[Vwdiesel] Exhaust ideal and oil pan?

LBaird119 at aol.com LBaird119 at aol.com
Tue Apr 3 02:38:38 EDT 2007

In a message dated 4/2/2007 7:12:39 PM Pacific Daylight Time, 
tonyandlillie1 at earthlink.net writes:

> So, it's interesting that in all the years of hotrodding, I've never seen a 
> calculator for exhaust sizing on an engine. There are calcualtors for 
> injector size, carb sizing, tires sizing, etc... Anyhow, this comes form my diesel 
> 82 Jetta needing an exhaust system. I'm going to change the mainfold to the 
> dual setup, and wondering what the ideal size is for the rest of the system. 

  You probably don't see a calculator for exhaust size because 
it's so dependant on so many things.  Cam, exhaust port size, 
desired rpm range, what rpm you want your torque at, intake 
you have, type of muffler and so on all can affect the size of 
exhaust you need.
  For a NA, 1.6 VW TD 2" to 2 1/4 is about right, 2 1/2 inch 
for a TD.  I believe an expansion chamber would be especially 
helpful on a TD but haven't been able to really test, compare 
or prove it.  I thing that due to some tests that were done on 
efficient, 90 degree exits for turbos.

> Do diesels opperate the same as a gas car in this theory, or is it 
> completely different? 

  Basically it's completely different.  In a gasser you want a certain 
amount of back pressure to keep the air/fuel charge in the cylinder 
during valve overlap.  Since there's no fuel in the air charge on a 
diesel, a little blow through only costs a little bit of air but with no 
throttle, you're getting a lot more air than a gasser gets anyway.  
Basically the less restriction the better design one that uses the 
pulses from other cylinders to scavange or create a vacuum and 
you're all the better!  :-)

> The car is a 1.6 NA, BTW.
> Also, I was under the car today, and I noticed there is a fitting on the 
> back of the oil pan right above the drain plug. It is about an inch in diameter 
> by an inch in length. Is this probably an oil pan swapped form a TD?

  Sounds like it.  Makes a 90 upward bend and threaded?

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