Falken

"Note that with really good engine management, a pp can be driven on the street quite successfully.

http://www.rotaryengineillustrated.c...l-port-14.html

Can someone explain how this works? I doubt it could kill the noise. Low end power? I don't get it.

peejay

Noise is entirely down to the exhaust. My stockport, P-port, and streetport all sounded the same on the same exhaust system.

Now, normally, streetable exhausts and P-ports do not mix because high overlap engines are very sensitive to tuning and backpressure issues. You end up making less power than a good streetport.

Torque, however... a P-port has ungodly amounts of midrange torque. Below about 2k they suck, but when the hammer's down they *pull*.

That's also the key: they do not make very much power at part throttle.

I took mine out because I can't afford a streetable yet free flowing exhaust system right now, building a streetported engine was cheaper. (I basically only drive my RX-7 on 200+ mile trips, so a decently quiet exhaust is essential)

edit: I forgot... DRIVABILITY. The P-port was atrocious on a carburetor, although my carb setup *was* less than ideal. With EFI it was a pussycat. Idled almost smoothly (about as well as my streetport) and it didn't buck anywhere near as bad as with a carb when at low throttle openings. I could even drive it in the city without having to do the WOT/neutral/WOT/neutral tango to keep from breaking U-joints. But the exhaust was just too restrictive and it caused a bunch of tuning issues at WOT.

Idling: http://www.youtube.com/watch?v=Tr7vU3cbH6E

Falken

What about engine life?

peejay

What about it?

If you're using carbon apex seals and winging it up high all the time, then yes life will be short. So will a street port under the same conditions. Engine life doesn't much have to do with the port as it does the RPM range used and the parts used. Keep it in stock RPM type ranges (under 8000) and it will live a long life.

There are a few rally cars here that use stock internals, 8000-ish redline, and peripheral ports, and they don't have any undue longevity issues.

Falken

I was thinking ceramic seals with a redline of 9ish. Someone told me I'd get 10,000 miles out of it if I was lucky.

Yes, its a streetcar.

20BTTwannaBE

question,
how much life do you think i would get with a stock 20BT? Not running to much boost...

peejay

With those conditions you should see triple that with carbon seals. With ceramics, essentially wear doesn't happen and you'll be limited by the side seals and oil control O-rings, which in street use last essentially forever. They wear, but even after 200k it is minimal. (Maybe not ideal for power, but an engine will still run fine with .004" gap instead of .002")

Falken

So a PP 20B can be streetable with some good ITBs and carbon seals?

If that's true it would make my month.

peejay

I don't know anything about 20Bs. My gut feeling is that the more displacement you have, the harder it is going to be to have a quiet exhaust, since it now has to be free flowing for 400+hp instead of 225+hp, but the amount of flow at idle is still small so it's going to be louder at idle/cruise.

On the other hand, a stock de-turboed 20B would crap all over any street driven 2 rotor, just from the boost in displacement...

Falken

Im not really as concerned with the noise as I am with the engine life. Engine life is largely what will determine my port type.

If I can get a PP three rotor to last 40k miles before a rebuild than I think that's the route I might go.

ultimatejay

iTrader: (1)

Peejay, it sounds like you had a carb/tune issue on your Pport because I know quite a few people running pports with ida carbs and they can idle less than 1000rpm and they don't buck. If you know how to mod and tune an IDA carb right you can get a pport very streetable.

peejay

If I had the money for an IDA, I would have run one. IDAs are super expensive, they don't exactly grow on trees. A used IDA and a handful of jets would have cost more than the entire car did.

I was using a Holley... with a decidedly less than optimal intake setup because I wanted 14" runners and it all had to fit under the stock hood.

And I only had about 15 minutes a day to tune it... including 10 minutes to get it started and warmed up.

The main problem was runner wet out, and the lack of runner independence which really screwed up the ability for it to pull air through at idle. It would idle down at 700rpm, actually, but not on its own.

It was a HUGE difference with EFI. It sounded mean and angry but it drove very well. Just not much power because instead of the 2 1/4" straight through system I was running previously, I was using a mishmash of header, stock midpipe, some sort of muffler, and a 2 1/2" cat that has a whole bunch of pipe cuts and resleeves in it.

Actually, it's the same exact system as I am using on my 13B (the header is slotted to work with 12A and 13B) and it put down 154hp at the wheels with a too rich mixture... my guesstimate is that the P-port was maybe 110-120hp at the crank with the EFI... they do NOT like restrictive exhausts!

Falken

Thanks for the replies, but I have decided to go with a large streetport, the main reason being induction method. Although I have always envisioned this engine to be naturally aspirated, I think it's a good idea to leave the turbo option open in case I ever feel like having 600whp instead of 300...and with a PP that would be significantly harder.

That option alone is worth the loss of 50whp that I would get from running large side port. If speedsource only came up with 380ish at the wheels through a racing tranny I doubt I'm going to find any more than that through a PP, and some N/A 20Bs on this forum are already creeping up towards those numbers with a side port.

j9fd3s

iTrader: (3)

they fired the speedsource car up at sevenstock. not sure what rpms it runs at idle (900-1500?) but it idles quite nicely. its too loud for the street, but not by much. its also using RB housings, or something like, as they use the hose type attachment

ITB is probably mandatory for a PP

an NA motor will basically last indefinately, especially if its a weekend street car