View Single Post
kellcats521 kellcats521 is offline
Registered User
 
kellcats521's Avatar
 
Join Date: Feb 2005
Location: Atlanta Metro
Posts: 219
Quote:
Originally posted by Craig 930 RS
I know it seems odd, but according to some of the top engine builders, it turns out that the metallurgy involved does not make a difference in any aspect.

I'd assume the Carrera head have larger ports and valves than a stock 930 head - the SC heads used on my car (from 78-79) certainly do.

In the old days, the inefficient turbochargers pretty much relied on gas velocity to produce power - the modern TCs are so much better and pump so much more air that sheer volume becomes an issue........and a "bigger pipe" to deliver the goods becomes a goal, of which a part is manifold, heads, and in a different aspect, the exhaust.
The Carrera heads absolutely have bigger ports, but valve sizes are equal. I agree that the metallurgy has no effect on performance, it will/would only effect which head exceeds it's thermal load faster or at a lower temp.

I think the boat has been missed here - Noah is using a computer simulation (like the program "Engine Analyzer") to predict performance of different components, of which the program is NOT showing significant or measurable improvement when using the SC heads vs. the 930 heads. I expect that Noah has imput all of the specific parameters of each head and cam combination, along with intake and boost info, and the program is predicting TQ and HP.

Again, my experience with the specific program 'Engine Analyzer' was that boosted applications tend to be a bit conservative. The program seems to lessen the significance of port size and volume in boosted applications compared to looking at them in a N/A application. In other words, porting/enlarging the heads on a boosted motor produced bigger TQ/HP increases on the dyno than Engine Analyzer predicted.

The program seems to follow the old mantra that porting doesn't help boosted applications. While it's true that pressurizing the intake/cylinder will overcome some flow-related issues that would effect a similar N/A motor, the converse is absolutely not true - porting/enlarging a boosted motor's intake has just as much positive effect on TQ/HP as it does in an N/A application, and maybe more in some cases.

My initial comment regarding the SC head and 930 cam combo was related to what I expected the Engine Analyzer prediction to be - I expect that the 930 CAM cannot keep the valves open long enough to actually benefit from the increased port size of the SC head, irrespective of the boost or N/A application. I would expect that the bigger ports in the SC head need more cam to actually see any benefit, and I'd expect that a program like Engine Analyzer would predict the same thing.

I am curious if any Porsche performance shops are using programs like Engine Analyzer to work out the modifications they develop and/or sell. I do know that in many racing venues these programs are indispensible in developing engines for specific applications.

Pat Kelley
Old 04-18-2007, 07:56 AM
  Pelican Parts Technical Article Directory    Reply With Quote #8 (permalink)