Logic of the Tenere Exhaust System and Possible Improvements? - .: XT660.com

josephau · # 1 13-08-08, 22:58

I posted this issue in another forum but have so far received very little feedback, so please don't mind me if you have already read this:

Please forgive my technical illiteracy. On the new 2008 Yamaha Tenere, can someone please explain to me why there are two pipes coming from the engine case? From what I can see, it seems to be a 2-in-1 system given the stock exhaust which is a giant flat box. So if I change that exhaust into a Akrapovic or GPR that looks like it splits from the single pipe into two separate pipes that lead to two separate exhausts:
1) would that become a 2-1-2 system then, 2 from the head into one pipe then splits into two again?
2) would this setup give a better airflow and hence slightly more power than the stock setup?
3) someone on this forum said about just keeping one pipe to one exhaust, would this one-pipe-one-exhaust setup be better than 2-1-2?

JMo · # 2 11-09-08, 00:19

Hi Josephau - I think I replied on that other forum too - the twin header pipes are mainly due to the position of the valves, and to allow them to clear the (single) frame down tube... as you say, they then combine into a single pipe that goes into a honking great box at the back...

Personally I can't see why a single silencer wouldn't offer the same if not better performance... the main reason for a twin silencer system (such as that on the CRF250 for example) is to give more sound absorption material for the same amount of exhaust flow...

If you are overly worried about noise (and hey, we all should be) then a more open single pipe should improve flow considerably over the (cat choked) stock system.

Hope that helps?

JennyMo xxx

Kev · # 3 11-09-08, 10:59

You need 2 headers because the XT motor has 2 exhaust valves.

2-1-2 will produce more HP up top, then a 2-1.

2-1 will produce better low end torque with less HP up top, then a 2-1-2.

A single Can produces more DB's then a twin Can exhaust system & requires more baffling to keep it quiet.

josephau · # 4 16-10-08, 19:33

Quote:

Originally Posted by Kev

You need 2 headers because the XT motor has 2 exhaust valves.

2-1-2 will produce more HP up top, then a 2-1.

2-1 will produce better low end torque with less HP up top, then a 2-1-2.

A single Can produces more DB's then a twin Can exhaust system & requires more baffling to keep it quiet.

Hi Kev, firstly, I never thanked you for the valuable tip. So many thanks. Curious, could you let me know if this single can can really produce the hp and torque as shown in the inserted graph of this link: http://www.off-the-road.de/index.php?id=808&L=1 (the first single can). Sorry it's in German, but basically it's a single can exhaust with 4kg weight saving and 3hp more. I am surprised to see the increased hp is through the whole rpm curve. Any of your observations would be appreciated.

Kev · # 5 17-10-08, 13:36

The dyno sheet reflects a good torque gain in the low to mid range. How ever the HP claims are not quite correct the gain at peak is 1.7HP & the mid range is around the 2hp mark not 3HP. http://www.mr2ownersclub.com/converter.htm

I also wonder if this bike had a PCIII fitted at the time of the dyno run, with this HP result on a XTX/R you would need a fueling device + both filters + cans.

This Can shows a good gain over all & is what I would expect from the type of system.

josephau · # 6 17-10-08, 15:52

Many thanks Kev. The manufacturer claims that it is achieving those results WITHOUT any power commander, air filter change or ignition cable change. That is exactly what I wonder if the dyno is true and if the 2-1 system can really achieve that consistent improvement across the rpm curve.

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