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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> altitude change performance question /cgi-bin/YaBB.pl?num=1400555736 Message started by rijopiatt on 05/19/14 at 20:15:35 |
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Title: altitude change performance question Post by rijopiatt on 05/19/14 at 20:15:35 I'm taking my first long trip on my 2012 S40 this summer. I live in Indiana and I'll be going to Wyoming with alternate routes to Colorado or New Mexico depending on weather conditions at the time. Will the change in altitude create a performance issue that I need to be prepared to compensate for? Rick in Indiana |
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Title: Re: altitude change performance question Post by Serowbot on 05/19/14 at 22:15:40 You tune your bike for where you ride... if this is a one time thing,.. just ride through it... Thinner air at higher elevations will cause a little loss in power, and some popping... Just enjoy the trip... ;)... |
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Title: Re: altitude change performance question Post by rijopiatt on 05/20/14 at 04:52:23 Explain the "popping" please. |
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Title: Re: altitude change performance question Post by Serowbot on 05/20/14 at 06:37:04 "Afterfires" on deceleration... Most carbed bikes will have rich pops on decel in the mountains... No harm.... you don't correct for it, or else you'd be lean when you come down... Just enjoy them, they're fun... Great echo's in the canyons... ;D.... |
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Title: Re: altitude change performance question Post by Bubba on 05/20/14 at 09:40:15 I make altitude gains/losses on a regular basis...from 5000 to over 10,000 in the Rockies... The most that has happened is that I get lots of decel pops on my way down from the passes...I could stop and adjust my air screw to compensate but I'm usually having too much fun to worry about doing that! ;D |
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Title: Re: altitude change performance question Post by Dave on 05/20/14 at 10:09:38 477067676434353D36050 wrote:
I almost hate to post this......but it is a thought. The pops and bangs on deceleration happen because with the throttle closed there is a high vacuum that is pulling a lot of air past the almost completely closed throttle.....while the only fuel being supplied is through the idle circuit that is adjusted for a normal vacuum. With so little fuel flowing there too much air and not enough fuel for the spark plug to ignite the mixture. The unburned fuel and air goes into the header and is ignited by the hot exhaust....or by the next flame that does come out of the cylinder. Our carb has a TEV (Throttle Enrichment Valve) that is supposed to supply additional fuel flow during these periods of high vacuum and low throttle opening.....not sure how effective it is. OK....the potential controversy. During those times when you are going down the steep grades, and the throttle remains closed for long periods of time, and you just keep going blat,blat,blat,blat,blat for long period of time.....wonder what would happen if you pulled the Enrichment Knob out a notch or two during the long descents to see if it would richen things up a bit and eliminate the noise. (This should not be done when the throttle is going to be applied....as the engine would be too rich). It could be that the TEV is already adding fuel and the use of the Enrichment Knob may not be able to add any additional fuel through the idle circuit. My hills in KY are short, and I don't have any problems with this issue. My only concern would be if too much fuel is added...and it starts gumming things up and washing down the cylinder wall with unburned fuel. Dave |
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Title: Re: altitude change performance question Post by Bubba on 05/20/14 at 10:17:59 I'll try that sometime but the roads over the passes (at least the ones I'm on) are pretty much twisty's up and down... I do occasionally just coast along (in gear) but mostly it's for a brief time and pulling/pushing the enrichment knob would get old pretty fast... |
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Title: Re: altitude change performance question Post by Serowbot on 05/20/14 at 10:21:14 I don't think it's a "too much air" issue... as,.. the popping decreases as elevation decreases... (angle of decent being the same from 9k down to 2.5k)... Thinner air... more popping... "rich pop"... .. but,... I'll be riding up the Lemmon in a few days... I'll give the enrichment valve a tug, and see... :-?... |
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Title: Re: altitude change performance question Post by thumperclone on 05/20/14 at 10:24:47 I live at 4500' ride over the grand mesa at 11000' quick snap throttle closings gets some pops also high rev engine braking its all in the wrist |
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Title: Re: altitude change performance question Post by Dave on 05/20/14 at 10:59:03 Well...I ride around between 500' and 800'. Any lower and I am in the Ohio River.....and higher and my wheels aren't on the ground. I suppose that some of that popping noise you guys hear is your ear drums! ;D |
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