Thread: Flat-4 Power!!!
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Old 10-02-2000, 03:15 PM   #7
bash555
Scooby Newbie
 
Member#: 1539
Join Date: May 2000
Chapter/Region: MAIC
Location: NOVA
Vehicle:
2005 STi
'71 914

Question

Well, I don't know about you guys, but in all of my VW expierence, Counter weights add rev potential and case/bearing longevity.

check out the VW cranks:



I have never built an Engine w/o a counter balanced crankshaft. It's such a difference it can't be explained.

In the pic above, the crank on the left is counterbalanced and the one on the right is stock. When not counterbalanced, the stock crank tends to actually flex at higher revs which causes the pistons to get "cocked" sideways in their bores. Massive scoring tends to occur at that point.

Hey Joel 1.8L (long time no see, 2 years now I think),

I believe some of the 911 enignes had balance shafts that were geared directly to the crank much like a VW camshaft.
Note: most late model 911 enignes have OHC.

Finally, Inline 6,12-cylinders and flat 6,12 cylinder engines are inherently balanced due to any given piston to be either 120 degrees away from each other(6cyl) or 60 degrees (12cyl).
Think of it this way.
120 x 3pistons = 360 degrees.
(double this for 6cyl)

60 x 6pistons = 360 degrees.
(double this for 12cyl)

Its basic geometry that the Egytptians figured out eons ago. 'member the pyramids??

It's all about the balance.

oh yeah, so why did Porsche need put in the balance shaft???
Well, they didn't need to, it was just a way of fine tuning the balance of the engine.

Notice that the M3 and the 911 have either of these 2 layouts. Porsche has run flat 12s in their racing program before.
They don't run them today because, (as Subaru found out in their flat 12 development for F1 a couple of years back) that for fitting and maintenance, the flat 12's would not sit as low in the chassis as a V engine would. Lower engine equates to lower CG , i.e. better handling which is half the game for roadracing.

Enough rambling out of my ass,

cheers,
DB

12sec 68 Ghia (in pieces at the moment)
Totaled 97 Probe GTS (too many pieces)RIP
71 Porsche 914 1.7L
(very tired engine, my daily)
69 Saab Sonnett 3 1.5L
(all fibreglass with a V4, now that is a "buzzy" engine)







[This message has been edited by bash555 (edited October 02, 2000).]
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