86FC RX-7

Whats the best kind of port for a S5 Turbo motor? Bridge, periphial, street? Can any of them be used togethor, like a street and a bridge or a bridge and a perriphial? what do the diffrent ports do?

Project84

Click here and read about porting.


It doesn't explain peripheral porting. Basically this is a new engine config. The intake comes in through the rotor housing and the exhaust goes out through the plates, backwards from the way it is now. This is how the rotary engine in the RX-8 is set up.

gergrx7

http://fc3spro.com/TECH/PORT/porting.html
heres a page about porting with pictures

86FC RX-7

Thanks for the links but i dont think they helped much, they just kinda showed me what they looked like. Im looking for more in-depth info on like what each one does. And what would be better for a turbo application.

White_FC

Peripheral ports are definatly not a new thing at all, quite the contrary to that actually.

And the Rx-8 does not have any ports in the periphery of the rotor housing. They have both inlet/exhaust ports in the side plates.

Peripheral porting is basically the most 'exteme' porting as far as power/efficiency at high RPMS goes.
Could be made streetable aswell.

RETed

Stick with a street port unless you want to compromise engine longevity.
A bridge port will break and possible take the whole motor with it when the bridge breaks - are you willing to take that chance?
Peripheral ports are not streetable, and basically make no power under 6,000RPM.


-Ted

White_FC

But lots of people call bridge ports not streetable aswell... All depends how hardcore you are i guess.
What about a 'conservative' brideport with a fairly thick bridge? that wouldn't break nearly as easy, no?

This is a pretty good read about Periphreal ports


Something pretty interesting out of that thread.
"This PP definetively don't bog! It takes full load from 2000 rpm (160nM torque) and idles at 1200 rpm. Mainly of a hi flowing dysa in the rotorhousing and some tuníng. Here's some more numbers.

4500rpm: 136hp 211nM
5000rpm: 145hp 208nM
5500rpm: 165hp 210nm"

Which is very interesting, they definatly do make power below 6kRPM RETed.
A fair bit more than stock in fact.. I'm pretty sure any factory N/A 13b motor released from mazda wasn't making anywhere near 136HP at 4,500rpms?...
The power does seem to climb substaintially after 6kRPM, but it definatly makes better power than stock below that RPM aswell.

RETed

I don't bother with "thin" BP's - they are a waste of time in my book.


There is a way to make a small PP work, but why bother?  You go through all that work just to brag you can run a PP on the street?  A true race PP barely makes any power under 6kRPM - there's a lot of compromise porting techniques out there.  A full race PP would make significantly more power up to than this small PP; with those numbers you posted it looks like it might do 200hp, while a full race PP would crack 300.


-Ted

White_FC

Since everyone will probably be too lazy to read that thread this is one line I left out...
" 8000rpm:269hp 236nm"

So,
136HP @ 4.5kRPM
269HP @ 8kRPM

Thats pretty good if you ask me

Why are thin BP's a waste of time? surely if you made them well there would still be gains to be had over just a normal 'street' port?

RETed

There was a guy tuning a PP, and be broke 305rwhp.  Some of the more radical BP's (i.e. J-Bridge) can hit 269 also.  Unless you run purpose-made PP housings, you'll need to block-fill the housings and then machine in the PP inserts; I wouldn't call this job trivial.


Ah this is one of the arguments I've got going on NoPistons Forum, and you're right...you do get some gains from a small BP.  My philosophy is if you're going to compromise housing life, why not go big bridge?  It's a lot of work to BP a housing, and it doesn't take much more work to port a full bridge.  I do not have data on small NP's with thicker bridges, so I cannot comment on how much it affects longevity.  Some of the more aggressive street ports that can come close to what a small BP can do, so why compromise?  Others argue they want the BP sound, but I find that a poor choice to go with a small BP...


-Ted

White_FC

Yes, definatly not a trivial job to make a PP housing...
All my point was with the HP thing was that it was making 136hp@4.5kRPM and 269hp@8kRPM... To me that is far from a radically non-linear torque curve like it sounded like you were describing.
People over here are just cracking 300hp on bridgeports that don't cut into the rotor housing _at all_ (part of the class rules). Pretty fair effort I reckon.

Fair enough then, I can see your reasoning there. It's just from what i've read and what i've experienced first hand BP motors tend to have much more mid range than a big 'street' port motor, they always seem to be peaky.

Project84

I didn't mean "new" as in it was just discovered yesterday. I mean new as in its a "new" configuration for the intake port locations. Every other port is built off of the stock location. The peripheral port uses a new location for the intake port. When I wrote that, I wondered if someone would take it out of context.

Here is a peripheral port housing, courtesy of Racing Beat

White_FC

Haha lol, sorry man.. My bad on that one.
Just sounded like you ment it the other way.

Edit: I've always wondered why RB did their PP like that... with the port angled 'down'.
MFR ones go 'straight' into the housing, no?
Seems a bit counter-intuitive to put them facing 'down' against the flow of air?

Project84

Email them and ask them why. They may have a reason for doing it. I don't know why they do it like that.

RETed

I think port development is still in it's infancy, and there are ways to break early "guidelines" on what a port does and doesn't do.  I've been toying with a PP port idea that would be streetable but wouldn't lose too much low end as you have described...



Like I said before, it's possible - longevity experience is still not established yet...



-Ted