 Dynamic CR Opinions - WebCam 86b/86c |
|
|
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
|
  |
| yeahmag |
 Jul 1 2026, 03:20 PM
Post
#1
|
|
Advanced Member  Group: Members Posts: 2,484 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California 
 |
My next autocross motor is coming together, but I'm a little hung up on the CR. For your calculating pleasure:
Bore: 96mm (3.77953") Stroke: 78mm (3.07087") Deck Height: 0.045" Cylinder CC: 50cc Connecting Rod Length: 5.325" IVC @ .050": 54 degrees (WebCam 86b/86c) Gas: 91 octane E10 CA gas I get: STATIC Compression Ratio:10.69:1 DYNAMIC Compression Ratio:8.2:1 To get it down to roughly 9.5:1 static and 7.5:1 dynamic CR I need to: * Find 6cc - 8cc in the head or dish the piston * Go to a HUGE DH of 0.085", which I find completely unacceptable Any opinions on 1) how hard it will be to find 8cc in the heads or 2) if putting a small dish in the piston? My calculations have the dish at something like: * Dish Diameter: 82mm * Dish Depth: 1.7mm Thanks! |
   |
 
|
| worn |
Jul 1 2026, 04:59 PM
Post
#2
|
|
Winner of the Utah Twisted Joint Award Group: Members Posts: 3,616 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest
|
I have built engines but have much to learn. Why is extending the length of the cylinder by the use of spacers or gaskets so bad?
|
|
|
|
|
14 User(s) are reading this topic (13 Guests and 0 Anonymous Users)
1 Members: yeahmag
|
Lo-Fi Version | Time is now: 1st July 2026 - 05:13 PM |
Invision Power Board
v9.1.4 © 2026 IPS, Inc.