Join Date: May 2009
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The cheapest way to go fast is nitrous, but there aren't any "kits" for the Smart application... One of the issues, is the throtte-by-wire. If you're spraying nitrous/fuel and the ECU/TCU decides to shift gears on you -- it'll close the throttle and that would cause a backfire. With a cheap fogger application, the large internal volume of the Smart's intake manifold would cause a BIG backfire which would probably split the manifold. With individual port foggers or fuel injector nitrous adapters, you might get away with it as the intake manifold wouldn't be filled with an explosive mix of nitrous and fuel. You'd still get a backfire if the throttle closed on you while spraying nitrous, but it would probably be more like a "sneeze" and result in no damage. I know that Littodevil is working on the tuning for a nitrous setup using hardline fuel injector nitrous adapters that he's adapted/machined while others have already implemented nitrous setups on their Smarts. It is a bit inconvenient refilling a nitrous bottle, but that's a small price to pay if all you want to do is go fast.
If I were to do nitrous on the Smart, I'd use hardline fuel injector adapters. These aren't to be confused with the Nos brand fuel injector adapters as those are poly-line low pressure adapters. You essentially discharge the high pressure fuel and nitrous into separate distribution manifolds through metering jets which controls the ratio of fuel and nitrous. From the distribution manifolds, plastic lines deliver the fuel and nitrous to the adapters to spray directly at the intake ports in the head. These low pressure adapters are a headache... Because you've got lengths of poly-line which need to get filled with fuel through a tiny metering orifice back in the distribution manifold, you have to use a timer which has a timing offset in it to give the fuel lines time to fill before the nitrous solenoid opens. With hardline adapters, the fuel and nitrous jets are in each adapter. Any air in the fuel lines quickly gets evacuated through the metering jets... Anyway, people who have used the Nos low pressure fuel injector adapters often complain about burnt pistons because the fuel lines on the cylinders furthest away from the distribution manifold take too long to fill with fuel and those cylinders end up running too lean.
Anyway, the only person I know which has hardline fuel injector adapters machined for the Smart is Littodevil, but his setup is still in development. Still, a setup like this would probably meet your budget -- and it wouldn't change the exhaust loudness or alter the day-to-day driveability. If you add in a separate fuel system (methanol) instead of tapping into the gasoline fuel lines, you can inject more nitrous for more power. Methanol slows the burn rate of the nitrous/fuel mix -- so you don't have to program-in timing retard (probably by using a piggy-back ECU, which would go over your budget). Without timing retard, you'd probably be limited to 25HP or so. Using methanol, you could inject more nitrous/methanol to get maybe 35HP? It may not sound like much, but 35Hp is a 50% gain from stock!