Cormac Shoots Qatar: Exhaust Porn From The First MotoGP Race

The upper exhaust on the KTM RC16, for the rear cylinder bank of the V4. No torque back pressure valve on it, unlike the Ducati and Aprilia.
The mesh on the end of the exhausts was introduced when the number of engines per season were limited after the 2008 financial crisis. The mesh prevents sizable stones from entering the engine and damaging it in the case of a crash.

Suzuki's Akrapovic-made 4-into-1-into-2 exhaust is exqusite in every way. Note the pipe joining the two exhausts just before the end. Stabilizes them. What's remarkable is that the exhaust is unchanged for this year, despite the engine producing a lot more power.

The Yamaha M1 uses another Akrapovic-made pipe (Akrapovic suppliers four of the six MotoGP factories). This particular pipe is so clean it is unused. You can see the weld on the interior part of the pipe, through the honeycomb mesh.

Both Aprilia pipes, newly fitted again, as you can see by how clean the inside of the lower pipe is. Like the Ducati and Honda, the exhaust pipes consist of two 2-into-1 pipes, one for each bank of cylinders of the V4. But upper and lower pipes are slash-cut to give them a larger surface area.
Aprilia switched from Akrapovic to SC Project this year, and the exhausts have undergone a slight redesign

Here's the upper exhaust, from the rear cylinder bank. Torque back pressure valve is on top, which opens and closes to produce more back pressure at low revs.
This exhaust is slash-cut now, unlike the early part of last year. This gives the exhaust a larger exit surface without increasing the diameter of the pipe.

The lower pipe. It is a slightly different shape, a little stubbier than last year's example. It may also be slightly larger, if the scratches on the surface are anything to go by. It is clearly touching down in corners.
The soot on the beehive mesh is another sign this pipe has been used in anger.

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Not sure I buy the "slash cut increases exit area" argument. To take advantage of that, the exhaust would have to turn a corner (to approach the grill at 90 degrees), hardly efficient. It would not surprise me to find that vectors are involved, and the dominant direction of the exhaust and its incident angle against the mesh determines effective "area". Additionally, if there is a performance effect, I wonder if it wouldn't be based more on the "impedence" of the end of the pipe. By this I mean, a sharp exit that is 90 degrees to flow would have a sharp, strong reflected pulse due to strong impedence mis-match (this could easily be undesirable). A slash cut has a "sloppy" reflection with the reflected pulse smeared out and weakened. 

Does the slash cut increase the exit area of the pipe to compensate for the area lost to the grille.

By expanding from a ~60mm round pipe to a slash that is oval ~60x~90mm (or whatever) you are creating a low pressure area where the exhaust exits the pipe which in turn "pulls" the higher pressure gases behind it for a decrease in back pressure??? At any rate it would be certain not to create back pressure at the outlet. Mainly though, it just looks cool 

That last pic showing scratches on the exhaust from the bike touching down in corners. That pipe. That high. Tucked in so tightly. Touching in corners. Wow.

Agreed. The scratches are perpendicular to the direction of travel. Also, there are small scratches on the screen portion that could  never come in contact with the pavement unless through “ incidental “ contact.

Having replaced many many exhaust over my middling club racing “ career “ due to running out of grip because of ambition usually outweighing my talent made this an easy diagnosis. Good eye, though !

We're you like us, part of exhaust choice was "it crashes really well?"

Ran M4 or Leo Vince. The M4 could really go through hell. Like 20 wrecks.

I love the slash pipe looks! (Titanium?) welds on these are all really sexy. 

That Aprilia - does the rider get a hot foot? I’m guessing not.

I saw pics of Ducati's long pipe during early testing but nobody seemed to know if it was possibly a distraction or something real.  It was on Bastianini's bike so it must be for real???  Any thoughts?

It is real. And the speculation that it was a distraction could be seen as a distraction?

Meta! Second derivative! Paradox.


I got lost in Sector 3.  I thought I was still in Sector 1.  What were you saying to me?  -JM


Given what Pecco has said about the 22 engine being abrupt or too harsh I think the long pipe was an attempt to calm the engine, bring the torque peak down, maybe at the expense of a bit of top end, which they can afford. I also think it didn't work. "Let Jorge and Johan figure it out", Gigi says, "Pecco you go back to 21 binky. Jack, are you still here?"

I'm gonna be a divider once again and say I LOVE the Gresini colors. Damn that looks good to me. Race bikes SHOULD be bold unconventional colors IMO. Kawasaki racing green with Muzzy, Lawson, Rainey et al, Yellow with speed blocks, Blue and White for Cooley. We gotta get back to bright colors. The times are too gray for black bikes, let's have some sunny, optimistic colors for a few years. Woohoo!

When i first saw the colours i thought eww, that's hideous but they looked great during the race.

I feel like crying every time I think of how much we are missing by losing him so young. That bike is my favorite of all-time. When I win the lottery...

Even if you win the lottery, as far as I know they're all in museums now and not available. And there were only, what, five or six of them built? Despite my addiction to bikes and racing, that's the only bike photo on the wall in my study (rather grandiose name for a re-purposed bedroom).

This Britten device has consumed a portion of my brain since seeing it on the CYCLE WORLD cover in 1992. Pure passion and ridiculous engineering. If only there was a way for GP racing to go back to it's roots and wasn't such a business while still allowing David to report on it while earning a decent living. Heaven on Earth! I recently shed some tears of joy and nostalgia while watching a video of Michael Dunlop doing a commemorative lap of the Isle of Man TT circuit on a Gilera 500/4.