Does size matter? It’s a question that has plagued humanity for centuries. When it comes to turbochargers at an event like drag racing, bigger is always better. And what’s better than making it on old diesel engine!
Tuned cars are never exactly what people expect them to be at first glance, especially to people who aren’t into modified cars.
It’s a very fast W202, but is it an AMG? Nope, it’s a diesel. So a 320CDI engine? Nope, it’s not even a CR engine; it’s a old school Mercedes engine. So it’s got the famous OM606 6cyl engine? No, the 5cyl OM605. It can’t be that powerful though, can it, it’s a diesel!? It’s 450bhp! But diesel’s don’t rev. Well this one pulls hard all the way to 6500rpm thanks to a big Holset HX35 Billet Hybrid turbo. So it’s laggy then with that massive turbo? No, it spools up super fast. Okay, we think you get the idea now. This thing blows all the typical misconceptions out the water in style, and we’re here to show you how it’s done.
While the big brother to this engine, the 3ltr 6cyl OM606, has almost legendary status in diesel tuning, the OM605 is less famous, so why use the 605? They are hungry of RPM and really make the power when tuned properly. And besides, highly tuned OM605s sound awesome; the big turbo 5cyl breathing through a 4-inch exhaust sounds like a mix between an ‘80s Audi Quattro rally car and a huge American big rig!
You see, most diesels don’t rev simply because they’ve been designed that way. They’re intended to make good grunt from almost idle, and have great fuel economy, so generally have a tiny little turbo that strangles power as the revs rise, as well as a fuel system and engine design only really intended for low rpm use.
Even tuned diesels with uprated turbos still run relatively tiny turbos for the capacity compared to petrol engines, but this one? Well, this one has a beast of a turbo: a Holset HX35 Hybrid turbo with a twin scroll T3 turbine housing. Transmission is well know 716.654 combined with BMW M5 clutch and really really light flywheel (just 5,5kg!)
And the exhaust is just as manly too, with a 4inch diameter from the turbo right to the tailpipe. This, combined with the fact the OM605 has an amazingly well-flowing head and cam set-up for a diesel, means from an airflow point of view, this 5cyl diesel can seriously rev if needed. But what about fuel? A big part of the reason diesels don’t tend to rev high or make big power is the fuel systems are generally not capable of that.
But this OM605 has taken a step back in technology to take a huge leap forward in performance, as Scott has binned off the factory electronic diesel injection set-up for a fully adjustable mechanical injection system, and a seriously beefy one too. While a race spec mechanical set-up isn’t exactly the last word in refinement and economy, it can supply the massive amounts of fuel needed to be revving like a petrol engine would and making 450bhp and 706Nm at a hefty 2.6bar boost, which soon could be turned up to 3bar!
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