Date: Mon, 4 Jun 2001 14:45:45 EDT
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: Update on Waterboxer vs Transplant Power Options
Content-Type: text/plain; charset="US-ASCII"
Mark,
I've been staying out of this exchange till now but have to offer a few
comments.
First, I have the published power curves for the WBX and Audi engines. These
curves are done by VW and represent more than a few dyno runs. I can send
references or scan the curves from the original papers if you are interested.
Second, after painful experience, I can assure you that the power figures and
the curve shapes obtained on chassis dyno runs are fleeting and take serious
work to reproduce. Estimated power gains are based on technical fiction
unless based in a real measurement. Anecdotal estimates (based on the
evidence given by a vested advocate) are generally as meaningless as
unwritten assurances by car sales personnel. Anecdotal measurements (single
results) have some limited value compared to anecdotal estimates.
Measurements of power at the wheels on the road can be made and are probably
are more accurate than chassis dyno measurements. This requires a straight
and level stretch of highway, an accurate stopwatch, a calibrated speedometer
and immediate knowledge of the mass of the vehicle (as in weigh it with a
full tank in the same test configuration just before the test). Many sites on
the Internet treat the subject in detail. Also, an inexpensive device called
the "Road Dyno" is available to seriously map the power curve. I am currently
testing this device. Unfortunately it requires a PC computer to support both
hardware and software and I am currently trying to get Virtual PC and the
Powerbook G3 to cooperate, but no success yet. This system measures the
acceleration of the vehicle on the millisecond timescale to measure the power
curve.
Third, I have copies of the summary design information for the waterboxer
(1.9 and 2.1 liter engines) detailing some of the engineering that went into
the original hardware. These articles are still in the original German. I
will eventually translate them, but other projects are more pressing. I could
pass on scanned copies as requested.
Fourth, (in response to your comment that triggered this note) as owner of an
inline 4 conversion ('90 8V, 1.8 L Digifant), I am happily buzzing along with
the original DZ transmission. With my 215/75 x 15 Yokohama Geolander AT+
tires, my tach shows 3740 rpm at 60 mph in 4th. It also shows 5860 rpm at 65
mph in 3rd. The engine is redlined at 6500 rpm and on several desperate
onramp merging maneuvers, I have run up to 70 mph (6300 rpm) before
downshifting. I have buzzed across the godforsaken southwest (LA to Corpus
Christi, TX and back) fully loaded with A/C pumping at a cruising speed of 75
mph (4680 rpm). This system has faithfully taken me from LA to Banff and
Jasper while often exceeding 85 on California's Interstate 5. Maximum top
speed (CA 14 at 1:18 - 1:35 AM - synchronized to the maximum CHP donut sales
spike) is just a bit between 95 and 100. The uncertainty is related to the
difficulty in keeping this whale on the road at that velocity. Engine
compression is regularly monitored and I have the oil analyzed at roughly
8000 mile intervals. To date, no change in heavy metals or engine
compression. I did the conversion more than 5 years ago and have logged more
than 50,000 reliable miles. I am pleased to note that even with my gauge
fetish and many of my modifications to the engine system, I am in for less
than 20% of Ken's Tiico billing. (I also think the TIICO conversion costs are
outrageous!)
I will further admit that this rampant wisdom about avoiding high rpm engine
applications is aggravating my virtual ulcers (verges on technical
prejudice). What is the basis of the concern?
A. Is it engine lifetime? This is a legitimate concern in the case of
engines designed for sub 4000 rpm operation (as in most American Iron). But
for machines designed (piston rings, cylinder wall metallurgy, valves and
valve seats) for high speed operation (5000 to 6500 rpm) 250,000 mile
longevity is built-in. Indeed, the peak connecting rod shock loads and
bearing stress loads are often greatest for small displacement engines when
the engine is operated at full load at low rpm. In the European market the
inline 4 engine routinely sees continuous duty at 5500 to 6000 rpm.
B. Is it noise? This should be an irrelevant issue for properly schooled
veterans with Westfalia 1.6 N/A Diesel experience. This engine is nearly 10
dB quieter than the stock diesel. Soundproofing helps, as does closing the
windows and using the A/C. Nonetheless, the entire issue of high rpm noise
from the inline 4 comes down to the muffler system. Properly designed and
implemented, (length is key) the engine can be quieted down to near Cadillac
levels. Stealth Vanagons!
B1. Mozart (in town) and Wagner (on the way to Texas) at 120 dB in the cabin
also soothe the whining beast. (See recent post on stereo system).
C. Is it fuel economy or fuel efficiency? This is another severely distorted
perception. Its a heavy foot that drains the tank of a properly maintained
engine/vehicle package not rpm. I have been meaning to post a polemic on fuel
efficiency based on experiments I did over our latest 3000 mile adventure on
the US Interstate system. But to summarize, the actual fuel economy was
established by load, not simply velocity. Following load using my trusty VDO
vacuum gauge, I tested long term constant vacuum running with constant RPM
cruising. MPG varied from 12 to 24 mpg. The results are consistent with fuel
consumption maps published by VW and these I have translated. These show that
the fuel consumed is related to the work required and not simply to the
swept volume of air at a fixed Air/Fuel ratio.
The work required is provided by burning the amount of fuel necessary to
provide the torque demanded. As you know, the torque delivered to the wheels
is multiplied by the gearing. So for the waterboxer transmission running a
4.57 axle and 0.85 top gear, the effective multiplier is 3.88 while the
diesel DZ transmission with a 5.83 axle and a 0.85 top gear will have a
torque multiplier of 4.955. This gives the DZ trans a 28 % higher torque
output for any given engine output. Another correction of up to 10% needs to
be made for different tire diameters (compare revs per mile) to get the final
powertrain geared torque advantage.
The torque required to push the vanagon at a steady speed is related to the
speed, the frontal area, the mass of the vehicle, the instantaneous change in
elevation (uphill, downhill and in between), and frictional losses due to
alignment, tire pressures and various bits hanging out all over front or back
(lawn chairs, bikes, dogs, etc.). The engine output torque curves you cite
are the maximum output possible at a given rpm. Of course, the engine can put
out significantly less power at any given rpm by reducing the input energy
(fuel). The real operating efficiency of any gasoline engine is determined by
the part throttle (partial load) fuel use. Inefficient engine, more fuel per
pound foot of torque delivered. As you might expect, successful engines
deliver more part throttle torque per unit fuel input but such engineering is
full of compromises. The design of the combustion chamber, the head and valve
train, the intake and exhaust systems all contribute. The engineering result
is generally optimized for the operating rpm range anticipated for the
desired application. Waterboxers have been optimized for lower rpm operation
and the inline 4 is tuned for maximum efficiency at higher rpms. I don't have
the data here with me, but as I recall the fuel consumption curves only start
to rise (for the 1.8 L engine) around 5400 rpm. The minimum is around 4000
rpm. In contrast, the waterboxer curves are strongly peaked and show maximum
fuel efficiency at 2800 rpm with fuel use rising more sharply at both higher
and lower rpm. The inline 4 has a much flatter curve vs rpm and in general is
significantly lower than the WBX.
Therefore (phew, sorry) the fuel consumed is directly related to the
percentage of available torque needed to drive the vanagon at any given set
of conditions. The torque curve will fall off (efficiency) after the peak
maximum. This falloff occurs at lower rpm for the WBX and for many inline 4's
this fall off begins at 5000 rpm. So at 28% higher rpm than the WBX engine
(DZ application again), the inline 4 has more available torque, and pushing
the vanagon requires about 28% less of it than the WBX system, so fuel
economy must be better and engine lifetime must be enhanced, etc. etc.
D. But then there is lust to consider. The inline 4 with lower gearing is
rather sprightly. The temptation to dust off other unsuspecting minivans
(including, dare I say it, other Vanagons) is often overwhelming.
Particularly with the added sweetness of the Vanagon Diesel badge clearly
displayed on the rear hatch. Such pleasures eat fossil fuels at a prodigious
rate. Your mileage may vary.
But a few unsettling notes are in order to close off this piece objectively.
1. Passing power on hills is marginal especially at speeds of 65 mph and
above.
2. Reserve power at high altitudes is very poor.
3. The power profile of the larger displacement Subaru engine could be more
appropriate. After all, 1.8 L is still more or less 1.8 L, and a competently
designed 2.2 or 2.5 L engine should do better.
4. The 2.0 L VW inline with the 8V non-crossflow head and Motronic (closed
loop O2 sensed) ECU should have better performance than the system I have
described.
5. In response to my ongoing post mid-life crisis, I am currently preparing a
2.0 L Audi 3A bubble block which will run the 8V Digifant head, stock
compression, a SAAB T3 turbo charger operating at 4 to 6 psi (controlled by
the SAAB APC system), SAAB fuel injectors, a G60 pressure controlled ECU and
modified intake manifold with integral air-to-liquid intercooler. Hopefully
this will have the torque of the 2.0 L engine with on demand modest power
assist.
Hope this helps someone. This is posted in an antiresponse to recent vendor
and reputation bashing submittals.
Frank Grunthaner
