With the exception of the Turbo / GT3, the Cayman S 3.4 is the best engine of the all the current Porsche line-up, because the 82.8mm stroke is way too long. For track use, the shorter the stroke the better. God bless the 3.4
<table cellspacing="1" cellpadding="1" summary="" border="1">
<tbody>
<tr>
<td></td>
<td>Stroke</td>
<td>Bore</td>
<td>Displacement</td>
</tr>
<tr>
<td>Cayman</td>
<td>78</td>
<td>85.5</td>
<td>2,687</td>
</tr>
<tr>
<td>Cayman S</td>
<td>78</td>
<td>96</td>
<td>3,387</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Carrera</td>
<td>82.8</td>
<td>96</td>
<td>3,596</td>
</tr>
<tr>
<td>Carrera S</td>
<td>82.8</td>
<td>99</td>
<td>3,824</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Turbo / GT3</td>
<td>76.4</td>
<td>100</td>
<td>3,598</td>
</tr>
<tr>
<td>GT3 RSR</td>
<td>76.4</td>
<td>102.7</td>
<td>3,795</td>
</tr>
</tbody>
</table>
While short stroke motors reduce the piston speed (while maintaing the same revs) and produce less load on the reciprocating parts and bearings, I'd have to disagree with your premise.
Stroke gives a cylinder its displacement and torque. Without those, you'll be going nowhere fast (wide bore with very short stroke will produce very little torque and very little power unless the revs are VERY high). Since the redline on the Cayman is no higher than the Carrera S 3.8L, I'd say there is no advantage gained at all...
The ratio of bore to stroke is important and in general oversquare motors (more bore than stroke) give more free revving, I would hardly say that reducing stroke alone is a worthy goal. I'd rather reduce moving mass, so that a motor could cope with long stroke and high piston speeds without reducing reliability.
Edited by - grant on 09/28/2006 12:02:48 PM
shorter stroke means a smoother engine in my experience
<blockquote id="quote">quote:<hr id="quote" noshade="noshade" height="1" />
shorter stroke means a smoother engine in my experience <hr id="quote" noshade="noshade" height="1" />
Yes, I think there's some truth in that. As a footnote, the early Ferrari V12's from the 166 Barchetta had a 2.0L displacement - stroke was 58.8mm
</blockquote>
Edited by - grant on 09/28/2006 1:41:00 PM
