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> >I would love to provide a Ve plot vs rpm. However, I think we would have
to
> >put the system on a dyno to get the data. One way of looking at the
EDDIE
> >is that it does, in effect, increase Ve (Volumertic efficiency). My
> >calculations indicates max increase is around 115%. And for that
> >particular figure it was for around 5700 rpm. I would expect approx the
> >same through at least 6500 rpm. Some things start to happen above that
rpm
> >that makes me leery of hazarding any further extrapolation.
> >
> >At least that is my take on it. Could be wrong, have been before and
will
> >be again.
> >
> >Be seeing you in about 1 1/2 weeks, Charlie (provide the Wx holds good)
> >
> >Ed Anderson
> >
> Hi Ed,
>
> I was trying to ask about the Q, or 'peakiness' of the tuning technique.
> My point about the 5k to 6k rpm is that with the 2.17 gearbox, rpms
> outside that range aren't of any real interest in a fixed pitch a/c
> engine application. Even with a fairly high 'Q', if you tune for your
> expected cruise rpm (somewhere between 5k & 6k?) how much will you give
> up if you don't have in-flight adjustable tube length? My assumption is
> that with a fixed pitch prop on a fast clean plane like the RV-class
> planes, you will turn at least 5k when you begin the takeoff roll & not
> exceed 6k or you will run into problems with the prop tips approaching
> the sound barrier. Is the peak so sharp that it will require varying the
> tube length over a 1k rpm band?
>
> I realize that the Lemans racer was using the variable helmholtz tuning
> method, but the variable length intake pipes were intended to move the
> torque peak over a several thousand rpm range to allow accelerating out
> of 20 mph curves & still pull well at 240 mph. My confusion is why
> tuning over a several thousand rpm range is needed in an a/c (Unless of
> course the Eddie effect is EXTREMELY high Q requiring tuning over a 1k
> range).
>
> Or have I completely missed the point & the goal is actually to tune for
> air temperature?
>
> (now even my fingers hurt.)
>
> Charlie
>
>
Hi Charlie,
First, I need to check my typing a bit better. I mentioned above that
the EDDIE increased the Ve 115%, what I should have said is that the EDDIE
increased Ve to around 115% - big difference.
Ok, I understand your question, now. Thanks for giving me another try.
Well, it is I suppose a bit "Peaky" in those ranges. The effect is mostly
on the lower RPM side of the targeted EDDIE rpm. Right, now it appears that
the effect would be noticable certainly within 150 rpm of target rpm as
possible as much as 300 rpm below the target rpm (But, probably not more
than 50 RPM above the targeted RPM). I think the effect fades fairly quickly
after that. I will sit down and work on that to see if I can come up with a
better answer. But part of the problem is deciding where the effect cut-off
is. Its actually extends considerably wider than that - but, the power
increase has decreased so much beyond the 300 rpm spread, you probably
wouldn't notice it.
Now having said that. There is the thing called the dynamic chamber. Its
purpose is to broaden (spread) the increased torque over a wider rpm band. I
have a 25 page briefing on how that works, but since, I am intend to "chase"
the EDDIE rpm with my variable maniflod (hopefully), I want all the energy
at the one rpm I am operating at the time. Again, the pulse only provides so
much increase in power and the wider you spread it the less the effect is at
any one rpm - IF you don't have some way to change the target RPM. The
question is the effort worth the price to be able to change the target rpm?
You could set the target for say 5600-5800 rpm. On a cold day you would
probably see the power increase if your static can get as high as 5200 rpm.
On a warm day, you probably wouldn't see much until airborne. However, with
the 2.17:1, I cruise around 5300-5500 rpm. I can bump it up to 6100 to
check my top speed, but just burn too much fuel for me to leave it there for
long. So I might target the EDDIE for 5700 rpm knowing that the effect
falls below that rpm. Possibly get some assist on take off, most likely
would in climbout after the prop unloads a bit and you pick up some rpm, and
definedly would at cruise.
What I think it boils down to is that if you are going to fabricate your own
manifold, this will become simply another tool and factor to consider along
with all the rest. It won't make a silk purse out of a sow's ear, if your
basic induction system suffers, the EDDIE won't save it.
Employing this effect has trade offs just like the rest of the process.
Some folks will say, Hey, if I want real power I'll go with a turbo, super,
or nitrous oxide. Others, will attempt to twike ever bit of power out NA
wise, this will probably be of more interest to the latter group.
Hope I came closer that time, Charlie
Ed
.
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