Novacaine

I have been reading up on these things and I don't understand why they can't be made streetable as most people claim or even hold a normal idle. If it is a custom job, there is no reason that you cannot define what you want the intake port opening and closing times to be because it is determined by the apex of the rotor and you can place the port anywhere on the rotor housing. you could set it up to have the same overlap as a street port if you wished. you just have to locate the intake port farther up on the rotor housing. I was just wondering if I was missing something because it seems that this type of porting would be completely customizable far beyond the normal porting options and allow for better flow charactistics into the engine. This only applies if you don't use the mazda peripheral port housing and you are doing a custom job yourself.

Whether it is worth the time and effort as compared to normal porting is another question because of the extra porting work and custom intake manifold needed, but it would not hurt the reliability of the motor because if it isn't built for 9000+RPMs it should be fine. If anything I would think it would flow better than the regular ports (straight path into chamber) while maintaining a streetable overlap in the port timing.

keivi

Im sure you can, but Im pretty sure that if you want streetable then you just stick with a streetport. The only people who spend the insane amounts of money to do a p-port are the people who want insane amounts of power. Which means non-streetable. So to answer your question, yes its most likely possible...is it worth it? most likely not.

banzaitoyota

I really should get off my *** and slap it together and go to the dyno

banzaitoyota

But, since the Stuska is an old analog torque dial no-one would believe the numbers

Novacaine

I don't see the insane amount of money in it, just a lot of time. If you aren't building it for insane power then other than the custom intake manifold, which is correctly sized using the available equations with a mustang TB, which if you are attempting this you should be able to do. The MegaSquirt N Spark can be used to take care of the EMS. If you go carbed and the first gen dizzy then the intake manifold gets much easier. A Header and a free flowing exhaust. most of this if you have the skills and knowledge shouldn't be too bad and a lot of it you would have anyway if you were going to the point of porting your engine.

I'm not trying to ruffle feathers, I'm just bored at work

http://www.yawpower.com/pic25.html
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Dan H

Have you heard a P-port in person? I have and its veeeery loud. Thats why they aren't streetable. Cops will be all over you waiting to write up tickets. Now, there are people who will say its possible to quiet it down with a more restrictive exhaust but when you do that, you'll be restricting flow, so it makes more sense to go with a bridgeport or half-bridge.

eyecandy

iTrader: (19)

You can quiet them down to a streetable level, the proplem is they do not like to idle below 1800-2k ( I have seen some close to 1k, but not sure how they got it) and they lack low end power (streetable power. This is all due to the fact that there is port overlap.

To be honest there is more port overlap with a brodge-port, even harder to get to idle, along with power coming on a few reves higher. I think pretty much on both cases you need to be above 4-5k.

Do some searching I did alot over the last few years and there is alot of info to be had here.

Novacaine

I can understand the noise, but my whole point was that the idle and power band don't have to be out of a streetable range if the port is created in a designed spot so that the overlap isn't so bad. The really big overlap comes from the mazda racing peripheral port housing that they made, which were designed for peak power in the really high RPMs, but in a custom made housing the overlap can be controlled.

I have never seen a peripheral port in person, so this is all just based on my knowledge from reading up on it, but I don't understand why when everyone talks about them they are ressigned to the racing only with power only around the extremely high RPM range. That is were it makes the most sense, but couldn't a P port be designed to be usable in say an application where the needed power comes at a lower RPM by reducing the overlap?

13btnos

iTrader: (1)

What's the use of small PPorts to make it streetable because that is what you will be doing is limiting the size of the port so as not to make too much overlap. That's defeating the purpose of the port. Personally I would go with a streetable bridge one that is not cut into the waterseal. Makes good power and can get it to idle pretty decent but still is pretty loud for the streets. And that's another thing PPorts don't like too much restriction on the exhaust side. And if you don't mind being pulled over and harassed by cops go ahead and build one and give us your results. It would be nice to see one running on the streets though.

RandomHero

iTrader: (2)

Well, you couldnt just place the ports anywhere you want to reduce overlap, the intake ports are just above the exhaust ports because thats when the working chamber has its largest volume (aside from the expansion stroke). If you were to fill in the side ports and mount a pp higher up to reduce overlap, the swept volume would be lower due to the rotor's position being closer to the housing.

Novacaine

Is there any advantage to the air/fuel misture going directly into the engine instead of having to curve through a side port right before it enters? Also the cross sectional area of the port can be very large without affecting the overlap/timing because there aren't restrictions of the seals as there is on the side of the rotor.

Novacaine

ahhhh, thank you, that is what I was missing I guess. That would seriously mess thing up wouldn't it.

actually looking at this diagram, it seems that mounting the P-Port up higher on the housing would not miss the swep volume of the engine because it would be open at the time when the volume would be the largest.
http://www.yawpower.com/rotcyc.gif

peejay

Insane amounts of money... uh-yeah, sure.

I probably have about $50 in my peripheral port engine, and about $50 in the intake manifold (mainly because of the tubes, $20 each, ouch!!). There's some crossover since I used remnants from the intake tubes to make the port sleeves for the rotor housings.

Besides the epoxy, the most expensive "piece" was the Right Stuff sealant, $15 for a half-size caulk tube. But OTOH I only used about half of it. The engine ran fine before disassembly so all rotor seals were re-used. Generic O-rings were used on oil passages, and coolant seals were made from "special" material that was free for the taking... silly roommate thought it was aircraft grade 18 gauge hookup wire.

I've done streetports, and they tend to be peaky since the only way you can increase port timing is to close the intake port later. This hurts low-end and midrange power. If you could instead open the port earlier, you don't lose your low-end and midrange, instead losing out on power at low throttle openings. Fair trade in my opinion, anything you can do to make more midrange is better since high RPM isn't a very good idea from the longevity and acceleration standpoints. I'm cheap, so shoft lifespan is a bad idea, and I like to cover ground quickly, so accleration is important. Plus, burger-stand presence is very important and you don't get that idling like a stone stocker

peejay

Mazda spec idle speed for a peripheral port engine is 1000rpm.

PORT OVERLAP DOES NOT KILL LOW END. It kills *part throttle*.

Evidence: All of those RX-8's out there. No overlap, lots of port timing anyway. Late closing. 160lb-ft of torque at ungodly RPM, 230ish HP at even more ungodly RPM. Any decent 13B peripheral port will ownulate it for torque, with a torque curve flat as Kansas, and it will be beating RX-8 peak power at *far* lower RPM.

Look up "lobe separation angle" with regards to camshaft timing. Same exact principle. For a given duration (port window), a wider LSA will made more peak HP and idle better but will have a soft midrange. Shorter LSA (more overlap) makes slightly less peak HP, much more midrange, and idle quality goes to crap.

RETed

Yep, if you understood intake / exhaust (valve) port timing, then you'd understand why it's "not streetable".
It's the same as if you ran a "big cam" on a piston engine.


Yes, that would make sense, but...
You just lost the advantage of the huge vacuum created by the rotor "opening" into the intake cycle.
With a "supercharger", this wouldn't matter, cause intake charge is being crammed in - BIG HINT.



-Ted