pk797

Finally someone that actually gets it!

88 Intergra is right on. You guys are talking about how big your ports are and eventualy your going to come to find out; that the is such a thing as to much of a good thing.

Such as "blow-by".

Which by the way is (from what I understood) a condition caused by over-porting in which your new ultra large intake ports are now opening and closing so late followed by a ultra large exhuast port that is now also opening early and closing late that it actually throws of the hole compression/combustion cycle and is now recylcing a large amount of "[/I]blow-by[I]" gases instead of fully compressing and then fully combusting them the way it should to get the good strong power stroke your really looking for.



Chew on this a bit, before you go for your grinders. You and your motors will be glad you did.



PK797 NYC

MPM

I'm with pk797 and 88 IntegraLS. The ideal situation is to increase the velocity of the intake charge without increasing the port runner and/or port size to much. Much more efficient. The same holds true for exhaust porting and exhaust sizing. As long as you don't pass the point of diminishing returns your ok.



This is ofcourse greatly simplified but there are those of you that know what I mean.

mazdaspeed7

Hold on. Everyone is jumping on the bandwagon against my exhaust port, but do you have any PERSONAL experience with it? I would guess not. My motor doesnt have a much low end as stock, but i have plenty as far as drivability is concerned. Oh, and my car idles at 600 rpm, EVEN with that huge exhaust port. Theres more to drivability than just the ports. It takes a whole package to produce good results.



One of my friends with an 87 GXL drove my car, and he had no problems with the low end, and he loved how progressive the powerband was, and how it built up power as the revs climbed.



Its not for everyone though. My car is WAY louder than it was on stock ports. But I wouldnt have it any other way.

pk797

Mazda7

In my own personal experiance I come to know that why''ll some porting can be good (if done the right way) it's not the whole ball game and it's definetly not going to help if you over do it.

Keep in mind the biggest ports mated to a stock turbo/intake/throttle body/etc is not going to make the kind of horepower/torque/mileage you may be looking for.

Also when you port a rotary it not like porting a piston motor. This is because by open the ports on a rotary your also lengthing the "port timing", and that my friend effects everything especially low end power. Which like it or not, is were most races are won or lost.

To make a good strong, reliable motor with any kind of usable torque/powerband it must be done with a good overall plan.

The whole build-up has to be put together with that kind of goal in mind.

In other words big ports doesn't necessarly equal to high horsepower[B].

By the way how's your gas milage now?



Pk797 NYC

Judge Ito

I wanted to add that, besides changing intake opening and closing when the engines is ported. People that are starting to port their own engines need to learn that a port needs to increase in the amount of CFM that the port flows from factory, versus a ported one. for example a factory port might flow 140cfm per port, is your job to make that port flow as much cfm as possible in comparison to the stock cfm. if a stock port flows 140cfm a really good port job will allow that same side housing to flow over 200cfm's

cfm = cubic feet per minute. Soon Ill be back online helping the rotary engine community again.

BDC

That's correct and well said, Ito. That's the whole point of it -> it boils down to the amount of air the engine can injest and exhale over a given period of time. In porting, it's not so much about "bigger is better" rather than how you handle the end points of both the short radius and long radius and how the nitride plating is matched to the cast iron below.



An easy way to see how the stock port flows is the old "cigarette smoke" trick. For any smokers, take in a puff then exhale it into the port tunnel. You can see how the air twists, turns, and moves in a stock port. It'll give you a good idea of how things can be re-worked so the port becomes more efficient at moving air and keeping it moving quickly.



B

mazdaspeed7

20 mpg with that motor. It would be higher if I didnt spend most of my time on the highway at 85-90 mph. Did you miss the part where I said porting is only one component of a build? Everything on my car was set up to take advantage of my porting. I agree that huge ports on an otherwise stock car are a waste. But my car is totally opposite. Everything was done around that motor, and the results were great. My car drives as good as a stock car at worst, and probably better than most. My drivability is great, and as far as reliability goes, I had 10 times more problems with a stock motor than Ive had with this one.





Tell me this, all of you who have pretty heavily modded cars that are bashing me for my ports. Can you just toss your keys to someone else, and not worry about them having problems driving it? I can.

jasonD

Has anyone seen this before? I think they fill the hole with epoxy to make the primary port bigger, is it worth doing and would the epoxy hold?

jasonD

Finished port

Fd3BOOST

I have heard some about the epxoy resins but my major concern would be the resin holding tight to its place. If it were to come loose or chip you would have a serious mess on your hands.