what to do ?

 

That only works on side port engines, not peripheral ports.

 

It's hard to get any real HP unless you take your motor apart. Do you have any current mods?

I would suggest a good equal length header design like the one at rotaryshack.com (called the max power header), followed by a good high flow 3" cat that will withstand some heat and a good stainless muffler. Maybe an MSD Digital 6 box for your leading ignition.

If you get a header, make sure you ask for the O2 sensor bung and maybe one for EGT as well. Also you will probably want to wire open your 5th and 6th power ports. You might be able to get some power with a piggy back Air/Fuel controller if you have an EGT gauge.

HP without porting your motor is probably limited to around 160whp - 180whp. Another relatively cheap mod would be to scrap your FI and get a racing beat lower intake manifold with a 48mm weber carb. A good intake manifold with carb and exhaust would make your car come alive but still wouldn't beat an STI or EVO. But these bolt on's would still work great for when you decide to have a shop do some porting.

 

im gonna turbo my rx7 na and i was wondering how much horsepower can the na rear shaft hold ???

 

Define rear shaft? Are you talking about the engine e-shaft or driveshaft or rearend/axles?

 

Since we're on the topic of PPs. Am I right in saying proper length for a PP exhaust runner to collector is 89"-94" or 10"-18" ? When people say that PP's are sensitive to their exhaust setups, are they referring to the "resonant tuning" effect and/or exhaust back pressure?

 

they are picky about both actually, but each does different things.

the length primarily affects the RPM the powerband is at. the math is complex because the exhaust gas is hot, but basically the lengths work in multiples, so 18" and 90" both tune the the same rpm*

if the length tuning of the exhaust matches the port timing, flow, and intake tuning, power will be up everywhere, but especially at the peak. if its off, say you put a header tuned to 9000rpm on a stock engine, you loose everywhere, as its not optimal.

generally a long system will have a more broad powerband, and a short system will have a higher narrower peak.

backpressure mostly affects overall power. the rotary has no exhaust valves, so any hinderance to exhaust flow = less power.

the PP engine is more sensitive to backpressure than a side port because with MFR type port timing the intake port and exhaust port spend a lot of time open together, or in overlap. they also flow better, on a bridgeport the exhaust gas has to flow in the port, and over the side of the rotor to get to the intake. on a P port, the rotor movement wants to push the exhaust gas toward the intake port.

i have played a little with this on my PP, but i don't have any real solid numbers, i hope to go play with this on the dyno, it'll probably be a couple of months though.

if you're building an exhaust from scratch, i'd use slip fits, so you can change stuff around. the rear muffler is also a challenge, you need something that can FLOW but also remove a lot of DB, while not melting. ive seen a couple of MFR mufflers and its like a small sherman tank, they are BIG and BEEFY

*the 18 and 90 numbers were chosen as examples, they may not actually tune to the same rpms, it should be close though.

 

Assuming same exhaust duration, EGTs, same pipe diameter and no constriction or anything that would change tuning aspect of system, like resonators etc. With such thing all the math can be thrown from window

https://www.rx7club.com/naturally-aspirated-performance-forum-220/informative-exhaust-tuning-what-part-system-actually-tunes-883371/

This is something what should be tried. Something like short system with megaphone terminating into large box, where all tuning will end. And then just mufflers with sufficient flow.

 

how about the racing beat true dual exhaust system on a pport motor how would it affect it? lose or gain in hp? and how would it affect the powerband?

 

I have a set of Racing Beat 13b PP housings, I was told they would make 300-320 whp. Don't know if it's true, But I also have the Racing Beat 51ida Weber to go with it.

 

Whoops!

very true.

 

use em! YOU will love it!

 

nobody has a dyno graph NA semi p or peripheral 13B ??

 

Ive been looking for one too. I know the powerband is high but Im just curious as to what is going on lower. And even more curious to see what a motor runing PP secondary and side port primary looks like compared to just PP

 

 

 

many many thanks for your dyno graph.
what is the length of your runners up to collector ... I had almost same torque but only 249hp ...

 

I need help to improve the peak hp and more usable rpm band.
gears on my road race car made to rev 10,000 for my local track.
http://tinypic.com/r/fmryc7/6

 

hi all,
in all our experience with N/A 13B PP 400hp is the max output as the rotor can only suck so much air and fuel. the realistic outcome would be around 350 to 360 Hp at the engine. we have made 350hp with good torque.
But at the end of the day on the track you need a good package of torque and hp. currently the 13b bp we are running is making 320hp at 9000rpm the runners are long and have itb setup. chasing just outright Hp doesnt get you far as your usable torque band is minimial.
the centre bearing crank does support if you are revving past 11500rpm but on the track we have had no success with them. They are perfect for drag racing use under high boost and short distances. (harmonics is the killer)
(I might be wrong but that was our experience with the centre bearing setup i would ask the local circuit rotory racers if they use them)

cheers

 

Why would the center support bearing cause problems?

 

We don't know why, but we have back to back two identical motors built for circuit racing and the centre bearing engine didn't last. And the more we looked into it around our racing class most if not all competitors scraped the centre bearing motors. We think it's harmonics. Anyway if your not going to turn the engine past 10000rpm shouldn't be bending the e shaft. We are still using the same e shaft for the last 5 years.

Cheers

 

yesterday I saw on ebay one rotaryshak max power header for N/A good price

 

I'm going to throw this out there even though I have no experience with the subject of the thread.

I come from a tool and die back ground and a rule of thumb is that the location of fixturing is always better than the desired result of the fixture. In other words, the dowel pin clearance and location would have to be much better than the bearing clearance and location, according to our rule of thumb.

Measure up your dowel pin bores in the plates and housings and then compare them to your desired bearing clearance and I think it will be clear why the center bearing is tricky.

 

good info right there!

 

why are you selling ? going turbo?