rotary>piston

Does anyone have a picture of basically the porting limits on a 6 port engine? I want to get creative, but I need to know how far I can go. If not, where can I buy a crappy housing to practice/explore on?
One other question: when porting, is duration or pure size more important?

drago86

Dont go very far at all twards the oil seal ( you can go to the edge of it, or if your brave a lil into it's track) You should also have corner seal marks on the used housing, dont go to far into these, and dont go to ver much higher cus the timings allready fairly late. As far as casting thickness im not sure, but considering the limitations of the above 3 factors the only place that would matter is down. You can still make them fairly big though, Search for some of the pics of what Judge Ito did with 6-ports.

Fd3BOOST

iTrader: (7)

Like I said man you have alot oif meat there to take out.
Do what you will.
The shape of the port is the most important thing to pay attention to not the size.

88IntegraLS

There is a ton of shaping and bowl work, as well as free port area (that does not change timing) possible with an S4 NA center housing. The end housings are far less exploitable because they are already timed pretty wild. All you could do with the secondaries is shape the bowl (which helps) or have the ports open earlier. For a street car, I would not open them earlier except for the sixth ports which are only open above 3799 rpm.

Get a cheap center housing off Ebay for $10 and get a dremel, die grinder and some stones. It is a lot of fun!

relvinnian

I have talked with experts and have now done some of my own designing. First, I would like to say that precision timing and very exactly measured porting is very important to obtain the most power. When you are plotting the limits as well as the timing changes you will find that this is a VERY time consuming process. For that reason you can save alot of time doing these measurements then creating a precision template out of sheet metal.

If you want to be creative and not use other people's templates this is the way to go. I plan on scraping a couple housings to find these limits. I personally want to know the exact limits for timing, as well as the angle of entry allowed by the way the casting slopes down. You can feel these and gauge a pretty fair estimate as well.

Other than that it is all in what you want. As you rotate the rotor you can easily see exactly where the port starts to open along the water jacket side, as well as how the top edge closes it. As far as the oil seal side, there is no effect on duration or even flow to be had, and I have not modified this at all. As the rotor passes you can feel through the port, that there is NO room to port in (and no reason).

Also think about things like velocity and scavenging.

I have never messed with 6-port housings but the same rules apply, just a different casting. Can't you gauge the approximate limits?

relvinnian

In a PM from rice racing, he also recommends keeping the opening of the primary and secondary ports the same. The closing (top edge) he extends up and straightens it. From his pictures I checked out it looks like this would be done to close the port more suddenly (talking about rotor position). Both of these things make perfect sense to me, he is the MAN.