[Vwdiesel] Diesel talk for beginners --- ( Does a Diesel engine slow down the Car like a gasser does ? )

[Doyt W. Echelberger]

I hear you, Hagar, and agree that you have raised an interesting question.

We science types try to depend on facts for deciding such matters, rather 
than authority.

So, I propose a few tests: Let the person who believes a diesel engine 
provides no braking (the non-believer) get behind a diesel Rabbit with a 
cold engine, that is parked and in first gear, with the engine off and the 
wheels locked straight ahead. The guy who believes it DOES provide 
braking  gets in the driver seat behind the wheel, to steer and operate the 
clutch. The driver window is down. The car is in a big empty parking lot on 
a hard flat surface on a clear dry day about 6-7pm, no traffic, no policemen.

The non-believer starts pushing the Rabbit and the believer keeps the 
clutch pedal down and disengaged.

As soon as the Rabbit is moving at a steady pace (about 5 seconds) the 
believer lets out the clutch.

After another 5 seconds of pushing, the non-believer stops pushing and the 
believer puts on the parking brake and gets out of the car.

Then they calmly discuss the matter, based on their findings. They define 
terms and seek to find agreement about the braking effect of a diesel 
engine that isn't being fueled.

Then they do another test, only this time they put the same car at the top 
of a long hill, away from other traffic of course. This time, they both get 
in the car and the non-believer drives. He starts the diesel, puts it in 
first, and lets it idle. He lets off the brake and lets out the clutch and 
the car moves off, coasting down the hill in first gear with the engine 
running. They ride along for about 10 seconds, making observations. The 
believer then pushes in the clutch and they coast for ten more seconds, 
making observations. Then the non-believer lets out the clutch and engages 
first gear again. They make observations.

The non-believer then shifts into second and lets the car continue to idle 
and coast down the hill for another 10  seconds. They make observations and 
again disengage the clutch and coast for 10 seconds and make more observations.

The non-believing driver then shifts to third gear and lets out the clutch 
for 10 more seconds, then pushes in the clutch and they coast for 10 
seconds and  make more observations.

OK, you understand,,,,they try 4th gear the same way, and then 5th gear if 
it has one and if the hill is long enough.

They discontinue their testing and drive to a cool shady bar and order some 
cold beer and maybe a pizza, and sit around for about half an hour, 
discussing the tests and their observations.

Then they have another round of cold beers and talk some more.

If either one has been converted at the end of these tests and 
deliberations, he settles up the bar tab.

That sounds like an agreeable experiment, if you can find a long enough hill.

The next day you run the same tests, using a gasser Rabbit.

On the third day, you just go to the bar and order the beer and pizza and 
talk about what fun it was.

On the fourth day, you write up a joint report and both sign it, and tell 
us what kind of beer you liked best.

This series of tests can be run with soft drinks if required, but I can't 
guarantee the results.

Doyt
 >>>>>>>>>>>>>>>>>>>>>>
At 02:41 PM 6/19/2005, you wrote:
>Oh, we could get into quantatives, but I disagree with Hagar on the
>brakeing issue.  Essentially a VW diesel does not brake at all.
>Just that a high idle provides more net thrust (torque).
>
>Val
>
>Val and ALL : -----answer : YES YES YES it does.  -----like a gasser 
>?   ---BUT better.
>
>I call for Doyt Echelberger to explain whether his student has it "RIGHT" .
>
>As a slow down device "Braking"  device --Engine  can be compared to an 
>Air Compressor
>to compress Air   takes energy ? RIGHT ?   so that is what slows you down. 
>RIGHT ?
>Right so far ?.
>
>Road retarter ? ---bet your ass.       The higher the Compression the more 
>it retards. RIGHT ?
>
>A long time ago ---eons ? we had a real good discussion about this 
>issue.   And I Hager
>made a lot of tests on  1.6L NA and Turbo  and 1.5 L  NA  Diesel 
>Rabbits  ----and NO way
>can my testing be ---dismissed.   ----I Hagar has a very keen cognizant 
>mindset.
>
>Someone said that a gasser did more retarding due to the "Butterfly" 
>valve   (wrong mostly).
>
>Now did BOSCH use a venturi and a "Butterfly" valve on diesels at one time 
>? ---YES.
>
> >From a "PHYSICS"  point of view ?   the higher the compression  ---the 
> more it will
>be a "RETARDER" , -----period READ MY LIPS.
>
>SO WHAT    is the problem ??? ----simple   ---the fuel must be turned 
>off------then it is
>a matter of valving.   -----------   Jake brakes do not work ?  ----well 
>then I shall   have them
>stopped from use in front of my Tar Paper shack  ----just like it is 
>closer to town.
>
>Yes   there is a Highway sign to that effect ----here close to town 
>limit.-----A NOISE
>regulation.
>
>A Rabbit can not change Valving  -----but she sure can turn the Juice 
>off.     ---like
>Bunny Bondo does  ----and she retards very much like a gasser.
>
>Remember British Columbia  is blessed with testhills.----and Bunny and 
>Hagar goes
>there regularly.
>
>Finally a Diesel will slow you down ---like NO gasser ever did  Cubic inch 
>for Cubic inch..
>
>
>Hagar.
>
>PS :     Doyt Echelberger am I right  ?.        ---- I do agree that the 
>butterfly vacuum does
>take energy from the crank --and that is helpfull in a slowdown (on 
>gassers).      and
>Diesels by the way..