Thursday, July 8, 2010

Sand, Gravel and the Darkest BlacK

Diesel is dirty. There I said it. It shouldn’t be but I seem to find with this motor that everything that is dirty is an order of magnitude more so than I’ve seen in dismantling even a dirty petrol engines. Today’s rant is directed at the intake and intake manifold. One of the brilliant ideas for making diesel cars produce less emissions is EGR (exhaust Gas Recirculation [Google it]). This is nothing new as it’s been done in Gasoline cars for long long time. It works for a diesel too for the same reasons, but with the increased particulate emissions of diesel engines and the fact that diesel fuel is a light fuel oil and not a aromatic like gasoline, combine to make a black sandy mess of the intake system. This intake plenum as well as the runners to the intake valves are covered with a sooty, gravely, oily, dark black MESS! (Sort of like the gulf). This doesn’t seem to have affected the engine when it was run in its detuned state on the world’s highways. However it is completely unacceptable for an engine that I need to run at the top of its game. After finding this, it is looking more and more likely that after I get the motor running and the rest of the bike started, this motor is going to have to come apart and get cleaned and freshened up. This may not actually have any effect on the performance of the motor, but there is no way in hell it would be prudent to leave a condition like this. Plus it is imperative that I know exactly what going on in this motor to have any confidence in it. Also I need to provide as pure a baseline as I can for when we begin real tuning for power. I’d love to buy virgin motors from Mercedes but I am just a poor surf of meager means. So as much as I loathe the idea of adding more work to this project by having to rebuild this motor, here we are.
Dirty intake port

The manifold after I scrubbed for about 30min. It still has plenty of crap in it and I managed to break off the little nipple for the hose MAP (Manifold Absolute Pressure) sensor. Yea me!

One note:
I’m not an expert on port design but I know a thing or two about a thing or two. These ports look fairly bad from a flow perspective. You can’t really see it in the pictures but they look like they are designed to induce swirl, which is good, but there are a number of relatively sharp corners and obstructions that look they were designed in there as a compromise to compactness. Also, the port direction from the manifold goes through a number of direction changes before it enters the approach to the valve head and to top it all off the cross sectional area as you run down the port changes abruptly and without what looks to be any ratio to the distance down the port. I know with the turbo and being a street car some of this is not critical but I am really looking forward to getting a spare head and doing some serious porting and flow experimenting. I think there is a huge amount to be gained here. I also want to design a new intake plenum too and that may actually come first. This of course is all after I have a bike on the salt. Till that point there isn’t too much point I guess.
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