Who is THE man to ask about peripheral porting?

No one seems to know alot about them but i dont want to spend all the cash building one if its a complete wast of time!

Thanks..........Chris

 

They're really not good for street use. Mainly for racing. Can't quieten them down enough without killing the power, plus they don't really start producing power til around 9k rpm, and don't idle well below 2k rpm. Street port is really the best way to go.

 

Obviously you have no idea what your talking about and have never owned one. Please dont say things like you just did unless you have actualy dtiven one or own one. The one thing i hate seeing on here is people mis informing others.

CJG

 

It's funny you mention that because there was a guy here that had his bridge ported motor dynoed this week.
The owner was not too impressed with the results and was wondering if he could have done a PP instead of the BP. His mechanic told him it was a waste of time and produced power way too late etc., the usual blah blah!To make a long story short I showed him one of my customers PP dyno runs. Although both motors had the same peak power the PP motor made more bottom and midrange power than his BP motor. It was higher at 5k rpm by 25hp, 50hp at 6k rpm, 75hp at 7 to 8.5k rpm, 45hp to about 9.5k rpm and gradually decreased until they both peaked which was around 10.5k rpm.
The moral of the story is that not all PP and BP motors are created the same. It's the complete combination that makes the difference.

crispeed
87 Rx-7 TII
9.204@150.47mph
2600lbs
un-tubbed

 

Heya Cris, care to post or PM me a couple of PPT dyno sheets, i'm thinking about going PPT or semi PPT with a motor in the future.

Cheers
Shane

 

Generally the number a lot of people throw around is that peripheral port engines really start rocking around 5k rpm and pull like crazy till redline (10-13k depending on setup).

To answer one of your questions, I believe RICE RACING knows quite a bit about p-ports.

 

NSU RO80's and NSU Spyders came with PP rotaries from the factory so they can be made to behave on the street, I believe the reason most PP's aren't very streetable is beacuase they aren't built to be streetable they are built for peak performance

 

That's a good point to mention!

 

There are a lot of factors to change the way a PP responds, same as with any other porting. The size of the port, length and shape of the manifold tubes, the throttle body/bodies, exhaust porting, the distance where the two/three exhaust tubes joins together and all the exhaust beyond that.
What will make one run at it's peak on the track is going to make for a very unstreetworthy car. But a balance can be found.

 

Sorry bout the misinformation, just going by what someone told me many years ago. I'm sure they can be made streetable, but bout all states have some sort of noise ordenance, so why waiste the time and money to build one if u can't drive the thing everyday without getting stopped just about every mile.

 

Yep yep yep!

NSU used smallish ports. Peak torque and HP figures were at similar RPM levels as a stockport 12A. Much more power though (130hp vs. 100hp) and the Ro80 engine was 10A-sized.

It would be unfair to characterize all side port engines by the biggest meanest street port engines (aka peaky bitches) so why characterize all PP's by the biggest meanest PP's?

I guarantee you that you can build a street port that's just as "bad" to drive as a big peripheral port.

Incidentally - NSU got around the rough running at low RPM/load by fitting all Ro80s with automatic transmissions. The torque converters took up the slack until the engine was spinning fast enough/loaded down enough to run smoothly.

 

theres a guy around here with an ro80 and a running spider, the spider will idle happily at 700-800rpms all day, and its a one rotor pp

mike

 

So the Mazda D port peripheral housing will be made for racing and the smaller round port will be more usable for lowering the power band?

Is there any info i can read up on the positioning of the Turbo and trottle bodys or is it just Experimenting and Experiance.

 

I may be wrong but i have a Bridged plate and out of intrest i had a play with a rotor etc and it looked like the opening timing was simalar to the position of a P/P would be? does this mean they would be simalar running all things beeing the same (inlet,exhaust Turbo etc)? or would the bath of the rotor create more overlap effect on the P/P?

 

The timing may be similar on a bridgeport but on a peripheral port the entire port opens at that point whereas a small edge of the bridgeport only is open and then gradually the rest of the port opens. If this were a piston engine the duration may be the same but the amount of lift within the duration is completely different producing different powerbands.

There are some guys running peripheral port engines in airplanes using really long intake runners. They run them across the top of the engine and collect them in a plenum above the spark plugs. This puts the power peak at around 6500 RPM. The power band would probably be pretty good up to that point if it were on a street car but ultimate power is limited. The same engine with really short runners might not start making power until above this point but it will make more ultimate power. It all depends on how you design it.

 

Inlet wise i was thinking of going slightly longer than the one on the pic with a 48mm set of Throttle bodies.

 

That is one sure EVIL looking rx-7!

crispeed
87 RX-7 TII
9.204@150.47mph
2600lbs
un-tubbed

 

so what exactly are the drawbacks of a pp engine.

 

even more overlap than a bridge and having to make a new intake system.

 

what about drilling the port higher up to reduce overlap?

 

There is a problem with bolt holes.

Have a look at Scalliwag's Thread on making them.

Dont forget theres a big bath in the rotor that opens the port not realy ealier than a Bridge but alot more.

 

Indeed! They have one of the rotary buildups going on right now I'm paying most attention to. Really looing forward to it!

 

MikeLMR...good point I was wondering when someone else would mention that. Race engines suck on the street because they're made to adapt to the street, if you make a street engine adapt to a race series then you don't have that problem anymore. Less compromises and problems. It's all in the know how, I'm quite sure that we and hell even Mazda themselves haven't found nearly half of the tricks of the rotary just yet. Development takes time and lots of research and we should never say what CAN'T be done. Things that weren't possible yesterday happen every day now, why would that be different with cars?

 

Peak HP is typically at 9500. Sometimes up to 10500 with BIG ports. Low end torque sucks. Motor doesn't start to make good power until 7200rpms.

It's a high rpm tempermental screamer. YES, you can put one in a street car but you need wide open exhuast and big chokes in the carb to get the most power. So when you put it in a street car with mufflers that spends most of it's life under 4000rpms, ideling, and stop and go traffic you see where it's not friendly.

Redline is typically 10,400 rpms. People quoting 11-13k redline have never driven one or talked to the engine builder. Bearings just don't last long and apex seals tend to dissapear at those rpms.

-bp-

 

OK, If you say so.