Date: Sun, 22 Nov 1998 13:14:49 -0600
Reply-To: Blue Eyes <lvlearn@MCI2000.COM>
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Blue Eyes <lvlearn@MCI2000.COM>
Organization: Vexation Computer
Subject: VW Racing Diesel information and low rpm highway cruising
Content-type: text/plain; charset=us-ascii
I just talked to a person in England named Desmond who reads a magazine
published there called Cars and Car Conversions. This magazine is mainly
about high performance petrol engines, so diesel content is very limited. But
the VW diesel TDI rally cars surprised them with their convincing
performance. So they ran a story about these cars. I have just asked him to
directly post to the Vanagon List and the VW Diesel List a synopsis detailing
the most interesting specific information they included in that article.
Meanwhile, here's a few bits of information from Desmond:
"VW has a 5 cylinder 2.5 tdi golf 4 which they race and it can stuff out 275
bhp
and 300+ ft-lb torque and can kick a bmw m3 ass."
"Also bmw has a new 2.0l tdi 16 valve engine which pushes out 222 ish bhp!"
"If there are any details about the vw tdi you want in particular please e
mail me a
list.
Desmond"
Well, I did, and asked him to post a copy to each of these Lists. I provided
to him the posting addresses for each List.
It has come to my mind as a result of this discussion that we know certain
things, which together imply an interesting suggestion. These diesels aren't
turning high rpm like petrol motors. They are installed in light weight
racers. In some of their racing events, they are geared to go very FAST. So
I've got to believe some factory final drive ratios exist and are available
with low numerical drive ratios. We can't learn about them by inquires over
the parts counter at our local VW dealerships.
I saw a post indicating that if you want to buy a ready-to-race VW diesel
racer, the factory will sell one to you. Through bull dog tenacity, the
sealed pages may yet be opened for us to see what's available if we learn the
right incantations to say (special hidden parts numbers) and whose ego to
stroke (special racing department parts supply division?) while passing cash
over their palm. Sounds just like the US auto parts situation was 30 years
ago.
I haven't objected too much to the List's high revving Vanagon gearing
discussion, but ONLY so long as you limit you motor choices to petrol motors
or grossly undersized diesels which are so small they are forced to run well
outside their most efficient load/rpm range just to sustain road speed. But
so far as I'm concerned, any basic mechanical engineering evaluation of
Audi/VW group's direct injection TDI motors' published BSFC concentric ring
maps and their rated horsepower at those low rpm indicates that an overall
ratio of 3.70, is WAY too high for highest mpg coast to coast highway
cruising. If you think that 1700 - 1900 rpm diesel operation where typical
direct injection TDI motors make the most power per gram of fuel hurts them,
then please tell these over the road trucks to stop going 500,000 to a million
miles on synthetic oil before they need their first major overhaul doing
exactly that. They also don't trash themselves fast because they are turning
slowly and easily but with lots of turbo boost, just as a direct injected TDI
VW motor could do pushing a proportionally smaller load. I challenge any
suggestion that continuous operation at 1900 rpm putting out 40 - 50
horsepower would hurt these motors. As a matter of fact, I predict that the
most efficient diesel highway cars and vans of the future will be running
"fast idle" rpm like this just as the big trucks do today. Why? Because it's
the right way to do it. And eventually the best makes the less efficient
unmarketable. Remember you read it here first and how skeptical people were.
The Audi A6 six speed 140 hp TDI comes factory geared to do 33.0 mph per 1000
rpm. So at 75 actual mph, it's turning 2,273 rpm. It can accelerate its 2956
"kerb" weight plus test crew weight from 50 to 70 mph in 12.1 seconds (Diesel
Car Magazine test report, page 30, April 1995). So that respectable full
throttle top gear acceleration started at 1,515 rpm at 50 mph!! Try that with
any VW petrol motor and it will choke and bog and it wouldn't surprise me if
your average train out accelerated it. As a matter of fact, I doubt that it
could even sustain 50 mph wind loads if they were geared that tall. Floor it
and slow down? So please don't try to apply your gas motor experience
generated thinking to these new style direct injection TDI motors. It just
doesn't fit. And the differences are widening. The torque ratings on the
newest generation of these motors are wildly up since that early 1995 test.
TDI diesel performance improvements are evolving much faster right now than
gas motor performance improvements. That 140 hp 5 cylinder Audi motor only
made 214 lb-ft of torque at 1,900 rpm. What torque did you read the new unit
injection 4 cylinder motor was supposed to be delivering Per Lindgren? "It
is a sweet engine, with lots of torque. (there's a new 115 hp version coming
up, with torque up 60 Nm from the 110 hp (285 vs 225))"
Think I'll jump in the Spa so the flames don't burn off my eye brows.
John
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