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Graves to stock exhaust....mpg question

M

MGN54

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Feb 13, 2013
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Purchased a very clean 08 with the retro body kit that I'm really enjoying. When I originally test rode the bike, it had a Graves carbon exhaust on it. Has a PC3 that was dyno tuned at dealer. Between when I test rode it and bought it, I asked the owner to put the oem exhaust back on for another test ride as I wasn't head over heals with the sound of the Graves. What I found, or at least what I thought I found, was more torque down low. I bought the bike with the oem exhaust on it. Was wondering what going back to oem would do to mpg since I didn't remap the pc3? would it be about the same? Getting about 36 mpg with the oem with mixed riding. Thinking that I might reinstall the Graves and see how I like it now that I have gotten used to the oem. And I want to see how mpg does on it since the pc3 was tuned to it.

Didn't mean to ramble! TIA

Mark
 
The extra power down low is because of the exup valve in the stock exhaust, regulates back pressure to get more down low. With a slip on you will get more up top because your increasing air flow which it needs up top. If it's running the map for the slip on you might be running a little rich, you can see my signature to see what all i have on my bike. On a pretty easy day, alot of 55 and 60 mph roads i've gotten a little over 40mpg out of mine. Usually when i ride more aggressive it goes from 35 to 40mpg.
 
delbert said:
F

I thought we had all agreed in previous posts that the exup valve on the gen 2 was for noise control only
Click to expand...

That's true...

I'm pretty sure the OP is experinecing more low end torque due to the more restrictive OEM muffler, which hurts the top-end. Exhaust design usually involves this sort of tradeoff.
 
Yep, exup valve is in open position and was disconnected when the Graves was put on. So I'm kinda liking jared p's idea of putting the Graves back on and adding the one tooth down sprocket for the lower giddy up. I may reinstall the Graves and see about the the sound. If I feel I can live with it, then I'll go the sprocket next.
 
I have experimented with the stock muffler versus a straight through slip-on, and found that the gas mileage did not change at all.

Performance wise, the slip-on helped considerably on the top end, a little bit at midrange, and I thought it remained about the same on the low end.

My EXUP remains wide open at all times, as far as I've been able to tell.
 
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