Re: Old air filters for R1100S needed

[Brian Curry <bmwbrian@xxxxxxxxxxxx>]

Catchingup, ditto on oilheads@xxxxxxxxxx

At 03:03 PM 3/3/2005 -0500, Don Eilenberger wrote:
>>>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? 
>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.

Acceleration and knowing the mass rotational inertia gives you the torque.

>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.

Yup.

>>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.

Yes, and an inertial dyno will not tell you much about surging, as it is a
steady state issue, and an inertial dyno is never in a steady state condition.

>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.

Yes.

>>>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.

And they really don't clean "well".  Maybe good, but not well.  As for
"hands-on feedback on your machine and keeps you in control," I have no
idea of what he is speaking of.  I don't see how a K&N with its initial
costs, and cleaning and oiling costs in time and money can be cheaper than
not changing the paper filter.

>>>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.

Since I was the one that thought of, and did this, Don is exactly correct.
We were looking for ANY change, not a 50% change.  Any change would
indicate that the air filter size was marginal to some extent.

It sure is not and it has a LOT of magin available.

>>>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
>restriction.

Somewhat lost here, but I think this is when we occluded the snorkel.  That
demonstrated that closing off a small port in the inlet air flow path DID
have an effect.  IOW, we can see the effect of choked off air flow.  And we
saw none w/ half the stock AF covered, so there is and was none.  IT is NOT
a restriction.

>>>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).

Sorry, but you are wrong.  And ignorant of the work that car manufacturers
have used for years to compensate for other engine design trade offs.

When the engine is operating at the acoustically tuned range, the cylinder
packing occurs whether the carb is wide open or throttled.  The degree of
packing, or packing effect, varies with throttle position.

 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.

Yes, and a LOT of time changing parameters and seeing the effects.  And
that it is repeatable and not a testing methodology fluke.

>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.

With a LOT more miles on my bike!

 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.

Yup.

>>>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 :-)

Yup, always up for DATA gathering.

>And I'll CC this to Brian Curry for comment since he is usually my partner
>in crime doing dyno runs..

Yup, better to have someone beat you on a dumb idea then than after the
runs are done.

- -- -----------------------------------------------------------------------
"DEERS SLAYER"       |   It is a capital mistake to theorize before one has
Brian Curry          |   data. Inevitably one begins to twist the facts to
K75RTs both coasts   |   suit the theories.
Chester Springs, PA  |   --Arthur Conan Doyle
OBIWAN #23 10% #3    |

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End of oilheads-digest V2 #55
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