So I've got this idea stuck in my head that I want to do a full PP on my next motor. Not that I really need it to hit my goals(only looking for around 600-650, could be done on a BP or SP), but I love doing things differently. My last setup was a GT4294 on a HBP and made 530 @ 18psi. I would've boosted it higher, but the Microtech I was using did not have the 3-bar upgrade.



My question lies in the port timing. I really don't want to have to rev more than 8500 RPM(9K MAX), and I am going to be driving this on the street. As for my idea of streetable: my previous setup would not idle at all, had no heat/ac, very loud, but I still considered it streetable. I would like to make a rectangular shaped port to maximize area while keeping overlap to a minimum. I know people have done this before from pictures I've seen, but I can't seem to find any timing numbers and powerband characteristics.



Does anyone have any experience with this and would be willing to share some information?



Thanks.

 

Go to Paul Yaws web page: WWW.yawpower.com and look in the technical articles for a list of port timings from various model years. The last one is the factory Pport housing timing.



If you stay within that timing, it will be streetable. My Pport car can drive slowly even with a 2:00-1 first gear. The bridgeported car is a nightmare at low speeds, and is towed to the false grid with a tractor.



Lynn E. Hanover

 

Has anyone has problems with exhaust gas reversion on a turbo PP?

 

square PP??? hmmmm...never seen that.



have any pics of it??? very interested in seeing that. any benefits to it???

 

More port area with less overlap, I've seen it a few times on 7club.



http://www.rx7club.com/attachment.php?atta...mp;d=1130391404

 

The 12A factory Pport housings came with a "D" shaped port. Flat on the bottom with a rounded upper (closing) line. The first hop up trick for these was to make it a flat or only slightly arched closing line. Lowers velocity a bit, moves the peak power up the RPM band a bit makes more power total.



Over 310 HP at 10,000 RPM



Lynn E. Hanover

 

you have a picture of that Lynn?

 

Not available to me at the moment. Just ink up a housing and lay out the open and close lines per the factory Pport. Leave a good 5/8" along the sides to support the apex seal. Use a solid apex seal or the early small corner piece seal.



Lynn E. Hanover

 

thanks...imma try that out today on a spare 12a core i have.

 

the factory played with turbo race engines in the 80's, and they ended up with a twin turbo bridge port setup for two reasons. first reason, the bridge port was for less overlap, vs the pp. think in miliseconds, not in degrees here, something the yawpower guys were talking about. secondly the 2 turbo setup was to lower backpressure. they used 2 ht-20 turbos. i dont have the specs on those, but we do know that the ht-18's are what is in a turbo II, and these are larger.



these turbo motors didnt see the light of day too much, you've seen em in the 86 racing beat bonneville car, it makes 530hp@8500rpms @15psi.



also notice 20years later the RB PP turbo motor (its for sale) uses 1 turbo....