Quote:
Originally Posted by superapan
Oh, it's an M pump? I thought that was for OM617? Where is the RS203 used then?
First impressions is worsened performance. I don't fully understand diesels. I know they run lean by design, but can this be a case of it becoming TOO lean, from the turbocharging? I expected same performance, since I haven't touched the pump, but it got worse...any ideas?  |
The M pump has been around since the OM616/617 days and probably longer than that in non-Benz applications. It became the standard pump on the OM60x series engines.
Turbocharged engines either run excessively rich under a no-boost condition, or have some scheme to increase fuelling with boost pressure. Mercedes (and a lot of other manufacturers in the 70s/80s/early90s) went with the aneroid capsule (ALDA). The basic idea being that as boost pressure built, the fuel was enriched to build boost further ensuring that the fuel was matched to the incoming air for complete combustion, lack of smoke, and good economy.
If you just bolt a turbo to an N/A engine and do nothing to the stock fuel setting, you've just installed a restriction in both the intake AND the exhaust. There is no excess fuel to spool the turbo, and even if it did build any meaningful pressure, you have no additional fuel to take advantage of the extra air charge.
I don't know about tuning the OM606 style pumps or if you could get away with swapping in a pump from an OM603 turbo (there are far more people that know WAY more than I do about things like that on the Super Turbo Diesel forum), but something's gotta get done to increase fuel or that turbo is pointless!