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Old 03-12-2010, 10:52 PM   #97 (permalink)
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Pasta - '96 Volkswagen Passat TDi
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Originally Posted by Frank Lee View Post
Unless the homebuilt unit could easily beat gasser efficiency...
I've been talking to some "people" about it. The design I'm working on is a pre-combustion type (for starters, might move on to something else later).

Regardless, it should be able to at least match, if not beat efficiency of the gasoline unit.

The engine math is already being considered, and I can't use the OE pistons anyway, so I'm thinking about having Arias or someone else mock some pistons from another engine to fit in the 4.9.

I can get rods for an old 240 I6 which bolt in and up the R/S ratio to 1.71, which will also up the compression a bit since the rods are .4" longer.

I still have to check clearances and deck the block a little, and then deck the head. Most of the compression (I'm looking for a static CR of ~17-18:1) will be had from the new pistons, though. Milling the head/block deck surfaces will account for whatever I can't get using the new slugs.

I've been working the numbers on this for about 5 years now... it's a shelf project. I touch it when I get ambition to beat myself up a little bit.

The crank and OE rods have shown to be good to - and maybe past - 400 HP/400TQ, and the OE pistons and gudgeons won't be used anyway. The gudgeons (wrist pins) are replaced with solid units bushed with brass in a slip-fit floating setup.

I'm still looking into piston designs, which is where Arias comes into play (unless someone else comes through first, but they're the ones I'm talking to right now).
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