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Bore v. Stroke (Last Long Post I Promise)
Wow I am posting like a MADDOG! Okay guys In doing the research for that
little post I made I came across another oddity. The fact that, for the
most part, most high performance engine manufacturers (Porsche, Ferrari,
BMW, etc. etc.) use engines that have a larger bore than stroke (except
the M3 engine for some reason). Now I know the theoretical advantage of
this (exposing more piston surface area to allow quicker, more even
burning); , my question is what is the advantage of using the OPPOSITE;
i.e. having the stroke bigger than the bore. All VW engines have this,
including the 1.8T. For comparison here are some different strokes and
bores for different engines:
Car Cylinders HP Liters HP/Liter Bore/Stroke
Mazda Protg Four 122 1.8 67.78 83mmx85mm
Mosler Raptor Eight 446 6.3 70.79 102.4x95.3*
Passat Four-Turbo 150 1.8 83.33 81x86.4
Crown Vic Eight-Super 355 4.6 77.17 91.4x91.4
Nissan R390 Eight-Tturbo 550 3.5 157.14(!) 85x77*
Chrysler 300M Six 253 3.5 72.79 96x81*
Porsche 911 Six 296 3.4 87.06 96x78*
Honda VTEC V6 Six 210 3.0 70 89x93
BMW M3 Six 240 3.2 75.00 86.4x89.6
Ferrari Dino Six 180 2.0 90 86x57*
VW VR6 Six 172 2.8 61.43 81x90
My VR6 Six 189 2.8 67.50 81x90
Okay enough. Anyway, it is interesting to notice that there seems to be a
pretty even split between cars with bores bigger and cars with strokes
bigger. It is also interesting to notice that the VR6 really isn't that
impressive in the HP/L category. Plus, the VR6 seems to have an low bore
compared to the other sixes. Stroke seems to be on par with other cars of
the same size. One really interesting this is that the Honda VTEC, which
is able to spin REALLY fast, has a very long stroke! Kind of disproves my
theories in the previous post (although they use Nikasil liners in the
cylinder) Any tradeoff? If you want to see a excel spreadsheet
comparison of pretty much every engine in the US market let me know.
What's the point of all this? Well what is the damn advantage of the two.
Is bigger stroke or bigger bore better? Someone of you out there MUST
know.
Okay, I will make this my last long winded post for awhileDiscuss amongst
yourselves.
Mark "In a Talkative Mood" Radelow.
Ps. You notice that the 1.8T an VR6 share the same bore? I wonder if
this is a coincidence.