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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

Quite a nice set of curves and some interesting data.

>>Reading dyno curves takes some care. The eye is easily fooled and sometimes
>>dramatic vertical increases (in HP or torque) are not eye-balled right or
>>not recognized in proportion. In other words, large practical changes at low
>>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? 

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.

>Don has not some but A LOT of experience with Dyno testing
>>it is
>>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 another.

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 opinion
>>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 and
>>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, oiled
>>foam such as Uni (not K&N  which is oiled gauze) breathes well, cleans well,
>>provides hands-on feedback on your machine and keeps you in control, and is
>>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 is
>>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 performance.

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 and
>>also, oddly, a fairly clear reduction at lower rpms...which you'd never
>>expect. That certainly suggests that the front-end breathing is impaired (or
>>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

>I don't have enough knowledge of Dynos to see what he missed interpeting.
>>Moto One are quite enthusiastic about improving the intake path with
>>megabuck bits of plastic but others definitely are not. For sure, the intake
>>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 tuning
>>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

>>Having said all that, would somebody PLEASE let me know if the ECU corrects
>>for changes in filter resistance (other than the obvious if just occasional
>>presence of the O2 feedback)?

If you're anywhere near NJ, we could always dyno it :-)

>>Ben Barkow, Toronto... 39 seasons on Beemers, 44 as a biker,
>>1961 R69s/rod, 1967-1999... really sup'ed up and fast
>>1984 R80RT/rod, 1998- 5 extra peak ponies in a wider flatter power band,
>>  much modified 2-into-1 exhaust, CR 9.5, Keihin PJ 34mm oval carbs,
>>  Uni filter, dual-rate springs with cartridge emulators,
>>  BT45/S11, Saeng fairing
>>1999 R1100S, 2004- Leo Vince exh, JetHot coatings
>I will forward this to Don and see what he thinks.
>Bill Kenney
>formerly 96R1100RS

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