Bart_dood,

Your response is exactly what prompted me to start this thread. Check the link I posted earlier. More is often NOT better, and I was really hoping for small port 3.0 data... Where this does come into play is the appropriate sizing of intake and exhaust components, and informed camshaft selection. Build something past your limiting component and you throw money away AND lower system efficiency.

RWebb,

Thanks for the tip. I'll look now.

Chris

Ok so something that might be worth doing is some simple calcs, you know the peak power of the engine, so its fairly easy to establish an air flow rate, then compare the air flow rate numbers and port size to other cylinder heads? I bet you can find data on port sizing and flow rates, see if you can estimate if the 911 ports are too big/small or just right?

I suspect (although I got no data to back it up) that they are either about right or slightly on the large size. Because they are at an angle to the valve (more straight than the usual 90 degrees) they have a less restrictive short side radius to the valve, this will help the flow balance more evenly around the valve and promote better overall flow although possibly with a detriment to swirling and mixing of the fuel/air.

Bart_dood,

It is the dearth of information like this which prompted me to ask the question in the first place.

I bet you could find data to support your theory. Then, with some simple calcs, you can prove your assumptions.

As an alternative theory, the angled placement of the fuel injector within the Carrera manifold might be skewed enough to promote enhanced swirl due to the overwhelming mass of liquid (unvaporized) fuel entering the high velocity air stream. Of course, this could only be true if you were injecting behind an open valve, which is effectively false.

Helmholtz tuning of intake and exhaust, incorporating camshaft variables and multiple fluids and phases, concurrent sonic and subsonic flow elements, using simple calcs...

I'm going to need a bigger bar napkin.

Chris

Just out of interest what is the goal of your engine build? more torque? more peak HP? if you want lazy horsepower a turbo is the way to go.

Again, not direct to your question, but wouldn't some "fancy" back cut, small stem valves with multi angle valve jobs that might be improved on the combustion side be a way to gain some low lift flow.

That isn't black art and only requires a call to a custom valve manufactor. I know that the domestic racing market valves don't look the same as a valve from 85' so why do we live with that here? Its not like OEM Porsche valves are a bargain at the prices I was quoted. I'm certainly not suggesting cheap imports, but something short of Ti (for endurance sake) should suffice.

On the topic of domestic tech cross over: Why aren't we seeing the beehive springs attempted in our applications? Sure, we don't run the lift numbers or quite as high of a reciprocating mass in our valve train but the reduced weight/strength might yet provide some benefit. I might pose this question in engine building section.

With all due respect to how truely unique aircooled Porsche's are you don't find alot of bang for your buck in a design that has a thermal effiecency of roughly 26%
regards

racing97,

I can't speak for others here, but I think Porsche has done quite well. Part of my interest lies in improving the system efficiency which you point out. There are plenty of muscle car forums that exist outside your criteria as well. If you want to start a thread about Carnot efficiency, I'll be only too happy to come in and point you to a Honda site. Adiabatic fantasies aside, what else do you have to offer?

Chris

BTW, did you know that the spell check offers "ricer" as a suggestion for your username? :eek:

Luke,

I am inclined to agree with you. I had the +1 manifesto ready for posting last night, but got bumped offline. I'll post a link related to your suggestions when I have the opportunity.

Meanwhile, anybody have numbers for the 3.0L CIS heads?

C

The only info I have is from a project quite a few years ago, and I really can't recall the situation. My notes say the heads were 3.2 and ports were stock as well as the valve head diameter of both intake and exh, but the valve stems and guides were reduced to5/16ths from 9mm. So this I am sure effects the numbers a little.
Lift IN & EX @ 28"

.050, 33, 30
.1 , 56, 52
.15 95, 77
.20, 135, 100
.25, 171, 119
.30, 207, 134
.40, 246, 158
.50, 255, 179
I also believe the intake port was 150cc and the exh 66cc but I can substaniate that.
regards

We have had heads made for us that use the new other than tulip valve profiles.. with 8 mm stems..

and with

using Ferrea or DelWest components