Scott Jones Kicks Off Qatar 2012: Shots From Thursday

Welcome to 2012. Gentlemen, start your engines.

The traditional start to the MotoGP season. The group photo photographer scrum

Lorenzo lost his number 1 plate last year, and now he wants it back.

Meta photo. Herve Poncharal eavesdrops on one half of his team

There's a lot riding on that single word

Ivan Silva. He has a Russian first name for a reason, you know

Bradley's bike

Randy de Puniet and Mattia Pasini play the popular paddock game "Hair or Hat"

Eyes on the prize: a return to a factory bike

Time to defend that #1

The Doctor's Office

Hayden's 2012 got off to a strong start. 3rd in FP1 - though on soft tires.

Class Photo #1: MotoGP 2012

Class Photo #2: Moto2 2012

Class Photo #3: Moto3 2012

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What's that on Bradley's exhaust?

That thing going into his exhaust looks way too big and beefy to be just a sensor, particularly as it looks like there might be a braided hose coming out of it (hard to be 100% sure cause of the gear level obscuring things). That almost looks like a water injection system, a la the late 500cc days... Could it be?

Total votes: 45

Bosch wideband O2 sensor Its one of the few parts on these bikes that are the same as mass production pieces.

I thought water injection was done on the intake side?


Total votes: 39

Can be both

(Sorry for the late reply ;) ).

Water injection can be done on induction, primarily for cooling the mixture and combustion, so allowing for leaner mixes. On the 2-strokes my impression was that it was done into the exhaust - I got this impression from pictures published in magazines in the 90s of undressed NSR500s that seemed to show this, and from comments that said it was an exhaust system. Google finds articles backing up my impression, that it was exhaust side, but not pictures of the system.

The reason for exhaust side water-injection is 2-stroke specific: efficient induction on a 2-stroke depends on back-pressure from the exhaust at just the right point, to stop fresh mixture leaving. This back-pressure is from a reflected pulse of the previous combustion, and the timing of it depends on the characteristics of the 2-stroke pipe - e.g. the length and shape. Water injection into the exhaust increases the density of the gas in the pipe to be changed, affecting the propagation speed of the pulse through it, and so allows the characteristics of the pipe to be tuned to the current RPM.

Basically, it allowed for a wider power-band.

Total votes: 40

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