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 Altitude mixture adjustment

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johnlt




PostSubject: Altitude mixture adjustment   Sun May 05, 2013 9:07 am

The WR250R is a fuel injected bike but does NOT have an O2 sensor. Does it change mixture with changes in altitude and if so, how does that work.
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bigg

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PostSubject: Re: Altitude mixture adjustment   Sun May 05, 2013 9:23 am

The US bikes do NOT have the O2 sensor. The European model does. Last time I was at the stelvio pass at 2757 m (9045 feet), I did feel some loss of power even with the O2 sensor. however, this was really only noticeable in 4th gear or higher (which are useless on that road anyway). 1,2,3 felt good even with luggage, but it felt like it had a little less oomph at the lover RPM, but would pull strongly as usual (almost), in the upper half.

not sure how the O2 sensor is programmed for primarily, and if it has an upper limit of control over the fuel mixture. up to 2000 m I noticed no change in power, only once over 2500 I could feel the bottom half of the rev range was lacking a bit of go, so maybe the programmer can't fully adjust to such high altitudes perfectly.

why the US model doesn't have one I'm not too sure. and by logic, without an O2 sensor, the bike can't adjust to ambient/elevation conditions. so the fuel mixture would stay the same no matter of your elevation.
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xy500




PostSubject: Re: Altitude mixture adjustment   Sun May 05, 2013 9:55 am

Doesn't it have a MAP sensor?
if so that will compensate for variations in pressure.
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bigg

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PostSubject: Re: Altitude mixture adjustment   Sun May 05, 2013 10:28 am

You are right. It does look like it has a MAP sensor. so it does make changes to the A/F mixture according to altitude.

however, if I got it right, it works on a principle of a non-feedback controller. so the MAP just tells the ECU what the outside pressure is, and the ECU will calculate how much fuel SHOULD be needed for these conditions.

the O2 equipped bikes have the extra benefit of a proper controller, which will check the results of the MAP and ECU calculation, measure the difference to what it should ACTUALLY be and tells the ECU to adjust given the error it measures in the exhaust.

that about right?
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motokid
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PostSubject: Re: Altitude mixture adjustment   Sun May 05, 2013 10:45 am

If the o2 sensor could really do what it's supposed to do there'd be no need for an aftermarket efi controller.

I'm guessing the o2 sensor can make very minor adjustments, but expecting it to make a bike smooth from sea level to 10,000 feet is probably asking for too much.


The o2 sensor is probably much more a concession for emissions requirements than performance.

As in, it looks good on paper and satisfies some requirement from a pollution perspective.

Even with an o2 sensor, don't most people feel it's necessary to get an efi programmer for the same basic mods people do here in the states?


_________________
2008 WR250X
Gearing: 13t - 48t
Power Commander 5 / PC-V
Airbox Door Removed - Flapper glued - AIS removed
FmF Q4
Bridgestone Battlax BT-003rs
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f1isbest

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PostSubject: Re: Altitude mixture adjustment   Mon May 06, 2013 9:15 am


Mine runs great in very rugged terrain at over 13,000ft MSL in Colorado.






http://i78.servimg.com/u/f78/17/70/24/42/img_0412.jpg


Bob
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Old Rider

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PostSubject: Re: Altitude mixture adjustment   Wed May 08, 2013 2:28 pm

Wow, I have that same picture. Except mine was taken about 15-20 years ago and I was on a KTM400. cheers
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Old Rider

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PostSubject: Re: Altitude mixture adjustment   Wed May 08, 2013 2:30 pm

johnlt wrote:
The WR250R is a fuel injected bike but does NOT have an O2 sensor. Does it change mixture with changes in altitude and if so, how does that work.

Why don't you ask this over at BMWST? Some really smart guys over there. thumb
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xy500




PostSubject: Re: Altitude mixture adjustment   Wed May 08, 2013 7:52 pm

motokid wrote:
If the o2 sensor could really do what it's supposed to do there'd be no need for an aftermarket efi controller.
It does do what its supposed to to, no o2 sensor tunes a whole vehicles map.
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motokid
Moderator
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PostSubject: Re: Altitude mixture adjustment   Wed May 08, 2013 7:58 pm


xy500 wrote:

It does do what its supposed to to, no o2 sensor tunes a whole vehicles map.

So I'm guessing you missed everything I posted after the first sentence? Rolling Eyes




motokid wrote:
If the o2 sensor could really do what it's supposed to do there'd be no need for an aftermarket efi controller.

I'm guessing the o2 sensor can make very minor adjustments, but expecting it to make a bike smooth from sea level to 10,000 feet is probably asking for too much.


The o2 sensor is probably much more a concession for emissions requirements than performance.

As in, it looks good on paper and satisfies some requirement from a pollution perspective.

Even with an o2 sensor, don't most people feel it's necessary to get an efi programmer for the same basic mods people do here in the states?


_________________
2008 WR250X
Gearing: 13t - 48t
Power Commander 5 / PC-V
Airbox Door Removed - Flapper glued - AIS removed
FmF Q4
Bridgestone Battlax BT-003rs
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