[Vwdiesel] Diesel braking - again

[Shawn Wright]

On 6 Jan 2004 at 2:46, Erik Lane wrote:

> ok, i've been thinking about this. sorry to bring this
> up again, but i just can't get it off my mind. :)
> 
> 

I haven't read all the posts on this topic, but I'll add my seat of the pants experience 
with 20 years of driving VW diesels ('81 Rabbit NA, '85 Jetta TD, '85 Jetta NA, 
some newer TDIs owned by parents)

-generally speaking, none of the diesels brake as well as a gas engine in the same 
vehicle. I attribute this mostly to lack of a throttle plate on diesels, and partly due 
the fuel cutoff employed by some gas engines upon deceleration. (this assumptions 
may not be correct, but recall that Mercedes used a throttle plate on some models, 
presumably to improve engine braking).

-currently owning two '85 Jettas, one TD and one NA, I can say the TD brakes 
significantly better than the NA, which I attribute to the more restrictive 
intake/exhaust path provided by the turbo, which, when fuel delivery is at idle, 
makes the engine less efficient. For example, coasting down a local steep hill in 5th, 
starting at 80km/h, the TD will gain about 10km/h, whereas the NA will gain more 
than 20km/h on the hill, same transmission, wheels, etc. This assumption of course, 
could be wrong, as could the first one... ;-)

--
Shawn Wright
http://Zuiko.sls.bc.ca/swright
'88 Westy 375k
'85 Jetta D 263k
'85 Jetta TD 482k (retired)
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