Date: Wed, 8 Aug 2001 14:14:11 EDT
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: 2.0L AUDI Turbo thots
Content-Type: text/plain; charset="US-ASCII"
Pensioner,
A vigorous sortie indeed! It would appear that we are at cross purposes. You
wish to turn the transmission innards into a shimmering hydrocarbon dispersed
metallic pate, whilst I naively hope to only flirt with disaster. Having
already fed the furry (local, only local) transmission men several fiscal
banquets already, I have concluded that the fundamental weakness of this box
is the manual trans.
Based on several anecdotal reports, my information suggests that the 4 speed
manual is in the trans shop eating my lunch at 200 + #ft of torque. Now there
may be some uniquely blessed players on the AlCan highway pumping 225 #ft
through that metastable drive train (hopefully with a spare trans behind the
rear seat). But as a fervent believer in statistics and vengeful gods, I do
believe disaster awaits Brian, and I lurk on the Subaru/Vanagon list for the
details.
Now as for some numbers. Of course, I completely agree that HP is just a
numerical exercise on the torque curve and torque rules as the only
meaningful number.
The original Vanagon Diesel put out a maximum torque of 76 #ft at 2000 rpm.
It developed 75 from 1600 to 3300 rpm. Output dropped to 67.5 at 1300 rpm and
3950 rpm. Twas this output that the original trans was designed (the gas 1.6
L actually, but I don't have those numbers) to handle, with a typical
Germanic safety margin. 200 #ft is a 266% design margin. Pretty good. BTW,
the torque max for the European turbodiesel in the Vanagon was 105 #ft at
2400, 94 #ft or more from 1600 to 3600, and 75 #ft from 1300 to 4600 rpm. The
Audi 2.3L 5 cylinder engine (gas) put out 142 #ft at 4000 and 112 or more
from 1500 to 6000. The 1.9 TDi engine is rated at 90 bhp at 3750 and 155 #ft
of torque at 1900. Almost finally, the European 2.5L V6 TDi is rated at 231
#ft at 2100 rpm.
My best info says that repaired 3/4 hub Vanagon manuals are breaking with 1.9
TDi engines, but I have no direct evidence. The evidence is anecdotal and not
direct. My previous statement of 200 #ft max comes from discussions on s
everal European boards. I sent a letter to the original Vanagon design team
but never got a response. Nonetheless, Michael Sullivan, with far more money
than I is running the 1.9 TDi without reported incident. Could also be that
the syncro trans is a hardier beast. Wouldn't know. I haven't finished
translating the article on the syncro design.
As to the turbocharged Audi 3A 2.0 L gas engine torque curve, torque max is
185 to 192 #ft at 3000 rpm, with 175 #ft or more delivered from 2200 to 4700
rpm. On the low rpm side, the torque drops to 150 #ft at 2000 rpm and on the
high side it drops to 140 at 6000 rpm. From my perspective this is good,
essentially twice the original diesel maximum torque over the entire
reasonable engine operating range (2000 to 6000 rpm).
Now there are several serious limitations here in Audi turbo 3A
implementation. All chosen because I have assumed a 160 bhp/190 #ft
limitation on the Vanagon trans. Several nutsos in the VW community are
pumping more than 400 #ft of torque at 4000 rpm with turbocharged 2.0 liter 8
valve engines. I chose to stay with the stock 10.5 to 1 compression ratio to
maximize low rpm torque and general engine functionality (and brake specific
fuel consumption) before the turbo can reasonably supply boost. This limits
the maximum boost pressure to 10 psi gauge. The nutso's are running 18 - 21
psi at 8.5 to 1 compression ratios with stock 2.0 liter bottom ends.
Non-negligable number of molten piston reports at 18 psi and above. I also
chose to use the SAAB APC boost control system which limits boost by keeping
it just below the knock or detonation onset at any rpm. I could still add
internal water vapor injection to bring the max boost level up to 12.5 psi
gauge, which would bring the torque level on the Audi 3A to around 250 #ft
but I'd only consider this if AATransaxle had a special on 5 speeds with tool
steel gears and synchronizers for $500 or less.
OK, I'm certainly trying to get VR6 performance when needed, trying to get
the brake specific fuel consumption numbers from a high volumetric efficiency
2.0 liter inline 4 when cruising and trying to hold on to the remarkable
mechanical durability of the VW 2.0 liter inline 4 to boot. Yeah its probably
a fantasy, but it keeps me from reading rasty texts on the internet, or all
night vigils at the MBE system on Saturday night.
My comments about gear ratios should be a matter of record in the archives.
Comparing my 5.86 to 1 rear to your 4.86 to 1, says that for any given engine
rpm in top gear, my system will put down 20 percent more torque at the drive
wheels. Number is approximate but would be even higher in comparison with the
syncro because of additional powertrain losses. So, my 188-192 #ft torque max
should be compared to yours as 226 to 232 #ft. so your engine (? - 2.5 or 3.3
or) and mine should have about the same thrust at the wheel.
So, my engine bay will be stuffed, so will yours. My system will have the 4
ring logo and will be embued with the aroma of AugustinerBrau and Wagner and
the echo of the p-wagens, whilst yours will have the zest of Kirin rice beer
the silken strains of a woodflute and the memory of the Subaru 360. Besides,
I am more comfortable in deutsch and the gotterdamerung as compared to the
essence of Kanji and the Shinto.
Now there is a real question on the design margin on the Audi vs. the Subaru
engines. The VW 2.0 inline 4 is a proven 250,000 mile engine. The general VAG
overbuild ratio on water-cooled engines is rumored to be 2.5 to 3.0 times
application specification. I have no knowledge of the Suburu approach.
Clearly the turbo is stressing the engine and trans. Of course, for
equivalent speeds and conditions (70 mph, 5300 pound loaded Westfalia,
dodging Amarillos on the Permian Plateau in Texas at 110 F in the shade), the
stress on the Audi 3A is identical to the stress on my current VW RV 1.8 L
(certified 300,000 mile capable engine), since the power level required is
the same. If I call on the enhanced power level of the turbo for 20% of its
driving time, I would expect a 35% to 40% increase in net total stress.
Sucker will probably only last another 150,000 miles. But by then the PD TDi
might well be in NA and tool steel racing 5 speed Vanagon transaxles may
abound! Aah yes, 5 and 20 nubile ... all wrenching ... Better stop here!
Hopefully, Darrell at AA trans or equivalent will put his offspring through
Harvard on your nickel and not mine! Oh, yeah, TDi is definitely the better
choice!
Frank Grunthaner
In a message dated 8/7/01 7:51:17 PM, al_knoll@PACBELL.NET writes:
<< With all due respect to Frank's talents, I am curious as to the torque
curve
for the turbo 2.0. My motor will have a torque peak of some 225 lbs-ft at
4500 RPM with 190 lbs ft at 2000 RPM. A current installation gets between
16 and 18 mpg with an admittedly "spirited" driver with the standard 0.86
top and a 4.86 ring and pinion ratio in a "sing crow" vanagon.
Check www.smallcar.com and boink the appropriate pointer on the home page
for details.
My "4WD BNB" weighs in at 5000 with a full load of water, tequila, chorizo,
frijoles negros, fly rods, telescopes, computers, and the various
accoutrements necessary for life out of the kudzu zone.
The vanagon after all is a truck. In Bessie the Charolais Camper, the truck
has a GVW of two and a half tons. Stock it is underpowered, underbraked and
handles like the veritable gummi kau. With suitable user improvements it
can maintain the economy of use, cruise effortlessly at velocities
guaranteed to garner the hairy eyeball from the local gendarmes and actually
stop from 75MPH in a distance less than what it takes to turn a supertanker.
Back to the turbo thinking, the 2.5 4V DOHC Subaru provides the necessary
165 lbs-ft with a proven 250Kmi design life motor. AND you can learn to
curse in Kanji for those times that require such utterances. Any turbo
motor short of the Cummins or Detroit or CAT motors is more fragile than
it's normally aspirated counterparts. The bottom line is torque, that's
what turns the wheels. Horsepower is a by product of being able to deliver
gobs of torque at high rpm. For a "vanagon truck" the 2.5l AUDI TDI is
ideal. Gobs of torque, fantastic fuel effiiciency, and all the kewl fly by
wire control systems. Can you get one here? Need you ask?
"de gustibus non disputandum est" of course and Frank's result will be both
esthetically and performance wise pleasing.
Recommended upgrades. 15" wheels. Larger brakes. Better suspension.
Better headlights. 3.3l SVX motor.
What does it all cost? One Vanagon sing crow westie and around 10KUSD.
There are no similar RVs available for under 40KUSD. The closest is the
Tiger on the Astro AWD chassis. A comparative bargain.
Fordzilla (460CID Quadravan) cost 7500 USD used, gets 10MPG on a good day
has parts available at any Ford dealer, ugly as the proverbial pigs butt
sleeps as many as you like, outside. Will haul a 5000lb trailer up phone
pole without even breaking a sweat. But it's not a westie. It can handle
almost any off road situation but it's not a westie. Empty, it has
accelleration that makes the rice boys cringe. Fully loaded with two tons
of gear, bicycles, water, ... it will outrun any vanagon ever made. But
it's not a westie. With two 120 A alternators and 600W of lighting you can
jacklight tarantulas in New Mexico from somewhere in south eastern Nevada.
But it's not a westie.
With 125 gal of fuel you can go 1000 miles between ga$ fill ups. But it's
not a westie.
So you decide on your objective, get the cat a day job and live your dreams.
cheers,
pensioner
>>
