Date: Wed, 20 Jun 2001 21:27:19 -0800
Reply-To: Mark Keller <kelphoto@ISLANDNET.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@ISLANDNET.COM>
Subject: Re: Update on Waterboxer vs Transplant Power Options
Content-Type: text/plain; charset=us-ascii
Frank,
I read your comments on the recent post involving bad things on the
list. I had written the article you referred too. I wrote a response,
see below, but didn't send it for a variety of reasons. Mainly I don't
want to fight over opinions and I felt that my comfort level with list
postings was limited to what I could do by helping others in a tangible
way. My comments about High Rpm power and such were just my own way of
looking at the topic. But here goes a few of my questions.
> 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.
>
I felt your post was impressive in the manner which you have applied
technical knowledge to a real world application. I was particularly
interested in the power/fuel consumption at high Rpm data you referred
to. I would very much like to see the evidence to that effect if you
could link or post it.
> 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.
>
Another item on high rpm that wasn't brought up is that piston ring
speeds in excess of 1000 ft per minute, around 4000 rpm on the
waterboxer, have higher wear due to harmonic resonance, if you could
comment further I'd appreciate it. This tidbit came from a mechanic that
works extensively on race motors and such, so I don't where the data
came from. I did correlate a green zone on the waterboxer tach up to
this piston speed so felt there was some merit to it.
The other comfort issue was would a new VW engine driven at RPM's you
advocate still have a "warranty"? I called VW, and got someone that
didn't have any inclination mechanical. My person sense is that the RPM
speeds do have an effect on engine life, and the manufacture's limit of
liability would not include high rpms.
Original unsent draft
Frank,
Thanks for your comments. I feel your last paragraph where you said:
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.
It is thi "on demand power" that I have been referring to. I define this
as the power reserve while cruising 65 mph and 3800. If I want to
either maintain this speed up hill, or carry more weight at this speed,
and up hills or pass someone, I would prefer to have the power available
without downshifting, or having to get a run at the obstacle or risk
bleeding off speed. I believe your
new motor address this issue well-- on demand power assist.
Sincerely,
Mark Keller
91 Carat
FrankGRUN@aol.com wrote:
>
> 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?
>
> 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
>
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