Why do the exhaust ports have those difusers in them and is there any benefit to removing them, since I have the engine apart anyway?

 

From the training manual, pg. 4-18:

"A partition has been provided with the insert to create a two stage opening of the exhaust port for smoother exhaust flow."

 

it may be partly for low end, but it also has a baffling effect to reduce noise. 20B-REW's (Cosmo 3 rotor) and 13B-RE's (Cosmo 2 rotor) also had baffles in the exhaust ports despite being turbo. Those were luxury cars and they needed to be smooth and quiet.

My old nonturbo engine did not have the baffles. It made it a lot harder to control noise and keep the tone from being harsh. But I imagine it picked up a few topend hp.

 

Awesome, thank you. I've been looking for a good page of info on porting, like the differences between a street port and bridgeport. I just want to see what's involved, see if there are any easy ways to clean up the ports a little w/o special equipment, and learn a bit. The diffuser is removed when a port job is done, is this correct? Any good pages on this? I saw some build threads in FAQ and search, but nothing that taught you anything about porting really, just that they did it.

 

the baffles help reduce noise just a tad, and take about 3hp away

 

3hp across the RPM band or at the peak? or are you just joking?

 

search the rotary car performance section of this forum. It's more oriented towards the details of engine building.

There is also an n/a performance section

 

Here's a pretty good porting thread: https://www.rx7club.com/rotary-car-performance-77/noobs-guide-porting-56k-beware-619991/

 

So, you're saying there is something to gain from taking these out.

Also wondering this.

I will start looking in there from now on, thank you.

That was a very good thread, thanks. I learned a lot from that.

 

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By golly, your right once again! All non turbo series four RX-7 had/have 'em. If it ain't there, someone took 'em out after they were installed at the factory. The jpgs are from the 1986 Training Manual that NZCONVERTIBLE made availabe on the net.