rwd-pog

Recently i have been reading a lot of information regarding peripheral port engines, as i suspected most of the engines have a lot of port overlap and only run well at higher rpm. I have however read in a couple of posts that some people have pp engines that they use on a daily basis and that tickover consistently at around 900rpm.



My question is, can you make a useable pp engine that behaves on the road i cannot see any way of reducing overlap other than moving the inlet upwards which would surely have negative effects elsewhere.



Any response would be greatly appreciated.

TYSON

Mine idled smoothly at 1000RPM but needed 4000RPM to pull away from a stop. And deafeningly loud.



"Streetable" is in the opinion of the police on your streets.







[media]http://www.youtube.com/watch?v=3RlCJvKlXw0[/media]

rwd-pog

That idle's pretty smoothly do you know what port timing that is and is it just a round tube pressed into the housing or has the end been shaped to minimise overlap. Is it a 2" internal diameter pipe.

TYSON

just a 2" ID tube horizontally into the housing. I don't know the port timing, I had the dimensions I used around somewhere.



I don't know how much power it made, before I got it properly sorted on the dyno it suffered what looked like some kind of lubrication failure

rwd-pog

When i made my 13bpp i did the same thing 2"ID tubing in horizontally, but since then i have seen people angling the tube into the housing and also altering the shape at the end of the pipe so its more square, which seems like it could make the engine more usable by improving the port timing. But i don't know whether it has much affect thats why i thought i'd stick the post up.

j9fd3s

i have a PP too. mine is a 12a, to mazdas race port timing, and a 48ida carb. i can get it to idle down to 750-800 rpms. that's not the problem



the problem is NOISE. its LOUD. the engine is also the first PP i've played with, so the tune is half assed. so far its got way more power than a stock 12a, even from 2000rpms. that's about as far as i've gotten so far, its LOUD.



i think having less overlap will help, but once you mock it up, you'll see that there is still a TON of it...



the KEY is probably EFI. the carb+distributor is a compromise.



i'm hoping to street mine too, i have a ways to go though

wolfgang

I believe the Suzuki RE5 had a PP from the factory, and it idles around 800 - 1000.



One member had an idea for swappable insert that could adjust timing. It was basically a circle with a sleeve that bolted into it. I don't think he ever made it.



Most of the noise is created from the instant the exhaust exits, as the seal passes over it, and from when the seal closes. I have heard that a 10mm round chamfering the exhaust hole helps on both the start and finish.



I also hear bolting on a turbo does cut down the noise.



I have not had time to test both of these ideas myself though.

89 Rag

A certain local engine builder daily drives a PP repu, exhaust isn't any worse than a built V8 with headers and flowmasters.



It will make an old lady **** herself if you punch it going through a tunnel or underpass though.

j9fd3s

this is true. he's notorious here for dumping a PP 13B in his repu (in the 80's!) it would do 0-100mph in the length of the chevy dealership...

rwd-pog

I was trying to think of ways of reducing overlap while still having the same inlet surface area or better. I made up this quick picture of my plan, it consists of two inlets which are siamesed into one pipe at the carb end. And also uses a small bridge to support the apex seal and stop it bending into the port and breaking.



I think this would shorten the overlap and hence reduce exhaust noise (admitidly not to a huge extent)and also the two small inlets would increase the port velocity to help low speed torque and idle. Sorry about the quality of the image but you get the idea. about .imageshack.us/img30/doubleinletport.png/1/][/URL][/img]