · #3 05-21-2006, 08:01 AM

Does a larger compressor wheel give you better low-RPM boost? You'd think it might take longer to spool up.

I know the stock set-up can over-boost the engine if you set the wastegate actuator for it, so more high-end can't be the goal.

t walgamuth · #4 05-21-2006, 08:16 AM

i have no application specific knowledge for your question, but generally a bigger turbo will increase high rpm power and take longer to spool up. if you want better low speed response you generally want a smaller turbo.

there are even cars out there that have from the factory two turbos one small and one large so that they cover both ends.

tom w

TheDon · #5 05-21-2006, 09:22 AM

depending on what turbo you have.. garrett or KKK adjusting the wastegate can either be a cake walk or a pita. boost controllers IMHO are not worth it. i guess i say that because i own a triple K. but if you have a garrett you are open to the posibilities of swapping the turbine side of the turbocharger. i know not of one o for the KKK... i think the holset turbo might cause lag.. alot of it

1983/300CD · #6 05-21-2006, 09:46 AM

Quote:

Originally Posted by t walgamuth

i have no application specific knowledge for your question, but generally a bigger turbo will increase high rpm power and take longer to spool up. if you want better low speed response you generally want a smaller turbo.

I was responding to:

Quote:

Originally Posted by Hit Man X

A T3/T4 hybrid is a bit better choice as it'll use stock exhaust manifold and have a larger compressor side.

...and reconciling with the idea that overboost is possible on the high end of things with the stock setup.

t walgamuth · #7 05-21-2006, 11:44 AM

i did not intend to disagree with you. frankly i didnt understand your post. i was just adding my limited knowledge and thoughts.

tom w

Hit Man X · #8 05-21-2006, 04:10 PM

Oh I agree, a T3/T4 isn't worth it on a stock IP. You could drop a grip on one with a ball bearing center and it'll spool like stock with better efficiency on the high end.

There's so much voodoo behind turbo specs (heck, some have three exhaust housings alone to choose from not including the wheels) you better know exactly what you're going to do for the proper unit.

Garretts are a PITA to adjust, that's why I got the MBC for mine. Well worth it, now I'm one step closer to how it ran at 50K miles. Injectors are next and to time that pump.

I have an extra KKK I may/may not install on the SD. I keep reading mixed stuff on it. I don't plan to run more than 12psi and I THINK that's all it is good for as it also spools quicker than the T3.

ConnClark · #9 05-22-2006, 11:54 AM

I'm currently looking for a turbo off an 86 or 87 SDL to try use its compressor wheel and compressor housing on my OM617 turbo. It has a trim of 50 and is a much better match in my opinion. With this combo (if it fits) I should gain at least 1 hp from reduced back pressure alone at the upper rpms.

1983/300CD · #10 05-22-2006, 01:50 PM

If the turbo is spinning freely, the backpressure should be minimal at high RPM. Inertia will keep it going.
The KKK is designed to reach boost pressures above 15 PSI. The wastegate and overboost sensor are there because of this. If it hit the wall at 13 PSI, neither would be necessary.

Actually, I've heard that the KKK's can run away with boost at over 4K RPM. For instance, if you're holding at 4K and you have the boost set for 13, it can gain boost pressure and actually shoot over 15! Never witnessed it myself. I guess that's another one for Mythbusters.

If you really want to improve your turbo, look into a variable geometry turbocharger. The compressor vanes change shape at different RPM's. This gives good boost at lower RPM's and changes so as to not overboost at high RPM's. But that's real money.

PanzerSD · #11 05-22-2006, 10:51 PM

Oooooooooooooooook.

what happens to the 617 when it is overboosted, lets say, I defeat the protection and giver hot hell and blow 15 or 16 thru it? hypothetically speaking of course...

#12 05-23-2006, 01:59 AM

Quote:

Originally Posted by Got_The_Benz

Oooooooooooooooook.

what happens to the 617 when it is overboosted, lets say, I defeat the protection and giver hot hell and blow 15 or 16 thru it? hypothetically speaking of course...

If you defeat the overboost protection and cut the wastegate line, you will get WAY more than 15-16psi. More like 25-30psi.

The results: Depends on how long you allow it to happen.

Worst case, the compressor wheel blows up and sends lots of metal bits in to a 5000rpm engine.

Second: You bow the head gasket when you get around 25psi.

Third: If none of the above happen, you melt a piston.

If you are VERY lucky, you will only hurt the rings and make your cold idle/starting suffer.

ConnClark · #13 05-23-2006, 10:38 AM

The stock turbos on these cars aren't really good for much more than 14 to 15 psi of boost before the compressor wheel efficiency starts to suffer.

vstech · #14 05-23-2006, 11:01 AM

Quote:

Originally Posted by ForcedInduction

If you defeat the overboost protection and cut the wastegate line, you will get WAY more than 15-16psi. More like 25-30psi.

The results: Depends on how long you allow it to happen.

Worst case, the compressor wheel blows up and sends lots of metal bits in to a 5000rpm engine.

Second: You bow the head gasket when you get around 25psi.

Third: If none of the above happen, you melt a piston.

If you are VERY lucky, you will only hurt the rings and make your cold idle/starting suffer.

I would think 5000 rpm is quite low for a turbo.