Learn Me: Rotary Engine porting

I have a chumpcar RX7 that I would like to make some more power with. We have done alot of work on teh handling and comfort of the car. Now I want some POWAH!

The engine is an S4 engine with S4 manifolds and S4 wiring and computer. The AUX ports are currently removed (we never see below 4K anyway). All emmisions are removed as well.

The car has an OBX header, no air pump, no power steering, no AC, and no mechanical fan.

The car was dynoed at 143hp at the wheels a couple of months ago.

What are the best templates to use? Is it necessary to upgrade any of the supporting systems? Is there a hint or trick to doing the porting?

How much HP should I be able to make "reliably"?

Thanks!

Rob R.

Print out my avatar. Problem solved

(It's the actual port template used on my engine)

Seriously, I don't see any point to porting a 6 port. I've done huge street and small bridge ports on them, and they aren't much different from stock. If you have the engine apart, radius any sharp edges in the ports, but beyond that don't waste your time.

hmmm...

How would you go about picking up 20 to 30 hp? Don't say turbo, because I really can't do it.

In reply to wvumtnbkr:

Ummm.....exhaust driven supercharger?

In reply to MrJoshua:

What you did there.... I see it.

V8 swap!

When you say the aux ports are removed, do you mean you have them wired open? I hope so. You may want to invest in some RX-8 style port ramps for them.

You can also get higher compression s5 rotors (along with the counterweights) and a set of turbo rotor housings (which don't have the stupid baffle in them) and do a bit of exhaust work on them. An S5 intake setup would also be good.

Oddly enough, I may have a set of two S5 engines for sale soon, one of which has turbo rotor housings.

wvumtnbkr wrote: hmmm... How would you go about picking up 20 to 30 hp? Don't say turbo, because I really can't do it.

Have you ever thrown a wideband in the car?

The stock computer tuning has the engine running super super rich at WOT, like 10-10.5:1, in order to be as kind as possible to the cats. There is a lot of power in getting fuel out. I've heard of IT racers running as low as 25psi fuel pressure to get power.

30-35hp is doable from where you're at.

Knurled wrote:

wvumtnbkr wrote: hmmm... How would you go about picking up 20 to 30 hp? Don't say turbo, because I really can't do it.

Have you ever thrown a wideband in the car? The stock computer tuning has the engine running super super rich at WOT, like 10-10.5:1, in order to be as kind as possible to the cats. There is a lot of power in getting fuel out. I've heard of IT racers running as low as 25psi fuel pressure to get power. 30-35hp is doable from where you're at.

^ What he said in both cases.

When I ported my S4 6 port, I lost a lot of low & midrange until I put the megasquirt in. The stock ECU couldn't deal with the different fuel map required.. Maybe I'm a crappy porter, though :) The high end was definitely nicer, but with the stock map it was a bit of a stretch to get into the good zone. This was a long time ago, though.

wideband on the dyno says I am between 13.2 and 13.9 AFR in the 4500 to 7500 range. Accomplished by changing the restrictor in the map reference line.

I think that is why the car is making 143 at the wheels.

If you can tell externally that the Turbo housings are different, I can't do it. The S5 manifolds are out because I am not using 100 points on that (I could go turbo for the same cost).

When I run the stock restrictor in the map reference line to the stock location, I lost 12 to 15 hp in the upper RPM ranges. The AFR was down around 11.5 with everything in the stock configuration (regarding the map sensor).

Light porting can't hurt, and the aux port sleeves with rx8/pinapple racing inserts (or make your own based on pictures...isnt rocket surgery) should gain something. The aux ports just wide open don't help from what I've seen, better to have higher velocity with the inserts.

You really only need the turbo exhaust port inserts, they can swap into your na housings by removing the roll pins and putting in new pins. Then it looks like na housings...

Honestly you need to run turbo irons and intake manifold that has been shortened some. With a massively long defined auto works header its awesome. I've personally driven a 230whp 4 port 13b with that and s5 na rotors. Buuuut it sounds like you are limited in a racing series.....more conservative engine mods and a tune will be your best bet, rather than massive porting and exhaust sizes...

I have a complete S5 intake system that I would sell if your interested. Also I have one S5 high compression rotor if you want it. I think the other one is a bit suspect.

If you're putting a restrictor in the MAP line then you may be getting too much timing, as well.

Knurled wrote: If you're putting a restrictor in the MAP line then you may be getting too much timing, as well.

No E36 M3. I didn't know that. Hmmmm.