333pg333

Interesting on the port shape of the 2.7. Wonder if the flatter area was found to be more suited to bigger bore n/a motors? Assume this was the head off the 968rs? This is what they term 'D' shape porting, yes?
Is it more traditional on n/a or boosted motors?

thingo

I'm pretty sure the ports on the 968rs are quite small, race classes were classified by horsepower in those days. I think there are pics somewhere on rennlist.

blown 944

From my experiece the "D" shape was developed to allow the short side airflow to be slowed down as to not impeed the speed and volume of the long side. Initially it was adapted to the exhaust runners and obviously it was used in the intake bowl area.

If you look at the 2.7 head it is evident that they were using the wider port to maximize airflow and had to create a pretty severe short side angle to acomodate the added long side flow.

What I find odd is that they did not go so far as to create port shape that would help the shrouded side of the valve and keep the other side to a smaller area to maintain a higher velocity.

Probably was done out of simplicity and mass production.

Thom

As far as I know the 968 turbo S/RS head was the same as a 951 head, at least as far as inlet ports are concerned. It's the outlet ports that were a lot smaller than on the 951 head.

67King

The bigger the port in the same head, the more pronounced it needs to be. In other words, the tighter the bend relative to ID, the more you need to add the feature.

refresh951

Pretty much have my Arduino code worked out for the flow bench. Arduino is just amazing. Starting to get the hang of the programming end. Using a multiMap function for the transfer functions. Using the following orifice equation:





I used the know mass flow value from the Lightning MAF and the pressure sensor and solve for the orifice coefficient and area (and other constants). Then approximate the mass flow at 28" WC (or any pressure for that matter) with the derived values. Then with temp and pressure solve for CFM. Approximating the valve as an orifice seems a fairly reasonable assumption and has been tested by many and shown to give reasonably good results.

refresh951

Worked quite a bit on my flow bench this weekend. Finished the Arduino code and completed the hardware assembly. Purchased a 6.5 hp Craftsman shopvac for $100 and it is unbelievably powerful. Did some quick testing tonight and it looks like it is working. Going to calibrate it with an orifice tomorrow night and hopefully I can start doing some testing on the stock head to get a baseline

67King

smoothe the clay into the port do you dont have a step

Voith

Nice progress, cant wait for results with different port shapes

URG8RB8

Very nice work Shawn!

Dutch944

Nice Shawn! I wish i had the time to do all of this..

teamcrossworks

I wish I had the brain power. LOL

Tedro951

I only have the brain power to check this thread and Shawn's work!

I won't clog the thread with future posts, but thanks for going through this fire drill, Shawn!

refresh951

Wow, all this time and I had no idea I left the spark plug out. I wondered what goes in that hole! Thank you so much.

URG8RB8

I thought I told you a few minutes ago on the phone that the spark plug went in that hole? Well, now you know anyway.