BLUE TII

iTrader: (9)

TonyD89 Thanks for the info Blue TII. Very goods conceptual information. I had planned on using motorcycle ITB's and thought, wow, I could have a semi PP too! After reading your post, I don't think it's really possible.

Like I said, what I wrote is all just my pet theory.

If you want a sure thing Logan at Defined actually built a 475rwhp 20B semi-p-port so you can copy that. He started with the motorcycle TB on semi-p-ports and made 428rwhp.

SPENT-IT You brought someones intake into the thread and have not said a word or any good info about what im asking, just a bunch of nothing and confusion.

Here is a recap/retrospective thread about Logan's 475rhwp semi-p-port 20B we all keep referring to. You must excuse us, it is well known/documented on this forum so the regulars just expect everyone to know about it as we do.

https://www.rx7club.com/build-thread...istory-937570/

lastphaseofthis i see injectors on the back side feeding the peri ports
i see three orange injector connectors facing upwards.
which begs the question why not periport as the primarys like you suggest... i think there is something we're not seeing.

If my memory serves me, when I suggested the p-ports as primaries he was on the 428rwhp modified stock manifold w/ motorcycle TB set up. It did have injectors, but they were just there to plug the hole. I think this set up worked so well for him he just refined it with the later intake manifold and never tried primary p-ports (though he added injectors there).

SPENT-IT Some guy with a real nice red RX3 SP and many others have that style of semi-pp intake and that's what i was planing to do on my 13B build. I bought a 20B now im looking to do the same thing with a twist...longer runner because of the style of intake availability makes it hard to join at a lower point.


Pro-Jay has a 20B manifold like their old 2 rotor semi-p-port Holley 4150 style or their two newer style single plate TB styles you describe, but they are $3,300.

Expensive, but then again if you bought the 9x Jenvy ITBs and the GZ LIM you are at $3,600.

Pro-Jay's (like most) semi-p-port manifolds are set up for turbo cars where high flow for the massive power they are making is the most important thing, not power under the curve. Therefore, they have the short runner to the semi-p-port off the secondary side port runner.

I am sure it would work great NA, but you might be able to eek out a little more power under the curve if not peak power with a different design for an NA application.

lastphaseofthis

iTrader: (8)

which raises yet another interesting question...
what did he use for this 4 rotor setup? side port primaries again??
further more.. i've partially assembled the semi pp engine( with 44mm pports) that i am putting together.. and it looks like i'm going to continue to follow logans design. with a much longer primary, and shorter secondary.
there is simply a very small gap for the intake charge to make it down to the exhaust port. and its also a 90 degree bend. minimal backpressure will be the key.

BLUE TII

iTrader: (9)

what did he use for this 4 rotor setup? side port primaries again??


I believe that motor is a full peripheral port race style motor not using the side ports.

a very small gap for the intake charge to make it down to the exhaust port. and its also a 90 degree bend. minimal backpressure will be the key.


I think that is why semi-p-port works so well for turbo motors like the bridge port. The rotor physically blocks port flow to the exhaust side during overlap for some duration.

Maybe not completely for the semi-p-port but enough to impact flow in the dynamic situation (intake flow has to start/stop/start/stop instead of flow just switching from intake to exhaust/exhaust to intake/intake to exhaust like in the full race p-port).

The larger full race p-port is cut down to where the port opens up the slot in the rotor to help communicate with the exhaust stroke.

This is great for NA design where there is no restriction to airflow out the exhaust (our entire atmosphere is available), but not so great when you have a compressor map limiting total airflow.

All the intake going out the exhaust takes away from the total CFM available from the turbo/supercharger's output so you have to use a larger turbo/supercharger to make the power you want and if you use a turbo the exhaust side is highly stressed from all the overlap air/fuel manifold burn being used to drive the huge turbo.

Anyways, more blah blah blah theory.

TonyD89

iTrader: (10)

Well Blue, my plan was for one ITB per side port (four ITB from a four cylinder motorcycle). My original plan was for as big of a bridged primary I could get and to stage the secondary throttles. I think I posted in another thread about how staging the motorcycle ITB's seems very difficult and I also think it was you that suggested a secondary butterfly to keep them shut.

I don't really know how one could do the semi-PP without running on two bodies for the semi and two for the combined primary and secondary side ports. This is possible but again, more complication. Or abandon the primary separation and combine the semi with the primaries?

Thoughts?

BLUE TII

iTrader: (9)

To simplify you could do what Mazda did and you hint at.

Have your primary ports' (whatever port style you choose) TB open with the throttle cable and have the secondaries ports and tertiary ports open with a TB (or sleeve or slide or whatever) all at once (set rpm and triggered when no manifold vacuum to keep staging out of partial throttle) just before the primaries start dropping torque.

You should be able to tune that with M.A.P. and R.P.M. as it will be all primary ports under varying vacuum and then basically a full throttle map when vacuum drops out and all your secondary/tertiary port activation starts to happen.

At least that is how I envision it working.

lastphaseofthis

iTrader: (8)

i plan to run 3. one for primary on a GSL-SE center housing, it has the smallest port, and the least opening/closing time, giving the best potential for idle to ~1800 rpm range, from there the p ports take over.

then later... i may run 5, the two extra feeding the secondary side ports. i'm pretty sure the long loop intake feeding my primarys is going to result in great torque. i'm just not sure if the engine is going to want more air then what the primarys can feed.. this is of course if the idle isn't gone to **** because of exhaust gas reversion.. which i'll just have to see/ tune for.

TonyD89

iTrader: (10)

Thanks Blue TII. All info is good info.

I was shooting for using the MC TB's as is. Just as Logan found out, they basically come with all the stuff and are cheap. Lastphase, yes, one could add a TB, get real complicated on the linkages and/or activation, I just don't know...

My original idea was use as is MC TB's and add a secondary RPM or MAP activated secondary throttle to the outer two with 5/6th working six port end plates.

lastphaseofthis

iTrader: (8)

i don't plan to buy new TBs but some of the smaller Tbs on cars from the 90s at the local you-pull-it, will do nicely, and they're cheap! which is more reasonable to be modified welded to.

i might pick up motor cycle Tb's from ebay, depending on what i find on the next hunt.