I'm curious as to the reason(s) why PP engines are commonly N/A.

Initially I figured due to the larger intake ports but then I asked the question: If we keep the port opening & closing times semi-close to a street port and resized the intake port-diameter..... However I dont know any real reason why PP's are commonly N/A.

 

there is a thread in the fabrication section of a guy who is building a peripheral port turbo with an 80mm turbo

 

my first thoughts would be:

1. cost (purchase or fabrication)
2. misinformation/ignorance propogation

i'd also imagine most people that run them actually race and the rules of their class dictate what can and can't be done.

 

^^Exactly. Their banned from turbos so they push it as far as they can N/A.

I always thought that it had to do with engine life though.

 

Its physically NOT possible to do that. A P-Port, even if mild is almost completely open by the time a street port just begines to open.

But as far as turbo-ing, theres nothing wrong with it and it works quite well (Hell Racing Beat did it back in the 90's with success).

~Mike.............

 

in its racing history, mazda first started with the 2 rotor na's, but by 81, they decided they needed more power, after some years of development, they came up with a bridgeported twin turbo engine. apparently the PP has too much overlap, maybe not in degrees, but maybe area?

they went with the bridgeport, and the engine was raced once, and then basically shipped to racing beat for the FC bonneville car.

after that they stayed NA, but added rotors

 

Whats up Mikey?....

The pp turbo engines have a short life, due to in short "overlap" in order to make an exhaust big enough to balance the charge you would and will encounter why to much over lap. A Lower combustion charge(na power) with give you less worry about being even as the pressure rises.

Just my thoughts ....

They do work though !

 

I've got some info to go on.. If i uncover anything worthy of posting on my turbo-PP ideas I'll post back;

thanks to those who chimed in

 

I am not sure if you are talking about road racing or drag; but there are a few drag PP + Turbo drag cars out there.

3/4 chassis - El Duke
Full Chassis - The New Vivian

Both cars run on or below 7.4 at the 1/2 mile. It seems that the PP + Turbo is not an easy combination to tune/work on; that is for sure!

 

https://www.rx7club.com/rotary-car-performance-77/one-method-improving-rx-8-power-739941/

 

topfuel tube chassis dragster is 4 rotor Peri Port Turbo, sourced from rx7magazine.

 

you got any links?
i couldn't find anything on them..

 

Sigh... there is a lot of misinformation on turbo p ports, to design a good turbo pport the port needs to be higher in the rotor housing to lower overlap. So the question is why do they not do this to NAs to lower overlap? Easy they are now open during an extended time after the compression stroke starts, in a NA this will push the fuel air charge back into the intake but the turbo will over come this to a point. For a proper turbo PPort you need to do the math, the intake must close before the engine overcomes the turbo plus a little. This also makes the engine idle REAL high and REAL hard to start. You can put a turbo on a normal pport but due to the overlap the extra power made at a given boost level, fuel consumption, turbo life, etc are not on par with the same setup with a bridge.

on top of all that a PPort is a high compromise engine, if the same power can be made with a little more boost and will last longer, use less fuel, have better throttle response, a larger power band, etc on a bridge why use the PPort?

Edit:
Racing Beat's 3 rotor turbo PPort, and its cheap

Edit2:
If you look in the store RacingBeat sells NA and turbo PPort housings

 

Why should be ports higher?? We want to open intake ports around 80-100° before TDC for max. VE%. How much higher?? 10 degrees? 20 degrees? Its fallacy, don´t forget, that on right combination of parts, EMP is lower than IMP(same as N/A engine-relying rather on pressure waves, but these same waves are in turbo engine too)
This is same in every porting, closing timing is on us, for desired powerband.
I don´t see anything what would affect turbo life. Also, given lower pumping looses of peripheral porting, BSFC at full load can be lower.
What is compromise on Peripheral port?? As I see it, PP, at full load is best for any aplication. Of course, on low load, it will suffer most. Longevity of given porting is highly questionable, as properly done porting will not change engine longevity. Larger power band? Again, what has highest VE% and at the same time, broadest spread of that curve? PPort...

 

EMP is lower than IMP on a "normal" engine, but don't forget the PP doesnt have valves, AND there is a around 150 degrees of overlap that FLOWS VERY WELL. the PP is happy to put the HOT exhaust gasses right into the next intake stroke.

a bridge has more overlap in degrees, but it won't flow as well, because its smaller, and partly shielded by the side of the rotor.

closing timing in a PP is about 80 degrees, which is the same as the rx8.

not saying you couldn't do a turbo PP, but there are some tradeoffs

 

Liborek;
You move the port higher for the reason i listed, less overlap and keeping port area up. port *and valve* timing effect on VE of an NA and turbo engines are nothing alike, in fact overlap KILLS the VE of a turbo engine as all the new charge from the turbo is pumped right out the exhaust port . In a turbo engine you want as little overlap as you can get click for a good short rundown on timing/ overlap and turbos it is for a piston engine but the info is still valid.
I may not have been clear enough about the "extended time after the compression stroke starts" as in it is extended more so than an NA PPort.
It kills turbo life due to the overlap, to get lets say 15psi the turbo needs to spin faster than if it where lower overlap to make up for the loss of a lot of air just flowing out of the exhaust. All the air that just bypassed the engine also has fuel in it, that can be ignited by the flame front at high rpm that can put extra heat into the turbo as well.
saying that an engine has no compromise due to " As I see it, PP, at full load is best for any application." to an auto-x / street car guy will not work. As a street car most of the time you are under 50% throttle and need some volume control with a good idle, for autox you need a long power band, an idle, still some noise control, good throttle response from light to full and class restrictions. Do not take this the wrong way, If i could afford to get my vert and one more i would love a PP. I stand by what i said, The PP is a high compromise engine if it where not there would be more of them running and people would not try things like semi-PP engines.

Edit: I should add that back pressure may be higher than boost levels in some cases that add the reverse effect

 

I´m fully aware of overlap. Yes, high overlap engines like to pull exhaust gases to intake stroke but only at low load/idle. At full load, its not a problem.
I have been collecting various informations about IMP/EMP ratio of many turbo engines, and basically, in good flowing combination, intake pressure is always higher than exhasut pressure-but not as vast, that would cause fresh charge escaping straight to the exhaust-if it was the problem, it would be very same in N/A engine with strong scavenging...

 

Tuned lengths of manifolds(mainly intake) aply very same no matter engine working at 14,7 PSI or higher... Link you posted relying on street cars with smallish turbines and awful IMP/EMP ratio-in such case-zero overlap-best, but in case of rotaries with single turbos and appropriately sized turbine/housing, IMP is always higher than EMP(to the point of WG opening-but it is for another long thread). Fresh charge in no case could escape throught overlap-almost no pressure difference...
for that reason I stated that low-load is suffering most... But it doesn´t makes PP engine any more compromise than side porting-its always compromise for intended aplication.
In case of Turbo PP, John Deere and NASA, as far as I know, didn´t use anything else in terms of porting, and I´m sure they didn´t care about overlap-as it is just by-product of sufficient intake/exhaust duration. No exhaust blowing to the intake, no fresh air straight to the exhaust...lowest BSFC what turbo rotary ever seen...
Here are some interesting threads-many opinions, some facts, what works for someone, doesn´t works for others...many of BS theory...
https://www.rx7club.com/single-turbo-rx-7s-23/p-port-vs-b-port-vs-street-port-turbo-13b-491629/
https://www.rx7club.com/single-turbo-rx-7s-23/p-port-debate-492021/
also thread which started these two...
https://www.rx7club.com/showthread.p...8&page=7&pp=15

 

Ok guys bear with me on this, just something ive thought about. Imagine this...

an intake manifold with regular side ports for low rpm and butterfly valves for a peripheral port operated higher in the mechanical throttle range, or electronically controlled. driving around its normal, but when you get on it, more flow. you would keep the stock location for the main butterfly valves, only get a larger one(s).

Im sure someone has though of this, but what im asking is why it would or wouldnt work. Cost would be high... but pretend youre a lottery winner.

 

Overlap is always there, closing some throttle will not change it-high vacuum caused by excessive pumping looses of almost closed throttle bodies will pull exhaust gases to the fresh charge-misfiring-brap, brap...

Yes, it has been discussed many times. Search for terms like "semi-PP", "combo port"...

 

i've been playing with an N/A PP engine.

you're correct in theory, actually executing it would be really hard.

the intake and exhaust are really well connected

 

this is the real world not paper, how ever you match IMP/EMP on paper over how ever big a rpm band it will never play out like that. Overlap is bad! or at least over rated and has been proven to not be needed. I also think its sad that rotary fans are stuck in this five porting options world, stock, street, 1/2 bridge, bridge and peripheral and you cant use anything other than what is normal for that port. This line of thought is holding us back, intake and exhaust port TIMING plays a huge part in the performance of a rotary. The redneck v8 guys can figure it out.... why can't we.

 

Only in street aplications where emissions, noise control, smoothness... are hurdle and not matching combinations of parts that can´t take advantage of it... Todays street cars with variable valve timing can take advantage of it-for example BMW 3 liter twin turbo:low load/idle-less overlap, high load/midrange-large overlap, at high rpms it goes again back to less overlap, not for purpose of reduce it but delaying intake valve closing and earlier exhaust opening...

Yes, I think its because most people on these forums jump on bandwagon of what is written on rotary related sites or what they heard-despite its usually BS. Everyone talks about street, bridge... but not many people think in degrees-let alone degrees and area relationship. Redneck V8 guys are much more to numbers-lifts, durations, LSA... I think that overall, almost every regular member over this forum(or rather all rotary forums) should take some time and learn basics of internal combustion engines... I highly recommend to read through threads what I posted, despite its large parts are hating and BS theory.(Crispeed, RICE RACING, Enzo 250, BDC-people with vast experience with large overlap turbo, even Full PP).

 

when i turn my keys i'll tell you whether it was a good idea or not.

i get the feeling it'll be a great one

 

You're intake port is a good example of the higher port like the Racing Beat turbo PP housings by the looks of things, your exhaust would be a little lower still if it where me but its hard to say with just pics. I think you're setup should run well. If you do end up being unhappy with it try a little shorter exhaust port, Just ±1º overlap can have a noticeable change.