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Fw: Old air filters for R1100S needed

Forwarded to Oilhead list from Don Eilenberger by way of Bill Kenney:

- ----- Original Message ----- 
From: "Don Eilenberger" <deilenberger@xxxxxxxxxxx>
To: "william kenney" <tnt720@xxxxxxxxxxxxxxxx>; <oilheads@xxxxxxxxx>
Cc: "Brian Curry" <bmwbrian@xxxxxxxxxxxx>
Sent: Thursday, March 03, 2005 3:03 PM
Subject: Re: Old air filters for R1100S needed


> Bill - since I expect this to bounce, not being a member of
> oilheads@xxxxxxxxx - feel free to forward it to them..
> Just some brief comments:
> At 11:03 AM 3/3/2005, william kenney wrote:
>>Reply from Ben:
>>>Many thanks, Wendell, first I've seen Don Eilenberger's curves. Many more
>>>curves and quite a lot of discussion can be found at Moto One

 Don's reply : ....... Quite a nice set of curves and some interesting data.

>>>Reading dyno curves takes some care. The eye is easily fooled and 
>>>dramatic vertical increases (in HP or torque) are not eye-balled right or
>>>not recognized in proportion. In other words, large practical changes at 
>>>and lower rpm (which matters most to most of us) are overlooked.
>>>Because the time course of the runs is not known and couldn't be much
>>>controlled in any case (I have some experience with /7 dyno testing),

  OK - question here...  all of my runs, and as far as I can tell all
> of moto-one runs were done as a '3rd gear rollon' - which is pretty
> much standard for an inertial dyno (which the Dynojet that I use and
> the one that they use is).  Time has nothing to do with the curves..
> they are a plot of RPM vs HP at any given instant in time as the
> engine accelerates.
> Does it take time to do the curves?  Sure. Is it used in the calculations? 
> Sure.
> Does it factor into an inertial dyno curve - nope.
> Think on it. The inertial dyno plots acceleration vs time of a large 
> rotating mass,
> and it measures (and uses as the X axis) the instantaneous RPM.
> Stopping time, or slowing it down isn't an option on this sort of dyno..
> if you stop at some RPM in the hopes that power will build up - you've
> stopped accelerating the drum, so that factor goes to 0 and you can't
> calculate the power.

Ben :

>>>not clear how the curves really relate to ECU performance apropos the O2
>>>sensor or, for that matter, how surging arises as the bike settles into
>>>steady-state when on the road or how the two really relate to one 
> Very true.. we weren't after those sort of facts - we just wanted to
> measure the stock intake filter vs options such as no filter and a
> partially blocked filter.
> Doing these sort of curves would require a "brake dyno" - one that uses
> mechanical force to resist the turning of the drum. This allows you to
> hold the RPM at a certain point and see if the engine will continue
> making the same power. Unfortunately - due to the design of this sort
> of dyno (big, heavy, requiring some way to dissipate the energy used
> to resist turning the drum) - it is fairly uncommon.
>>>Although I thought it would be uncivil earlier to offer my baleful 
>>>on K&N filters, I would now like to comment with the following well-known
>>>1. you can't make a change to any single thing in your stock aspiration 
>>>ordinarily expect an improvement,
> Agreed - and the point of these plots.
>>>2. paper filters are a pretty good compromise practical solution from the
>>>point of view of manufacturers and
> Also agreed. We have not seen evidence that changing ONLY a filter will
> result in more power on any BMW engine we've tested.
>>>3. all things considered from the point of view of do-it-yourselfers, 
>>>foam such as Uni (not K&N  which is oiled gauze) breathes well, cleans 
>>>provides hands-on feedback on your machine and keeps you in control, and 
>>>far cheaper.
> Oiled foam is a much better filter than the K&N IMHO, but bang for the 
> buck,
> it's hard to beat the stock paper one.
>>>In the test you mention, Eilenberger blocked 50% of the air intake (which 
>>>a pretty meaningless thing to say) and expected 50% reduction in power.
>>>That's plain nuts. I feel you are wrong to take his point seriously.
>>I think you will find that Don was trying to see if 50% reduction would 
>>have ANY not 50% reduction in power. Showing  the stock filter still had 
>>sufficient surface area to adaquetly filter air without degrading 
> Bill is correct here. I didn't expect (and I've been accused of being
> nuts, but not on dyno runs) an exact correlation to blocked filter area
> vs power, but it provided some data for how much performance IS lost if
> the filter is partially blocked.
>>>What he did find, but did not interpret, was a large reduction in power 
>>>also, oddly, a fairly clear reduction at lower rpms...which you'd never
>>>expect. That certainly suggests that the front-end breathing is impaired 
>>>at best, marginal) in the stock form but the degree of impairment and the
>>>benefits are hard to guess.
> Actually - what I saw was about what I expected. Some decrease in power
> and a decrease that gets more significant as the volume of air going
> through the engine increases (increasing RPM).  It was roughly a 10%
> loss at peak, and somewhat less at lower RPMs. The increase in percentage
> loss also was fairly linear, which I'd also expect with a fixed intake
> restriction.

>>>Moto One are quite enthusiastic about improving the intake path with
>>>megabuck bits of plastic but others definitely are not. For sure, the 
>>>is often part of the tuning (although I personally view intake or exhaust
>>>"tuning" to be unsound outside of racing). So changing the front-end
>>>breathing is likely to make some changes somewhere, given the typical 
>>>logic of modern bikes. Sometimes even introducing restrictions can be
>>>beneficial to some part of the curve.
> I think you understand that making one change to one factor on the bike
> is likely to have very little to no effect on the performance, and 
> sometimes
> a deleterious effect on overall performance.
> I think BMW has quite a bit of experience in extracting as much usable 
> power
> from their engines given the required operating parameters (emissions, 
> surge,
> longevity, practical to manufacture.)  Could this be improved on? 
> Probably,
> but usually it involves a compromise with one of the above parameters.
> My personal K75S had ALL the go-fast stuff done to it by the former owner,
> shaved head, ported and polished, oversized valves, K&N..  and it made
> EXACTLY the same HP as Brian Currys bone stock K75RT. It might make more
> now since the mixture at that time was sub-optimal (lean from lack of
> use) and now is better. Gotta get it back on the dyno sometime soon.
> Point being - the go-faster claims don't always work. BMW did their
> homework.
>>>Having said all that, would somebody PLEASE let me know if the ECU 
>>>for changes in filter resistance (other than the obvious if just 
>>>presence of the O2 feedback)?

> If you're anywhere near NJ, we could always dyno it :-)
 And I'll CC this to Brian Curry for comment since he is usually my partner
> in crime doing dyno runs..
> Don Eilenberger, AKA SquidBOOF, Spring Lk Hts, NJ
> JMP#1 FOT2.A deilenberger@xxxxxxxxxxx
> NJ Shore BMW Riders web page: http://www.njsbmwr.org/
> Moderator - BMW E39 Enthusiasts: http://groups.yahoo.com/group/bmwe39
> "One should do the stuff that makes you smile" - Ulf Bertilsson


End of oilheads-digest V2 #51