[Vwdiesel] ECO -- VW ----( Hagars ECO -- Bunny Bondo )

Val Christian val at swamps.roc.ny.us
Thu Apr 14 12:52:44 EDT 2005


I have a little, uh, reconstruction, of a detoriorated duct from the
inlet to the aircleaner box.  When that's done, I'll have dimensional
measurements, and if I get carried away, I can slap a transducer on 
the inlet and sweep it, to see if the measurement matches the 
dimensional predictions.

Inlet tuning is great for something like a generator, which is run at
a constant RPM.  If one wants a wide RPM range benefit, then it's 
necessary to tune the cavity for a lower Q, which means less 
"efficiency" but over a broader range.  

Now if we could tune the cavity with a variable displacement device,
and adjust timing of the cam and pump parametrically, and real-time,
then we could probably beat Hagar's Bunny.

On your 91 NA, which is what I've driven for years, how do you find 
the total power capability?  Mine is a Jetta, and all my previous diesels
were Rabbits.  They had plenty of excess power.  The Jetta, doesn't
live up to the first part of it's name.  At cruise, it's OK, except
when in mountainous territory, it's kinda like flying a glider.  That
is, it's an exercise in kinetic and potential energy management.
That's not a problem by my way of thinking, except that there are allot 
of thirsty horse SUVs which would like to run me over, just to get ahead.
The TDI doesn't have that problem, and with similar mileage.  So I 
suppose that's an improvement.  But the complexity is higher, and when 
the beast gets older, that's a headache.

Consider the relative complexity of adapting a TDI to a stationary 
genset, vs. a NA.  In the end, onceseveral problems get solved, the 
TDI might indeed be a better powerplant for that application.
For example, my guess is that the cruise computer, tweaked, would be
adequate for genset frequency regulation.  But getting there could be
a problem.

A turbo will cut the noise, and that's real attractive.

As for reliability, in the 80's I had personal experience with a handful 
of turbo'd aircraft engines.  Yes, the parameters are different.  For
example, they are regularily run at 100% power (takeoff), and then spend 
the bulk of their life at 65 to 75% power.  And due to liability concerns 
(read liability insurance) and certification costs, replacement parts are
killers.  Pre-sticker shocked on replacement turbos, I bought a car a 
couple of years earlier than I really needed to, just to avoid the ECO.
Additionally, while I don't recall anyone on this group bashing the ECO, 
I do remember some bad press back when it was introduced.

One final turbo observation...I notice that even the ground maintenance
diesel powerplants are getting turbos these days.  25 and 35 hp engines.
Small, and from what I am told by the friendly sales folks, the 
early reports are 4000 hours plus on turbos and engines.  I have a 
Ford 1510 25 hp class tractor, which is a 3 cyl NA, and reports from a 
nearby city are that one of the landscape outfits there had 8000+ hours
on three tractors with no major engine problems.  When I last talked
with them, the other parts of the tractors were starting to fail.
(I can identify with that, because I have a transmission differential 
lock problem which will need attention.  I baby the thing.)

Back to radiometrics, and paying for the next car...


> True, wave tuning is to a certain frequency, with diminished effects on either side. A turbo eliminates wave tuning completely. I believe what VW tried to do was get some torque higher up in RPM range by use of tuned runners. I currently am driving 91 N/A, and am sometimes amazed at the power available above 3k RPM. 
> I am very curious as to the results of your calculations when you get to it. Please keep us informed. 
> For whatever it is worth to you, I shun turbos for the same reasons as you, and am very happy getting 49MPG US at 70 - 75 MPH. IMO you called that one right on.
> Bob
> ******
> The problem is that the tuning is limited to a certain frequency, which
> means a certain RPM.  In the case of my 91 NA, I believe that the 
> tuned system is for about 50 MPH.  I haven't measured and done the calculations
> yet.  But after the rebuild, I will.  Because I want to quiet the system
> for operation at 70 to 75 MPH, which is more the norm on the highway
> at commute time.
> Putting a turbo inline can simplistically be considered the introduction
> of a DC injection point in a tuned circuit, which changes the impedance 
> of that circuit.
> Of course, its possible to put multiple resonances into a system. 
> "Yep, 78 miles to the gallon in this puppy at 48 MPH, and 73 at 63 MPH.
> At 55 MPH, it's down to 30 MPG."
> In 91, I bought one of the last NA diesels VW sold, because I didn't 
> want the added complexity of a turbo, and the attendant reduction in 
> reliability.  I called that one wrong.
> -Val
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