View Single Post
tailwind22 tailwind22 is offline
Registered User
tailwind22's Avatar
Join Date: Jun 2012
Location: Moses Lake, WA
Posts: 969
Originally Posted by kenikh View Post
I just had a long conversation with John Dougherty about 993SS cams in a 3.4L 930. Per his recommendation, 993SS are generally not recommended for turbo engines under 9.0:1 (no typo) static CR at book cam timing. He said that if you advance the cams 4 degrees, 8.5:1 will work. Although he's never tried it, he expects that it might be a little laggy, especially if you're running a slower spooling turbo.

Once you're on boost, it all changes, of course.

Based on my calcs, at-idle static CR (on book timed) 993SS cams is even lower than for GT2 cams, meaning you can expect lazy performance off idle. Advancing the timing will net you a little more dynamic compression at idle, but you still shouldn't expect anything better than somewhere between 964 and GT2 performance off the line.

The OP stated he wants more off the line grunt at the expense of top end power. 993SS cams are not the solution for his problem. From his initial post, it sounds like he is running DC15 cams, which although nice, will give up a little off idle grunt compared to an SC cam.

In reality, the OP is probably best off emailing with John Dougherty to get a custom ground cam - ideally something with near stock overlap to maximize off-idle compression, with a little more lift dialed in to allow a little more top end power than the stock cams. A DC 10/12/13 may be a good option in this pursuit.

FWIW, my CIS 8.5:1 CR, 3.4L motor is now coming together with 993SS cams, K27-7006, 40I/38E ports, knock control and twin plugs. Knock control means I'll be able to run a sharper advance curve which should mitigate some of the off idle laziness. Cams will be timed w/ 4 degrees of advance. I'd of course be best served with fast spooling ball bearing turbo, but budget isn't accommodating right now. I'll let you guys know what they are like once I do.
Thanks, very informative.
89 Porsche 911 Targa & 91 Porsche 964 Carrera 2
73 Porsche 911 RSR Tribute with Rothsport 3.5 motor
76 Porsche 914 Raby motor
73 Porsche 914-6 GT Tribute
69 Porsche 911E fully restored
Old 10-08-2014, 12:04 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)