Polishing the ports?

[Ticket55]

So i was toying with the idea of stripping my rx7 lump down and polishing all the ports, (well the exhaust ones). But i was just wondering if it is actually worth it? I know there isn't much to taking the rotary lump apart, but has anyone got any experience in doing this? And am I correct in saying you only do the exhaust ports? My boss at work said I'd be wasting my time (but then he's old and grumpy, and said the same thing about my car all together! lol). Any advice would be appreciated .

Also, apologies if there is a thread on this already, i did a quick search, but nothing came of it.

 

[TCJBOLDIE]

Polishing the exhaust ports will help to keep them cleaner.Porting the inlets will also help increase power. With the inlets you have a number of options-Extend ports, bridge ports, monster bridge and peripheral ports.
Remember they will all increase the RX drinking problem.

 

[PDDesign]

Don't know much a rotary engines, but have spent hundreds of hours messing about with a flow-bench and can tell you that (in my experience at least) polishing makes no discernible difference to flow (notwithstanding what TCJBOLDIE says about it helping keep the exhaust port clean!)

 

[TCJBOLDIE]

Polished ex ports will be/should be smoother due to the less clingy surface for carbon to hang on to.
Inlet ports shape is more important than finish.
The consensus is that inlets should have a finish somewhat similar to a honed cylinder bore especially downstream of the injectors or carbies to help/improve the incoming AF mix .
I can't argue with your experience/results re pros & cons of polishing inlet tracts.

 

[Ticket55]

Fair enough, thanks guys

 

[SLEEPER]

Polisihing is often confused with porting .
. If doing the latter make sure you know what you are doing - you cant put it back once it has been removed

The need for porting depends completely on the individual design . Some engines benefit more than others

 

[davalav]

Here you go buddy!

I watched it a while ago, and although they PORT AND POLISH I figured it would show you exactly how its done.

By the way, your boss is silly. Rotary engines are an incredible feat of engineering.

 

[BAD63R]

I did a full porting, enlarging and polishing on an entire 3.2 V6 Vauxhall engine. Still got the thread on here somewhere if you want to see it. But I managed to get it up to 247bhp. Biggest thing I found is that it's all very well porting and polishing etc, but unless every part of the air way allows the same amount of air through, you will only cause a bottle neck effect. Polishing is a waste of time for improvements other than smoother air flow and as said above, less rough surface for particles to attach to.

 

[Ticket55]

Thanks alot guys! Sorry for late reply, just moved into my first house with the mrs so been silly busy! Im getting rid of the rx7 end of this month, cant really justify it anymore im afraid . But your replys were very helpful and that video is great!

 

[T9 man]

I wish you the best of luck in your new home buddy

So what are you going to replace the RX-7 with then, any ideas yet?

 

[Ticket55]

Loads of ideas, and thats pretty much where it ends haha!

I would love an s14/15, or skyline. But realistically, ill prolly end up with a 1994 suzuki swift!

 

[jarrus]

as said, inlet need to be slightly rough to allow better atomisation of fuel in the air stream, and exhaust ports are better off being like glass

 

[TAZ67]

I polish to a mirror finish only combustion chamber's and exhaust ports. Inlets are hand finished with 100grit emery to help with aerodynamic efficiency of air/fuel mixing better and minimize fuel drop out. Manifolds matched and pinned so minimising alignment points of port to manifolds. But shape of ports are more important than the polishing in increasing power of a engine!