Posted Thursday, March 25, 2010 @ 01:59 PM
The concept of a tuned exhaust for a 4 stroke engine is based on the assumption that an obstruction free run of pipe expidites the oxygen depleted exhaust out of the cylinders more completely and quickly, giving the engine better "breathing" and a fresher (more oxygen) charge of air for combustion.
I like the explanation in the article below to understand what is happing in 4 stroke tuning.
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch4.pdf
Another good one is "How to Hotrod VW engines"
http://books.google.com/books?id=0EaJuPx71_oC&pg=PA43&lpg=PA43&dq=4+cycle+tuned+exhaust+for+VW&source=bl&ots=hK6OCnFcky&sig=YH8OnNaZosQ6GCMhEEBTG-HhaBk&hl=en&ei=n6SrS6XGH4L-tQOatZXdDA&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC8Q6AEwBg
I think that it can be made even easier for our RF4D's because of the existing exhaust layout.
Simply get the right length pipe for each cylinder, cut straight off and your done.
You will not get much additional muffling but if it is just performance you are after then its the lightest and easiest to make.
Going the 4 into 2 into 1 will get you even better muffling and perhaps a bit more performance if everything measures out perfectly but at more complicated piping and weight.
Simply extending the current pipes to the right length sounds like a no brainer. (And cutting out the holed section)
Also, dont forget that better "breathing" will require the mixture to be adjust more rich.
If you were already rich you are in good shape, but some monitoring of CHT and EGT temps would be a good idea.
I wonder if cylinder head temps and fuel consumption is effected very much?
Ray
[Edit by jb92563 on Thursday, March 25, 2010 @ 02:13 PM]
--------------------
