sorry

 

your a genius why didn't I think of that kinda like the 787b.

 

I agree with you on this, it would be better to definately have a manifold made specifically for this app. I'm not saying it's the only way or the right way just that it makes the most sense. I also think that most people that try this will blow a seal before they kill the motor due to wear.I've also heard of people running PP's with descent mileage.

 

Well, that's pretty good actually! 30k miles is more than enough for me!
What his car also turbocharged?

That makes sence what you say about why it should be better than a bridge port. Maybe the 6-12 month thing was what I heard for an all out race engine.

 

I know the car ran 30K. The engine is still running around in another car to the best of my knowledge. It was fairly reliable... except that we always had a little fouling problem due to the plugs being so cold. It was n/a with what I think started life as a Weber 48 d/draft, that had been modified to 51mm. We did, however shift around 9500RPM with the MSD's set to 9800. Great motor. Completely streetable if you liked driving it. I can't tell you how many times we drove the car to the store to buy bread just so we could have an excuse to go get into some meyhem.
amemiya,
I was actually considerint some Honda throttle bodies or something right at the port and having them boost or RPM actuated. That would really **** off the Honda guys. The throttle bodies they use to flow to their entire engine... we could use 2 of them for our "auxillary" power.
I think some motorcycle butterflies would probably be the perfect size. My bike has 2- 54mm tb's (v-twin).
Don.

 

Actually thats a decent size port as it is additional to the large street port thats already there.

 

A well prepped BP or PP will live a long time. A big monster port that eats well into the rotor housings will (more likely) die first due to the seals being cut and jackets being filled in. Water leaks are usually the first sign of the engines demise. A bridge with a meaty sized bridge section will live pretty well as long as a similarly maintained and driven extend port engine.
I know of a 10a pp in a r100 hillclimb car that revs like there is no tomorrow, and has beening doing it for at least 12 years.
It gets down to attention to detail in the building and then driving style and maintenance. Race engines tend to have a shorter life than road engines because they have the living daylights revved out of them. note, these have all been normally aspirated engines. The same "should" hold true for a forced induction engine.

One question about closing off the butterflys to the pp and running it on the side ports, wouldn't there still be the "PP overlap period" (and associated engine grumpyness) as the port is still there and still open while the exhaust is open - granted, there will be no fuel/air going into the pp's inlet tract, but there will still be a mix in the combustion chamber from the side port, and this will still be capable of going out the exhaust port via the gaping cavern that is the pp.

 

buzz,
I never thought of that. Shouldn't the exhaust port be pretty much closed by the time the side intakes are open? I know that there will be some overlap, and some exhaust gas in the chamber that is the PP, but I don't think there will be as much flow. I guess it also depends a lot on port placement and size. This is something to think about. Thanks for bringing up another issue. I was also going to leave the primary's stock and do a mild "street" on the intermediates.... kinda like a 3 stage intake. Hell, this thing is gonna be as complicated as the factory twin seq. turbo system by the time I'm done.
Don.

 

The combi-port (I like the "jetty port" name - half a bridge too bad it can be confused with J-port) will cause exhaust dilution, that's why they will still idle nice n' lumpy, but looking at it objectively, even at part throttle the actual airflow will be coming from the side ports until the secondary ports (be they secondary side bridge or peripheral) so there won't be as much vacuum as when idling, so less exhaust dilution when under part load. And when the secondaries do open, look out!

 

A friend had been toying with the idea of a normally aspirated partial PP running full size p-ports on secondaries and mild porting on the primaries through the centre plate. THis is because local registration laws specifically preclude PP's, and they have a maximum 96db noise limit for pre 1986 vehicles (his is a 1970-something holden gemini wagon - a small isuzu thing to all non-aussies). He'd wanted a traditional looking inlet to fool the inspectors and a standard type idle until the pp secondaries kicked in. After kicking the idea around it occured to me the issue of the port overlap will still be present, even though the p-port will be devoid of it's own inlet charge. I'd expect there to be no overlap between the side ports and the exhaust port, but the p-port will be open in between the side port and exhaust port... perhaps diluting of "venting" some of the inlet back out the exhaust. It wouldn't be much, but we would expect it to give the big, loud idle.
On a small and late opening P-Port like the in scoot pics the "potential" (and I have to call it that as I cant confirm it actually happens) overlap period would be very minimal.

 

How many degrees overlap does a stoc TII have? I know the intake ports don't open until the rotor face starts to pull away from the rotor housing, at which point the exhaust port is pretty much closed. I guess that you will have to port the crap outta the exhaust port to make it worthwhile, and that may give you some overlap if you move the closing up. Am I thinking correctly that if the intake ports are closed while the exhaust is open, then you won't have reversion?
Don.

 

the location of that partial P looks like it would yeeled the roughly the same timming. what do you think?

 

The partial would have a later opening than a Mazda factory race housing due to the lower lip of the port being higher. It would, however, open much earlier than a standard or street port. I would be more like the timing of a bridge with relieved housings. It may open just a bit later, depending on whose bridge you compare it to and exactly where the pp is cut.
Don.