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Old 06-12-2010, 05:49 PM   #1 (permalink)
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Cams and mpg

Is there one part of the cam spec that decreases your fuel mileage in particular or is it a combination of factors assuming the no other mods are made and no changes to riding style? The reason I ask is my Andrews 27 bike with 495 lift gets 50 mpg, my Andrews 37 bike with 510 lift gets 47 mpg but my SE255 bike with 550 lift gets 20 something mpg. Common sense would tell me the higher the lift, the lower the mpg. Am I right or wrong? Would switching to a Woods Tw6 with a "mild" 510 lift increase my mpg (forget about where the torque curve comes in for now) Thanks for your help!!!
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Old 06-12-2010, 06:11 PM   #2 (permalink)
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has nothing to do with lift. more likely duration and timing events and also the tune. vacuum signals are all altered by the timing events.

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Old 06-12-2010, 06:34 PM   #3 (permalink)
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IMO, a great abundance of overlap is not a good thing for MPG. Mostly, it's in the tune.
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Old 06-13-2010, 07:02 AM   #4 (permalink)
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First off I am assuming that the cams were all in different bikes so the comparison of these cams and fuel mileage is somewhat of an apples to oranges thing because each bike is different. Secondly, I would strongly suggest that, if you are only getting 20 something miles per gallon with the 255 cams which are fairly mild cams, you have major tuning issues. The lousy tune is much more responsible for the poor fuel mileage than this cam or that cam.
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Old 06-13-2010, 09:49 AM   #5 (permalink)
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100%

MPG in the 20s is a piss poor tune. I get mid to upper 40s with S&S .640 cams in a 124".
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Old 06-13-2010, 11:47 AM   #6 (permalink)
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big john, tell us how you added fuel to the 255 bike. there lies the answer.
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Old 06-13-2010, 11:53 AM   #7 (permalink)
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My 95 incher is way over breathed. It does 40+ mpg consistently, in town riding, better on the high way. 2" intake, 1.623" exhaust, TW67G, 1.67 rollers. Big lift, closes late, a lot of over lap. I tuned it with an O2 sensor on a 3/8" copper tubing manifold shoved up the front pipe, watching the signal on a Fluke meter, strapped over the speedo while riding it. The tune is critical.
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Old 06-13-2010, 04:05 PM   #8 (permalink)
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Ok...............all consistent answers, not the cam specs but the tune itself, shows how much I know, I guess that's what this forum is for! Thank you everyone for resonding!

Yes guydoc77, they were different bikes, I just thought that was strange so i through that out there.

claydball: I always reset the trip A at fuel ups and try to run as close to empty as possible so as to get a true average.

damn colonel sanders......................I am way jealous!!!! must be a hell off a ride when you twist that throttle!
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Old 06-13-2010, 04:49 PM   #9 (permalink)
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claydbal is reading this now saying WTF is this?
well john, that too. lol. but i was asking about what type device you installed to tune your motor.
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Old 06-13-2010, 04:58 PM   #10 (permalink)
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Thanks, Big John. There are plenty of bikes here that could walk off and leave me though. Mine is a relatively mild build but I fully intended it to be to better serve my purpose for it.

For me, the beauty of this build is how docile (no, not powerwise!) it is. It does everything it should and nothing it shouldn't. No bad manners. No bogs, no hiccups, nothing jerky. Everything is smoooooooth. Starts easy, doesn't run hot even in 100+ degree weather. I almost never notice any heat coming off of this engine. It never pings regardless of the throttle position, RPM, or hot weather. And it gets fantastic gas mileage to boot.
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Old 06-13-2010, 05:22 PM   #11 (permalink)
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Oh duh, I got suckered into the Screaming Eagle Race Tuner.
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Old 06-13-2010, 05:30 PM   #12 (permalink)
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claydbal is reading this now saying WTF is this?
see, theres your answer! just find someone that can tune and problem solved!
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Old 06-13-2010, 07:05 PM   #13 (permalink)
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Quote:
Originally Posted by claydbal View Post
see, theres your answer! just find someone that can tune and problem solved!

boy, ain't that the truth! tune with what tuner??? i thought this sert was supposed to be the cream of the crop! or are you just saying the person specifically?
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Old 06-13-2010, 11:27 PM   #14 (permalink)
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claydbal is reading this now saying WTF is this?
the sert is ok, just find someone with a good rep who can tune. be prepared to travel.

good luck.
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Old 06-14-2010, 12:10 AM   #15 (permalink)
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Quote:
Originally Posted by claydbal View Post
the sert is ok, just find someone with a good rep who can tune. be prepared to travel.

good luck.

ah, that was going to be my next question, WHERE??? hehehehe
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