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2000 R1100RT uneven acceleration


jefcrouch

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I just purchased my first BMW about 1,000 miles ago (2000 R1100RT) and LOVE the bike. One fault that it has though is that when accelerating moderately hard (anything above about a 6 on a 1 – 10 scale), the acceleration is not smooth on the power curve. When I first get on it, it will accelerate normally for a second or 2, then it seems to bog down a little or hesitate for another second or two before moving on up the power curve just fine beyond that. Seems to occur mostly between around 4200-4800 rpm. I took it to my local BMW dealer for a checkup on this issue. After balancing the throttle bodies, the owner of the dealership personally rode the bike and informed me that there is nothing wrong other than what he described as being “the nature of the beast” and that this is universal with the R1100RT. He said that about all he could potentially do about it is to move the “hesitation” up or down the power band somewhat but that it can’t be eliminated. He further indicated that BMW ultimately solved this universal problem by introducing the dual spark plug feature on later model bikes.

 

So, my question is, am I being fed a line of bull (by the way, I purchased the bike from the same dealer) or is this indeed a universal shortcoming of the bike? I’ve heard of surging problems while attempting to maintain a constant speed, but I haven’t heard of this problem. Input would be appreciated.

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ShovelStrokeEd

No, it is not surging, which occures at steady state, light throttle openings.

 

Nor is it normal, if anything can be considered normal. 4000 RPM is kinda low in the RPM band to be applying a bunch of throttle, particularly in the higher gears. Under those conditions, I prefer a downshift. A good help for the situation is adjustment of the throttle position sensor. Factory settings tend to have this at around 0.320 VDC at idle and a good number of us have experienced a considerable improvement in throttle response by setting this voltage to ca 0.380 Volts. It is simple enough and a search on +TPS +voltage will reveal all as to how it is done.

 

The reasoning is as follows, in that the Motoronic uses throttle position as one of the two primary inputs in determining where on the fuel map it should be. The other is RPM. By upping the TPS baseline voltage you will change the location on the map for a given throttle position (usually richer) and that may well cure your problem.

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There is a definite flat spot in the power curve in the oilheads at around 4,000 rpm. It is noticeable but not particularly dramatic or troublesome. If the hesitation of this kind of nature (i.e. a little less power in the 4k range than others) then it may be typical of an oilhead engine, but if it is problematic or really bogging down then that is definitely not normal.

 

The dealer may be confusing your complaint with part-throttle surge which is a common issue with oilheads, and one which dual plugs will provide some assistance. But your description doesn't sound like surging and I don't think that lack of dual plugs or any typical oilhead performance issues account for it. Maybe get a second opinion from another dealer?

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The answer to your quest is GS intake tubes. Do a search, there's lots written on them. If I can make a file attachment work (this forum seems awful fussy about attachments) you'll see a graph of torque and HP differences with stock tubes and GS tubes.

667739-RS-GS_intake_chart.jpg.aba4742f73d1dd9da7a615e76bb01739.jpg

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The answer to your quest is GS intake tubes. Do a search, there's lots written on them. If I can make a file attachment work (this forum seems awful fussy about attachments) you'll see a graph of torque and HP differences with stock tubes and GS tubes.

Interesting! The attachment certainly describes the problem albeit for an RS. I've not noticed it on my 00 RT but then I stopped noticing anything on the RT way back when I discovered surging and PTTR. I just assume everything to be normal or as the dealer put it "the nature of the beast".

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russell_bynum

The attachment certainly describes the problem albeit for an RS.

 

RS and RT are identical in this case (same motor/cam/air-fuel map/etc). The GS tube mod works the same on both bikes.

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The answer to your quest is GS intake tubes. Do a search, there's lots written on them. If I can make a file attachment work (this forum seems awful fussy about attachments) you'll see a graph of torque and HP differences with stock tubes and GS tubes.

 

Got to agree. thumbsup.gif Put GS tubes on my 1100RT and the improvement in smooth acceleration was very noticeable. clap.gifclap.gif Just add a Remus to encourage frequent use of the improved performance grin.gifgrin.gif

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[quoteGot to agree. thumbsup.gif Put GS tubes on my 1100RT and the improvement in smooth acceleration was very noticeable...

 

Ditto here. GS tubes helped my RT. Also, adding Techlusion R259 makes a dramatic difference in engine smoothness and drivability around town, with zero surging.

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The "GS Tubes" issue is new to me. Would that be the intake manifold? or throttle housing? or other part definition?

 

thx

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